Hyperbrance .pdf

Hyperbranched polymers: from synthesis to applications

C. Gao*, D. Yan*

College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China

Received 20 August 2003; revised 20 August 2003; accepted 18 December 2003

Abstract

Over the past 15 years, hyperbranched polymers have received much attention due to their unique chemical and physical

properties as well as their potential applications in coatings, additives, drug and gene delivery, macromolecular building

blocks, nanotechnology, and supramolecular science. Hyperbranched polymers can be prepared by means of single-

monomer methodology (SMM) and double-monomer methodology (DMM). In SMM, the polymerization of an ABn or

latent ABn monomer leads to hyperbranched macromolecules. SMM consists of at least four components: (1)

polycondensation of ABn monomers; (2) self-condensing vinyl polymerization; (3) self-condensing ring-opening

polymerization; (4) proton-transfer polymerization. In DMM, direct polymerization of two suitable monomers or a

monomer pair gives rise to hyperbranched polymers. A classical example of DMM, the polymerization of A2 and Bn

ðn . 2Þ monomers, is well known. Recently, a novel DMM based on the in situ formation of ABn intermediates from

specific monomer pairs has been developed. This form of DMM is designated as ‘couple-monomer methodology’ (CMM)

to clearly represent the method of polymerization. Many commercially available chemicals can be used as the monomers in

these systems, which should extend the availability and accessibility of hyperbranched polymers with various new end

groups, architectures and properties. Because a number of comprehensive reviews have been published on SMM, research

involving DMM is emphasized here. In addition, recent developments in the modification, functionalization and application

of hyperbranched polymers are described.

q 2004 Elsevier Ltd. All rights reserved.

Keywords: Hyperbranched polymer; Dendritic polymer; Polymer brush; Modification; Functionalization; Application; Surface

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

1.1. History of hyperbranched polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

1.2. Synthesis methodology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

1.2.1. SMM—polycondensation of AB2 monomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

1.2.2. SMM—self-condensing vinyl polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

1.2.3. SMM—self-condensing ring-opening and proton-transfer polymerizations . . . . . . . . . . . 188

1.2.4. DMM—polymerization of two types of monomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

2. ‘A2 þ B3’ methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

0079-6700/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.progpolymsci.2003.12.002

Prog. Polym. Sci. 29 (2004) 183–275

www.elsevier.com/locate/ppolysci

* Corresponding authors. Tel.: þ86-21-54742665; fax: þ86-21-54741297.

E-mail addresses: [email protected] (C. Gao); [email protected] (D. Yan).

http://www.elsevier.com/locate/ppolysci

3. Couple-monomer methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

3.1. General description of CMM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

3.2. ‘A2 þ BB02’ approach to hyperbranched poly(sulfone amine)s and poly(ester amine)s . . . . . . . . . 201

3.3. ‘A2 þ CBn’ approach to hyperbranched poly(urea urethane)s . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

3.4. ‘AB þ CDn/Cn’ approach to hyperbranched poly(amine ester)s and poly(amide amine)s . . . . . . . 208

3.4.1. ‘AB þ CDn approach’ to hyperbranched poly(amine ester)s . . . . . . . . . . . . . . . . . . . . . . 208

3.4.2. ‘AB þ Cn’ approach to hyperbranched poly(amide amine)s . . . . . . . . . . . . . . . . . . . . . . 211

3.5. ‘Ap þ CB2/Bn’ approach to hyperbranched poly(ester amide)s and polyesters . . . . . . . . . . . . . . . 212

3.5.1. ‘Ap þ CB2’ approach to hyperbranched poly(ester amide)s . . . . . . . . . . . . . . . . . . . . . . 212

3.5.2. ‘Ap þ Bn’ approach to hyperbranched polyesters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

3.6. ‘AAp/Ap2 þ B2’ approach to hyperbranched polyesters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

3.7. ‘A2 þ B2 þ BB02’ approach to highly branched copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

4. Modification of hyperbranched polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

4.1. End-capping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

4.2. Terminal grafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

4.3. Surface growing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

4.3.1. On the surface of Au . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

4.3.2. On the surface of SiO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

4.3.3. On the surface of Si . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

4.3.4. On the surface of PE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

4.3.5. On the other surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

4.4. Hypergrafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

5. Application of hyperbranched polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

5.1. Conjugated functional materials: optical, electronic and magnetic properties. . . . . . . . . . . . . . . . 242

5.1.1. Hyperbranched poly(phenylenevinylene) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

5.1.2. Hyperbranched poly(b,b-dibromo-4-ethynylstyrene) . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

5.1.3. Hyperbranched poly(arylene/1,1-vinylene)s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

5.1.4. Hyperbranched polyarylenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

5.1.5. Hyperbranched non-linear optical polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

5.1.6. Hyperbranched coumarin-containing polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

5.1.7. Hyperbranched polythiophenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

5.1.8. Hyperbranched polyanilines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

5.2. Polymer electrolytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

5.3. Nanomaterials and biomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

5.3.1. Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

5.3.2. Biomaterials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

5.4. Supramolecular chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

5.5. Patterning of hyperbranched polymer films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

5.6. Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

5.7. Modifiers and additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

5.8. Other applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

6. Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

1. Introduction

Hyperbranched polymers are highly branched

macromolecules with three-dimensional dentritic

architecture. Due to their unique physical and chemical

properties and potential applications in various

fields from drug-delivery to coatings, interest in

hyperbranched polymers is growing rapidly, as con-

firmedbytheincreasingnumberofpublications(Fig.1).

As the fourth major class of polymer architecture,

coming after traditional types which include linear,

cross-linked and branched architectures, dendritic

C. Gao, D. Yan / Prog. Polym. Sci. 29 (2004) 183–275184

Nomenclature

ACPA 4,40-azobis(4-cyanopentanoic acid)

AFM atomic force microscopy

ATRP atom transfer radical polymerization

BIEM 2-(2-bromoisobutyryloxy)ethyl methyacry-

late

bis-MPA 2,2-bis-hydroxymethyl propionic acid

BPEA 2-2-(bromopropionyloxy)ethyl acrylate

Bu4Nþ tetra-n-butylammonium

CAC critical association concentration

CAH 2-chloroethylamine hydrochloride

CMM couple-monomer methodology

CP chitosan powder

CPS chloromethylstyrene

D dendritic unit

DB degree of branching

DBOP diphenyl(2,3-dihydro-2-thioxo-3-benzoxa-

zolyl)phosphonate

DCC N,N-dicylohexylcarbodiimide

DIPC diisopropylcarbodiimide

DMA dynamic mechanical analysis

DMAc N,N-dimethylacetamide

DMAP 4-(dimethylamino)pyridine

DMF N,N-dimethylformamide

DMM double-monomer methodology

DPMP diphenylmethylpotassium

DSC differential scanning calorimetry

EG ethylene glycol

EHBP epoxy-functionalized hyperbranched polye-

sters

EL electroluminescence

EO ethylene oxide

ESI electrospray ionization

GTP group transfer polymerization

L linear unit

LALLS low-angle laser light scattering

LCST lowermost critical solution temperature

LDA lithium diisopropylamide

MA methyl acrylate

MAH maleic anhydride

MALDI-TOF matrix-assisted laser desorption/ioni-

zation time-of-flight

Me6-TREN tri(2-(dimethylamino)ethyl)amine

MHO 3-methyl-3-(hydroxymethyl)oxetane

MMA methyl methacrylate

Mn number average molecular weight

MOI 2-methacryloyloxyethyl isocyanate

MUA mercaptoundecanoic acid

Mw weight average molecular weight

NIR near infrared

NMP N-methyl-2-pyrrolidone

NMR nuclear magnetic resonance

PA polyaniline

PAA poly(acrylic acid)

PAAM poly(allylamine)

PCL poly(1-caprolactone)

PCS photon correlation spectroscopy

PDI polydispersity index ðMw=MnÞ

PDMA poly(2-dimethylaminoethyl methacrylate)

PE polyethylene

PEHO poly[3-ethyl-3-(hydroxymethyl)oxetane]

PEI poly(ethyleneimine)

PEO poly(ethylene oxide)

PG hyperbranched polyglycerol

PL photoluminescence

PMDETA pentamethyldiethylenetriamine

PMHO poly[3-methyl-3-(hydroxymethyl)oxetane]

PP polypropylene

PPMA phosphorus pentoxide/methanesulfonic

acid

PPO poly(propylene oxide)

PPV poly( p-phenylenevinylene)

PS polystyrene

PTBA poly(tert-butyl acrylate)

PTHF polytetrahydrofuran

PTP proton-transfer polymerization

PVK poly(9-vinylcarbazole)

ROMBP ring-opening multibranching polymeriz-

ation

SCROP self-condensing ring-opening polymeriz-

ation

SCVP self-condensing vinyl polymerization

SDS sodium dodecyl sulfate

SEC size exclusion chromatography

SHG second harmonic generation

SMM single-monomer methodology

T terminal unit

Td decomposition temperature

TEM transmission electron microscopy

Tg glass transition temperature

TGA thermogravimetric analysis

THF tetrahydrofuran

C. Gao, D. Yan / Prog. Polym. Sci. 29 (2004) 183–275 185

architecture consists of six subclasses: (a) dendrons and

dendrimers; (b) linear-dendritic hybrids; (c) dendri-

grafts or dendronized polymers; (d) hyperbranched

polymers; (e) multi-arm star polymers; (f) hypergrafts

or hypergrafted polymers (Fig. 2) [1]. The first three

subclasses exhibit perfect structures with a degree of

branching (DB) of 1.0, while the latter three exhibit a

random branched structure. Dendrons and dendrimers

with high regularity and controlled molecular weight

are prepared step by step via convergent and divergent

approaches. A linear polymer linked with side dendrons

is called as dendronized polymer. Dendronized poly-

mers can be obtained by direct polymerization of

dendritic macromonomers, or by attaching dendrons to

a linear polymeric core.

A number of excellent reviews have been published

on dendrimers, linear-dendritic hybrids, and dendro-

nized polymers, covering synthesis, functionalization,

supramolecularself-assemblyandapplications [1–34].

This article reviews the synthesis, modifications, and

applications of random hyperbranched and hyper-

grafted polymers, focusing on the recently developed

novel synthetic strategy for hyperbranched polymers.

1.1. History of hyperbranched polymers

As shown in Table 1, showing the development

of hyperbranched polymers, highly branched

artificial molecules have a long and complex history.

The history of hyperbranched macromolecules can be

dated to the end of 19th century, when Berzelius

reported the formation of a resin from tartaric acid

(A2B2 monomer) and glycerol (B3 monomer) [35].

Following the Watson Smith report of the reaction

between phthalic anhydride (latent A2 monomer) or

phthalic acid (A2 monomer) and glycerol (B3 mono-

mer) in 1901 [35], Callahan, Arsem, Dawson, Howell,

and Kienle, et al. [35–37] studied that reaction further,

obtaining results and conclusions still used today. For

example, Kienle [36] showed that the specific viscosity

of samples made from phthalic anhydride and glycerol

was low when compared to numerous specific

viscosity values given by Standinger for other

synthetic linear polymers, such as polystyrene. In

1909, Baekeland [38] introduced the first commercial

synthetic plastics, phenolic polymers, commercialized

through his Bakelite Company. The cross-linked

phenolic polymers are obtained by the polymerization

of soluble resole precursors made from formaldehyde

(latent A2 monomer) and phenol (latent B3 monomer).

Just prior to gelation, these polymers have a so-called

random hyperbranched structure.

In the 1940s, Flory et al. [39–43] used statistical

mechanics to calculate the molecular weight distri-

bution of three-dimensional polymers with trifunc-

tional and tetrafunctional branching units in the state

of gelation, and developed the ‘degree of branching’

and ‘highly branched species’ concepts. However,

both the experiments and calculations mentioned

above are based on polycondensation of bifunctional

A2 monomer with trifunctional B3 monomers, so

gelation occurs when the degree of polymerization

approaches the critical condition. In 1952, Flory [44]

developed the theory that highly branched polymers

can be synthesized without the gelation by poly-

condensation of a monomer containing one A

functional group and two or more B functional ones

capable of reacting with A (ABn monomer, n $ 2).

Finally, in 1982, Kricheldorf [45] obtained highly

Tm melting point

TPA terephthaldehyde

TPP triphenylphosphine

TsCl tolylsulfonyl chloride

UV–Vis ultraviolet–visible spectroscopy

WAXS wide-angle X-ray scattering

Fig. 1. Scientific publications as a function of publication year search-

ed by SCIE (ISI web of science) with hyperbranched as the topic.


branched polyesters by copolymerization of AB and

AB2 type monomers.

‘Hyperbranched polymer’ was first coined by Kim

and Webster [46,47] in 1988 when the authors

intentionally synthesized soluble hyperbranched poly-

phenylene. Since then, hyperbranched polymers have

attracted increasing attention owing to their unique

properties and greater availability as compared with

dendrimers.

1.2. Synthesis methodology

Up to now, the synthetic techniques used to prepare

hyperbranched polymers could be divided into two

major categories. The first category contains tech-

niques of the single-monomer methodology (SMM),

in which hyperbranched macromolecules are syn-

thesized by polymerization of an ABn or a latent ABn

monomer. According to the reaction mechanism, the

SMM category includes at least four specific

approaches: (1) polycondensation of ABn monomers;

(2) self-condensing vinyl polymerization (SCVP); (3)

self-condensing ring-opening polymerization

(SCROP); (4) proton-transfer polymerization (PTP).

The other category contains methods of the double-

monomer methodology (DMM) in which direct

polymerization of two types of monomers or a

monomer pair generates hyperbranched polymers.

Table 2 shows the synthetic methodologies and

approaches to hyperbranched polymers.

Fig. 2. Schematic description of dendritic polymers.

Table 1

History of hyperbranched polymers

Year Case Lead authors Reference

Before

1900

Tartaric acid þ glycerol Berzelius [35]

1901 Glycerol þ phthalic

anhydride

Smith [35]

1909 Phenolic þ formaldehyde Baekeland [38]

1929–

1939

Glycerol þ phthalic

anhydride

Kienle [35–37]

1941 Molecular size

distribution in theory

Flory [39–41]

1952 ABn polymerization

in theory

Flory [44]

1982 AB2 þ AB copolymerisation Kricheldorf [45]

1988–

1990

AB2 homopolymerization Kim/Webster [46,47]


1.2.1. SMM—polycondensation of AB2 monomers

A broad range of hyperbranched polymers, includ-

ing hyperbranched polyphenylenes [46–49], poly-

ethers [50–53], polyesters [54–76], polyamides

[77 – 82], polycarbonates [83], and poly(ether

ketone)s [84–87], are prepared via one-step poly-

condensation of ABn type monomers. If one group of

ABn monomers contains double or triple bonds, small

molecules may not be formed in the polymerization.

Through polyaddition of the ABn monomers, hyper-

branched polyurethanes [88–91], polycarbosilanes

[92–95], polyamides [96,97], and poly(acetophe-

none)s [98,99] have been successfully obtained.

AB3, AB4, AB5, and even AB6 monomers are also

used to synthesize hyperbranched polymers while

controlling the branching pattern [94,100].

1.2.2. SMM—self-condensing vinyl polymerization

SCVP was invented by Frechet and coworkers in

1995 [101]. This polymerization method is quite

versatile, as hyperbranched polymers can

be approached via polymerization of AB vinyl

monomers. In the reaction, the B groups of the AB

monomers are activated to generate the initiating Bp

sites. Bp initiates the propagation of the vinyl group A

in the monomer, forming a dimer with a vinyl group, a

growth site, and an initiating site. The dimer can

function as an AB2 monomer, and undergo further

polymerization to yield the hyperbranched polymer.

In SCVP, the activities of chain propagation of the

growth sites and the initiating sites differ, resulting in

a lower DB when compared to the DB of the

hyperbranched polymer prepared via polycondensa-

tion of AB2 monomers. The theoretical maximum DB

of SCVP is 46.5% [127]. On the other hand, SCVP

does exhibit some disadvantages. For example, side

reactions may lead to gelation, the molecular weight

distribution is usually very broad, and it is difficult to

determine DB directly via an NMR analysis. In order

to avoid crosslinking, living/controlled polymeriz-

ations such as atom transfer radical polymerization

(ATRP) and group transfer polymerization (GTP) are

combined in SCVP [121–126]. Monomers used in

SCVP and polymerization results such as number-

average molecular weight ðMnÞ and polydispersity

index (PDI, Mw=Mn) are summarized in Table 3

[101–126].

1.2.3. SMM—self-condensing ring-opening and

proton-transfer polymerizations

Hyperbranched polyamines [128,129], polyethers

[130–138] and polyesters [139,140] have been

prepared through SCROP. Table 4 shows some of

the monomers employed in SCROP and the polym-

erization results. Finally, hyperbranched polyesters

with epoxy or hydroxyl end groups [141–143] and

hyperbranched polysiloxanes [144] were synthesized

through PTP. A number of reviews have been

published on hyperbranched polymers prepared by

SMM [145–158].

1.2.4. DMM—polymerization of two types of

monomers

DMM can be divided into two main subclasses

based on the selected monomer pairs and different

reaction pathways. The classical one, the polym-

erization of A2 and B3 (or Bn, n . 2) monomers,

taken up in Section 2, can be called the ‘A2 þ B3’

methodology, and was first adopted intentionally

to prepare soluble hyperbranched polymers by

Table 2

Synthesis strategies and approaches of hyperbranched polymers

Methodology Approach Lead

author

Year Reference

SMM Polycondensation

of ABn

Kim/

Webster

1988 [46,47]

SCVP Frechet 1995 [101]

SCROP Suzuki/

Penczek

1992/

1999

[128,131]

PTP Frechet 1999 [141]

DMM

A2 þ B3 Polycondensation

of A2 and B3

monomers

Jikei/

Kakimoto

1999 [159]

Emrick/

Frechet

1999 [160]

CMM

A2 þ BB02 Yan/Gao 2000 [161,162]

A2 þ B2 þ BB02 Gao/Yan 2000 [163]

A2 þ CBn Gao/Yan 2001 [164]

AB þ CDn Gao/Yan 2001 [164]

Ap þ Bn Gao/Yan 2001 [164]

AAp þ B2 Gao/Yan 2001 [164]

Ap þ CB2 DSM

research

2000 [165,166]


Table 3

The monomers used in SCVP and the polymerization results

Monomer Condition Mn (GPC) PDI Reference

SnCl4 Bu4NþBr2 220 to 215 8C 660,000–17,000 9.8–2.9 [101]

ATRP 6280–1900 2.5–1.3 [102]

Bulk polymerization at 130 8C 4280 1.4 [103]

80 8C in toluene for 40 h 4410 1.38 [104]

Photopolymerization (UV light at 20 8C) 38,900 2.03 [105]

ATRP (50 8C, conversion ¼ 87%) 27,700 2.9 [115]

ATRP (24 8C for 0.5 h in bulk) 2270 14.2 [116]

100 8C for 18 h 18,100 1.91 [117,118]

ATRP in emulsion (90 8C for 44 h) 22,100 9.5 [119]

(continued on next page)


Table 3 (continued)

Monomer Condition Mn (GPC) PDI Reference

ATRP (24 8C for 26 h in benzene) 1990 6.6 [116]

ATRP (24 8C for 24 h in benzene) 650 4.3 [116]

GTP at 250 8C 1630 34 [121,122]

Copolymerisation at 50 8C for 24 h 5980 1.87 [124]

Table 4

The monomers used in SCROP and the polymerization results

Monomer Condition Mn (GPC) PDI DB Reference

Pd(0), 25 8C for 48 h in THF 1800 1.5 0.61 [128,129]

4170 1.43 0.38 [131]

BF3·OEt2, 210 to 4 8C for 48 h 1780 1.28 0.33 [136]

CH3OK, 95 8C for 12 h 6310 1.47 0.59 [137]

Sn(Oct)2, 110 8C in bulk 20,300–26,500 3.2 0.5 [139]

Sn(Oct)2, 110 8C in bulk 3000 2.8 0.5 [140]


Kakimoto [159] and Frechet [160]. Combination of

the basic SMM synthetic principle and the multi-

monomer character of ‘A2 þ B3’ methodology

results in the other DMM, relevant to Section 3:

couple-monomer methodology (CMM) based on in

situ formation of ABn intermediates from specific

monomer pairs due to the non-equal reactivity of

different functional groups [161,162]. Many com-

mercially available chemicals can be used as

reactive monomers for CMM, which should

extend the availability and accessibility of hyper-

branched polymers with various new end groups,

architectures and properties, without the danger of

crosslinking [161–167]. One aim of this review is to

introduce in detail the double-monomer method-

ologies, since both ‘A2 þ B3’ and CMM have been

incompletely covered or even omitted in prior

reviews.

2. ‘A2 1 B3’ methodology

The first intentional preparation of hyperbranched

polymers via the ‘A2 þ B3’ approach was reported

by Kakimoto [159] and Frechet [160], although the

method had been explored to prepare cross-linked

polymeric materials more than a century before

[38]. It is well known that direct polycondensation

of A2 and B3 monomers generally results in gelation

[39–43]. Thus, the crucial problem of this approach

is how to avoid gelation, and obtain soluble three-

dimensional macromolecules. Soluble hyper-

branched polymers can be obtained by stopping

the polymerization through precipitation or end-

capping prior to the critical point of gelation, by the

slow addition of monomer, or by using special

catalysts and condensation agents. Table 5 lists the

A2 and B3 type monomers reported in the literature

recent years.

The reaction between aromatic diamines (A2)

and aromatic tricarboxylic acids (B3) was first

investigated by Aharoni [168–171]. However, only

insoluble networks composed of aromatic rigid

segments were obtained. Although the direct

connection of aromatic rings by amide rings led

to good heat and flame resistance, as well as

high tensile strength and modulus, the cross-

linked materials possessed poor processibility.

Kakimoto [159] further studied the reaction, and

obtained soluble hyperbranched aromatic polyamide

with monomers 22, 23 and 24 as raw

materials in the presence of triphenyl phosphite

and pyridine as condensation agents through

consideration of the polymerization conditions

(Scheme 1).

When p-phenylene diamine (monomer 22)

reacted with trimesic acid (monomer 24) with a

feed ratio of A2 to B3 of 1/1 at 80 8C for 3 h with

a total monomer concentration of 0.21 mol/l

(3.3 wt%), no gelation was observed for the

polymerization. When the total monomer concen-

tration in N-methyl-2-pyrrolidone (NMP) was

increased to 0.31 mol/l or 4.9 wt%, cross-linking

occurred in 2 h at the same reaction conditions.

Addition of LiCl can accelerate the polymerization.

In the absence of LiCl, three equivalents of

triphenyl phosphite to monomer 24 were required

to gain a high inherent viscosity sample. In the

presence of LiCl, only two equivalents of triphenyl

phosphite were needed to obtain a polymer with a

high viscosity. If monomer 23, instead of 22, was

used to react with 24, soluble hyperbranched

aromatic polyamide was successfully achieved

with three equivalents of triphenyl phosphite. If

the amount of triphenyl phosphite was decreased to

two equivalents, gelation occurred when the reac-

tion was performed with LiCl even if the total

monomer concentration was decreased from 0.21 to

0.168 mol/l. So, gelation occurred more easily

for the polymerization of 23 and 24 than that of

22 and 24, which may be attributed to the higher

DB or the higher percentage of trisubstituted 24

units in the resulting polymer formed from 23 and

24. Gel formation was observed within 10–20 min,

and soluble hyperbranched polyamide was not

obtained when the feed ratio of A2 to B3 was set

to 3/2.

A powdery polymer was obtained by pouring the

reaction mixture into methanol containing 12N

aqueous HCl. The hyperbranched polyamides HP1

and HP2 aggregated in N,N-dimethylforamide

(DMF) even when LiBr was added to the solution

system. The resultant hyperbranched polymer with

carboxylic acid terminal groups was end-capped

with p-anisidine in order to avoid the aggregation

effect in the measurement of molecular weight.


The weight-average molecular weights Mw of the

end-capped samples HP3 and HP4 as determined by

SEC measurements with a laser light-scattering

detector for solutions in DMF containing LiBr

(0.01 mol/l) were 285,000 and 86,700, respectively.

The polydispersity indices for HP3 and HP4 were

5.26 and 4.93, respectively.

Frechet and coworkers [160] independently applied

the ‘A2 þ B3’ approach to synthesize hyperbranched

polyether employing 1,2,7,8-diepoxyoctane (25)

Table 5

The A2- and B3-type monomers used in ‘A2 þ B3’ methodology

A2 B3 Reference

[159]

[160]

[172]

[173,174]

[175]

[176]

[177]

(continued on next page)


as the A2 monomer and 1,1,1-tris(hydroxymethy-

l)ethane (26) as the B3 monomer. The initiation

and propagation steps are schematically shown in

Scheme 2. Tetra-n-butylammonium chloride (Bu4NCl,

5 mol% based on 25) was adopted as the nucleophilic

catalyst. Nucleophilic attack of the chloride ion on an

epoxide of 25 at the less-hindered terminal carbon led

to the formation of secondary alkoxide 25p. Equili-

brium between primary and secondary alkoxides was

established through rapid proton exchange, nucleo-

philic attack of primary alkoxides on the epoxide rings

resulted in the propagation of the formed oligomers,

and finally the formation of aliphatic hyperbranched

polyether epoxy HP5. As the feed ratio of 25 to 26

varied from 1.5 to 3, the resulting hyperbranched

polyether contained two types of terminal units (T),

one sort of dendritic unit (D), and linear ones (L) as

shown in Scheme 2.

Polymerization rates between 25 and 26 were too

slow to be practical in THF solution; the propagation

rates could be improved significantly via

bulk polymerization at temperatures above 100 8C.

Gelation can be avoided by removing the reaction

vessel from the heating bath prior to the critical point

of gelation. By increasing the feed ratio of 25 to 26,

the epoxy content of the isolated polymer

product increased, and the percentage of trisubstituted

B3 units in the resulting polymer also increased.

However, the PDI of the polyether increased with the

increase of molecular weight (,1.5–1.8 at Mw ,1000 and ,5.0 at Mw , 7000).

Aliphatic hyperbranched polyethers are viscous

liquids with glass-transition temperatures ðTgsÞ

below room temperature (about 220 8C for the

product with Mw , 8000) [172]. The decomposition

temperature ðTdÞ of a polymer with a Mw of about

10,000 is about 305 8C. Although HP5 is isolable by

fractionation into water, it is still a hydrophilic

material, as demonstrated by a contact-angle gonio-

metry value of 42–448 for a drop of water on spin-

coated films of HP5 on silicon wafers. After the

hyperbranched polymer was modified with hydro-

phobic chains (Scheme 2), the obtained products

HP6, HP7 and HP8 increased hydrophobicity over

Table 5 (continued)

A2 B3 Reference

[178]

[181]


the hydroxy-rich precursors, as demonstrated by

water contact angles that were 20–308 greater than

that for HP5.

The direct polymerization of 1,4-butanediol (27)

and triepoxide (28) under a variety of reaction

conditions using Bu4NCl as the catalyst was also

explored by Frechet et al. [172]. Again, the reaction

was very slow in THF solution. In bulk polymeriz-

ation, the reaction was much faster, and gelation

occurred after 30 h at 75 8C. Analysis by SEC

showed that the PDI of the soluble polymers

isolated before the critical point was extremely

broad ðMw=Mn . 20Þ: Unfortunately, the product

could not be separated from either the catalyst or the

residual monomers by fractionation, so it was

difficult to fully characterize the material.

Through the formation of a Schiff-base between

dialdehyde (29) and triamine (30), Dai et al. prepared

hyperbranched polyconjugated conducting polymers

which showed relatively strong fluorescence emission

and high conductivities (ca. 1023 S/cm) after doping

[173,174]. Hyperbranched conjugated poly(1,3,5-

trisvinylic)benzene was synthesized via a Wittig

reaction between 31 and 32 [175], discussed in detail

in Section 5.

Tanaka and coworkers [176] prepared a new

conjugated alternate copolymer (HP9) consisting of

triphenylamine and phenylene units (Scheme 3) by

palladium catalyzed Suzuki coupling of an A2

monomer, benzene-1,4-diboronic acid (33), and a

B3 monomer, tris( p-bromophenyl)amine (34). The

light-yellow powder polymer was isolated after

evaporating the solvent and then pouring the crude

product into acetone. The resulting conjugated

hyperbranched polymer had an average molecular

weight of 5400 and was soluble in organic solvents

such as chloroform and THF. The conjugated

polymer had an absorption band at 365 nm and

an emission peak at 430 nm. The cyclic voltammo-

gram of the polymer film deposited on a platinum

plate displayed reversible p-type doping and

undoping, with a color change between brown-

yellow (undoped) and green (doped). By using the

reference electrode of Ag wire and the supporting

electrolyte of a 0.1 mol/l Bu4NBF4 solution in

propylene carbonate, an anodic and cathodic peaks

were found at 1.2 and 1.0 V, respectively. In the

neutral state the polymer film was brown-yellow,

while in the doped state it turned green; 0.47

electron per monomeric units was found during the

redox cycle. This conjugated hyperbranched poly-

mer could potentially be used as a charge storage

material, such as an electrode for secondary

batteries.

Fang et al. successfully fabricated wholly aro-

matic hyperbranched polyimides by direct polycon-

densation of commercially available dianhydrides 35

[2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dia-

nhydride], 36 (3,30,4,40-diphenylsulfonetetracar-

boxylic dianhydride) and 37 (pyromellitic

anhydride) and triamine 38, employing a two-step

Scheme 1.


polymerization method [177]. First, the hyper-

branched polyamic acid precursors were prepared

by reaction of the dianhydrides and 38 in N;N-

dimethylacetamide (DMAc). Then, chemical or

thermal imidization of the precursors gave rise to

the final hyperbranched polyimides (Scheme 4).

Reaction conditions, such as the monomer feed

ratio, monomer addition manner, and concentration

strongly influenced the polymerization results. A

hyperbranched polyimide with amino terminal

groups was obtained when a dianhydride solution

was added to the solution of 38 with a 1/1 molar

Scheme 2.


feed ratio of A2 to B3 (manner 1). In comparison,

the addition of 38 to a dianhydride solution with a

2/1 molar feed ratio of A2 to B3 (manner 2) yielded

the anhydride-terminated hyperbranched polyimide.

The concentration of the added dianhydride or

triamine approached zero during addition to avoid

a high local concentration of added monomer, which

could cause immediate gelation. Higher concen-

tration of the feed monomers also led to cross-

linking. The total feed monomer content should be

kept below 0.2 mol/l for method 1 and 0.075 mol/l

for method 2. 1H NMR spectra showed that the DB

for the amine-terminated HP10, HP11, and HP12

were 0.64, 0.72 and 0.68, respectively. The

anhydride-terminated HP13, HP14, HP15 were

fully branched ðDB ¼ 1Þ due to the relatively high

content and high reactivity of the anhydride

groups. SEC determination revealed that the hyper-

branched polyimides HP10 and HP13 had moderate

number-averaged molecular weights (6400 for HP10

and 8400 for HP13) and broad molecular weight

distributions (5.8 for HP10 and 18 for HP13). No Tg

was observed for HP12 and HP15 using differential

scanning calorimetry (DSC); the Tg ranged from 339

to 295 8C for other four hyperbranched polyimides.

The amine-terminated polyimides showed a higher

Tg than the corresponding anhydride-terminated

ones, owing to their lower DBs and stronger

macromolecular interaction resulting from the

hydrogen bonds between amino groups. Thermo-

gravimetric analysis (TGA) showed that the hyper-

branched polyimides had a 5% weight loss at 450 8C

in N2.

HP10 and HP13 based on the monomer 35 showed

good solubility in strong polar solvents such as

DMAc, NMP, and dimethyl sulfoxide (DMSO), and

poor solubility in tetrahydrofuran (THF), acetone and

1,4-dioxane. However, the hyperbranched polyimides

Scheme 3.


Scheme 4.


based on monomers 36 and 37 were insoluble in all of

the aforementioned solvents.

To improve the solubility of aromatic hyper-

branched polyimides, a new triamine [1,3,5-tris(4-

aminophenoxy)benzene, 41] was introduced to react

with conventional dianhydrides such as 35, 39 (4,40-

oxydiphthalic anhydride) and 40 (3,30,4,40-benzo-

phenonetetracarboxylic dianhydride) [178–180].

The resulting hyperbranched polyimides exhibited

excellent solubility in strong polar solvents such as

DMAc, DMF, DMSO, NMP and m-cresol. It was

found that the polyimides made from 35 and 41

were soluble, even in common low-boiling-point

solvents such as THF, acetone and chloroform.

Photosensitive hyperbranched polyimide was pre-

pared by reaction of cinnamoyl chloride with

phenol-terminated hyperbranched polyimide gener-

ated from the end capping of the anhydride-

terminated hyperbranched poly(amic acid)

precursor of 35 and 41 with 4-aminophenol

during the course of polymerization. Highly

resolved patterns with a line width of 10 mm were

obtained via photolithography of the photosensitive

polyimide [179].

Two novel B3 monomers [tri(phthalic anhy-

dride), 42] and [tri(phthalic acid methyl ester),

43] were synthesized and used to polycondense

with 1,4-phenylenediamine (22) in a feed mole

ratio of 1/1, resulting in hyperbranched polyimides

(Scheme 5) [181]. The polymerization of 42 and 22

was termed method A, and that of 43 and 22

termed method B. In method A, direct reaction of

42 and 22 in the solution of DMAc afforded the

hyperbranched poly(amic acid) precursor. Further

chemical imidization of the poly(amic acid) in the

presence of pyridine and acetic anhydride (Ac2O)

gave the anhydride-terminated hyperbranched poly-

imide HP16. If the poly(amic acid) precursor was

end-capped with p-toluidine, and then chemical

imidization of the end-capped precursor occurred,

toluidine end-capped hyperbranched polyimide

HP17 was obtained. As shown in Scheme 5,

HP16 and HP17 can also be prepared via method

B through chemical imidization of poly(amic acid

methyl ester) and toluidine end-capped poly(amic

acid methyl ester) precursors, respectively. Polym-

erization by method A often generated a gel due to

high reactivity between anhydride and amino

groups, so the reaction temperature was set at

0 8C. In method B gelation was effectively avoided

by using diphenyl(2,3-dihydro-2-thioxo-3-benzoxa-

zolyl)phosphonate (DBOP) as a condensation agent

under room temperature (RT) at a concentration

lower than 0.1 g/l.

It is interesting that the polymers made by

methods A and B exhibit different properties from

each other, even though they have the same

structure. The precursor and hyperbranched poly-

imides made by method A are hardly soluble in

organic solvent at room temperature, but are soluble

upon heating in strong polar solvents, and the

solution remains homogeneous when cooled to room

temperature. By comparison, the precursor and the

hyperbranched polyimides made by method B are

soluble in DMAc, DMF, DMSO and NMP at room

temperature. Furthermore, the HP17 made by

method A has a high Mw (3.02 £ 105), a broad

PDI (23) and a low inherent viscosity

(hinh ¼ 0:28 dl=g in DMAc at 30 8C). The HP17

with a Mw of 1.25 £ 105 and a PDI of 2.63 made by

method B has a much higher inherent viscosity

ðhinh ¼ 0:97 dl=gÞ: The authors [181] explained this

phenomena, saying that the high molecular weight

component of HP17 made by method A was

actually a slightly cross-linked microgel formed at

the precursor formation stage.

The resulting hyperbranched polyimides have DBs

of 0.52–0.56 determined by 1H NMR, and Tgs of

212–236 8C as measured by DSC. Self-supporting

films were successfully fabricated by casting the

DMAc solutions of toluidine end-capped hyper-

branched poly(amic acid) and poly(amic acid methyl

ester) precursors onto glass plates upon heating.

Dynamic mechanical analysis (DMA) showed that

the storage modulus of HP17 films by method B

ranged from 3.1 to 4.0 GPa, similar to that of

their linear analogs. A TGA analysis revealed that

the 5% weight loss temperature of the films

approached 500 8C.

3. Couple-monomer methodology

Although the A2 þ B3 approach to hyper-

branched polymers holds some merit over the

conventional AB2 polycondensation approach, such


Scheme 5.


as facile preparation and commercial availability of

monomers, it still exhibits the major problem

of uncontrollable gelation, especially under

conditions of relatively high monomer concentration

and high reaction temperature. To avoid cross-

linking, the reaction must be performed under low

monomer concentration or slow monomer

addition, or the polymerization must be stopped

prior to the critical point of gelation. This strongly

limits the wide application of the A2 þ B3

approach in large-scale manufacture of hyper-

branched polymers. A new strategy with the

advantages of commercial availability of monomers

and lack of incidence of gelation is eagerly

anticipated.

3.1. General description of CMM

Flory’s gelation theory for the ideal polymeriz-

ation of A2 and B3 monomers is based on three

assumptions: (1) equal reactivity of all A or B

groups at any given stage of the reaction; (2) no side

reactions, and the reaction restricted to the conden-

sation of A and B groups; (3) no intramolecular

cyclization and chain termination in the process

[182]. If the first assumption is invalid gelation

should be avoided, leading to soluble hyperbranched

polymers with high molar mass. The new strategy

based on the non-equal reactivity of functional

groups in specific monomer pairs was invented

independently by Yan and Gao [161,162], and DSM

Research [165,166], and further developed and

extended by Gao and Yan. Because the two sorts

of raw monomers would preferentially generate one

type of ABn intermediate in situ in the initial stage

of polymerization, to produce hyperbranched macro-

molecules without gelation, we call the new strategy

for preparation of hyperbranched polymers CMM or

couple-monomer strategy.

Choosing a suitable monomer pair is the most

important step for the molecular design of a

hyperbranched polymer using CMM. The basic

principle of CMM is shown in Fig. 3. In monomer

AA0, if A is identical to A0, and B is equal to B0, CMM

degenerates into the ‘A2 þ B3’ polymerization. It is

anticipated that cross-linking will not occur if an

asymmetric monomer AA0 or B0B2 is used. If A0 has a

higher reactivity than A, CMM affords ‘AA0 þ B3’

polymerization; and if B0 is more active than B, CMM

presents ‘A2 þ B0B2’ and ‘A2 þ CB2’ polymerization

systems. When both A and B groups are different from

A0 and B0 groups, CMM gives an ‘AC þ DB2’

Fig. 3. ‘AA0 þ B0B2’ approach to hyperbranched polymers as a typical example for the basic principle description of CMM.


polymerization. In all of the designed polymerization

systems, AB2 intermediates will be generated in situ,

and further reaction of the AB2 species will result in

hyperbranched macromolecules. For example, if the

reactivity of the B0 group in the B0B2 monomer is

greater than that of the two B groups, AB2

intermediates can be formed in situ during the initial

reaction. Further self-polycondensation of the formed

AB2 species will give rise to hyperbranched polymers

without gelation. This reaction process is shown in

route 1 of Fig. 3. On the other hand, the molecule

containing four B groups should be generated if the

formed AB2 further reacts with a B0B2 molecule due

to the higher reactivity of B0 group. The species B4

can play the role of a core molecule in the preparation

of hyperbranched polymers, and leads to the narrower

molecular weight distribution. Further polymerization

of AB2 and B4 generates a hyperbranched macromol-

ecule with a core (route 2).

The molecular weight and terminal functional

groups of the resulting hyperbranched polymers can

be adjusted by the feed ratio of the two monomers.

Higher molecular weight product can be obtained if

the molar feed ratio of AA0 to B0B2 is adjusted from

1/1 to 2/1. When the feed ratio is lower than 1/1, lower

molecular weight products with B groups can be

fabricated. Products with A groups can be synthesized

when the feed ratio is greater than 2/1. If the feed ratio

is in the range of 1/1 and 2/1, hyperbranched

macromolecules with both A and B functional groups

can be synthesized.

CMM is essentially different from the conventional

method involving polycondensation of AB2 mono-

mers in the presence of multifunctional core moieties

(ABn þ Bm approach). Compared with the

‘ABn þ Bm’ method, CMM exhibits three character-

istics. First, the ABn and Bm compounds are generated

in situ from two or more monomers, which can be

commercially available. Second, no clear borderline

exists between the formation of ABn and its

polymerization. The polymerization reaction gener-

ally occurs as soon as the formation of an ABn

molecule occurs, although the molecule only appears

under special conditions. So, pure ABn or Bm

compounds formed in situ are not separated. Although

the reactivity between A and B0 groups is higher than

between A and B groups, hyperbranched polymers are

prepared in a single step from an A2-type difunctional

monomer and B0B2-type trifunctional monomer.

Finally, CMM can be used to design and develop

novel hyperbranched polymers with new architectures

and structures. Through the new strategy, series of

hyperbranched polymers with alternating different

units, for example ab0 and ab units, can be easily

fabricated. On the contrary, it is very difficult to

acquire hyperbranched polymers with the same

structure through the conventional ‘AB2 þ Bm’

approach or polycondensation of AB2 monomers.

3.2. ‘A2 þ BB 02’ approach to hyperbranched poly

(sulfone amine)s and poly(ester amine)s

The polymerization of an A2 type of difunctional

monomer and BB02 type of trifunctional monomer to

synthesize hyperbranched polymers is termed the

‘A2 þ BB02’ approach [161,162,183]. The BB0

2 mono-

mer contains one B functional group and two B0

functional groups. Both the B and B0 groups can react

with the A group, but the reactivities of B and B0

groups are different from each other. The difference in

reactivities may be attributed to the differences in the

chemical environment or chemical structures of the

two functional groups. If the reaction between B and

A is much faster than that between B0 and A, an Aa-

bB02 intermediate will be predominantly formed at the

initial stage of the polymerization. This intermediate

can be regarded as a new kind of AB02 monomer.

Subsequently, a core molecules with four B0 groups

will be formed, with further reaction leading to

hyperbranched macromolecules. Through this

approach, a series of hyperbranched poly(sulfone-

amine)s and poly(ester amine)s were successfully

prepared without any catalysts. Scheme 6 shows the

reaction mechanism and the selected monomers.

In the ‘A2 þ BB02’ approach, vinyl group is the A

group, and the active hydrogen of the secondary

amino group and the hydrogen of the primary amino

group are the B and B0 functions, respectively.

Because of the influence of the electron-donating

group attached to the secondary-amino group, B is

more active than B0 in the nucleophilic addition,

which has been demonstrated by monitoring the

reaction process with in situ Fourier transform

infrared (FTIR) spectroscopy.

Polymerizations of 44 (divinyl sulfone) and 51 [1-

(2-aminoethyl)piperazine] were carried out in either


water or organic solvents such as chloroform and

DMF under mild temperature (20–60 8C) [161].

When the feed ratio of 44 to 51 was 1/1, no gelation

was observed for a total monomer concentration

below 7.0 mol/l, and in situ FTIR measurements

showed that the reaction was completed after

approximately 5 h. A higher concentration results in

extremely fast reaction times, and a very high local

temperature, resulting in loss of control of the

polymerization. Solid state product rapidly appeared.

The solids were generally soluble in aqueous HCl

solution, although sometimes they were found to be

gel particles, insoluble in any solvents tested. When

the feed ratio of 44 to 51 was set at 3/2, gelation was

not found when the reaction mixture was kept in

solution. The resulting hyperbranched poly(sulfone-

amine)s contain large amounts of amino and vinyl

groups (Scheme 7), which further reacted and finally

led to cross-linking after the solvent was removed

from the system. If the terminal amino groups were

protected with hydrochloride acid or the vinyl groups

were end-capped with added amines in the solution,

no gelation was observed even though the product was

separated from the solution. The resultant solution,

including the hyperbranched polymers, can be

preserved for a long time (at least one year), and

used as material for other functional macromolecular

building blocks.

Hyperbranched poly(sulfone amine)s were also

successfully prepared from 44 and 52. Monomer 53

(N-ethylethylenediamine) and 44 reacted in either

water or organic solvents such as chloroform, DMAc,

DMF, and NMP to yield hyperbranched polymers

[183–185]. Similar to the reaction between 44 and 51,

no gelation was observed when the feed ratio of 44 to

53 was 1/1. The resulting hyperbranched polyamines

were characterized with 1H NMR and FTIR. Amino

groups were clearly detected, while no signals of the

carbon–carbon double bonds could be measured,

which suggested that the vinyl groups had completely

reacted with the amino groups, so that the resulting

polymers had terminal amino groups.

For reaction with a 3/2 feed ratio, the polymerization

medium dramatically influenced the results. If the

reaction was performed in organic solvents, no gelation

occurred, even after 30 days. The hydrochloride of

Scheme 6.


the product was highly soluble in water, and the sample

end-capped with benzoyl chloride was soluble in

organic solvents such as chloroform, DMF and NMP.

If water was used as the reaction medium, the reaction

solution turned into a turbid heterogeneous mixture at

around 15–20 min, and cross-linking was observed at

12–15 h. The turbid mixture turned transparent in the

aqueous HCl, indicating that no networks formed in the

initial stage. This phenomenon, termed ‘pseudo-

gelation’, may be caused by the interactions between

water and the oligomers formed from 44 and 53.

The reaction between 44 and 54 (N-methyl-1,3-

propanediamine) is very similar to that between 44

and 53 [186]. No cross-linking was found in organic

solvent for monomer feed ratios of 1/1 or 3/2.

The ‘pseudo-gelation’ phenomenon appeared at

12–18 min, for polymerizations carried out in water,

and gelation occurred at 15–20 h for a reaction with a

feed ratio of 3/2.

For the reaction systems described above

(44 þ 51, 44 þ 53, and 44 þ 54), product can be

obtained by two means: (1) pouring the reaction

solution into the mixture of concentrated aqueous HCl

and a precipitation agent such as acetone, methanol or

ethyl ether to obtain protonated hyperbranched

polycations; and (2) pouring the reaction solution

into ethyl ether and drying the precipitate under

vacuum at room temperature to afford hyperbranched

polymers with copious active amino groups. SEC

measurements with water as the solvent and PEO as

standards showed that the resulting hyperbranched

poly(sulfone amine)s had moderate apparent Mns

Scheme 7.


(20,000–40,000) and very narrow PDIs (1.2–2.5),

which was in agreement with the in situ formation of

the core molecules in the reaction system. A peak in

the mass spectrum of the sample taken from the

reaction system at initial reaction moment corre-

sponded to the core molecules.

The dendritic units (D), linear units (L), and

terminal units (T) of the hyperbranched poly(sulfone

amine)s in a 1/1 feed ratio are the tertiary

amino, secondary amino and primary amino groups,

respectively (Scheme 7). The terminal units of the

polymers in a 3/2 feed ratio contain primary amino

and vinyl groups. The DBs of the resulting hyper-

branched polymers can be determined from the

corresponding 1H NMR spectrum. Theoretically, a

hyperbranched polymer prepared by polycondensa-

tion of an AB2 monomer has a maximum DB of 0.5 if

the reactivity of the two B groups is the same [127,

187,188]. Because of the higher reactivity of the

secondary amino group over the primary amino

Scheme 8.


group, the DB of the prepared hyperbranched

poly(sulfone amine)s ranged from 0.51 to 0.75. The

DB of the product generated from a 3/2 feed ratio is

higher than that with 1/1 feed ratio. By comparison,

the DBs of the hyperbranched polyamidoamines made

from AB2 monomers containing vinyl and primary

amino groups are also much higher than 0.5 [96,97].

The commercially available cross-linking agent,

ethylene diacrylate (monomer 45), can be used as a

raw material to synthesize water-soluble hyper-

branched poly(ester amine)s via a Michael addition

(Scheme 8) [189]. In situ FTIR measurements showed

that the secondary amino groups disappeared at

approximately 3 h, and that the reaction was com-

pleted after 72 h in a dilute solution. In the mass

spectrum of the reaction mixture taken from the

polymerization system of 45 and 51 at 3 h, the AB02

intermediate ðm ¼ 299:4Þ and its dimer (598.7) and

trimer (898.1) can be found as peaks at m=z ¼ 300:4;

599.8 and 899.2, respectively. Propagation occurred

as soon as the formation of AB02 occurred although the

reactivity between A and B0 is not as high as that

between A and B, so it was hard to separate the pure

AB02 species from the reaction mixture.

The initial molar ratio of 45 to 51, 52, 53 or 54 was

set at 1/1 and 3/2. Relatively high molecular weight

products were prepared in organic solvents. Chloro-

form was a good solvent for the reaction in which

the highest molecular weight poly(ester amine) was

obtained. When the monomers were added to water

for the reaction, a heterogeneous mixture appeared at

first due to the poor solubility of 45 in water. After

several minutes a homogeneous solution appeared.

This phenomenon indicates that the Michael addition

of amino groups to vinyl groups can occur smoothly in

water, resulting in oligomers soluble in water.

However, hyperbranched poly(ester amine)s with

high molar masses were not obtained in water,

attributed to degradation of the ester bonds.

Reaction conditions such as temperature and

monomer concentration have a strong effect on the

Michael addition polymerization. No gelation

occurred for polymerization with a 1/1 feed ratio.

When the feed ratio was increased to 3/2, cross-

linking was not yet observed in a dilute solution at low

temperature. When the reaction temperature was

lower than 40 8C, gelation was not observed after 30

days. At higher temperatures, networks formed

depending on the monomer concentration: if the

feed volume ratio of the two monomers to solvent was

greater than 2/1, gelation occurred quickly; while gel

did not appeared if the volume ratio was lower than

1/2. HCl usually helps the solubilization and protec-

tion of amine-containing compounds, and soluble and

stable hyperbranched poly(ester amine)s with term-

inal amino and vinyl groups can be obtained by

precipitating the reaction mixture with acetone and

aqueous HCl.

The Mws for hyperbranched poly(ester amine)s

measured by SEC with water as the eluent and PEO as

standards ranged from 15,000 to 25,000. Again, their

molecular weight distributions were very narrow

(1.28–1.40). The DBs of the polymers were also

higher than 0.5, approaching 0.58–0.75.

If monomers 47, 48 or 49, instead of 45, are

adopted to react with 51, 52, 53, or 54, hyperbranched

poly(ester amine)s containing ethylene oxide units in

their frameworks can be produced according to the

same reaction conditions and procedure as

the preparation of HP20, HP21, HP22 and HP23.

The number average degree of polymerization (DPn)

and the molecular weight of the resulting product

depend on monomer purity.

All of the hyperbranched poly(sulfone amine)s and

poly(ester amine)s mentioned above are highly

soluble in water and certain organic solvents such as

chloroform, DMF, DMAc, NMP, DMSO, and are

poorly soluble in THF.

The steric and electron-accepting effects of the

adjacent groups influence the reactivity of the vinyl

groups. For example, only oligomers were obtained

through the use of monomer 46, instead of 45,

reaction with the BB02 monomers. Monomer 50 (1,4-

divinylbenzene) is also often used as a cross-linking

agent. Using lithium amide catalyzed anionic poly-

addition of 50 to the compounds with two secondary

amino groups, Tsuruta and coworkers [190,191]

prepared linear polyamines with Mns of 1000–5000.

Monomer 50 cannot react with amino groups without

a catalyst. In the presence of a strong base such as

lithium alkylamide, only branched products with Mns

below 8000 were obtained in our laboratory.

In summary, the control of the structures and units

with suitable monomers, the simplicity of polymeriz-

ation process, and the efficiency in avoiding gelation

would make the ‘A2 þ BB02’ approach, and the new


hyperbranched polycations with many terminal amino

groups prepared via this method, very attractive in the

large-scale manufacture and application of polymeric

materials.

3.3. ‘A2 þ CBn’ approach to hyperbranched

poly(urea urethane)s

Linear polyurethanes and polyureas are now

widely used in rubber, plastics, fiber, and coatings.

It is well known that polyurethanes or polyureas can

be prepared by polycondensation of diisocyanates

with dihydroxyl compounds or diamines. Because of

the high reactivity of isocyanato groups (–NyCyO)

against the nucleophile, it is hard to obtain an AB2

monomer with an isocyanato group. Therefore,

hyperbranched polyurethanes or polyureas cannot be

directly synthesized from AB2 monomers. Generally,

an AB2 monomer containing a functional group such

as a carbonyl azide that can be transferred in situ into

the isocyanato group is synthesized in advance, and

then polymerization of the formed monomers leads to

hyperbranched polyurethanes or polyureas [88–91].

However, it is very difficult to apply the prepared

hyperbranched polyurethanes or polyureas owing to

the complexity of the synthesis and the purification

procedures.

Through the ‘A2 þ CBn’ approach, hyper-

branched poly(urea urethane)s can be easily

prepared by direct polymerization of commercially

available diisocyanates and multi-hydroxyl amines

(Scheme 9). A2 monomers containing two isocya-

nato groups are industrial chemicals that have been

widely used in the manufacture of linear poly-

urethanes and polyureas. A CBn monomer has one

amino group and n hydroxyl groups. The fast

reaction between the A group and the C group in

CBn affords ABn and Bn–Bn intermediates at mild

temperature. Further reactions between isocyanato

and hydroxyl groups at higher temperature give rise

to hyperbranched polymers with alternating ureido

and urethano units [192–194].

This reaction process has been monitored with in

situ FTIR spectroscopy. The reaction between mono-

mer 57 and 62 was selected as a typical example. It

was found that the carbonyl groups (CvO) of the

ureido units (–HNCONH–) first rapidly appeared as a

peak at 1632 cm21, with a significant decrease in the

absorption band of the isocyanato group at

2261.6 cm21 during the initial minute. The peak at

1632 cm21 then stayed constant, and the carbonyl

groups of the urethano units (–HNCOO–) appeared

as a new peak at 1705 cm21, and gradually increased

with decrease of the absorption peak of the isocyanato

groups. After approximately 200 h, the absorption

band of the isocyanato groups disappeared from the

spectrum, the hydroxyl group absorption still clearly

observed. This data shows that the one isocyanato

group of 57 quickly reacted with the amino group of

62, resulting in the formation of intermediate 67. Then

self-condensation of intermediate 67 along with other

formed species generated the hyperbranched macro-

molecules HP24 with ureido and urethano units

(Scheme 10). Similar results were obtained for other

reaction systems of ‘A2 þ CBn’.

The peaks of the ABn and Bn–Bn species formed

during the initial reaction period were also detected

with mass spectroscopy. For example, the molecular

ion peaks 67 ðm ¼ 327:4Þ and 72 ðm ¼ 432:6Þ were

found as two peaks at m=z ¼ 328:3 and 433.4,

respectively. Their corresponding m þ Naþ ion

peaks were also observed at m=z ¼ 350:3 and 455.4,

respectively. The mass spectrum measurements for

Scheme 9.


other reaction systems indicated that the ABn and Bn–

Bn intermediates did form in the initial stage.

Reaction conditions such as temperature, concen-

tration, and monomer feed ratio strongly influenced

the reaction. The temperature during the initial several

hours should be kept below 25 8C, otherwise,

insoluble product was generated. Gelation was barely

observed for the polymerization in a feed ratio of 1/1

(A2/CBn) at given conditions. For the reaction with a

3/2 feed ratio (A2/CBn), cross-linking mainly

Scheme 10.


depended on the temperature and concentration.

Gelation occurred within several minutes in the

conditions of high concentration (1.0 mol/l) and

high temperature (60–80 8C), whereas at low con-

centration (0.15 mol/l) and low temperature (20 8C)

gelation was not observed. SEC with 0.05 M LiCl in

DMAc eluent at 70 8C showed that the resulting

hyperbranched poly(urea urethane)s had a moderate

Mws ranged from 18,000 to 130,000, and relatively

narrow PDIs with typical values of 1.7–3.5.

The DBs of the prepared hyperbranched polymers

were determined with 13C NMR spectroscopy. For the

polymers made from A2 and CB2, there are two

hydroxyl groups in the terminal units, one hydroxyl

group in the linear units, and no hydroxyl group in the

dendritic units. Scheme 11 shows the three repeating

units of the polymer derived from the reaction

between A2 and 64. The terminal ((C H2OH)2) and

linear (C H2OH) units can be assigned independently

in the 13C NMR spectrum, so the DB can be calculated

with Eq. (1)

DB ¼ ðD þ TÞ=ðD þ T þ LÞ

¼ ðT 2 1 þ TÞ=ðT 2 1 þ T þ LÞ

< 2T=ð2T þ LÞ ¼ 1=ð1 þ L=2TÞ ð1Þ

DBs calculated from Eq. (1) ranged from 0.42

to 0.56.

Scheme 12 shows the structure of the hyper-

branched polymers made from A2 and CB3 (65). It

was found that there are two sorts of branched units

(Scheme 13), so the DBs were much higher than 0.5,

approaching 0.7–0.74.

Although the reactivity of the primary hydroxyl

group is greater than that of the secondary hydroxyl

group, the poly(urea urethane)s made from A2 and

CB5 (66) are also highly branched (Scheme 14). In

their corresponding DEPT-135 13C NMR spectra,

the ratio of the residual primary hydroxyl group

(CH2OH) in the resulting polymer to the primary

hydroxyl group (CH2O–) is higher than 50%. There-

fore, it can be deduced that the secondary hydroxyl

groups of 66 also reacted with isocyanato groups, and

highly branched polymers containing a high density

of hydroxyl groups were formed. Tgs of the obtained

hyperbranched poly(urea urethane)s measured by

DSC were 25–50 8C. The hyperbranched poly(urea

urethane)s are soluble in polar organic solvents, such

as DMF, DMAc, DMSO and NMP.

3.4. ‘AB þ CDn/Cn’ approach to hyperbranched

poly(amine ester)s and poly(amide amine)s

3.4.1. ‘AB þ CDn approach’ to hyperbranched

poly(amine ester)s

The monomer AB contains one A and one B

functional group, which cannot react with each other.

Monomer CDn has one C and n D functional groups,

and C cannot react with D. The reaction between B

and C is more easily conducted than that between

A and D. At mild temperatures, the B group reacts

with the C group to form an ADn intermediate.

Hyperbranched macromolecules can be produced by

self-condensation of ADn under stronger conditions

(Scheme 15). If the methyloxy carbonyl (CH3OCyO),

the acrylate group (CH2yCHCO), the secondary

amino group (HN–), or the hydroxyl (–OH) moiety

are selected as A, B, C and D groups, respectively,

water-soluble hyperbranched polyesters with

tertiary amino units in their backbones can be

prepared [195,196].

Some side reactions may occur between AB and

CDn reactions during the initial stage. For example, at

least three intermediates 78, 79 and 80 may be

generated in the reactions of 77 and 62 as shown in

Scheme 16. The reactions between A and C or D can

be suppressed by using methanol as solvent, since

methanol would be generated accompanying with

Scheme 11.


formation of 79 or 80. Measurements of in situ 1H

NMR with diethylamine and 1,4-butanediol as model

compounds confirmed that the reaction between the

methyloxy carbonyl and the amino or hydroxyl group

was negligible under mild conditions.

The reaction temperature during the initial stage is

very important in the preparation of a high molecular

weight product. In the mass spectrum of the sample

taken from the reaction system at room temperature,

the molecular ion peak of 78 ðm ¼ 191:2Þ appeared at

m=z ¼ 192:3; and the peak of 78 coupled with a Naþ

appeared at m=z ¼ 214:2: The molecular ion peaks of

the dimer (M2Hþ), trimer ((M3Hþ), and tetramer

(M4Hþ) of 78 were found at m=z ¼ 351:5; 510:5; and

691.7, respectively. No peaks attributed to 79 and 80

were detected. As a comparison, the peaks of 79 and

Scheme 12.


80 did appear in the mass spectrum on increase of the

reaction temperature to 60 8C during the initial stage.

The existence of 79 and 80 may lead to cross-linking

in the next reaction stages, so it is better to keep the

temperature in the initial period below 40 8C for the

polymerization of AB and CDn monomers.

To improve the conversion ratio of 62 or 77 and

shorten the reaction time of the initial stage, the feed

ratio of AB to CDn is a little higher than 1/1 (typically

1.05–1.1/1). The residual 77 was removed from the

reaction system by reduce-pressure distillation on a

revolving-distillation apparatus. After the residual

MA and the solvent (methanol) were removed, an

amount of catalyst (0.5 g per mole of CDn) was added

to the reaction system. Under vigorous revolving and

vacuum distillation, the mixture was kept at 60 8C for

1 h, 100 8C for 2 h, 120 8C for 2 h, and 135–150 8C

for 2 h. After reprecipitation of the raw product from

DMSO into acetone, hyperbranched poly(amine ester)

with a yield of 75–80% was obtained.

Compared with zinc acetate anhydrous [Zn(CH3-

CO2)2], tetrabutyl titanate [Ti(C4H9O)4] exhibited

higher catalytic efficiency for the polymerization. For

the same amount of catalyst, the molecular weight of

the product catalyzed with Ti(C4H9O)4 was higher

than that catalyzed with Zn(CH3CO2)2. Nevertheless,

insoluble product was formed if the amount of

Ti(C4H9O)4 was too high (.2 g per mole of CDn).

The structures of the hyperbranched poly(amine

ester)s made from 77 and 62 or 66 are shown in

Schemes 17 and 18, respectively. Depending on the

reaction temperature and the catalyst, Mn of HP29

ranged from 10,000 to 260,000, and that of HP30

ranged from 38,000 to 66,000, with a narrow

molecular weight distribution. The molecular weight

of HP29 was generally greater than that of HP30

under the same reaction conditions. Inter- or intra-

molecular cyclization might have caused the lower

DPn of HP30 because of the high density of hydroxyl

groups in its repeating unit.

The terminal and linear units of HP29 can be

independently detected in a quantitative 13C NMR

spectrum. The DB of HP29 calculated with Eq. (1)

was slightly higher than 0.5 (0.52–0.56). Character-

ization by a quantitative 13C NMR spectrum showed

that HP30 was also a highly branched polymer,

although its DB cannot be accurately calculated due to

its complex structure.

There is one ester bond and one tertiary amino group

in each repeating unit of HP29 or HP30. Such a

structure is very attractive in the field of drug-delivery.

The hyperbranched polymers are degradable in water

because of their ester bonds. Owing to the introduction

of amino groups, the resulting polymers are easily

soluble in water. Furthermore, the acid groups formed

in the hydrolysis neutralize the amino groups. So, the

pH of the aqueous system of HP29 or HP30 can be self-

adjusted to about 7, which is an important parameter

for a good drug-delivery material [197].

TGA measurements showed that the 5% weight-

loss temperature for HP29 and HP30 is above 200 8C,

and the 10% weight-loss temperature is above 250 8C.

In the DSC curves, Tgs of about 10–20 8C were found

for HP29 and HP30, but the transition was not as

strong as that of general linear polyesters.

A methoxycarbonyl-terminated hyperbranched

polymers could be synthesized by the reaction of

methyl acrylate (77) with a compound containing a

hydroxyl and one primary amino or two secondary

amino groups (Scheme 19). The feed ratio and the

catalyst have a dramatic influence on the polymeriz-

ation. Gelation occurred for a ratio of 77 to

ethanolamine (82) lower than 2.1/1. Cross-linking

was not observed for a ratio higher than 2.3/1. In the

presence of Ti(C4H9O)4, the polymerization occurred

faster, and a higher molecular weight product was

approached under the same conditions. SEC measure-

ments with polystyrene as standards showed that

the methoxycarbonyl-terminated hyperbranched

poly(amine ester)s had apparent Mns of 35,000–

70,000. The onset decomposition temperature ðTdÞ of

HP31 was 275–290 8C.

Scheme 13.


3.4.2. ‘AB þ Cn’ approach to hyperbranched

poly(amide amine)s

Polyamines (Cn monomers) react with the

aforementioned AB monomer to yield aliphatic

hyperbranched poly(amide amine)s (Scheme 20).

The ACn or ACn21 intermediate should be formed

in situ at room temperature for a feed ratio of AB to Cn

of 1/1. Hyperbranched polyamines could then be

Scheme 14.


prepared by self-condensation of the intermediates at

higher temperatures and in vacuum. Interestingly, the

feed ratio of AB to Cn can be adjusted over a relatively

wide range from 1/1 to n=1; resulting in hyper-

branched polymers with various terminal groups. Due

to their different functional groups, the hyperbranched

polymers exhibit different properties. Therefore, the

structure and property of the hyperbranched polymers

can be controlled through the feed ratio of AB to Cn

[198,199].

The reaction conditions between AB and Cn are

very similar to those between AB and CDn. Methyl

acrylate (77) was added dropwise to the amine/metha-

nol solution. The reaction mixture was kept at room

temperature for 24–48 h, and then the solvent was

removed from the reaction system under reduced

pressure at 60 8C on a rotary evaporator. Under

vigorous revolving and vacuum distillation, the

mixture was kept at 60 8C for 1 h, 100 8C for 2 h,

120 8C for 2–4 h, and finally 135–150 8C for 2–4 h.

Pale yellow viscous solid hyperbranched polymers

were produced. Since no extra reagents such

as catalyst and condensation agent were added to

the reaction mixture, it was not necessary to separate

the raw product by reprecipitation, so the yield was

very high (.95%).

The Michael addition of 84 to 77 affords 91.

Intermediate 91 can be regarded as an asymmetrical

AC2 monomer that can further self-condense to give

rise to hyperbranched polymer HP32 (Scheme 21).

There are two kinds of linear repeating units in HP32.

The reaction between 77 and 85 would result

in a symmetrical AC2 intermediate (92) and an

asymmetrical AC3 species so the hyperbranched

polymer HP33 contains the hybrid structures of 92

and 93 (Scheme 22). The reaction of monomer 86, 87

or 88 with 77 yields more ACn or ACn21 species.

Thus, the corresponding hyperbranched polymers

have a more complex structure, and more types of

repeating units can be found. Both 89 and 90 have

three primary amino groups. Three asymmetrical AC3

intermediates (94, 95, 96) occurred when 89 was

employed to react with 77 (Scheme 23), and then

hyperbranched polymers with hybrid structures were

generated. Because of the symmetrical structure of 90,

only one AC3 species (97) was formed. The resulting

hyperbranched polymers HP34 have amido and

tertiary amino units in their backbones and many

primary amino groups in their terminal chains

(Scheme 24).

Variation of the AB to Cn feed ratio results in a

change in the structure and properties of the products.

For example, the solubility of the hyperbranched

polymer made from 77 and 85 decreases with an

increase in the feed ratio of 77 to 85.

All of the hyperbranched poly(amide amine)s

with a feed ratio of 1/1 described above are highly

soluble in water and polar solvents such as DMF,

DMAc, DMSO and NMP. The water-soluble

cationic hyperbranched polyelectrolytes may be

useful in the pigments, coatings, and gene delivery

or transport fields.

3.5. ‘Ap þ CB2/Bn’ approach to hyperbranched

poly(ester amide)s and polyesters

3.5.1. ‘Ap þ CB2’ approach to hyperbranched

poly(ester amide)s

DSM research first reported the ‘Ap þ CB2’

approach [165,166]. In their presentation, Ap and

Scheme 15.

Scheme 16.


CB2 were denoted as Aa and bB2, respectively [166].

They used 1,2-cyclohexane dicarboxylic anhydride as

the Aa monomer, and di-2-propanolamine as the bB2

source. Recently, Gao and Yan [200,201] developed

the ‘Ap þ CB2’ approach, using dicarboxylic anhy-

dride compounds as Ap. An Ap monomer contains two

latent functional groups; one A group will be formed

after the reaction of Ap with the CB2 group, giving rise

to an AB2 intermediate. Self-polycondensation of the

intermediate results in the hyperbranched macromol-

ecule (Scheme 25).

The reaction between 98 and 63 has been investi-

gated using electrospray ionization (ESI) and matrix-

assisted laser desorption ionization/time-of-flight

(MALDI-TOF) mass spectrometry, and size exclusion

chromatography (SEC) in combination with on-line

differential viscosimetry detection (SEC-DV) [166,

202,203]. The exothermal reaction of 98 and 63 nor-

mally leads to a species (102) having one carboxylic

acid group and two (2-hydroxypropyl)amide groups.

Ester bonds were formed through an intermediate

oxazolinium-carboxylate ion pair, and hyperbranched

macromolecules were generated under reduced press-

ure (5 mbar) at around 180 8C, without a catalyst

(Scheme 26).

The hyperbranched poly(ester amide) HP35 was

then modified in situ with 1-dodecanoic acid to obtain

hyperbranched resins with terminal long aliphatic

chains. Other hyperbranched poly(ester amide)s series

can be prepared by direct polymerization of 99, 100,

or 101 with 62 or 63 with similar reaction routes and

conditions. The Mns of the hyperbranched poly(ester

amide)s detected with SEC-DV by using polystyrene

as standards and dichloromethane as solvent and

eluent were very low (680–6000) [166,202,203].

3.5.2. ‘Ap þ Bn’ approach to hyperbranched

polyesters

Polyhydric alcohols (Bn) can directly polymerize

with the aforementioned dicarboxylic anhydrides,

Scheme 17.


forming hyperbranched polyesters (Scheme 27). The

reaction between 99 and 104 had been investigated by

Kienle et al. as early as 1929 [35]. However, only low-

molecular-weight product or insoluble materials were

obtained at that time. To obtain soluble high-

molecular-weight hyperbranched polymers, it was

necessary to re-investigate the reactions between

dicarboxylic anhydrides and polyhydric alcohols.

Because each hydroxyl group of Bn has almost the

same reactivity, gelation easily occurred in

the reaction. It is crucial to remove water from the

reaction system during the initial stage to avoid

network formation. The existence of water in the

monomers or solvents leads to the ring opening of

the anhydrides, giving difunctional A2 molecules and

leading to insoluble product within several hours.

Two routes were employed in the polymerization.

Scheme 28 describes a typical example. Route A

represents direct polymerization of the in situ

formed AB2 intermediate possessing a carboxylic

Scheme 18.


acid group and two hydroxyl groups (107). In route

B, the AB2 species was modified with methanol in

advance to afford the new monomer 108, and

then hyperbranched polyesters were prepared by

polymerization of the modified AB2. Only moderate

molecular weight product was obtained

(Mn ¼ 5000–20,000) via route A, even through

the reaction was performed under reduced pressure

at 140–150 8C for 10–20 h. The color of the raw

product was very deep, indicating that carbonization

Scheme 20.

Scheme 19.


Scheme 21.

Scheme 22.


Scheme 24.

Scheme 23.


or oxidization occurred in part of the polymers. As a

comparison, the products made through route B had

a high Mns (30,000–120,000) and an almost white

color [200,201].

The hyperbranched polyesters made from 103 and

polyhydric alcohols have carbon–carbon double

bonds in every repeating unit, so the cross-linked

membrane can be prepared by UV light irradiation.

The polymerization of 106 with anhydrides is

relatively difficult because of its poor solubility in

organic solvents; only low molecular weight product

was acquired.Scheme 25.

Scheme 26.


3.6. ‘AAp/Ap2 þ B2’ approach to hyperbranched

polyesters

TheAApmonomercontainsoneAandoneApgroup,

and Ap2 contains two Apgroups. As claimed above, one

Ap is a latent A2. In the ‘AAp þ B2’ approach, the

reaction between Ap and B groups generates an A2B

intermediate which can be self-polycondensed to attain

hyperbranched polymer [204,205]. Scheme 29 shows

the reported AAp and B2 monomers. Benzene-1,2,4-

tricarboxylic acid-1,2-anhydride (109) has a carboxylicScheme 27.

Scheme 28.


acid group (A) and an anhydride group (Ap). Because of

the much higher reactivity of anhydride group over the

carboxylic acid group in the condensation, a species

with two carboxylic acid groups and one

hydroxyl group can be presented. Then hyperbranched

polyesters can be prepared smoothly according to the

conventional polymerization conditions and process.

Similar to thereactionofAApandB2, the reactionofone

of the Ap of Ap2 with one of the B groups in B2

affords the species AApB containing a carboxylic acid

group, one anhydride group and one hydroxyl group.

Self-condensation of two AApB gives the A3B

species. Hyperbranched macromolecules can also be

prepared by further polycondensation of the A3B

molecules. The Ap2 monomers used are also given

in Scheme 29.

A typical example for the ‘AAp þ B2’ approach

is described in Scheme 30. The first step was

conducted at room temperature in chloroform. Two

intermediates (115 and 116) were formed. Hyper-

branched polymers were prepared through two

routes. In route A, direct polymerization of the

species 115 and 116 led to the carboxylic acid-

terminated hyperbranched polyester HP37. Polymer

HP37 contains two types of linear units (L1 and L2)

and two types of terminal units (T1 and T2). In

route B, A2B intermediates 115 and 116 reacted

with methanol, generating species 117 and 118,

respectively. Further polycondensation of 117 and

118 gave rise to ester-terminated hyperbranched

macromolecules HP38. Again, the products syn-

thesized using route B exhibited a higher molecular

weight than those synthesized using route A. The

former products have Mns of 20,000–120,000, while

the latter products have Mns of 3000–15,000. The

hyperbranched polyesters HP37 and HP38 were

further end-capped with 1-butanol, resulting in

HP39. It is well known that n-butyl phthalate is a

good plasticizer for polyvinyl chloride (PVC).

However, the low molar mass n-butyl phthalate

often releases from the PVC, which strongly

influences the quality of the plasticized product.

HP39 has a similar structure of n-butyl phthalate

and a much higher molecular weight. Furthermore,

the melting viscosity of hyperbranched polymers is

very low. It is expected that in the future HP39 will

become a better plasticizer for PVC or other

commercial plastics.

The reaction conditions and processes for the

reaction between dianhydrides and dihydroxy alco-

hols are the same as those employed in the reaction of

AAp and B2. Two routes were applied to prepare

hyperbranched polyesters (Scheme 31). Route B was

more efficient than route A for preparing higher

Scheme 29.


molecular weight hyperbranched products. Through

route B, hyperbranched polyesters with Mns ranging

from 15,000 to 100,000 can easily be synthesized,

according to the feed ratios. On the contrary, only

relatively lower molecular weight products (3000–

12,000) were made from route A. On the other hand,

almost linear oligomers appeared during the begin-

ning reaction period owing to the higher reactivity of

anhydride groups over carboxylic acid groups. Then

branched molecules were formed because the content

of carboxylic acid group is very high. However, the

DBs of the obtained products were lower than those

made from route B.

If one hydroxyl group of B2 is replaced by a

secondary amino group, water-soluble hyper-

branched poly(ester amide)s can be prepared

(Scheme 32) [206,207]. Direct polymerization of

benzene-1,2,4-tricarboxylic acid-1,2-anhydride (109)

with N-(2-hydroxyethyl)piperazine (127) failed to

produce macromolecular products although the

reaction occurred at a high temperature (160 8C) in

the presence of catalyst. When 127 was added to a

solution of 109 in DMSO, a precipitate was rapidly

observed, caused by the interaction between acid

and amino groups. To dissociate the aggregation

species, an organic base such as triethylamine was

Scheme 30.


introduced to the reaction system. However, a

powdery precipitate appeared again during polym-

erization after heating under reduced pressure.

Therefore, the carboxylic acid was modified with

methanol to obtain the intermediate 130 or 131.

Under mild conditions and in the presence of

catalyst such as phosphoric acid and tetrabutyl

titanate (Ti(C4H9O)4), hyperbranched polymers

were prepared, with moderate Mn (25,000–50,000)

and narrow PDI (1.4–2.5). Although the acid groups

were end-capped with methyloxy moieties, the

prepared hyperbranched poly(ester amide)s were

highly soluble in water because of their tertiary

amino and amido units.

Scheme 31.


3.7. ‘A2 þ B2 þ BB 02’ approach to highly branched

copolymers

CMM can be extended to prepare highly branched

copolymers with different DBs by copolymerization

of suitable difunctional monomers with the monomer

pairs described above. The DBs and some thermal and

mechanical properties can be controlled by the feed

ratio of the monomers. Here, we selected the

‘A2 þ B2 þ BB02’ approach as an example to recount

how to control the architecture and properties of the

resulting polymers in copolymerization [163,189,

208–210].

In the ‘A2 þ B2 þ BB02’ approach, the A2 and BB0

2

monomers are the same as those of ‘A2 þ BB02’

approach, and B2 is the molecule with two secondary

amino groups. During polymerization, the rapid

reaction between the A and B groups results in the

formation of an AB02-type intermediate. The linear

units formed from the reaction of A and B2 also are

embedded in the AB02 species, which indicated that the

segment between two branching points and the

number of linear units can be adjusted by the feed

ratio of B2 to BB02. On the other hand, the B0

4 species

will also be generated. Highly branched copolymers

with various linear units will be obtained from the

further self-condensation of the intermediates

(Scheme 33).

The feed ratio of A2 to the total B2 and BB02 was set

as 1/1, and the ratio of B2 to BB02 ðnÞ was varied. For

the reaction of 44 with B2 and BB02, the reaction

conditions such as temperature, time, concentration

and solvent influence on the polymerization [163]. A

homogeneous solution was observed throughout

Scheme 32.


the reactions carried out in strong polar organic

solvents such as DMF, DMAc, DMSO and NMP.

Nevertheless, a precipitate was found for B2 to BB02

ratios greater than 3/1 if water or chloroform was

utilized as the solvent. The phenomenon was

attributed to the crystallization of the formed

macromolecules rather than the appearance of a gel.

In fact, the precipitate was soluble in polar solvents

such as DMF and DMSO, and the hydrochloride of the

polymers was highly soluble in water. No gelation

was observed even through at a very high concen-

tration of the total monomers (1 g per 1 ml of solvent)

and at a high temperature (80 8C). The incidence of

cross-linking can be easily avoided under general

reaction conditions.

The polymerization procedure was investigated

with in situ FTIR spectroscopy. The reaction between

secondary amino groups and vinyl ones was surpris-

ingly fast, and completed within 1 min. The whole

polymerization only took 6–10 h even at room

temperature in a diluted solution. So highly branched

macromolecules can be approached within several

hours. The propagation of the molecules during the

initial short period can be detected clearly from

the corresponding mass spectrum. The dominant

reactions were well in agreement with the prediction.

Scheme 34 displays the dominant reaction pathways

at initial stage for the polymerization of 44 with 51

and 132 in a 1/1 ratio.

The structures of the highly branched copoly(sul-

fone amine)s made from A2, B2 and BB02 monomers

are shown in Schemes 35 and 36. Every polymer

contains two sorts of linear units (L1 and L2), one sort

of dendritic unit and one sort of terminal unit. The DB

can be calculated by Eq. (2)

DB ¼ ðD þ TÞ=ðD þ T þ L1 þ L2Þ ð2Þ

For a copolymer made from A2, B2 and BB02, D,

T and L2 depend on the reaction between A and B0.

Therefore, DB can be controlled through the value

of L1. When L1 is zero (no B2 monomer is added),

DB is that for a polymer made from A2 and BB02.

When L1 becomes a large value (large feed ratio of

B2 to BB02), DB approaches zero. Thus, DB of the

copolymer can be adjusted at least from 0.5 to 0 by

the feed ratio of B2 to BB02. On the other hand, each

repeating unit has a sulfone bond resulting from A2

monomer. So the total units are equal to the number

of sulfone units (S), and DB can be obtained by the

following equation:

DB ¼ ðD þ TÞ=S < 2T=S ð3Þ

The dendritic units (D) and terminal units (T) are

tertiary amino formed from the reaction between A

and B and primary amino groups. The methylene

attached to primary amino groups (CH2NH2) and the

methylene linked to sulfone bonds (CH2SO2CH2)

can be easily detected independently from the

corresponding 1H NMR spectrum. So DB of each

branched copolymer is conveniently available.

When the feed ratio of B2 to BB02 is changed from

1/5 to 5/1, the DB is varied from around 0.5 to 0.1.

The dependence of inherent viscosity on DB is also

interesting for the branched copolymers with different

DBs. Fig. 4 gives a typical relationship between DB

and hinh for the branched copoly(sulfone amine)s

Scheme 33.


ða ¼ hinh=MnÞ: In order to clearly reflect the increased

segment density on increased DB, Mn can be used as a

normalizing factor. With the same molecular weight,

hinh decreases slightly with increasing DB at first, and

then decreases dramatically after DB equals around

0.3. The results suggest that the segment density of a

branched polymer increases slightly, and then

increases significantly with the increase of DB after

a critical point. The studies for other copoly(sulfone

amine)s show similar behavior, and the critical DB is

0.3–0.35.

The DB also influences the crystallization of a

branched polymer. For the branched copoly(sulfone

amine)s containing piperazine units, one sort of linear

unit is the same. When the feed ratio of B2 to BB02 is

equal to 3/1 ðn ¼ 3Þ; crystallization and melting peaks

can be observed in the DSC curves of copolymers

made from 44, 51 (or 53) and 132 [163,208]. By

Scheme 34.


comparison, crystallization and melting peaks were

found for the copolymer made from 44, 54 and 132

with n ¼ 2 [209]. The copolymer side groups can alter

their thermal properties. The side group for

the copolymer made from 44, 54 and 132 is methyl

(–CH3), while that for the copolymer made from 44,

53 and 132 is ethyl (–CH2CH3). The steric effect of

ethyl is stronger than that of methyl in crystallization,

so the macromolecules with the units of 53 are more

difficult to crystallize than those with the units of 54.

Although there are no side groups in the unit of 51, no

crystallization was detected for the sample with n ¼ 2

because the ring of piperazine is more rigid than the

carbon–carbon single bond.

The crystallization is influenced not only by the

side groups of a branched copolymer, but also by

the stiffness of its main chain. Double-melting

endotherms were observed for the copolymers with

units of 133 [209,210]. Compared with the

copolymer made from 44, 132 and 53, the

copolymers made from 44, 133 and 53 are difficult

to crystallize, and no crystallization appeared for

the sample with n ¼ 3: Copolymers including units

of 133 are rather slow to crystallize, and no

crystallization peak can be observed at a normal

cooling rate (10–20 8C/min). Furthermore, Tgs were

not clearly for the copolymers found in DSC

measurements. The Tds for the copolymers in

nitrogen are about 285–320 8C, with the Td for a

crystalline sample higher 10–20 8C than that of an

amorphous one.

Branched copoly(ester amine)s with various DBs

could be synthesized using monomer 45 to react with

B2 and BB02 monomers [189]. Similar phenomenon for

the relationship of DB and hinh was observed for the

copoly(ester amine)s. Because the copolymers were

Scheme 35.

Scheme 36.


obtained as the hydrochloride, all of the samples were

amorphous.

As illustrated above, CMM exhibits generality,

simplicity, controllability, versatility and availability

in the preparation of hyperbranched polymers.

Although many new hyperbranched polymers have

been produced via the novel approaches aforemen-

tioned, CMM is still developing, and more hyper-

branched polymers with fundamental application

potentials will be found through this novel

methodology.

4. Modification of hyperbranched polymers

The properties of hyperbranched polymers are

often affected by the nature of the backbone and the

chain end functional groups, degree of branching,

chain length between branching points, and the

molecular weight distribution. Hyperbranched poly-

mers are often modified to tailor their properties for a

specialized purpose. Based on the highly branched

architecture and the large number of terminal

functional groups of hyperbranched macromolecules,

five modification manners have been developed: (1)

end-capping with short chains or organic molecules;

(2) terminal grafting via living polymerization; (3)

growing hyperbranched polymers on the surface, or

grafting from/onto the surface; (4) hypergrafting to

obtain hyperbranched polymers with a linear macro-

molecular core; (5) blending or crosslinking. The first

four methods will be discussed in this section, and the

fifth one will be discussed in Section 5.

4.1. End-capping

The large number of functional end groups

attached to the linear and terminal units of hyper-

branched polymers can be conveniently end-capped

with small organic molecules. In the end-capping

process three major purposes are emphasized: (1) to

exclude the influence of some functional groups on

the measurement of molecular weight; (2) to inves-

tigate the effect of terminal groups on the properties of

hyperbranched polymers; (3) to fabricate novel

functional polymeric materials.

Many experiments demonstrated that the nature of

terminal functional groups strongly influenced Tg;

solubility and even Td of a hyperbranched polymer.

Kim et al. [48] investigated the influence of end

groups on the Tg of hyperbranched polyphenylene

(Scheme 37), and found that the Tg can be varied over

a wide range, from 96 8C for the polymer with a-vinyl

phenyl end groups to 223 8C for the polymer with p-

anisol end groups although the modified hyper-

branched polymers have the same backbone.

Wooley et al. [56] reproducibly prepared hyper-

branched aromatic polyester by self-polycondensation

of3,5-bis(trimethylsiloxy)benzoylchloride(138) in the

presence of catalytic amounts of DMF or triethylamine

hydrochloride. Then a variety of different functional

groups were introduced into the hyperbranched macro-

molecules by modification of their phenolic groups

Fig. 4. Ratio of inherent viscosity to number-average molecular

weight ðaÞ as a function of degree of branching for the copolymer

made from divinyl sulfone (44), piperazine (132) and 1-(2-

aminoethyl)piperazine (51).

Scheme 37.


(Scheme 38). Tg of the hyperbranched macromolecules

modified with monobenzylester of adipic acid is only

6 8C, whereas it is as high as 197 8C with terminal

hydroxyl groups. The flexible alkyl units distributed

throughout the macromolecular structure may play the

role of plasticizers for the aromatic polyesters, reducing

Tg in comparison with that for samples with relatively

shorter end chains. Furthermore, the solubility was also

affected dramatically by the functionality of the chain

ends. The phenolic terminated polyesters are only

soluble in polar solvents, such as DMSO, NMP,

methanol and THF, while the end-capped products are

also soluble in non-polar solvents such as chloroform,

dichloromethane and toluene.

Surprisingly, the effect of phenolic groups on the

Tg for hyperbranched aromatic polyethers made from

monomer 139 is not so great as that for the polyesters

mentioned above [50], and Tg of the hyperbranched

polyether with hydroxyl terminated groups is only

38 8C (Scheme 39). It seems that several factors such

as the rigidity, polarity, length, and steric hindrance of

the terminal functional groups can influence Tg of the

resulting polymers.

For the hyperbranched poly(ether ketone)s made

from monomer 140 or 141, Tg increased by nearly

200 8C on going from an octyloxy terminal group to a p-

(carboxy)phenoxy terminal group (Scheme 40) [84].

Another feature for the hyperbranched poly(ether

ketone)s is that their thermal properties, for example

Tg; can be essentially independent of their macromol-

ecular architecture (DB), illustrated by a Tg for a

polymer with a DB of 0.49 that is almost equal to that for

a similar polymer with a DB of 0.15. Similarly, the

fluoro-terminated hyperbranched poly(ether ketones)

made from AB2, AB3, and AB4 monomers differ in DB

(0.49, 0.39, 0.71, respectively), but have the same Tg

(162 8C).

Few linear polyetherketones are soluble, they

crystallize easily. When compared to their linear

analogs, it is found that the solubility of a hyper-

branched polymer is dependent on both the nature of

terminal functional groups and its highly branched

architecture. The polymer with polar end groups is

soluble in polar solvents, and the non-polar-termi-

nated polymer is soluble in apolar solvents. The

fluoro-terminated sample is only sparingly soluble in

DMF and totally insoluble in DMSO and aqueous

solutions, while the phenolic-terminated polymer

is soluble in DMF, DMSO, and aqueous K2CO3 or

KOH solutions. In addition, the former is highly

soluble in relatively weaker polar or non-polar

solvents, such as chloroform and 1,2-dichloroethane,

whereas the latter is totally insoluble in these.

Shu and coworkers [87] prepared carboxylic acid-

terminated hyperbranched poly(ether ketone) from

5-phenoxyisophthalic acid (142), using phosphorus

pentoxide/methanesulfonic acid in a weight ratio of

1:12 (PPMA) as condensing agent and solvent.

Chemical modification of the carboxylic chain ends

led to hyperbranched poly(ether ketones) containing a

variety of different functional groups. DSC measure-

ments showed that Tg of the hyperbranched poly(ether

ketone)s were strongly related to the chain end groups,

with Tg increasing with increasing the polarity of the

end groups (Scheme 41). Compared with the car-

boxylic acid-terminated polymer or its ammonium

derivative (Tg of 226 and 236 8C, respectively), Tgs of

polymers linked less polar terminal groups such as ester

Scheme 39.

Scheme 38.


and ketone groups are lower than by about 100 8C. The

solubility of the modified hyperbranched poly(ether

ketone) made from 142 is similar to that for polymers

made from 140 or 141. The non-polar group-

terminated hyperbranched polymers are soluble in

non-polar solvents, such as chloroform and dichlor-

omethane, and the polar group-terminated polymers

are soluble in polar solvents such as DMF and NMP;

the ammonium derivative is even soluble in water.

Shu and coworkers [211] synthesized an ABB0

monomer (143) containing a pair of phenolic groups

and an aryl fluoride, activated toward displacement by

the attached oxazole ring. Nucleophilic substitution of

the fluoride with the phenolic groups resulted in the

formation of ether linkage, and subsequently the

hyperbranched poly(aryl ether oxazole). The end-

capping approach was used to chemically modify the

phenolic terminal groups (Scheme 42). As in the

preceding, Tg determined by DSC was very dependent

on the nature of the chain ends, increasing with

increasing end group polarity, e.g. Tg of the phenolic-

terminated sample is as high as 247 8C, whereas Tg of

the sample modified with 1-hexanol is only 119 8C. In

addition, the data summarized in Scheme 42 also

showed that Tg decreases with increasing length of the

end chain for samples with same sort of end groups,

and Tg of a sample with ester end chains is higher than

Tg of a polymer with ether end chains, for comparable

end chains length. Similar results are also observed

for hyperbranched aromatic poly(ether imide)s made

from N-{4-[1,1-di(4-hydroxyphenyl)ethyl]phenyl}-4-

fluorophthalimide (144) (Scheme 43) [212].

As indicated in the preceding, the thermal and

mechanical characters of hyperbranched polymers

can be conveniently manipulated via the end capping

method on the basis of the relationship between

terminal groups and properties. Generally, alkyl- and

ether groups-terminated hyperbranched polymers will

have relatively low Tg values, low melting viscosity

and low mechanical strength, and carboxylic acid- and

hydroxyl-terminated hyperbranched ones have rela-

tively high Tg values, high melting viscosity and high

mechanical strength. Kim and coworkers [213]

synthesized hyperbranched poly(ether ketone) ana-

logs with heterocyclic triazine moiety by polymeriz-

ation of monomer 145, and then modified the polymer

with flexible moieties (Scheme 44). The phenolic-

terminated hyperbranched polymer has a Tg of

264 8C, and the Tg of the methoxy-terminated

polymer is only slightly lower (260 8C). The incor-

poration of longer flexible moieties such as di- or

tetraethyleneoxy and stearyl units at the chain ends

Scheme 41.

Scheme 40.


greatly lowered the Tg values (169, 149 and 108 8C,

respectively). On the other hand, because the di- and

tetraethyleneoxy-terminated hyperbranched polymers

consist of a hydrophobic core and hydrophilic surface,

they may exhibit amphiphilic characteristics in an

aqueous phase. The investigation of self-aggregation

of the amphiphilic core–shell hyperbranched poly-

mers using a pyrene fluorescence probe showed that

the critical aggregation concentration (CAC) of the

tetraethyleneoxy-terminated hyperbranched polymer

was 12.6 mg/l, much lower than that of low molecular

weight surfactants, e.g. 2.3 g/l for sodium dodecyl

sulfate (SDS) in water [213].

The nature of end groups has also significant

effect on the thermal properties of the hyper-

branched poly(siloxysilanes) with flexible back-

bones. Miravet et al. [100] synthesized

hyperbranched poly(siloxysilanes) by polyhydrosila-

tion of methylvinylbis(methylsiloxy)silane (146).

End capping of the terminal silicon hydride groups

by hydrosilation with a variety of reagents gave

a diversity of terminal modified hyperbranched

poly(siloxysilane) materials (Scheme 45). Because

of the conformation freedom of the carbosiloxane

skeleton, the SiH terminated polymer made from 146

exhibits a very low Tg (2106 8C). After end capping

a SiH-terminated sample with di-tert-butylphenol

units, Tg increased significantly, by about 74–

104 8C. Phenyl ether- and chloromethylbenzene-

terminated polymers have intermediate Tg values

that are also greatly higher than that of the starting

SiH-terminated polymer. Conversely, the Tg values

of polymers having flexible triethylene glycol type

end chains are only slightly higher than that of

starting hyperbranched poly(siloxysilane) with SiH

end groups.

The influence of terminal alkyl groups on the

thermal and mechanical properties of aromatic

hyperbranched polyesters was also studied by

introducing alkyl chains with different length into

the end groups of hyperbranched polyester based on

3,5-dihydroxybenzoic acyl [214]. The degree of

modification was varied from 11 to 100%. The Tg

first decreased with increasing length of the alkyl

chain, but then did not decrease with further

increasing chain length, perhaps owing to the

possibility of crystallization. Thus, increase of the

degree of modification led to a pronounced decrease

of Tg, and an increase of the side chain crystal-

lization for long alkyl chain modification.

Scheme 43.

Scheme 42.


The measurements showed that modification with

C12 chains caused a pronounced decrease in the

complex viscosity and the moduli.

By contrast with the preceding, it must be

recognized that there are limits on the extent to

which the thermal properties for aliphatic hyper-

branched polyether polyols may be tailored by end

group modification. DSC measurements for the

hyperbranched polyglycerols (DPn ¼ 23–83;

Mw=Mn ¼ 1:2–1:5) as well as their propoxylated

derivatives esterified to different extents (23–100%)

with various carboxylic acids (C2 to C18, benzoic,

biphenylcarboxylic, and benzoic acid) indicate that Tg

of these hyperbranched polymers is mainly controlled

by two factors: (1) the extent of hydrogen bonding,

and (2) the formation of order structure (mesophases

and crystallization). The Tg values of the esterified

polyether polyols are in the range 258 to 222 8C.

The difference ðDTgÞ in Tg value between the original

and derivatized samples is only 29 to 34 K [215].

Gedde and coworkers [216] end capped the

hyperbranched aliphatic polyester originating from

2,2-dimethylolpropionic acid (147) with 1,1,1-tri(hy-

droxymethyl)propane (105) as core, affording three

hyperbranched polyesters with the same backbone

structures, but different terminal groups (acetate,

benzoate or hydroxyl groups) (Scheme 46). The DTg

(33 K measured with DSC) between the hydroxy-

terminated polymer and acetate-terminated samples

was less than had been anticipated.

On the other hand, end capping the hyper-

branched polymers with specific compounds is an

efficient approach to fabricate novel functional

polymer materials. Frey et al. [137,217] synthesized

Scheme 44.

Scheme 45.


hyperbranched polyether polyols by ring-opening

multibranching polymerization (ROMBP) of glyci-

dol (19), using 1,1,1-tri(hydroxymethyl)propane

(105) as core initiator. Then the hyperbranched

polyglycidols were end capped with acid 148 or 149

in the presence of diisopropylcarbodiimide (DIPC)

as condensing agent, affording hyperbranched poly-

ether with mesogenic end groups (Scheme 47)

[218]. The degree of functionalization of the

hyperbranched polyglycerols achieved 88% for the

lower molecular weight sample ðMn ¼ 1500 g=molÞ

and 73–79% for the higher molecular weight

samples ðMn ¼ 3500 g=molÞ: SEC measurements

showed narrow molecular weight distributions for

all the three samples ðMw=Mn , 1:2Þ: DSC, polariz-

ing microscopy, and wide-angle X-ray scattering

(WAXS) were used to investigate the liquid crystal-

line properties of the three samples. A dramatic

increase of Tg (40–50 8C) was observed for the

three samples. Apparently, molecular weight did not

strongly influence the formation of the mesophase.

The longer alkyl-terminated sample exhibits a much

higher transition enthalpy, indicating the presence of

more highly ordered smectic clusters.

Salazar et al. [219] synthesized hyperbranched

amino-terminated polyglycidols by end-modification

of terminal hydroxyls with tolylsulfonyl chloride

(TsCl), followed by nucleophilic substitution of the

tolylsulfonyl groups with secondary aliphatic

amines (Scheme 48). The hyperbranched amino-

terminated polymers obtained can be used as

macromolecular ligands in an oxidative coupling

reaction of phenylacetylene. It is found that the

amino-terminated polyglycidols–CuCl complexes

are more effective catalysts for the oxidative

coupling reaction than the reference monomeric

tertiary amines-CuCl, while less effective than

the most efficient N,N,N0,N0-tetramethylethylenedia-

mine–CuCl complexes. The performance improve-

ment for the hyperbranched polymeric ligands may

Scheme 47.

Scheme 46.


be attributed to two factors: (1) the better

complexation abilities, and (2) local increase of

the reagent concentration.

Bergenudd et al. [220] end modified the

commercially available hyperbranched polymer

Boltorne with 3-(3,5-di-tert-butyl-4-hydroxy-phe-

nyl)-propionic acid, resulting in hyperbranched

polymeric antioxidants. Then the antioxidants

were evaluated in squalane, and in polypropylene

(PP) films, to determine their oxidation induction

time. The hyperbranched antioxidants are more

effective than the commercial antioxidant Irganox

1010 in the liquid compound squalane, but inferior

in PP. Low mobility in combination with low

solubility may cause the lower efficiency in PP.

This result suggests that the macromolecular

antioxidants would be suitable as low volatile

stabilizers for liquid systems such as oils and

lubricants.

Wooley et al. [221] prepared a hyperbranched

polyfluorinated benzyl ether polymer (Scheme 49), by

deprotonation of benzylic alcohol and nucleophilic

substitution of p-fluorines of the two pentafluorophe-

nyl groups attached to 3,5-bis[(pentafluorobenzyl)ox-

y]benzyl alcohol (150). Then fluoroalkyl groups were

introduced into the polymer by chemical modification

Scheme 48.

Scheme 49.


of its p-fluorines with lithium trifluoroethoxide

and lithium 1H; 1H; 2H; 2H-perfluorodecanoxide.

Additionally, an X-ray opaque derivative was

obtained by end capping the pentafluorophenyl-

terminated hyperbranched polymer with p-iodophe-

nol. Contact angle measurements of water and

hexadecane on the films of fluoroalkyl-modified

polymers indicate a high degree of hydrophobicity

and lipophobicity. Interestingly, essentially equival-

ent hydrophobicity was obtained with 36 or 100%

1H; 1H; 2H; 2H-perfluorodecanoxy-substitution, with

only a 58 difference in the lipophobicity between the

former and the latter. Atomic force microscopy

(AFM) was applied to investigate the surface

morphologies and properties of the polymer films.

Tapping mode AFM images showed phase separation

in the partially 1H; 1H; 2H; 2H-perfluorodecanoxy-

substituted polymeric material. More than a two-

fold decrease in the coefficient of friction and

adhesive force for the 1H; 1H; 2H; 2H-perfluorodeca-

noxy-modified polymer was detected with lateral

force AFM using a silicon nitride probe.

An increase in the content of heavy atoms such as

halogens would decrease the absorption in the near

infrared (NIR), suggesting that the halogenated

hyperbranched polymers may be utilized as photonic

compounds. A good optical waveguide material also

requires the combination of low optical loss, con-

trolled refractive index, good thermal and mechanical

properties, and ease of processing. On the basis of the

high fluorine content of the AB2 monomer 3,5-

diphentafluorophenyl-1-(hydroxy)benzene (151) [51,

222], fluorinated hyperbranched polymer and its end-

modified products have been developed,

potentially useful for optical waveguide applications

(Scheme 50) [223,224]. Very low losses in the NIR,

0.1 dB/cm at 1550 nm, were demonstrated for the

hyperbranched polymer made from 151, because of its

amorphous structure and low C–H bond content.

Depending on the type and amount of the terminal

functional groups of the resulting polymers, the

refractive indices at 633 nm can be varied from

1.450 to 1.638, which matches the index of materials

involved in optical devices, and thus minimizes

backscattering at interconnections. The Tg of the

fluorinated hyperbranched polymer and its derivatives

ranged from 91 to 140 8C, and the temperatures of

initial decomposition ranged from 335 to 430 8C. A

highly crosslinked polymer was achieved by cationic

photoinitiating the fluorinated p-hydroxystyrene-ter-

minated hyperbranched polymer.

Radical addition reaction can be used to functiona-

lize the terminal groups of hyperbranched polymers.

Matyjaszewski and coworkers [113–116] prepared

Scheme 50.


a hyperbranched polyacrylate by ATRP of 2-2-

(bromopropionyloxy)ethyl acrylate (BPEA), followed

by addition of 1,2-epoxy-5-hexene to the polymer

chain end, resulting in epoxy-terminated functional

hyperbranched polymer (Scheme 51) [225].

In addition, a hyperbranched polymer with azo

chromophores end groups was prepared by modifi-

cation of a hydroxyl-terminated hyperbranched

polyester with ethyl 4-{40-[N,N-di(hydroxyethyl)ami-

nobutoxy]phenylazo}benzoate [226]. Depending on

the difference between interior (closer to the focal

unit) and periphery (distant from the focal unit)

hydroxyl groups in the hyperbranched polyglycerol,

core–shell-type hyperbranched polyglycerols were

fabricated by selective chemical differentiation [227].

Fluorescent chromophores were introduced into the

periphery of hyperbranched polymers via end-cap-

ping, affording fluorescent hyperbranched polymeric

materials [228–230].

4.2. Terminal grafting

Terminal grafting can also be called ‘grafting

from’. Grafting polymers from macromolecular

initiators prepared by modification of the functional

groups of hyperbranched polymers affords core–shell

multi-arm star polymers or hyperstars. Some proper-

ties, such as polarity, solubility and flexibility of the

hyperbranched scaffolds, can be conveniently tailored

through terminal grafting modification. Three polym-

erization methods (e.g. anionic, cationic and living/-

controlled radical polymerizations) have been

adopted to fabricate the hyperstars via reaction

processes including macromolecular initiator-first

and in situ grafting. To date, most of the hyper-

branched cores used are polyols.

Through a two-step, one-pot approach, Frey et al.

[138] obtained short poly(propylene oxide) (PPO)

multi-arm star polymers by anionic ring-opening

multibranching polymerization (ROMBP) of glycidol,

followed by anionic polymerization of propylene

oxide (Scheme 52). The resulting polyether polyols

containing up to five propylene oxide units per end

group showed apparent Mn values in the range 5000–

12,000 g/mol and narrow polydispersity ðPDI , 1:7Þ

by using DMF as eluent and poly(propylene glycol)s

with Mn in the range 1000–12,000 as samples for

calibration. The polarity of the highly hydrophilic

Scheme 51.

Scheme 52.


polyglycerols (PG) can be varied through this

approach. Depending on the length of the propylene

oxide segments, Tg of the grafted polymers varied

from 237 to 271 8C.

Through a macromolecular initiator-first approach,

Lutz et al. [231] synthesized poly(ethylene oxide)

(PEO) multi-arm star polymers by employing hyper-

branched PG and PG modified with short oligo(pro-

pylene oxide) segments (PG-b-PPO) as

polyfunctional initiators for the living anionic ring

opening polymerization of ethylene oxide (EO) in the

presence of diphenylmethylpotassium (DPMP)

(Scheme 52). In the case of PG without modification,

aggregation would occur after metalation, leading to

inefficient initiation and propagation. By comparison,

hydroxyfunctional PEO multi-arm star polymers (PG-

b-PPO-b-PEO) with Mn values in the range 34,000–

95,000 g/mol, and arm numbers in the range 26–55

were prepared smoothly with PG-b-PPO as macro-

molecular initiators in a core-first strategy.

The polydispersity ðMw=MnÞ of the three blocked

star polymers was lower than 1.5. Measurements of 1H

and 13C NMR demonstrated completely conversion

of the end groups of the propylene oxide-

modified initiator. Star polymers with higher molecu-

lar weights (Mn ¼ 180,000) can be obtained by

reinitiating multi-arm PEO stars. The arm length has

considerable influence on the thermal properties of the

prepared stars. Raising the length of the PEO chains

from 17 to 39 units results in an increase of the

melting temperature ðTmÞ from 33 to 52 8C, and an

increase of the melting enthalpies ðDHmÞ from around

88 to 133 J/g. These trends may be attributed to a

gradually lowered influence of the hydroxyl end

groups and the amorphous PG core on the thermal

properties of the stars with increasing arm length.

Thus, it is possible to tailor the thermal properties of

the multi-arm star polymers by the variation of the arm

length and functionality.

Poly(1-caprolactone) multi-arm star block copoly-

mers (PG-b-PPO-b-PCL) have been prepared based

on the propoxylated hyperbranched polyglycerol (PG-

b-PPO), with stannous 2-ethylhexanote (Sn(Oct)2) as

the catalyst [232]. With increasing ratio of monomer

to initiator, the length of the caprolactone arms

increased from 10 to 50 units, and the corresponding

apparent Mn values (SEC measurement was

carried out at 35 8C with chloroform as eluent and

polystyrene standards for calibration) of the hyper-

stars increased from 75,200 to 210,000, with narrow

PDI of the block copolymers ðMw=Mn ¼ 1:16–1:33Þ:

These hyperstars are very attractive in the biomedical

applications due to the biodegradability of the PCL

arms and the biocompatible core [233].

ATRP have also been utilized to prepare multi-arm

star polymers with PG core via the terminal grafting

strategy. Maier et al. [234] synthesized a hyper-

branched macromolecular initiator for ATRP by

modification of PG with 2-bromoisobutyryl bromide,

then polymerized methyl acrylate (MA) in the

presence of the initiator and CuBr/pentamethyldiethy-

lenetriamine (PMDETA) affording a multi-arm block

copolymers with polyether core and PMA arms

(Scheme 52). The length of PMA arms can be

controlled through monomer/initiator ratio and con-

version. No micro-phase separation of PG core and

PMA arms occurred as demonstrated with the DSC-

measurements (only one Tg for each hyperstar).

Hyperbranched polyether polyols made from 3-

alkyl-3-(hydroxymethyl)oxetane have also been

widely applied as core molecules in the preparation

of multi-arm star block copolymers. Similar to the

route employed by Frey et al. [234], Carlmark et al.

[235] synthesized a hyperbranched multifunctional

initiator with approximately 25 initiating points for

ATRP by reacting hyperbranched poly[3-ethyl-3-

(hydroxymethyl)oxetane] (PEHO) with 2-bromo-iso-

butyrylbromide (Scheme 53). Then the hyperstars

with PEHO core and PMA arms (PEHO-b-PMA)

were prepared by ATRP of MA in the presence of the

macromolecular initiator and CuBr/tri(2-(dimethyla-

mino)ethyl)amine (Me6-TREN) in ethyl acetate at

room temperature. Because of the inter- and intramo-

lecular reactions, gel would be easily formed in the

polymerization. In order to prevent crosslinking, the

concentration of propagating radicals in the system

must be kept low by dilution with solvents, stopping

the reaction after low conversion of the monomer, or

decreasing the amount of catalyst used. In the case

described above, the initiating sites-to-catalyst could

not exceed 1:0.1, otherwise, either gelation would

occur or the polymerization went out of control. The

most successful reactions were conducted with a ratio

of 1:0.05. Different from the thermal properties of PG-

b-PMA, two glass transitions were observed from the

DSC curves of the PEHO-b-PMA hyperstars,


suggested that phase-separation existed in the latter

block copolymers. The lower Tg at around 240 8C

originated from PEHO cores is hardly affected by the

length of PMA arms, while the higher one assigned to

PMA arms increased with increasing PMA chain

length.

Yan and coworkers [236] synthesized hyper-

branched poly[3-ethyl-3-(hydroxymethyl)oxetane]-

block-poly(2-dimethylaminoethyl methacrylate)

(PEHO-b-PDMA) via oxyanionic polymerization.

Potassium alcoholate macroinitiators with high initi-

ating efficiency was obtained by reaction of the

hydroxyl groups of PEHO with KH. It was found that

lower critical solution temperature of PEHO-b-

PDMA decreased with either increasing DMA chain

length or increasing pH of the solution.

Hou et al. [237] obtained hyperstars with hyper-

branched poly(3-methyl-3-(hydroxymethyl)oxetane)

(PMHO) core and short polytetrahydrofuran (PTHF)

arms via an in situ grafting approach (Scheme 53). The

cationic ring-opening polymerization of 3-methyl-3-

(hydroxymethyl)oxetane (MHO) was initiated with

BF3·O(CH2CH3)2. Because the rate constant for the

addition reaction between terminal units and MHO is

much lower than that of MHO homopolymerization,

the first stage polymerization in THF solution

produced PMHO, with copolymerization with THF

after the MHO was almost completely reacted. The

results were confirmed as compared with those

obtained using a two-step copolymerization, i.e.

homopolymerization of MHO and then addition of

suitable amount of THF to the reaction system to effect

the copolymerization. The 1H NMR measurements

showed that the average degree of polymerization of

THF arms increased from 0.41 to 3.86 on increasing the

feed ratio of THF to MHO from 0.5:1 to 6:1.

Commercially available aliphatic hyperbranched

polyester with 32 hydroxyl groups (Boltorne-H30)

was used as the core by Hult et al. [238] to prepare

PCL multi-arm star copolymers in the presence of

Sn(Oct)2. Rheological measurements of zero shear

rate viscosity, h0; showed that the star polyesters had

a significantly lower h0 than linear PCL. Dynamic

mechanical data indicated that the films made from

the shorter-armed resins were amorphous after curing,

while those from longer-armed resins were crystal-

line. Another multi-arm star copolymer with hyper-

branched poly[2,2-bis(hydroxymethyl)propionic

acid] core and PCL arms was obtained via a similar

route [239]. As a reference material, PCL multi-arm

star copolyesters initiated from a dendrimer were also

prepared. Comparison of the results obtained for

dendrimeric and hyperbranched initiators showed that

the reactivity of the terminal hydroxyl groups in the

dendrimer was considerably higher than in the

hyperbranched polymer.

Amphiphilic multi-arm star polymers with a

hydrophobic hyperbranched core and hydrophilic

graft arms have been reported by Weberskirch et al.

[240]. Modification of the hyperbranched polymer

derived from 4,4-bis(40-hydroxyphenyl)valeric acid

with 3-(chloromethyl)benzoyl chloride gave rise to

hyperbranched macroinitiator, followed by cationic

ring-opening polymerization of 2-methyl-2-oxazoline

Scheme 53.


affording the core–shell amphiphiles with up to 12

arms. Single star molecules ranging from 22 to 50 nm

in diameter were detected with photon correlation

spectroscopy measured in methanol and chloroform.

4.3. Surface growing

The method to modify the specific surface or

interface with hyperbranched macromolecules or to

graft hyperbranched polymers onto the surface is

denoted as ‘surface growing’ in this paper. The

grafted hyperbranched polymers can be regarded as

so-called polymer brushes, which are typically

anchored to a surface by one end of the polymer

chain, such that the polymer can extend away from

the surface [241]. Surface growing is an efficient

strategy to fabricate inorganic/organic-hyper-

branched polymer hybrid materials and functional

devices or improve the properties of surface

objects.

Four routes have been developed in these

modifications and functionalizations, as shown in

Fig. 5. Route 1 can be called the graft-on-graft

approach. The reaction procedure is similar to the

step-by-step synthesis methodology of a dendrimer.

Functional groups (D) are firstly introduced onto the

surface, followed by reaction of AB2 monomers or

multifunctional polymers with the D groups and

then reaction of CD monomers with the B groups

attached (in some examples, the addition order of

AB2 or CD is reversed). Repeating the reaction

between AB2 and CD grows hyperbranched

polymers with numerous functional groups onto

the surface. Route 2 is a ‘grafting from’ technique

of surface initiating polymerization in which the

initiating functional groups are incorporated onto the

surface and then initiate the polymerization of AB2

or latent AB2 (ABB0) monomers. In route 3, a

‘grafting to’ approach is used, whereby prepared

hyperbranched polymers are covalently linked to a

prepared surface. Route 4 called ‘surface adsorp-

tion’, hyperbranched macromolecules are directly

assembled or adsorbed onto the surface. Notably,

routes 1-3 are chemical methods, while route 4 is a

physical method. Therefore, both chemical and

physical approaches can be used to graft hyper-

branched polymers onto the surface.

A series of solid matrixes such as gold (Au),

silica (SiO2), silicon wafer (Si), aluminum (Al),

porous alumina (Al2O3), C60, carbon black, poly-

ethylene (PE), polypropylene (PP), and chitosan

powder (CP) have been adopted as supporting

substrates for the functionalization of hyperbranched

polymers. Some hyperbranched polymers grown on

the surface and their grafted approaches are listed in

Table 6.

4.3.1. On the surface of Au

Carboxylic acid functional groups are introduced

on a gold surface or the surface of gold-coated porous

alumina via the attachment of mercaptoundecanoic

acid (MUA) to the substrate, followed by the

conversion of the carboxylates to mixed anhydrides.

Then amino-terminated poly(tert-butyl acrylate)

Fig. 5. The surface growing routes for hyperbranched polymers.


(PTBA) is grafted on the surface through the

attachment sites of the mixed anhydrides. Hydrolysis

of the tert-butyl groups to carboxylic acid generates a

poly(acrylic acid) (PAA) layer. Repeating the steps of

the formation of mixed anhydrides, grafting of PTBA

and hydrolysis of tert-butyl groups affords multi-

grafting hyperbranched PAA layers [241–249]. A

typical procedure is described in Fig. 6. In order to

change the surface properties, the carboxylic acid

groups in PAA are further modified with other

molecules such as H2NCH2(CF2)6CF3 [242,245,

247], and molecules containing pyrene, ferrocene,

poly(ethylene glycol), 15-crown-5,3,4,9,10-perylene-

tetracarboxylic diimide, etc. [244].

4.3.2. On the surface of SiO2

The silica surface is also widely grafted with

hyperbranched polymers. Tsubokawa et al. [250]

achieved surface-grafting polymers with azo pendant

groups by reaction between 4,40-azobis(4-cyanopen-

tanoic acid) (ACPA) and isocyanate groups of grafted

polymer on a silica surface. The azo groups can

initiate the copolymerization of methyl methacrylate

(MMA) with 2-methacryloyloxyethyl isocyanate

(MOI). The isocyanato groups in PMOI can be

modified with ACPA, which can initiate copolymer-

ization of MMA and MOI. Thus, hyperbranched

copolymers can grow on the silica surface via the

graft-on-graft approach. Polymer chains possessing

peroxycarbonate groups may be obtained by copoly-

merization of tert-butylperoxy-2-methacryloylox-

yethylcarbonate with other vinyl monomers. Similar

to the azo groups, peroxycarbonate groups can initiate

the polymerization of vinyl monomers to give

hyperbranched polymers anchored to the silica sur-

face [251].

Reaction of terminal diamine-type polyoxyethy-

lene with epoxy groups previously introduced onto

the silica surface through 3-glycidoxypropyltri-

methoxysilane treatment leads to a modified surface

having numerous amino groups. By repeating

Michael addition of MA to amino groups followed

by amidation of the ester moieties with diamines

(which is similar to the synthesis of polyamidoa-

mine dendrimer), hyperbranched polyamidoamines

are grafted onto the silica surface [252,253].

Aminosilylated surface can also directly initiate

the ring-opening polymerization of aziridine to form

hyperbranched poly(ethyleneimine) (PEI) on a solid

support [254].

Table 6

Growing hyperbranched building blocks on the surfaces

Surface Introduced surface group Major building units or monomers Approach Reference

Au –COOH ClCO2CH2CH3 þ PAA graft-on-graft [241–249]

SiO-2 –NyN– MMA þ MOI graft-on-graft [250]

–OCO2O– CH2yCH-R graft-on-graft [251]

–NH2 MA þ H2N(CH2)nNH2 graft-on-graft [252]

–NH2 MA þ H2N(CH2)2NH2 graft-on-graft [253]

–NH2 Aziridine Grafting from [254]

–CO2CBr(CH3)2 BPEA Grafting from [255]

– PEI Adsorption [256]

Si –OH Hyperbranched EHBP Grafting to [257,258]

–OH HBP3/HBP4 Adsorption [259]

–NH2 Aziridine Grafting from [254]

–CO2CBr(CH3)2 BPEA, BIEM Grafting from [260]

PE –COOH ClCO2CH2CH3 þ PAA graft-on-graft [261–267]

–NH2 MA þ H2N(CH2)2NH2 graft-on-graft [268]

PP –COOH ClCO2CH2CH3 þ PAA graft-on-graft [269]

– HBP-Boltorn E2 Grafting to [270]

CP –NH2 MA þ H2N(CH2)2NH2 graft-on-graft [271]


Muller and coworkers [255] obtained hyper-

branched polymer–silica hybrid nanoparticles by

SCVP via ATRP of BPEA from silica surface linked

a-bromoester initiator layer. Meszaros et al. [256]

investigated the direct adsorption on silica wafers of

hyperbranched PEI with reflectometry, and showed

that significant charge reversal and shift in the

isoelectric point of silica wafer occurred because of

the adsorption of PEI.

4.3.3. On the surface of Si

A molecular surface coating with a thickness of

4.5 nm has been fabricated by reaction of epoxy-

functionalized hyperbranched polyesters (EHBP)

with the hydroxyl groups of silicon wafers via a

grafting to approach [257,258]. Around 3–4 epoxy

groups per molecule attached to the uppermost

surface layer provided residual functionality sufficient

to graft another polymer layer. It was found that the

grafted hyperbranched polymeric layers are very

robust and can sustain high compression and shear

stresses, while possessing high elasticity [257]. The

uniform polymer layers were homogeneous on a

nanoscale, without signs of the microphase separation

[258].

The commercially available Boltorne hyper-

branched polyesters with third and fourth gener-

ations (HBP3 and HBP4) can be directly adsorbed

on a bare silicon surface; the adsorption amount of

lower generation HBP3 is higher than that of HBP4

[259]. In a HBP3 adsorbed layer, surface coverage

is observed with thickness ranging from less than

1 nm to about 3 nm. For HBP4 located on the

surface, a stable, close-to-spherical shape with a

diameter of 2.5 nm is found throughout the whole

coverage, including both dense monolayers and

isolated molecules. This differing surface

behavior might be caused by the different molecular

flexibility and constrained mobility between HBP3

and HBP4.

Fig. 6. The general procedure for grafting hyperbranched poly(acrylic acid) layers on the gold surface by graft-on-graft approach.


Similar to the process for growth of hyperbranched

PEI and hyperbranched poly(BPEA) on the silica

surface [254,255], hyperbranched PEI [254] and

hyperbranched polyesters [260] have been success-

fully anchored to the silicon surface by ring-opening

polymerization of aziridine and self-condensing

ATRP of BPEA and 2-(2-bromoisobutyryloxy)ethyl

methyacrylate (BIEM), respectively, via grafting

from approach.

4.3.4. On the surface of PE

Bergbreiter and coworkers [261–267] have grafted

hyperbranched PAA onto the PE surface and modified

the pendant carboxylic acid groups of PAA with

fluorescent chromophores and hydrophobic molecules

by extending the chemistry employed in the hyper-

branched grafting on Au-coated silicon wafers

described above [241–249]. Oxidized PE films with

carboxylic acid functional groups are obtained by

oxidation with CrO3–H2SO4. Then amino-terminated

poly(tert-butyl acrylate) is attached to the oxidized PE

through amidation, so that subsequent hydrolysis of

the tert-butyl esters affords a PE film with one layer of

PAA grafts. Repetition of the process through 2–4

more cycles can produce heavily grafted PE films.

The resulting hyperbranched grafts exhibit

higher efficiency as platforms for further ionic

modification of PE by comparison with the simple

oxidized PE [261].

Amidation or esterification of ultrathin hyper-

branched PAA grafts with thiophenes having amino

or hydroxyl groups generated thiophene units-con-

tained interfaces that could be applied as substrates for

an oxidative polymerization method with FeCl3 as an

oxidant [265]. A conjugated fluorescence 2,5-coupled

oligothiophene has been fabricated within the hyper-

branched grafts, as demonstrated with its yellow–

green light emitted under UV irradiation. The

hyperbranched PAA grafts can also be used as

substrates for a mild hydrogen-bond-based grafting

method [266].

Nakada et al. [268] introduced amino groups to the

unsaturated pendant and bridge sites of a PE

substrate, followed by application of poly(amidoa-

mine) dendrimer synthesis methodology (repeating

the steps of 2-methoxycarbonylethylation and 2-

aminoethylamidation), resulting in ultrathin hyper-

branched poly(amidoamine) grafts. The amino

amplified PE films showed anionic exchange capacity

and could adsorb acid dye.

4.3.5. On the other surfaces

The techniques previously adopted with PE surface

can be extended to modify PP by hyperbranched

grafting with PAA grafts [269]. Hydrophilic and

hydrophobic surfaces were obtained by treatment of

the as-prepared PAA-grafted PP with alkali, and with

ethyl chloroformate followed by pentadecylfluorooc-

tylamine. The adhesion of the surface increases from

2 J/m2 for unmodified PP to 29 J/m2 for the PP with

five stages of hyperbranched grafting. Epoxy-termi-

nated hyperbranched polyesters (Boltorne-E2) were

grafted on the PP surface modified with maleic

anhydride (MAH) by melt blending in a twin-screw

extruder [270].

In addition, hyperbranched polyamidoamine was

grafted onto the surface of CP by repeating two

processes including Michael addition of MA to

surface amino groups and amidation of the resulting

esters with ethylenediamine [271]. C60-polystyrene

hyperbranched macromolecular thin films were also

reported [272].

4.4. Hypergrafting

Hypergrafting represents grafting hyperbranched

macromolecules to a multifunctional polymeric core,

and the resulting hybrid material is called a ‘hyper-

grafted polymer’ in this article. If the core used is a

linear polymer, a new sort of comb-like polymer

cylinder will be formed. As shown in Fig. 7, four

routes may be applied to obtain the hypergrafted

polymers: (1) graft-on-graft from a polymeric core

with functional side groups; (2) polymerization of

hyperbranched macromonomers; (3) polymerization

of AB2 or latent AB2 monomers initiated from

macromolecules; (4) direct grafting hyperbranched

molecules onto a polymer.

Using the graft-on-graft approach, Frechet et al.

prepared hypergrafted polystyrene (PS) and its copo-

lymers [107]. A linear backbone incorporating latent

ATRP initiating sites was first synthesized by nitroxide

mediated ‘living’ radical polymerization of PS and

chloromethylstyrene (CPS), followed by initiating

ATRP of CPS in the presence of Cu(I)Cl/2,20-

bipyridine complex, giving rise to PS cylinders.


The active side points of CPS units were used to further

initiate the atom transfer polymerization of other vinyl

monomers, affording hypergrafted polymers.

Poly(allylamine) (PAAM) grafted chain-pendant

hyperbranched PEI has been prepared by an in situ

reaction of PAAM with 2-chloroethylamine hydro-

chloride (CAH) in the presence of sodium hydroxide

[273]. The as-prepared polymers with abundant amino

groups can react with CAH to produce hypergrafted

polymers with multi-layers of PEI side chains. Poten-

tiometric titration and ultraviolet–visible (UV–Vis)

spectroscopy showed that the hypergrafted polyamines

can act as multidentate ligands for ions and form stable

complexes with Cu2þ, with about three EI dents per ion.

Frey et al. [274] reported polyethyleneimines

with apolar hyperbranched carbosilane side chains,

prepared by ring-opening polymerization of oxazo-

line-based hyperbranched macromonomers earlier

synthesized. The hypergrafted polymers can form

superstructures in solution and in bulk.

Knauss et al. [275] obtained branched PS macro-

monomers by slow addition of a coupling agent

(4-(chlorodimethylsilyl)styrene or CPS) to living

polystyryllithium. Then, hypergrafted copolymers

were produced by copolymerization of the macro-

monomer with PS or MMA.

Although the literature published on hypergrafted

polymers is limited, this new class of polymers is

likely to receive more and more attention and be

widely explored and used in a variety of potential

application areas such as supramolecular chemistry,

biomaterials, nanotechnology and molecule-devices

in the near future.

5. Application of hyperbranched polymers

5.1. Conjugated functional materials: optical,

electronic and magnetic properties

Because of their good solubility and excellent

processibility, three-dimensional hyperbranched

conjugated polymers are attracting more and more

attention as novel optical, electronic and magnetic

materials. Linear conducting polymers are usually all

para linked, while the hyperbranched polymers are

almost always meta connected and have a far more

limited conjugation. Consequently, very different

properties are found for the hyperbranched polymers

than their linear counterparts.

5.1.1. Hyperbranched poly(phenylenevinylene)

Lin et al. [175] synthesized hyperbranched

poly(3,5-bisvinylic benzene)s (HP42 or HP43) with

a relatively low yield and low molecular weight via

Gilch or Wittig reactions (Scheme 54). The SEC

measurement showed that Mn of the product made

from route A was 1934 with a PDI of 1.13, and the Mn

value of the sample produced from route B was even

smaller. The resulting hyperbranched polymers are

soluble in common organic solvents such as THF,

chloroform, dichloromethane and ethyl acetate. The

optical properties of HP42 are listed in Table 7.

The absorption maxima ðlabÞ determined with UV–

Vis spectroscopy are 290 and 310 nm with a molar

absorption coefficient in the order of 104, and the

fluorescence emission maximum ðlemÞ in dichloride

methane solution monitored occur for 359 and 369 nm

Fig. 7. Possible approaches to hypergrafted polymers.


with a fluorescence lifetime ðtÞ of 0.6–8 ns and a

quantum yield ðFfÞ of 36% for the excitation

maximum ðlexÞ at 305 and 325 nm. The incorporation

of the m-phenylene group decrease the effective

conjugation length and increase the bandgap, so

both the absorption and emission bands are blue

shifted in comparison with the widely studied linear

poly(p-phenylenevinylene) (PPV). The solid film of

HP42 fabricated by spin coating technique exhibits an

emission maximum ðlem;sÞ at 446 nm as excited at its

solid absorption maximum ðlab;sÞ; about 80 nm red-

shifted with respect to the value in solution. Enhanced

inter-chain interaction in the solid film may cause the

dramatic difference.

Scheme 54.

Table 7

Photophysical results of some hyperbranched conjugated polymers

No. Mn PDI lab (nm) lex (nm) lem (nm) lab;s (nm) lem;s (nm) Ff (%)a

HP42 1930 1.13 289, 310 359, 369 305, 325 446 36

HP44 2810 2.15 323, 405 457 329, 402 501, 529 26

HP45 315, 397 453, 480 306, 390 500 47

HP46 326, 406 453, 480 319, 405 508 100

HP47 330, 409 453, 480 322, 409 505 62

HP48 312, 396 462, 479 310, 382 492 69

HP49 2170 2.54 317, 402 453, 480 307, 389 470 90

HP50 2870 4.1 330, 405 461, 490 388 510 24

HP51 2840 4.3 332, 405 461, 490 332, 402 510 49

HP52 40,180 1.76 420 500

160 399 350 473

161 383 350 499

HP53 1077 1.44 284 285 450 0.1

HP54 2710 1.58

HP55 9080 2.24 309 343 398 49

HP56 4940 5.78 334 397 9

HP57 4770 3.4 400 31

HP58 4030 1.58 399 20

HP59 6240 2.15 398 10

HP62 28,000 2.5 351 400 484

HP63 2500 1.7 264, 419 404 533

a The fluorescence quantum efficiency was recorded with different standards.


Hyperbranched PPV derivatives with various of

2,5-aromatic substituted alkyl groups and terminal

groups were prepared by direct polycondensation of A2

monomer 31 (2,5-diR1O-1,4-bis(bromotriphenylpho-

sphinomethyl)benzene) or 154 (2,5-dimethoxy-1,4-

bis(chlorotriphenylphosphinomethyl)benzene) with

B3 monomer 32 (1,3,5-benzenetricarbaldehyde) in

the presence of strong base through a Wittig reaction,

followed by end group modification of the hyper-

branched polymers (Scheme 55). Their photophysical

properties were investigated in detail in solution and

solid films [276–280]. As shown in Table 7, all the

alkyl-substituted products showed a red shift in both

the absorption and emission peaks. No significant

variations in absorption and emission maxima were

detected on increasing the length of the side alkyl

groups, while marked difference was observed in their

fluorescence quantum efficiency, with the sample with

C5-alkyl exhibiting the highest Ff : On the other hand,

the terminal groups of the resulting hyperbranched

polymers showed slight or moderate influence on their

absorption and emission maxima, but great influence

on the photoluminescence efficiency.

HP49, HP50 and HP51 were used as the active

layer in electroluminescent devices. The turn-on

voltages of the single- and double-layer light emitting

diodes (LEDs) made from HP51 are approximately

6 V, and that of light emitting electrochemical cell

with HP50 as active polymers is 3 V [280]. Significant

enhancement in the device photoluminescent per-

formance was observed by dispersing HP49 in a linear

poly(9-vinylcarbazole) (PVK) matrix, owing to

energy transfer between PVK and HP49. For the

LED with PVK : HP49 ¼ 5 : 1 as the emitting layer,

bright blue emission up to 810 cd/cm2 was achieved at

a bias of 24 V, and the maximum transfer efficiency of

current density to brightness of the blend polymer

devices is as high as 0.27 cd/A, an order of magnitude

greater than that of HP49-based single layer devices

(0.025 cd/A) [278].

5.1.2. Hyperbranched poly(b,b-dibromo-4-

ethynylstyrene)

Fully conjugated hyperbranched polymers and

oligomers of b,b-dibromo-4-ethynylstyrene were

prepared via a Heck reaction (Schemes 56 and 57).

In the presence of triphenylphosphine (TPP), CuI and

bis(triphenylphosphine)palladium(II) dichloride,

polycondensation of 155 yielded HP52 with a Mw of

70,722 and a PDI of 1.76 [281]. HP52 showed an

emission maximum at 500 nm and a shoulder at

460 nm upon excitation at 420 nm. Similarly, blue

emission with a peak of 440–500 nm was found for

the oligomers of 155 synthesized by stepwise growth

when excited at 350 nm. Interestingly, all of the

oligomers except 161 exhibited two peaks in their

corresponding excitation spectrum [282]. The broader

and lower peak close to the absorption peak can be

attributed to emission from S1 state, but the origin for

the sharper and higher one located very close to the

emission peak is not yet clear.

5.1.3. Hyperbranched poly(arylene/1,1-vinylene)s

Dihydridocarbonyltris(triphenylphosphine)ruthe-

nium [RuH2CO(PPh3)3] catalyzed self-polycondensa-

tion of 4-((trimethylsilyl)ethynyl)acetophenone (162)

resulted in a hyperbranched polymer with regularly

alternating arylene and 1,1-vinylene units (HP53) by

Scheme 55.


catalytic addition of the ortho C–H bonds of

acetophenone group to the triple bond of the

trimethylsiylethynyl group (Scheme 58). The Mn

measured with SEC and 1H NMR for HP53 is 1077

and 2400, respectively. HP53 exhibited an absorption

peak at 284 nm and fluorescence emission maximum

at 450 nm with a Ff of 0.1% [98].

5.1.4. Hyperbranched polyarylenes

Hyperbranched polyphenylenes were first reported

as novel hyperbranched polymeric materials [46–49].

Suzuki polycondensation of AB2 monomer 3,5-

dibromophenylboronic acid or polymerization of

3,5-dihalophenyl Grignard reagents gave hyper-

branched polyphenylenes (Scheme 59). The polymers

obtained from the Suzuki Pd(0) catalyzed aryl–aryl

coupling reaction had Mws of 5000–35,000 with PDIs

less than 1.5. The resulting hyperbranched polyphe-

nylenes are thermally stable to 550 8C and soluble in

many organic solvents such as THF, tetrachloroethane

and o-dichlorobenzene although their backbones

consist only of rigid aromatic rings. Research on

Scheme 57.

Scheme 56.


the potential photophysical properties of the resulting

polymers was not reported.

Hyperbranched polyphenylenes with a higher den-

sity of benzene rings in one unit can be prepared by

Diels-Alder self-[2 þ 4]cycloaddition of AB2 mono-

mers, ethynyl-, propynyl and phenylethynyl-substi-

tuted tetraphenylcyclopentadienones, in the presence

of tetrabutylammonium fluoride (Bu4NF) at 180 8C

(Scheme 60). The Mws of the resulting hyperbranched

polymers determined by SEC with PS as standards

ranged from 3000 to 107,455 with PDIs of 1.66–6.85

[283]. It is notable that polymers with such a high, dense

packing of benzene rings are soluble in toluene or

benzene. Their potential application as the polycyclic

aromatic hydrocarbons has been proposed [284].

Tang et al. [285] successfully prepared soluble

hyperbranched polyarylenes containing various side

groups as shown in Scheme 61 by copolycyclotrimer-

ization of compounds with double triple bonds and

monomers with a single triple bond. The polymeriz-

ation can be carried out at lower temperature (65 8C)

if UV irradiation is employed to activate the Co

catalyst. The temperature for 5% weight loss of each

polyarylene is higher than 400 8C. The results and

photophysical data of the resulting hyperbranched

polyarylenes are summarized in Table 7. It is found

that the emission properties of the polymers can be

tuned by changing the comonomer pairs [286]. The

polymer made from 163a and 164b exhibits the

highest fluorescence quantum yield (49%) with 9,10-

diphenylanthracene as the standard. The emission

from the polymer with long side chains (HP56) is very

weak ðFf ¼ 9%Þ; possibly caused by self-quenching

due to absorption in the same spectral region. Because

of their excellent optical limiting properties, good

thermal stability and processing advantages, these

hyperbranched polyarylenes may be useful in the field

of functional materials and devices.

5.1.5. Hyperbranched non-linear optical polymers

Compounds possessing donor and acceptor

chromophores may exhibit non-linear optical

(NLO) properties. The NLO chromophores can be

Scheme 58.

Scheme 59. Scheme 60.


aligned as shoulder-to-shoulder, head-to-tail, head-

to-head, and random. Hyperbranched polymer with

4-(2-cyano-2-methoxy-carbonylvinyl)aniline as a

second-order NLO chromophore was synthesized

by Zhang et al. [287] via a one-pot Knoevenagel

polycondensation of 4-formyl-N,N-di(2-hydro-

xyethyl)aniline (165) and cyanoacetic acid with

N,N-dicylohexylcarbodiimide (DCC) as a water

acceptor and 4-(dimethylamino)pyridine (DMAP)

as a base (Scheme 62). The resulting hyper-

branched polymer was soluble in polar solvents

such as DMF and DMSO, with a Tg of 86 8C, a Td

of 330 8C in air and a hinh of 0.27 dl/g in DMSO at

30 8C. Each branched chain of HP60 looks like a

head-to-tail main chain backbone, so NLO proper-

ties are reasonably anticipated for HP60. The

second harmonic generation measurements indi-

cated that the second harmonic coefficient ðd33Þ for

HP60 was about 2.8 pm/V with a Y-cut quartz

crystal plate as a reference ðd11 ¼ 0:5 pm=VÞ:

Carbazole moieties were incorporated into the

backbones of hyperbranched polymer starting from

3,6-diformyl-9-(11-hydroxyundecyl)carbazole (166)

and cyanoacetic acid (Scheme 63) via a method

similar to that employed in the synthesis of HP60.

The d33 of the obtained hyperbranched polymer

HP61 was found to be higher than that of HP60,

reaching 7 pm/V. However, the d33 value is still

not large in comparison with linear main-chain

polymer containing the similar NLO moieties,

attributed to the decreased alignment of the NLO

moieties in the hyperbranched macromolecules

[288]. Light emitting devices consisting of poly(9-

tetradecanyl-3,6-dibutadiynyl-carbazole) as a hole

transport layer and HP61 as an electron transport

and emitting layer have been fabricated. Strong

Scheme 62.

Scheme 61.


emission with the maximum at 480 nm was

observed for the double-layered devices.

5.1.6. Hyperbranched coumarin-containing polymers

Coumarines (2H-1-benzopyran-2-ones) are widely

used as laser dyes and light emitters because of their

good photostability and high quantum yield of

photoluminescence (PL). Hyperbranched coumarin-

containing polymer (HP62) and copolymers have been

prepared by polycondensation of (6-(3-carboxy)cou-

marinyl)diacetylhydroquinone (167) and by copoly-

merization of 167 with m-acetoxybenzoic acid in

different feed ratios. The polymerization was carried

out at 200 8C for 1 h under nitrogen flow, followed by

reaction at 330 8C for 1 h more under reduced pressure

(0.1 mm Hg), as shown in Scheme 64 [289]. Signifi-

cantly, the measurements of 1H NMR suggested

that the resulting hyperbranched polymer and copoly-

mers had DBs close to 100%, which might result from

the high temperatures of the reaction. Under these

extreme conditions, the high mobility of the macro-

molecular chains can overcome steric hindrances,

enhancing the reaction between acetoxyl and car-

boxylic acid groups. The coumarin-containing poly-

mers showed Mns ranging from 21,000 to 54,000 with

PDIs of 2.3–2.7, and Tgs of 230–160 8C. The Tg

values of the resulting polymers increased on increas-

ing the feed ratio of monomer 167. Fluorescence

observations showed that all polymers were blue

emitters, in the range 484–497 nm. Measurements of

current density – voltage relationships for the

single layer electroluminescence (EL) devices with

the coumarin-containing polymers as light-

emitting material revealed that the higher the

content of coumarin units in polymer, the lower turn

on voltage.

5.1.7. Hyperbranched polythiophenes

As shown in Scheme 65, light-harvesting

hyperbranched polythiophene was prepared by

Scheme 64.

Scheme 63.


polycondensation of a Grignard reagent 169 with

Ni(bis(diphenylphosphino)propane)Cl2 as the cata-

lyst. The unsymmetrical AB2 monomer 169 was

synthesized by treatment of 2,3-dibromothiophene

(168) with lithium diisopropylamide (LDA) fol-

lowed by MgBr2 [290]. Determination of SEC with

PS as standard and THF as the eluent gave Mn and

PDI of the as-prepared hyperbranched polythio-

phene as 3400 and 1.3, respectively. It was found

that the solubility of bromo-terminated product was

low, and introduction of the alkyl groups onto the

periphery of the polymer improved its solubility. In

the structure of end-capped polymer HP63

(Mn ¼ 2500; PDI ¼ 1:7), only 2,3 or 2,5-linked

thiophene units are conjugated. So a gradient of

conjugation lengths exists in a single hyper-

branched macromolecule, resulting in a light-

harvesting effect, and thus enhanced light emission

or intramolecular energy transfer from the less

conjugated units to the longest conjugation frag-

ment. Furthermore, the conjugation length increases

on increasing the molecular weight of the resulting

polymer. A broad absorption band in the range of

220–600 nm appears in the UV spectrum of HP63,

consistent with the gradient conjugation structure of

the polymer. The emission maximum of HP63 is

533 nm for excitation at 404 nm. Compared with

their linear analogs, the hyperbranched polythio-

phenes have a much broader distribution of

conjugation lengths, which makes them potentially

better light-absorbing materials for efficient photo-

voltaic as well as light emitting devices.

In addition to the p–p and p–p conjugation

systems described above, a new structural class of

s–p conjugated hyperbranched poly(2,5-silylthio-

phenes) has been reported [291]. As outlined in

Scheme 66, an AB3 type monomer, 2-bromo-5-

trimethoxysiylthiophene (170), was firstly syn-

thesized, followed by addition of 170 to magnesium

turnings in THF, resulting in rapid formation of the

Grignard reagent. In situ polymerization

of the Grignard reagent gave hyperbranched

poly(2,5-silylthiophenes) (HP64). Hyperbranched

polythiophenes with different terminal groups were

obtained by reaction of HP64 with the appropriate

nucleophilic reagents. The resulting hyperbranched

polymers have Mns of 4460–6580 determined by

SEC and DB of 0.46 calculated from 1H NMR

spectrum. UV–Vis measurements indicated that a

high degree of conjugation through the silicon atoms

existed in the polymer backbones, demonstrated by

dramatic red-shift of the p–pp transitions in the

polymers (around 250 nm) in comparison to thio-

phene (230 nm). In addition, charge transfer from

Scheme 65.

Scheme 66.


thiophene to silicon was detected for the polymers,

according to their broad absorptions in the 300–

320 nm regions.

5.1.8. Hyperbranched polyanilines

Linear polyanilines (PAs) are well known and

have been widely studied as a conductive and

magnetic polymeric materials. However, the linear

polymers and their crosslinked products are hardly

soluble in solvent, leading to poor processibility.

Soluble PAs can be approached by the introduction

of dendritic units into the polymer backbones. To

date, soluble hyperbranched polyanilines and their

derivatives have been successfully prepared. The

AB2 monomers used to synthesize hyperbranched

PAs are shown in Scheme 67. The polymerization

of 3,5-dibromoaniline (171) was performed in THF

at 90 8C in the presence of 2,20-bis(diphenylpho-

sphino)-1,10-binaphthyl (BINAP) ligand and 1.1

equivalents of sodium tert-butoxide (tert-BuONa)

per amine [292]. The Mw and PDI determined with

SEC in THF for the hyperbranched PA were 7000

and 3.2, respectively. The hyperbranched PA

showed magnetic properties similar or superior to

that of its linear analogs.

Hyperbranched poly(triphenylamine) was syn-

thesized through aryl–aryl coupling of the AB2 type

Grignard reagent 172 [293]. The resulting hyper-

branched polymer was soluble in common organic

solvents such as THF and chloroform, and exhibited a

new p–pp transition absorption band at 360 nm,

possibly resulting from the conjugation between

biphenylene units and nitrogen atoms.

Hyperbranched polymers with alternating pheny-

lene sulfide and phenyleneamine units have

been designed, but attempts to obtain them by

self-condensation of monomer 173 or 174 failed,

and polymerization of monomer 175 gave insoluble

product [294].

5.2. Polymer electrolytes

A solid polymeric electrolyte should meet the

requirements of (1) being amorphous, (2) having a

high solvating power for appropriate ions, (3) good

ion transport, and (4) electrochemical stability. It is

well known that oligo(ethylene glycol) segments

satisfy the last three requirements, and hyperbranched

polymers are usually amorphous. Thus, hyper-

branched macromolecules possessing ethylene glycol

(EG) chains have been designed, prepared and used as

novel polymeric electrolytes or ion-conducting elas-

tomers. Table 8 lists the monomers used to synthesize

hyperbranched polymeric electrolytes and the proper-

ties of the resulting materials.

Hawker and coworkers [295] first prepared hyper-

branched poly(ether ester)s containing linear EG units

of varying lengths in good yields with high molecular

weights ðMw ¼ 50; 000–81; 000Þ by polymerization

of AB2 monomers (176, 177, 178) with EG segments.

The properties of the hyperbranched polymer derived

from hexaethylene glycol ðn ¼ 5Þ-lithium perchlorate

complexes were examined as polymeric electrolytes.

It is found that the Tg values of the complexes obeyed

the Di Mario equation for general polymeric electro-

lytes [295]:

Tg 2 Tg0

Tg0

¼ac

1 2 acð4Þ

In Eq. (4), Tg is the glass transition temperature of

the polymer–lithium perchlorate complex, Tg0 is the

glass transition temperature of the salt-free polymer,

and c is the mole ratio of LiClO4 to repeat unit of

polymer, a is a constant for a specific polymeric

electrolyte. DSC measurements showed that a was

equal to 0.049 for the hyperbranched macromolecule-

LiClO4 complex. The ionic conductivity (IC) of the

hyperbranched polymeric electrolytes increases with

both increasing temperature and concentration of Liþ,

with a value of 7 £ 1025 S cm21 being observed at

333 K for [Liþ] ¼ 0.62 mol per mole repeat EG unit.

Itoh et al. [296] synthesized the AB2 monomers

reported by Hawker via a different chemistry. BulkScheme 67.


polymerization of 176 or 177 in the presence of a

catalytic amount of dibutyltin diacetate at 165 8C

under nitrogen gave the hyperbranched poly(ether

ester) with Mn of 8800 (made from 176) or 21,000

(made from 177). Then the hydroxyl-terminated

hyperbranched polymers were acetylated with acetyl

chloride in the presence of triethylamine in dichlor-

omethane at ambient temperature, providing terminal-

acetylated hyperbranched poly(ethylene glycol)

derivatives containing diethylene and triethylene

glycols and 3,5-dioxybenzoate branching units with

Tg values of 276 and 259 K, respectively. Again, no

evidence of melting transitions was observed in the

DSC traces of the acetylated hyperbranched poly-

mers. The IC of the polymeric electrolytes is not only

affected by the testing temperature, salt concentration

and the chain length of EG, but it is also affected by

the sort of salt. Under the same conditions, the

polymer with LiN(CF3SO2)2 salt exhibits lower Tg

and somewhat higher conductivity compared with that

using LiCF3SO3, attributed to the greater mobility of

the polymer chains with the LiN(CF3SO2)2 salt

because the large and flexible (CF3SO2)2N2 ion can

act as a plasticizer for the polymer matrix. For the

hyperbranched polymer with triethylene glycols-

LiN(CF3SO2)2 system, the IC is 4.9 £ 1027 S cm21

at 30 8C and increases to 4.17 £ 1025 S cm21 at 80 8C

with [Liþ]/EG of 1.2.

The influences of the terminal groups, the length of

the EG unit, the composites of the linear polymeric

electrolytes blended, and the addition of filler on the

properties of the hyperbranched polymeric electro-

lytes were systematically investigated by Itoh and

coworkers [297–301]. By compared with hyper-

branched poly[bis(diethylene glycol)benzoate]

capped with acetyl groups (HP65 in Scheme 68),

hyperbranched poly[bis(diethylene glycol)benzoate]

capped with 3,5-bis[(30,60,90-trioxodecyl)oxy]benzoyl

groups (HP66) exhibited higher ionic conductivity

(7 £ 1024 S cm21 at 80 8C and 1 £ 1026 S cm21 at

30 8C) in the salt of LiN(CF3SO2)2 [297]. The

hyperbranched HP66 electrolyte showed an electro-

chemical stability window of 4.2 V at 70 8C and was

stable until 300 8C. Increasing the length of EG

Table 8

The monomers and salts used in the preparation of ion-conducting materials.

Monomer Salt Tg (K) IC £ 105 (S cm21) Reference

LiClO4 255 ðn ¼ 1Þ; 268 ðn ¼ 2Þ;

234 ðn ¼ 5Þ

7.0 (333 K),

1.0 (303 K)

[295]

LiCF3SO3,

LiN(CF3SO2)2

276 ðn ¼ 1Þ;

259 ðn ¼ 2Þ

4.17 (353 K),

0.05 (303 K)

[296–301]

LiClO4 1.74 (333 K),

0.14 (298 K)

[302]

LiClO4 63.0 (333 K),

0.66 (293 K)

[303]


segments in the terminal-acetylated macromolecular

unit to 6 ðn ¼ 5Þ; resulted in a hyperbranched polymer

electrolyte with LiN(CF3SO2)2 had a maximum

conductivity of 9 £ 1025 S cm21 at 80 8C with a

[Liþ]/[repeat unit] ratio of 0.6. Interestingly, addition

of hyperbranched HP65 to the system of linear PEO

and LiN(CF3SO2)2 salt can also improve the lithium

ionic conductivity and lithium/electrolyte interfacial

performance. The blend-based polymer electrolyte

with a HP65/PEO ratio of 20/80 in wt% and

[LiN(CF3SO2)2]0.125 showed a extremely high ionic

conductivity (8.1 £ 1024 S cm21 at 80 8C and

3.8 £ 1025 S cm21 at 30 8C), with an electrochemical

stability of about 4.9 V [298,299].

Composite polymer electrolytes based on PEO,

HP65, BaTiO3 (as a ceramic filler), and LiN(CF3SO2)2

salt were fabricated, and investigated as the electrolyte

for all solid-state lithium polymer batteries. The

optimized composite polymer electrolyte, [(PEO-

20 wt% HP65)12(LiN(CF3SO2)2)]–10 wt% BaTiO3,

in which PEO with a Mn of 600,000, HP65 with a Mn of

15,000 and BaTiO3 with a particle size of 0.5 mm were

employed, showed ionic conductivities as high as

5.2 £ 1023 S cm21 at 80 8C and 2.6 £ 1024 S cm21 at

30 8C, exhibited an electrochemical stability window

of 4.0 V, and was stable to 312 8C in air [300]. In

addition, another kind of composite polymer electro-

lytes with HP65, an inset ceramic filler such as a-

LiAlO2 or g-LiAlO2, and LiN(CF3SO2)2 salt were

prepared via solvent casting method. It was observed

that both nanosized fillers improved the mechanical

properties, ionic conductivities and lithium ion trans-

ference numbers of the hyperbranched polymer

electrolytes. The a-LiAlO2 filler was more effective

for improving the electrochemical compatibility with

a lithium metal electrode, while the g-LiAlO2 filler

was more efficient in enhancing the mechanical

properties of the hyperbranched polymer-based elec-

trolytes [301].

Hong et al. [302] synthesized hyperbranched

polyurethanes with EG units by polycondensation

of AB2 monomers 3,5-bis(20-hydroxy ethyleneox-

y)benzoyl azide (179) and 3,5-bis[(50-hydroxy-30-

oxopentyl)oxy]benzoyl azide (180), and prepared

composite polymer electrolytes using hyper-

branched polyurethanes, linear polyurethanes and

LiClO4 as raw materials. The IC of the composite

electrolytes could approach 1.35 £ 1026 S cm21 at

25 8C and 1.74 £ 1025 S cm21 at 60 8C for a ratio

of [Liþ]/[EG] (c) equal to 1/4.

The hyperbranched poly(glycidol) (PG) made

from monomer 19 was also applied as a

substrate for the composite polymer electrolyte

with LiClO4 salt [303]. The IC of the

composite reached 6.6 £ 1026 S cm21 at 20 8C

and 6.3 £ 1024 S cm21 at 60 8C.

Nishimoto et al. [304] prepared ethylene oxide-

based network polymer electrolytes with hyper-

branched ether side chains. The highest IC of the

electrolytes approached 1 £ 1024 S cm21 at 30 8C

and 1 £ 1023 S cm21 at 80 8C with lithium bis(tri-

fluomethylsulfonyl)imide (LiTFSI) as the salt.

5.3. Nanomaterials and biomaterials

5.3.1. Nanomaterials

Hyperbranched polymers and their substitutes can

be used as nanomaterials for host–guest encapsulation

and the fabrication of organic–inorganic hybrids, and

even directly used as nanoreactors for some reactions.

Amphiphilic hyperbranched polyglycerols (PGs)

with a hydrophilic core and a hydrophobic shell were

prepared by partial esterification of the pre-synthesized

hyperbranched PG with a fatty acid such as palmitoyl

Scheme 68.


chloride in the presence of pyridine, as shown in

Scheme 69 [305]. Water-soluble dyes such as Congo

red, bromophenol blue and rose Bengal can be

encapsulated irreversibly into the amphiphilic core–

shell nanocapsules via phase transfer from the water

phase to the organic phase (CHCl3). UV – Vis

measurements for the encapsulated nanoobjects

revealed that the dye was quantitatively extracted

from the aqueous layer into CHCl3 if the dye

concentration was lower than the saturation concen-

tration. The average encapsulation maximum

depended mainly on two factors: the molecular weight

of the hyperbranched core and the length of the alkyl

chains attached to the polymer scaffold. Interestingly,

the degree of substitution of terminal groups had only a

small influence on the encapsulation maximum. By

variation of the factors mentioned above, the encapsu-

lation maximum can be adjusted in the range of 0.7–

2.7 dye molecules per polymer molecule. Although the

encapsulation is irreversible, some chemical reactions

can still take place in the encapsulated core in the

organic phase. Comparison of these results with those

obtained from the linear analogs suggests that the

hyperbranched topology plays a crucial role in the

supramolecular encapsulation [306].

Encapsulation of sulfonated pincer-platinum(II)

complexes into amphiphilic nanocapsules was also

realized [307]. The incorporated Pt(II) complexes

showed catalytic activity in a double Michael addition

for homogeneous catalysis. Furthermore, PdCl2 or

Pd(OAc)2 were successfully encapsulated into nano-

capsules based on hyperbranched PG [308]. Stable

solutions of Pd colloids were prepared through

reduction of Pd(II) in organic solution. The metal

particle size increased with increasing the molecular

weight of the hyperbranched polymer. The metal

colloids were catalytically active.

Compositions of hyperbranched PPVs containing

different side alkoxy groups with nanosized cadmium

sulfide (CdS) were prepared and investigated using

static and dynamic fluorescence spectroscopies and

AFM [309]. Electrostatic force plays a key role in the

behavior of these compositions, with the interaction

between PPV and CdS particles controlled by the

chain length of side alkoxy groups. The presence of

hyperbranched PPV can efficiently decrease the self-

aggregation of nanosized CdS particles.

Hyperbranched polymer layered silicate nanocom-

posites were made using a hydroxy-terminated hyper-

branched polyester (HP67 in Scheme 70), prepared by

condensation of 2,2-bis-hydroxymethyl propionic acid

(bis-MPA) with a tetrafunctional ethoxylated pentaer-

ythritol core as the organic phase and sodium

montmorillonite (NaþMMT) as inorganic silicate

layers in deionized water [310]. WAXS measurements

showed that the silicate layer basal spacing could be

increased from 2.5–2.8 nm to 3.6–3.9 nm by increas-

ing the molecular weight of the hyperbranched

polyester (1.06 nm for the as-received NaþMMT).

Significantly, the nanocomposites can be redispersed in

organic solvent and that the functional groups in

hyperbranched polymers remain active, as demon-

strated by the reaction of the composites with methyl

diphenyl diisocyanate to produce a polyurethane net-

work. The initial exfoliated state of the silicate layers

did not change on incorporation of the polyurethane.

Hedrick et al. [311] prepared inorganic–organic

hybrid materials from NMP solutions of

Scheme 69.


a precondensed poly(silsesquioxane) (181 in Scheme

70) and the relevant hyperbranched polymers (HP68

and HP69 in Scheme 70) containing 4% water and 2%

base. In the hybrids, the content of hyperbranched

macromolecules was maintained at about 20 wt%. The

thermal stabilities of the composites were comparable

to that of the pure inorganic material 181. On the other

hand, the nature of the terminal groups of the

hyperbranched polymers had a strong effect on the

phase separation and morphology of the hybrids. For

example, the size scale of phase separated domains was

less than 50 nm for trimethoxysilyl-terminated HP69,

while that for phenol-terminated polymer was in the

order of 1–1.5 mm.

Mesoporous magnetoceramic materials were suc-

cessfully prepared using a hyperbranched organome-

tallic poly[1,10-ferrocenylene(n-alkyl)silyne] as

precursors (such as HP70 in Scheme 70) [312,313].

It was found that (1) the ceramization yield

increased with decreasing alkyl chain length of

the hyperbranched polymer precursors; (2) the

hyperbranched polysilynes are superior to their linear

analogs with respect to the pyrolytic conversion to

inorganic networks and the retention of elemental iron

in the ceramic materials; (3) a three-dimensional

mesoporous network of nanoclusters can be fabricated

with the simultaneous evaporation of volatile organics

and agglomeration of inorganic elements in

the pyrolysis of HP70; (4) the resulting iron silicide

nanocrystals made from HP70 exhibit a high magne-

tizability and a negligibly small hysteresis loss.

Copolymerization of 1-caprolactone with bis(hy-

droxymethyl)-substituted 1-caprolactone monomer 21

in a feed ratio of 4/1 in the presence of Sn(Oct)2

gave a hyperbranched aliphatic copolyester with a

DB of 0.15 and a molecular weight of 8000 g/mol

ðPDI ¼ 2:81Þ: The hyperbranched polyesters were

observed to be superior materials for templating

nanostructures in organosilicates, and a porous

organosilicate film derived from a hybrid containing

30 wt% polyester with an average pore size of 200 A

had been prepared [314]. As novel templating agents,

hyperbranched polyesters showed several merits, such

as higher solids content solutions, higher polymer

compositions in solution and better film quality than

obtained with linear and star-shaped polyesters.

Sol–gel processing of both linear and hyper-

branched alkoxy-substituted polycarbosilanes of

the type ‘[Si(OR)2CH2]n (R ¼ Me or Et)’ led to

cross-linked polycarbosilane/siloxane hybrid poly-

mers [315]. The molecular structure of these hybrid

gels and their pyrolysis to silicon oxycarbide ceramics

has been studied.

Hyperbranched polymers can also be utilized in

nanoimprint lithography [316]. A fascinating appli-

cation of the nanoimprint lithography technique is to

Scheme 70.


fabricate so-called quantum magnetic disks, compris-

ing single magnetic domain bits surrounded by a non-

magnetic material. Lebibet al. [316,317] employed the

commercially available hyperbranched poly(amide

ester) Hybrane, prepared by polycondensation of cyclic

anhydrides with diisopropanolamine as the top ima-

ging resist to control the critical dimension in trilayer

nanoimprint lithography. Dot arrays of 100 nm with a

critical dimension control accuracy better than 10 nm

were fabricated. Magnetic Co dot arrays with different

diameters and thickness were made with the same

mold. Compared with the frequently used PMMA, the

hyperbranched polymer showed higher etch resistance.

Recently, the technique has been applied at room

temperature and low-pressure, using Hybrane HS2550,

a semi-crystalline hyperbranched resist polymer, and a

high-density pattern replication with graftings of

75 nm line and spacing has been realized [317].

Hyperbranched polyesters derived from bis-MPA

and 4,4-bis(hydroxyphenyl)valeric acid have been

used as the matrix polymers for molecular imprinting

to cope with the major drawbacks resulted from

the conventional crosslinked imprinted polymers

[318].

5.3.2. Biomaterials

Because low-cost and well-defined hyperbranched

polymers with multifunctional terminal groups and

narrow polydispersity are available by improving

synthesis methodology and techniques, hyperbranched

polymers are receiving increasing attention in bioma-

terials application [319]. In this field, hyperbranched

polymers can play two main roles: biocarriers and

biodegradable materials. As carriers, hyperbranched

macromolecules can offer their interior or peripheral

functional groups to covalently fix bioobjects, or

depending on their core–shell architecture, to seques-

ter guest molecules. Some monomers used to prepare

hyperbranched polymeric biomaterials are summar-

ized in Scheme 71.

Scheme 71.


Hyperbranched aromatic polyamides as potential

supports for protein immobilization have been

prepared by self-condensation of AB2 monomers

182 and 183, or by polymerization of reactant pairs

(A2 þ B3, A2 þ B4 or A3 þ B3, with the correspond-

ing monomers being 22, 24, 184, 185, 186, 187,

respectively) [320]. A rigid structure of the

resulting hyperbranched polyamides is required for

their use as enzyme-supporting materials, particularly

in biotechnological processes with high flow rates.

Using 1-ethyl-3-(30-dimethylaminopropyl)carbodii-

mide hydrochloride as a coupling agent, a-amylase

was covalently attached to carboxylic acid-terminated

hyperbranched polymers. Evaluation of enzyme

activity revealed that the hyperbranched samples

with larger ‘holes’ in the structure or higher distance

between the trifunctional branching points (e.g. the

polymers made from 22 þ 186, or 184 þ 187) had a

greater affinity for the substrate and lower enzymatic

activity, while the samples with more compact

structure (e.g. the polymers made from 22 þ 24, or

22 þ 185) showed a weaker substrate affinity and

higher catalytic efficiency. Significantly, high bioac-

tivity retention was found for all the samples analyzed

three and six months after the binding reaction.

Although a decrease of the enzymatic activity was

observed for both the immobilized and the free

enzyme at pH 4.7 and 9.0, the residual activity of

the former was considerably higher than that of the

latter at pH 9.0. Therefore, hyperbranched polyamides

are suitable potential supports for protein immobiliz-

ation, and may open new perspectives for the

development of enzyme-based bioobjects with tuned

binding affinity, structural stability and catalytic

capability.

Steroidal ketones have been covalently linked to

the periphery hydroxyl groups on a hyperbranched PG

polymer support [319].

Park et al. [321] synthesized a hyperbranched

polymer having interior tertiary amino groups and

biodegradable units by bulk polymerization of

monomer 83 in the presence of core moiety 188.

The resulting hyperbranched poly(amine ester)s

showed Mns of 9100–11,400 determined from

SEC with PS standard and DBs of 0.58–0.62

calculated from 13C NMR spectra. Then the methyl

ester-terminated product was modified with benzyl

N-(2-hydroxyethyl)carbamate, followed by catalytic

hydrogenolysis with H2 over Pd/C, affording

primary amino-terminated hyperbranched polymer.

It was observed that the hyperbranched poly(amine

ester) with terminal amino groups is minimally

toxic and shows relatively high transfection

efficiency for DNA.

Oligosaccharides with branched architecture are

found at natural cell surfaces and in intercellular

systems. Chemical synthesis of hyperbranched ami-

nopolysaccharides has been achieved by acid-cata-

lyzed polycondensation of AB2 saccharide monomer

189, with 10-camphorsulfonic acid as a catalyst [322].

The as-prepared hyperbranched polysaccharide was

soluble in highly polar organic solvents such as DMF,

DMSO and pyridine, but insoluble in the organic

solvents of low polarity or water. The Mn of the

polymer was 6300 detected with SEC with PS as

standard and DMF as eluent. Interestingly, DB of the

resulting polymer calculated from 1H NMR was found

to approach 1. So almost perfect-branched hyper-

branched polymer was obtained.

Biodegradable hyperbranched polyesters were

prepared through one-pot copolymerization of L-

lactide (190) with DL-mevalonolactone (191), using

tin 2-ethylhexanoate as a catalyst [323], or poly-

condensation of AB2 macromonomer 193 as well as

copolymerization of 193 with other macromonomers

based on monomer 190, 192 or 194 [324]. Polym-

erization of 193 in the presence of core moiety 195

gave biodegradable hyperbranched elastomers with a

dendrimer-like structure [324,325].

5.4. Supramolecular chemistry

Supramolecules represent compounds beyond

molecules, with an order organized by non-covalent

interactions. As novel building blocks, hyperbranched

macromolecules might play important roles in the

following supramolecular areas: (1) self-assembly

films and layers; (2) core–shell amphiphiles; (3) self-

association objects; (4) macroscopic molecular

self-assembly; (5) liquid-crystalline materials; (6)

host–guest encapsulation.

An aldehyde-terminated hyperbranched PPV made

from monomers 31 and 32 was used as a self-

assembling building material [326,327]. The structure

of the hyperbranched PPV (HP71) is shown in

Scheme 72. The dehydration between aldehyde


groups of HP71 and alcohol groups of a pretreated

quartz slide in the presence of DCC resulted in

covalently linked films on the substrate. Then ordered

homogeneous self-assembled films were obtained in

situ by immersing the modified substrate in a chloro-

form solution of HP71. The morphology and aggre-

gated grain size of the self-assembled objects

examined by AFM depended on the immersion time

and the HP71 concentration. For a concentration of

3.3 £ 1025 M, the average grain size decreased from

143 to 50 nm when the immersion time was prolonged

from 1 day to 3 days. Investigations using AFM and

spectroscopy techniques showed that the self-assem-

bly film linked through covalent bond was more

homogenous and stable than the spin-coated film.

Excimers of HP71 were observed for the self-

assembled film, indicating strong interactions

between the excited state of the hyperbranched

macromolecules in the solid state.

Tang and coworkers [328–330] prepared hyper-

branched polyester with carboxylic end groups by

polycondensation of 5-hydroxyethoxyisophthalic acid

(196) with Zn(OAc)2 as a catalyst (Scheme 73). Self-

assembled films were successfully formed via an

electrostatic layer-by-layer adsorption approach

[331], from both aqueous solution and water–THF

mixture, using poly(diallyldimethylammonium chlor-

ide) as a polycation and HP72 as a polyanion with a

freshly treated quartz slide as the substrate [328]. The

self-assembly procedure was monitored by UV–Vis

spectroscopy and contact angle measurements. A

linear relationship was observed between the absor-

bance at 215 nm and the number of bilayers,

suggesting the same thickness for each assembled

bilayer. After four dipping cycles, the contact angle of

the surface increased from around 10–20 to 558,

indicating a dramatic change of the surface

hydrophilicity.

Pyrene-labeled hyperbranched amphiphiles with

hydrophilic core and hydrophobic shell were prepared

by reaction of hyperbranched poly(sulfone amine),

HP18, with 4-(1-pyrene)butyryl chloride (197), and

then with palmitoyl chloride in the presence of

triethylamine, as shown in Scheme 74 [332]. Fluor-

escence characterization exhibited that the core–shell

amphiphiles could self-associate to form micelles in

aqueous solution, with the excimer-to-monomer

intensity ratio ðIE=IMÞ increasing with increasing

attached palmitoyl units. The critical association

concentration (CAC) for the hyperbranched amphi-

philes is 2-5 g/l at pH , 7, or 2–3 g/l in a basic

solution ðpH ¼ 8:5Þ: Moreover, the hyperbranched

poly(sulfone amine)s without the hydrophobic shell

can associate in aqueous solution through hydrogen

bonds, as monitored with both fluorescence label and

probe techniques [333,334]. Significantly, the self-

association ability of the hyperbranched polymers

depends on their DBs, with the tendency for

association in increasing with the DB [333]. This

phenomenon may be partially attributed to the

different architecture of hyperbranched poly(sulfone

amine)s with various DBs, and partially to different

inter- and intra-molecular hydrogen bonds in the

hyperbranched macromolecules.

Scheme 72.

Scheme 73.


Pyrene-labeled hyperbranched poly(ethylene

imine) (PEI) containing different amounts of pyrene

per polymer was prepared by reaction of PEI with 1-

pyrenecarboxaldehyde [335]. The interaction of

the as-prepared pyrene-labeled PEI with the anionic

surfactant SDS in aqueous solution was also studied

by steady-state fluorescence [336]. The monomer

emission of pyrene increased with increasing SDS

concentration, indicating that the SDS molecules

protect pyrene fluorescence from quenching by

forming a polymer-bound micelles at the sites of the

pyrene groups.

An example of a non-covalent hyperbranched

polymer formed by self-assembly of AB2 monomer

via coordination interactions is given in Scheme 75,

where the counter anion X2 is BF42, ClO4

2, CF3SO3,

p-MeC6H4SO32 or BPh4

2. Removal of acetonitrile

through repeated evaporation and redissolving the

residue in nitromethane leads to intermolecular

coordination between cyano groups and Pd, forming

hyperbranched coordination polymer HP73 [337].

Quasi-elastic light-scattering, AFM and transmission

electron microscopy revealed that the size of the

assembled hyperbranched spheres changed from 100

to 400 nm with variation of the building block

structure and/or the counter anions.

Both thermotropic liquid crystalline hyper-

branched polyesters [338–341] or polyethers [52,

53] and lyotropic liquid crystalline hyperbranched

polyamides [79 – 82,159,342] made from ABn

monomers or specific monomer pairs have been

achieved, and their supramolecular behaviors have

been studied. Scheme 76 listed some AB2 mono-

mers used to synthesize thermotropic liquid crystal-

line hyperbranched polymers.

Because of the three-dimensional character of

hyperbranched macromolecules, some guest mol-

ecules can be encapsulated into their interior

cavities. Therefore, hyperbranched polymers can

be applied in the supramolecular encapsulation

Scheme 74.

Scheme 75.


as host macromolecular boxes. The related contents

have been mentioned in the ‘nanomaterials’ section

of this article.

5.5. Patterning of hyperbranched polymer films

Patterning of polymer films at micron or even

submicron resolution is of critical technological

importance in the microelectronics industry [343].

Because hyperbranched polymers have many func-

tional groups, moieties with interesting optical,

electrochemical, biological, and mechanical properties

can be incorporated into the hyperbranched polymer

films. Thus, patterning of hyperbranched polymer films

on the substrates is receiving more and more attention.

Related techniques including template-based approach

and photolithography have been developed by Crooks

and coworkers [343–346]. The templates consist of

self-assembled monolayers fabricated by micro-con-

tact printing (mCP) [347,348], while photolithographic

patterning relies on a photomask.

Two typical approaches to pattern hyperbranched

polymer films on a substrate are outlined in Fig. 8. The

mCP (approach A) consists of three key steps: (1)

applying CH3(CH2)15SH (C16SH) to the poly(di-

methylsiloxane) (PDMS) stamp, followed by pattern-

ing of the Au substrate by manual application of the

stamp to the surface for a short time; (2) exposing

the C16SH-patterned substrate to a 1 mM ethanolic

solution of HOOC(CH2)15SH (MUA) for 1 min; (3)

activating the carboxylic acid groups of the MUA-

patterned portions by a reaction with a mixed anhydride

and thena,v-diamino-terminated poly(tert-butyl acry-

late) (H2NR-PTBA-RNH2), subsequent hydrolyzing

of the grafted PTBA layer with MeSO3H to afford the

first layer of PAA (1-PAA), and yielding a hyper-

branched PAA films after two more cycles of

activation, grafting and hydrolysis. As a consequence,

the resulting polymer pattern is a negative image of the

stamp. On an inorganic substrate such as Au, polymer

layers with a thickness of 25 nm and critical lateral

dimensions in the order of 1 mm can be patterned

through the mCP approach. The method has been

extended to pattern hyperbranched polymer films on

Scheme 76.

Fig. 8. Two approaches to patterning of hyperbranched polymer

films.


organic substrate such as PE [345]. Significantly, the

fidelity of the underlying hyperbranched PAA patterns

is still maintained after grafting PEG on the PAA films

[347,348]. As pointed out by Crooks [343], however,

this approach has some disadvantages although it is a

fast, and flexible method for patterning polymer

surface. For example, the performance of multiple

patterning steps on a single substrate is very difficult,

and it is inconvenient to prepare a patterned surface

having two sorts of polymers with the mCP.

A method based on photolithography was devel-

oped to resolve the problems arising from the

template-based approach. For example, patterning of

multiple fluorescent dyes on hyperbranched PAA thin

films was achieved using photoacid-based lithography

(approach B) via three steps [349]: (1) covalent

grafting of hyperbranched PTBA thin films on a Au

substrate and then overcoating the polymer films with

a layer of photoacid, (2) utilization photolithography

to generate acid in the exposed region and catalyzed

hydrolysis of PTBA to form PAA, and (3) chemical

modification of the PAA regions with dyes.

The patterns fabricated can serve as templates to

segregate viable mammalian and bacterial cells.

Consequently, preparation of more complex struc-

tures by the patterning approaches is anticipated, such

as ensembles of organized tissues, including nerves

and blood vessels.

5.6. Coatings

Hyperbranched polymers have been used as the

base for various coating resins, such as powder

coatings [350,351], high solid coatings [352], flame

retardant coatings [353] and barrier coatings for

flexible packaging [354], depending on their high

solubility, low viscosity and abundant functional

groups.

The most widely studied hyperbranched polymers

in the field of coatings are the two products

commercially available at the time of this review:

Boltorne (hyperbranched aliphatic polyesters) [350,

352,354–358] and Hybranee (hyperbranched polye-

ster-amides) [351,359]. For the purpose of UV-curing,

the hyperbranched polymers are generally end-capped

with methacrylate or acrylate groups [352–358,360].

Resins based on hyperbranched polymers have lower

viscosities and higher curing rates than those of linear

unsaturated polymers.

5.7. Modifiers and additives

Based on their unique properties, hyperbranched

polymers can be applied as tougheners for thermo-

sets [361–369], curing, cross-linking or adhesive

agents [370– 372], dye-receptive additives for

polyolefins [373,374], compatilizers [375], disper-

sers [376], processing aids, and rheology modifiers

or blend components [48,377–383]. Table 9 lists

some hyperbranched polymers and their

applications.

The Boltorne three-generation hyperbranched

polyesters can act as outstanding tougheners in

epoxy matrix composites, and they can induce more

than a two-fold increase in the critical strain energy

release rate GIC for both low and highly cross-linked

matrices, without affecting either the viscosity of the

uncured resins or the thermomechanical properties of

the cured material. Until now, no other modifiers

could meet the challenges of property improvement

without loss of the general performance of the resin

system [361]. A quantitative thermodynamic theory

model for the prediction of phase equilibrium

behavior of thermoset-reactive modifier polymer

blends has also been suggested [366,384]. However,

the Boltorne hyperbranched polyesters cannot pro-

vide more efficient toughness for bismaleimide (BMI)

thermosets than a linear low molar mass thermoplastic

[363,364].

As early as 1992, Kim and Webster [48] had

pointed out that hyperbranched polymers could be

useful as polymer rheology control agents, and the

melt viscosity of PS blend decreased dramatically

after addition of a trace amount (about 5%) of bromo-

terminated hyperbranched polyphenylene to the PS

blending system, without affecting the thermal

stability of PS. Mulkern et al. [379] reported that

Boltorne-G4 is an excellent processing additive for

PS. The hyperbranched polyesters behave as lubri-

cants during processing, and as self-compatibilizing

toughening agents in the final formation of the blend.

A considerable drop in the blend viscosity of PS or

styrene maleic anhydride (SMA) copolymer was

immediately observed in addition of the hyper-

branched polymer modifier.


In the tubular film blowing process of linear low-

density polyethylene (LLDPE), Boltorne-H30 hyper-

branched polyester successfully acted as a processing

aid, and sharkskin was eliminated with no significant

influence on other physical properties of the LLDPE

films [378]. In processing, the hyperbranched polymer

has a tendency to migrate to the surface, leading to a

hyperbranched polymer-rich surface, which creates

the opportunity to tailor the surface properties for

various potential applications.

PP is a versatile and widely used polymeric

material. However, PP does not accept dyes, owing

to its non-polar structure as well as its high crystal-

linity, resulting from the high stereo-regularity of the

PP. The dyeability of PP with CI. Disperse Blue 56

can be markedly enhanced through the incorporation

of hyperbranched macromolecules such as the

Hybrance PS2550 (hyperbranched polyester-amide)

into PP prior to fiber spinning [373]. The amphiphilic

hyperbranched aromatic polyester prepared by poly-

condensation of 3,5-dihydroxybenzoic acid followed

by end group modification with dodecanoyl chloride

can also be used as a dye carrier in blends of PP or

high-density polyethylene (HDPE), with similar

Table 9

The hyperbranched polymers used as modifiers and additives

Hyperbranched polymer Role Blended compound References

Boltorne Toughener Epoxy resins [361,367]

Toughener Bismaleimide [363,364]

Toughener Vinylester–urethane hybrid [368,369]

Modifier PS/PS–SMA [379]

Modifier Diglycidyl ether of bisphenol-A [381]

Processing aid LLDPE [377,378]

Compatilizer PP/PA-6 blends [375]

Curing additive [370]

Processing aid PET [380]

Hybrane PS2550 Dyeing additive PP [373]

Dye carrier PP/PE [374]

Disperser Carbon nanotube [376]

Processing aid PC [382]

Processing aid bis(maleimide) [383]


dynamic–mechanical behavior of the blends com-

pared to that of the pure polyolefins [374].

To understand the physical properties of hyper-

branched macromolecular blends, the melt and

solution rheological behaviors of polymer blends

containing hyperbranched polymers with different

molecular weights or generations were investigated

[385–388]. Study of the rheological features of melt

processed hyperbranched polyesters (Boltorn Hx

series dendritic polymers) and their blends

indicated that the lower generation samples showed

shear-thinning behavior, while the higher generation

ones exhibited Newtonian behavior. Blends consist-

ing of two hyperbranched polyesters showed

only Newtonian characteristics in both steady

shear and oscillatory shear conditions if at

least one of the components behaved as a Newtonian

fluid [385].

5.8. Other applications

Applications of hyperbranched polymers for gas

and solution separation as well as chemical sensors

have been suggested.

Hyperbranched polyimides were used as gas

separation materials [389]. The synthesis route and

chemical structure of the hyperbranched polyimides

used are shown in Scheme 4. By controlling the

monomer feed ratio and manner of the monomer

addition, both amine-terminated and dianhydride-

terminated polyimides were obtained. Reaction of

the terminal groups with a difunctional crosslinking

agent afforded hyperbranched polyimide films. The

gas permeability coefficients of the as-fabricated films

were mainly affected by three factors: (1) the nature

of terminal groups of hyperbranched polymer; (2)

the crosslinking density of the film; (3) the ‘flexibility’

of crosslinking agent. The amino terminal

groups, lower crosslinking density and ‘rigid’ cross-

linking agent (e.g. terephthaldehyde, TPA) were

favorable to improved gas permeability coefficients.

A better separation performance was obtained for the

TPA-crosslinked hyperbranched polyimide mem-

branes than for their linear analogs or many other

linear polymeric membranes. For example, one

amine-terminated hyperbranched polyimide

membrane crosslinked with TPA exhibited fairly

high CO2/N2 separation performance and good

selectivity, i.e. PCO2¼ 65 barrier and PCO2

=PN2¼ 30

at 1 atm and 35 8C.

Hyperbranched PG, hyperbranched polyester Bol-

torne-H20, hyperbranched poly(ester amide)

Hybrane H1500, made from 1,2-cyclohexanedicar-

boxylic anhydride and diisopropanolamine, and

hyperbranched poly(ester amide) Hybrane S1200,

made from succinic anhydride and diisopropanola-

mine, are potentially useful in extractive distillation

and solvent extraction [390,391]. It was found that

hyperbranched polyglycerol and Hybrane S1200 had

remarkable separation efficiencies for the ethanol–

water azeotropic mixture.

Melt polycondensation of AB2 monomers 3,5-

trimethylsiloxyl benzoyl chloride, 3,5-diacetoxy ben-

zoic acid, and 5-acetoxyphthalic acid resulted in three

hyperbranched polyesters with the same backbones

and different end groups (e.g. OH, COOH, and OAc).

The hyperbranched polyesters proved to be promising

materials for chemical sensors, able to calibrate and

discriminate a series of alcohols and different

halogenated hydrocarbons [392]. In addition, Berg-

breiter and Crooks [393] reported a polymeric

‘molecular filter’ for chemical sensors, consisting of

hyperbranched PAA films and b-cyclodextrin

receptors.

6. Concluding remarks

In spite of the fact that highly branched topologies

and patterns have been widely observed in both

abiotic system and the biological world for tens of

billions years, intentionally synthesized hyper-

branched polymers still represent a new kind of

material with promising, attractive properties and

potential applications. Until now, hyperbranched

macromolecules could be approached through SMM

and DMM. In SMM, one type of ABn or latent ABn

molecules is adopted as the raw monomers. As a

consequence, hyperbranched polymers are available

via polycondensation of ABn monomers, SCVP,

SCROP, or PTP. On the other hand, hyperbranched

macromolecules also can be prepared by polycon-

densation of two types of A2 and B3 monomers,

‘A2 þ B3’ methodology, or by polymerization of

unsymmetrical monomer pairs based on in situ

formation of ABn intermediates, CMM. Through


CMM, hyperbranched polymers with alternating

specific bonds in the frameworks can be conveniently

produced in a large scale, without gelation, opening an

avenue for the functionalization and application of

hyperbranched polymers.

A hyperbranched polymer can be modified and

functionalized from its core to periphery by end

capping, terminal grafting, surface growing, hyper-

grafting and hybrid blending, achieving tailor-made

properties and complex structures. Hyperbranched

polymers and their derivatives are potentially useful

in the areas of supramolecular chemistry, nanoscience

and technology, biomaterials, polymer electrolytes,

coatings, additives, optical and electronic materials,

and so forth. Because the properties of hyperbranched

polymers such as solubility, polarity, capacity,

crystallinity, chain entanglement, melt and solution

viscosity or rheology, thermal stability as well as

rigidity (glass transition temperature) can be tailored,

more and more fascinating materials and devices

based on hyperbranched polymers will be success-

fully developed and fabricated in the future.

However, one should recognize that extensive

research of hyperbranched polymers, particularly the

aspect of functionalization and application, is still in

its infancy, and the main object to apply hyper-

branched polymers in industry fields is still a dream.

Thus, the opportunities for development space are

unlimited.

From our point of view, the following directions

deserve attention in the near future: (1) development

of new synthesis strategies and approaches based on

low cost for the whole system and good control of

the process and product; (2) preparation of novel

highly branched polymeric materials with hybrid

architectures via covalent linking or supramolecular

self-assembling (e.g. to obtain linear-hyperbranched,

hyperbranched – hyperbranched, hyperbranched –

polymer brush, or hyperbranched–dendritic hybrid

materials); (3) tailoring the properties of hyper-

branched macromolecules by living polymerization,

inorganic–organic blending, molecular encapsula-

tion, and other methods and techniques; (4) the

opening of new interdisciplinary application fields for

hyperbranched polymers, especially fields combining

hyperbranched polymers with nanotechnology,

micro-device technology, biology, supramolecular

chemistry, or single-molecule science.

Acknowledgements

This work was supported by the National Natural

Science Foundation of China (Nos 50233030,

20274024 and 20304007). The authors are much

indebted to Prof. Shoukuan Fu of Fudan University

(People’s Republic of China) for constructive discus-

sions and suggestions and Prof. Dr E. Goethals of

Universiteit Gent (Belgium) for providing reference

38 and helpful discussions.

References

[1] Frechet JMJ, Tomalia DA. Dendrimers and other dendritic

polymers. West Sussex: Wiley; 2001.

[2] Tomalia DA, Frechet JMJ. Discovery of dendrimers and

dendritic polymers: a brief historical perspective. J Polym

Sci, Part A: Polym Chem 2002;40:2719–28.

[3] Tomalia DA, Naylor AM, Goddard III WA. Starburst

dendrimers: molecular-level control of size, shape, surface

chemistry, topology, and flexibility from atoms to macro-

scopic matter. Angew Chem Int Ed 1990;29(2):138–75.

[4] Frechet JMJ. Functional polymers and dendrimers: reactiv-

ity, molecular architecture, and interfacial energy. Science

1994;263:1710–5.

[5] Caminade AM, Maraval V, Laurent R, Majoral JP.

Organometallic derivatives of phosphorus-containing den-

drimers. Synthesis, properties and applications in catalysis.

Curr Org Chem 2002;6(8):739–74.

[6] Turnbull WB, Kalovidouris SA, Stoddart JF. Large oligo-

saccharide-based glycodendrimers. Chem Eur J 2002;8(13):

2988–3000.

[7] Stiriba SE, Frey H, Haag R. Dendritic polymers in

biomedical applications: from potential to clinical use in

diagnostics and therapy. Angew Chem Int Ed 2002;41(8):

1329–34.

[8] Twyman LJ, King ASH, Martin IK. Catalysis inside

dendrimers. Chem Soc Rev 2002;31(2):69–82.

[9] Romagnoli B, Hayes W. Chiral dendrimers—from architec-

turally interesting hyperbranched macromolecules to func-

tional materials. J Mater Chem 2002;12(4):767–99.

[10] Hirsch A, Vostrowsky O. Dendrimers with carbon rich-cores.

Top Curr Chem 2001;217:51–93.

[11] Zimmerman SC, Lawless LJ. Supramolecular chemistry of

dendrimers. Top Curr Chem 2001;217:95–120.

[12] van Manen HJ, van Veggel FCJM, Reinhoudt DN. Non-

covalent synthesis of metallodendrimers. Top Curr Chem

2001;217:121–62.

[13] Kreiter R, Kleij AW, Gebbink RJMK, van Koten G.

Dendritic catalysts. Top Curr Chem 2001;217:163–99.

[14] Ashton PR, Balzani V, Clemente-Leon M, Colonna B, Credi

A, Jayaraman N, Raymo FM, Stoddart JF, Venturi M.


Ferrocene-containing carbohydrate dendrimers. Chem Eur J

2002;8(3):673–84.

[15] Balzani V, Ceroni P, Juris A, Venturi M, Campagna S,

Puntoriero F, Serroni S. Dendrimers based on photoactive

metal complexes. Recent advances. Coord Chem Rev 2001;

219:545–72.

[16] Dykes GM. Dendrimers: a review of their appeal and

applications. J Chem Technol Biotechnol 2001;76(9):

903–18.

[17] Esfand R, Tomalia DA. Poly(amidoamine) (PAMAM)

dendrimers: from biomimicry to drug delivery and biome-

dical applications. Drug Discov Today 2001;6(8):427–36.

[18] Crooks RM, Zhao MQ, Sun L, Chechik V, Yeung LK.

Dendrimer-encapsulated metal nanoparticles: synthesis,

characterization, and applications to catalysis. Acc Chem

Res 2001;34(3):181–90.

[19] Froehling PE. Dendrimers and dyes—a review. Dyes

Pigments 2001;48(3):187–95.

[20] Wiesler UM, Weil T, Mullen K. Nanosized polyphenylene

dendrimers. Top Curr Chem 2001;212:1–40.

[21] Sekiguchi A, Lee VY, Nanjo M. Lithiosilanes and their

application to the synthesis of polysilane dendrimers. Coord

Chem Rev 2000;210:11–45.

[22] Gorman CB, Smith JC. Structure–property relationships in

dendritic encapsulation. Acc Chem Res 2001;34(1):60–71.

[23] Vogtle F, Gestermann S, Hesse R, Schwierz H, Windisch B.

Functional dendrimers. Prog Polym Sci 2000;25(7):

987–1041.

[24] Frey H, Schlenk C. Silicon-based dendrimers. Top Curr

Chem 2000;210:69–129.

[25] Smith DK, Diederich F. Supramolecular dendrimer chem-

istry: a journey through the branched architecture. Top Curr

Chem 2000;210:183–227.

[26] Astruc D, Blais JC, Cloutet E, Djakovitch L, Rigaut S, Ruiz J,

Sartor V, Valerio C. The first organometallic dendrimers:

designandredoxfunctions.TopCurrChem2000;210:229–59.

[27] Stoddart FJ, Welton T. Metal-containing dendritic polymers.

Polyhedron 1999;18(27):3575–91.

[28] Roovers J, Comanita B. Dendrimers and dendrimer–polymer

hybrids. Adv Polym Sci 1999;142:179–228.

[29] Caminade AM, Laurent R, Chaudret B, Majoral JP.

Phosphine-terminated dendrimers—synthesis and complexa-

tion properties. Coord Chem Rev 1998;178:793–821.

[30] Majoral JP, Caminade AM. Divergent approaches to

phosphorus-containing dendrimers and their functionaliza-

tion. Top Curr Chem 1998;197:79–124.

[31] Venturi M, Serroni S, Juris A, Campagna S, Balzani V.

Electrochemical and photochemical properties of metal-

containing dendrimers. Top Curr Chem 1998;197:193–228.

[32] Matthews OA, Shipway AN, Stoddart JF. Dendrimers—

branching out from curiosities into new technologies. Prog

Polym Sci 1998;23(1):1–56.

[33] Moore JS. Molecular architecture and supramolecular chem-

istry. Curr Opin Solid State Mater Sci 1996;1(6):777–88.

[34] Schluter AD, Rabe JP. Dendronized polymers: synthesis,

characterization, assembly at interfaces, and manipulation.

Angew Chem Int Ed 2000;39(5):864–83.

[35] Indirectly referred to the paper reported byKienle RH, Hovey

AG. The polyhydric alcohol–polybasic acid reactions.

I. Glycerol–phthalic anhydride. J Am Chem Soc 1929;51:

509–19.

[36] Kienle RH, van der Meulen PA, Petke FE. The polyhydric

alcohol–polybasic acid reactions. III. Further studies of the

glycerol–phthalic anhydride reaction. J Am Chem Soc 1939;

61:2258–68.

[37] Kienle RH, van der Meulen PA, Petke FE. The polyhydric

alcohol–polybasic acid reactions. IV. Glyceryl phthalate

from phthalic acid. J Am Chem Soc 1939;61:2268–71.

[38] Odian G. Principles of polymerization, 3rd ed. New York:

Wiley; 1991. p. 125–32.

[39] Flory PJ. Molecular size distribution in three dimensional

polymers. I. Gelation. J Am Chem Soc 1941;63:3083–90.


polymers. II. Trifunctional branching units. J Am Chem Soc

1941;63:3091–6.


polymers. III. Tetrafunctional branching units. J Am Chem

Soc 1941;63:3096–100.

[42] Walling C. Gel formation in addition polymerization. J Am

Chem Soc 1945;67:441–7.


polymers. V. Post-gelation relationships. J Am Chem Soc

1947;69:30–5.


polymers. IV. Branched polymers containing A–R–Bf21

type units. J Am Chem Soc 1952;74:2718–23.

[45] Kricheldorf HR, Zang QZ, Schwarx G. New polymer

syntheses. 6. Linear and branched poly(3-hydroxy-benzo-

ates). Polymer 1982;23:1821–9.

[46] Kim YH, Webster OW. Hyperbranched polyphenylenes.

Polym Prepr 1988;29(2):310–1.

[47] Kim YH, Webster OW. Water-soluble hyperbranched

polyphenylene: a unimolecular micelle? J Am Chem Soc

1990;112:4592–3.

[48] Kim YH, Webster OW. Hyperbranched polyphenylenes.

Macromolecules 1992;25:5561–72.

[49] Kim YH, Beckerbauer R. Role of end groups on the glass

transition of hyperbranched polyphenylene and triphenyl-

benzene derivatives. Macromolecules 1994;27:1968–71.

[50] Uhrich KE, Hawker C, Frechet JMJ, Turner SR. One-pot

synthesis of hyperbranched polyethers. Macromolecules

1992;25:4583–7.

[51] Miller TM, Neenan TX, Kwock EW, Stein SM. Dendritic

analogues of engineering plastics: a general one-step

synthesis of dendritic polyaryl ethers. J Am Chem Soc

1993;115:356–7.

[52] Percec V, Kawasumi M. Synthesis and characterization of a

thermotropic nematic liquid crystalline dendrimeric polymer.


[53] Percec V, Chu P, Kawasumi M. Toward willowlike thermo-

tropic dendrimers. Macromolecules 1994;27:4441–53.

[54] Hawker CJ, Lee R, Frechet JMJ. One-step synthesis of

hyperbranched dendritic polyesters. J Am Chem Soc 1991;

113:4583–8.


[55] Kambouris P, Hawker CJ. A versatile new method for

structure determination in hyperbranched macromolecules.

J Chem Soc, Perkin Trans 1993;1:2717–27.

[56] Wooley KL, Hawker CJ, Lee R, Frechet JMJ. One-pot

synthesis of hyperbranched polyesters. Polym J 1994;26:

187–97.

[57] Wooley KL, Frechet JMJ, Hawker CJ. Influence of shape on

the reactivity and properties of dendritic, hyperbranched and

linear aromatic polyesters. Polymer 1994;35:4489–95.

[58] Turner SR, Voit B, Walter F. Hyperbranched aromatic

polyesters. Polym Mater Sci Engng 1993;68:57–8.

[59] Turner SR, Voit B, Mourey TH. All-aromatic hyperbranched

polyesters with phenol and acetate end groups: synthesis and

characterization. Macromolecules 1993;26:4617–23.

[60] Turner SR, Voit B. Hyperbranched polyesters with car-

boxylic acid end groups. Polym Prepr 1993;34(1):79–80.

[61] Turner SR. Hyperbranched polyesters and polyamides.

Polym Mater Sci Engng 1996;74:437–8.

[62] Voit B, Turner SR. Synthesis and characterization of high

temperature hyperbranched polyesters. Polym Prepr 1992;

33(1):184–5.

[63] Turner SR, Walter F, Voit B, Mourey TH. Hyperbranched

aromatic polyesters with carboxylic acid terminal groups.


[64] Malmstrom E, Johansson M, Hult A. Review of hyper-

branched polyesters. Polym News 1997;22:128.

[65] Johansson M, Malmstrom E, Hult A. Synthesis, character-

ization, and curing of hyperbranched allyl ether–maleate

functional ester resins. J Polym Sci, Part A: Polym Chem

1993;31:619–24.

[66] Hult A, Johansson M, Malmstrom E, Sorensen K. Synthesis

and polymerization of liquid crystalline donor–acceptor

monomers. Macromolecules 1996;29:1649–54.

[67] Malmstrom E, Liu F, Boyd R, Hult A, Gedde UWG.

Relaxation processes in hyperbranched polyesters. Polym

Bull 1994;32:679–85.

[68] Malmstrom E, Johansson M, Hult A. Hyperbranched

aliphatic polyesters. Macromolecules 1995;28:1698–703.

[69] Malmstrom E, Hult A. Kinetics of formation of hyper-

branched polyesters based on 2,2-bis(methylol)propionic

acid. Macromolecules 1996;29:1222–8.

[70] Malmstrom E, Hult A. Hyperbranched aliphatic polyesters

based on bis-MPA and various polyol cores. Polym Mater Sci

Engng 1995;73:349–50.

[71] Magnusson H, Malmstrom E, Hult A. Structure buildup in

hyperbranched polymers from 2,2-bis(hydroxymethyl)pro-

pionic acid. Macromolecules 2000;33:3099–104.

[72] Trollsas M, Hedrick J, Mecerreyes O, Jerome R, Dubois P.

Internal functionalization in hyperbranched polyesters.

J Polym Sci, Part A: Polym Chem 1998;36:3187–92.

[73] Kricheldorf HR, Stoeber O, Luebbers D. New polymers

synthesis. 78. Star-shaped and hyperbranched polyesters by

polycondensation of trimethylsiyl 3,5-diacetoxybenzoate.


[74] Kricheldorf HR, Loehden G, Stoeber O. Telechelic, star-

shaped and hyperbranched aromatic polyesters. Polym Prepr

1995;36(1):749–50.

[75] Kricheldorf HR, Stukenbrock T. New polymer synthesis.

XCIII. Hyperbranched homo- and copolyesters derived from

gallic acid and b-(4-hydroxyphenyl)-propionic acid. J Polym


[76] Trollsas M, Hedrick JL. Hyperbranched poly(1-caprolac-

tone) derived from intrinsically branched AB2 macromono-

mers. Macromolecules 1998;31:4390–5.

[77] Uhrich KE, Boegeman S, Frechet JMJ, Turner SR. Solid-

phase synthesis of dendritic polyamides. Polym Bull 1991;

25:551–8.

[78] Kricheldorf HR, Bolender O. New polymer synthesis. 98.

Hyperbranched poly(ester-amide)s derived from naturally

occurring monomers. J Macromol Sci, Pure Appl Chem

1998;A35:903–18.

[79] Kim YH. Lyotropic liquid crystalline hyperbranched aro-

matic polyamides. J Am Chem Soc 1992;114:4947–8.

[80] Yang G, Jikei M, Kakimoto M. Synthesis and properties of

hyperbranched aromatic polyamides. Macromolecules 1999;

32:2215–20.

[81] Yang G, Jikei M, Kakimoto M. Successful thermal

self-polycondensation of AB2 monomer to form hyper-

branched aromatic polyamide. Macromolecules 1998;31:

5964–6.

[82] Ishida Y, Sun ACF, Jikei M, Kakimoto M. Synthesis of

hyperbranched aromatic polyamides starting from dendrons

as ABx monomers: effect of monomer multiplicity on the

degree of branching. Macromolecules 2000;33:2832–8.

[83] Bolton DH, Wooley KL. Synthesis and characterization of

hyperbranched polycarbonates. Macromolecules 1997;30:

1890–6.

[84] Hawker CJ, Chu F. Hyperbranched poly(ether ketones):

manipulation of structure and physical properties. Macro-

molecules 1996;29:4370–80.

[85] Morikawa A. Preparation and properties of hyperbranched

poly(ether ketones) with a various number of phenylene

units. Macromolecules 1998;31:5999–6009.

[86] Shu CF, Leu CM, Huang FY. Synthesis, modification, and

characterization of hyperbranched poly(ether ketones).

Polymer 1999;40:6591–6.

[87] Shu CF, Leu CM. Hyperbranched poly(ether ketone) with

carboxylic acid terminal groups: synthesis, characterization,

and derivatization. Macromolecules 1999;32:100–5.

[88] Spindler R, Frechet JMJ. Synthesis and characterization of

hyperbranched polyurethanes prepared from blocked iso-

cyanate monomers by step-growth polymerization. Macro-

molecules 1993;26:4809–13.

[89] Kumar A, Ramakrishnan SA. Novel one-pot synthesis of

hyperbrached polyurethanes. J Chem Soc, Chem Commun

1993;1453–4.

[90] Kumar A, Ramakrishnan S. Hyperbranched polyurethanes

with varying spacer segments between the branching points.


[91] Versteegen RM, Sijbesma RP, Meijer EW. Synthesis of [n ]-

polyurethanes and hyperbranched polyurethanes. Polym

Prepr 1999;40(2):839–40.

[92] Mathias LJ, Carothers TW. Hyperbranched poly(siloxysi-

lanes). J Am Chem Soc 1991;113:4043–4.


[93] Muzafarov A, Golly M, Moller M. Degradable hyper-

branched poly(bis(undecenyloxy)-methylsilane)s. Macro-

molecules 1995;28:8444–6.

[94] Yoon K, Son DY. Synthesis of hyperbranched poly(carbo-

silarylenes). Macromolecules 1999;32:5210–6.

[95] Lach C, Frey H. Enhancing the degree of branching of

hyperbranched polymers by postsynthetic modification.


[96] Hobson LJ, Kenwright AM, Feast WJ. A simple one pot route

to the hyperbranched analogues of Tomalia’s poly(amidoa-

mine) dendrimers. Chem Commun 1997;1877–8.

[97] Hobson LJ, Feast WJ. Poly(amidoamine) hyperbranched

systems: synthesis, structure and characterization. Polymer

1999;40:1279–97.

[98] Londergan TM, You Y, Thompson ME, Weber WP. Ru-

catalyzed synthesis of cross-conjugated polymers and

hyperbranched materials. Copoly(arylene/1,1-vinylene)s.


[99] Lu P, Paulasaari JK, Weber WP. Hyperbranched poly(4-

acetylstyrene) by ruthenium-catalyzed step-growth polym-

erization of 4-acetylstyrene. Macromolecules 1996;29:

8583–6.

[100] Miravet JF, Frechet JMJ. New hyperbranched poly(silox-

ysilanes): variation of the branching pattern and end-

functionalization. Macromolecules 1998;31:3461–8.

[101] Frechet JMJ, Henmi M, Gitsov I, Aoshima S, Leduc M,

Grubbs RB. Self-condensing vinyl polymerization:

an approach to dendritic materials. Science 1995;269:

1080–3.

[102] Gayor SG, Edelman S, Matyjaszewski K. Synthesis of

branched and hyperbranched polystyrenes. Macromolecules

1996;29:1079–81.

[103] Hawker CJ, Frechet JMJ, Grubbs RB, Dao J. Preparation of

hyperbranched and star polymers by a living, self-condensing

free radical polymerization. J Am Chem Soc 1995;117:

10763–4.

[104] Wieland PC, Nuyken O, Schmidt M, Fischer K. Amphiphilic

graft copolymers and hyperbranched polymers based on (3-

vinylphenyl)azomethylmalonodinitrile. Macromol Rapid

Commun 2001;22:1255–60.

[105] Ishizu K, Mori A. Synthesis of hyperbranched polymers by

self-addition free radical vinyl polymerization of photo

functional styrene. Macromol Rapid Commun 2000;21:

665–8.

[106] Ishizu K, Mori A. Novel synthesis of branched polystyrenes

by quasi-living radical copolymerization using photofunc-

tional inimer. Polym Int 2001;50:906–10.

[107] Weimer MW, Frechet JMJ, Gitsov I. Importance of

active-site reactivity and reaction conditions in the

preparation of hyperbranched polymers by self-condensing

vinyl polymerization: highly branched vs. linear poly[4-

(chloromethyl)styrene] by metal-catalyzed living radical

polymerization. J Polym Sci, Part A: Polym Chem 1998;

36:955–70.

[108] Knauss DM, Al-Muallem HA. Polystyrene with dendritic

branching by convergent living anionic polymerization. II.

Approach using vinylbenzyl chloride. J Polym Sci, Part A:

Polym Chem 2000;38:4289–98.

[109] Al-Muallem HA, Knauss DM. Synthesis of hybrid dendritic-

linear block copolymers with dendritic initiators prepared by

convergent living anionic polymerization. J Polym Sci, Part

A: Polym Chem 2001;39:152–61.

[110] Jiang X, Zhong Y, Yan D, Yu H, Zhang D. Hyperbranched

copolymers of p-(chloromethyl)styrene and N-cyclohexyl-

maleimide synthesized by atom transfer radical polymeriz-

ation. J Appl Polym Sci 2000;78:1992–7.

[111] Paulo C, Puskas JE. Synthesis of hyperbranched polyisobu-

tylenes by inimer-type living polymerization. 1. Investigation

of the effect of reaction conditions. Macromolecules 2001;

34:734–9.

[112] Malmstrom EE, Hawker CJ. Macromolecular engineering

via living free radical polymerizations. Macromol Chem

Phys 1998;199:923–35.

[113] Matyjaszewski K, Gaynor SG, Kulfan A, Podwika M.

Preparation of hyperbranched polyacrylates by atom

transfer radical polymerization. 1. Acrylic ABp monomers

in living radical polymerizations. Macromolecules 1997;30:

5192–4.

[114] Matyjaszewski K, Gaynor SG, Muller AHE. Preparation of

hyperbranched polyacrylates by atom transfer radical

polymerization. 2. Kinetics and mechanism of chain growth

for the self-condensing vinyl polymerization of 2-((2-

bromopropionyl)oxy)ethyl acrylate. Macromolecules 1997;

30:7034–41.

[115] Matyjaszewski K, Gaynor SG. Preparation of hyperbranched

polyacrylates by atom transfer radical polymerization. 3.

Effect of reaction conditions on the self-condensing vinyl

polymerization of 2-((2-bromopropionyl)oxy)ethyl acrylate.


[116] Matyjaszewski K, Pyun J, Gaynor SG. Preparation of

hyperbranched polyacrylates by atom transfer radical

polymerization. 4. The use of zero-valent copper. Macromol

Rapid Commun 1998;19:665–70.

[117] Hong CY, Pan CY, Huang Y, Xu ZD. Synthesis of

hyperbranched polymethacrylates in the presence of a

tetrafunctional initiator. Polymer 2001;42:6733–40.

[118] Hong CY, Pan CY. Synthesis and characterization of

hyperbranched polyacrylates in the presence of a tetrafunc-

tional initiator with higher reactivity than monomer by self-

condensing vinyl polymerization. Polymer 2001;42:

9385–91.

[119] Yoo SH, Lee JH, Lee J-C, Jho JY. Synthesis of hyper-

branched polyacrylates in emulsion by atom transfer radical

polymerization. Macromolecules 2002;35:1146–8.

[120] Gaynor SG, Edelman S, Matyjaszewski K. From hyper-

branched to crosslinked polymers by atom transfer radical

polymerization. Polym Mater Sci Engng 1996;74:236–7.

[121] Simon PFW, Radke W, Muller AHE. Hyperbranched

methacrylates by self-condensing group transfer polymeriz-

ation. Macromol Rapid Commun 1997;18:865–73.

[122] Simon PFW, Muller AHE. Synthesis of hyperbranched and

highly branched methacrylates by self-condensing group


transfer copolymerization. Macromolecules 2001;34:

6206–13.

[123] Sakamoto K, Aimiya T, Kira M. Preparation of hyper-

branched polymethacrylates by self-condensing group trans-

fer polymerization. Chem Lett 1997;1245–6.

[124] Liu H, Wilen C-E. Hyperbranched poly[allyl ether-alt-maleic

anhydride] produced by the self-condensing alternating

copolymerization approach. Macromolecules 2001;34:

5067–70.

[125] Coessens V, Pintauer T, Matyjaszewski K. Functional

polymers by atom transfer radical polymerization. Prog

Polym Sci 2001;26:337–77.

[126] Patten TE, Matyjaszewski K. Atom transfer radical polym-

erization and the synthesis of polymeric materials. Adv

Mater 1998;10:901–15.

[127] Yan DY, Muller AHE, Matyjaszewski K. Molecular

parameters of hyperbranched polymers made by self-

condensing vinyl polymerization. 2. Degree of branching.


[128] Suzuki M, Li A, Saegusa T. Multibranching polymerization:

palladium-catalyzed ring-opening polymerization of cyclic

carbamate to produce hyperbranched dendritic polyamine.


[129] Suzuki M, Yoshida S, Shiraga K, Saegusa T. New ring-

opening polymerization via a p-allylpalladium complex. 5.

Multibranching polymerization of cyclic carbamate to

produce hyperbranched dendritic polyamine. Macromol-

ecules 1998;31:1716–9.

[130] Bednarek M, Biedron T, Helinski J, Kaluzynski K, Kubisa P,

Penczek S. Branched polyether with multiple primary

hydroxyl groups: polymerization of 3-ethyl-3-hydroxy-

methyloxetane. Macromol Rapid Commun 1999;20:369–72.

[131] Magnusson H, Malmstrom E, Hult A. Synthesis of

hyperbranched aliphatic polyethers via cationic ring-opening

polymerization of 3-ethyl-3-(hydroxymethyl)oxetane.

Macromol Rapid Commun 1999;20:453–7.

[132] Chen Y, Bednarek M, Kubisa P, Penczek S. Synthesis of

multihydroxyl branched polyethers by cationic copolymer-

ization of 3,3-bis(hydromethyl)oxetane and 3-ethyl-3-

(hydroxymethyl)oxetane. J Polym Sci, Part A: Polym

Chem 2002;40:1991–2002.

[133] Vandenberg EJ. Polymerization of glycidol and its deriva-

tives. A new rearrangement polymerization. J Polym Sci,

Part A: Polym Chem 1985;23:915–49.

[134] Tokar R, Kubisa P, Penczek S, Dworak A. Cationic

polymerization of glycidol: coexistence of the activated

monomer and active chain end mechanism. Macromolecules

1994;27:320–2.

[135] Dworak A, Walach W, Trzebicka B. Cationic polymerization

of glycidol. Polymer structure and polymerization mechan-

ism. Macromol Chem Phys 1995;196:1963–70.

[136] Yan DY, Hou J, Zhu XY, Kosman JJ, Wu HS. A new

approach to control crystallinity of resulting polymers: self-

condensing ring opening polymerization. Macromol Rapid

Commun 2000;21:557–61.

[137] Sunder A, Hanselmann R, Frey H, Mulhaupt R. Controlled

synthesis of hyperbranched polyglycerols by ring-opening

multibranching polymerization. Macromolecules 1999;32:

4240–6.

[138] Sunder A, Hanselmann R, Frey H. Hyperbranched poly-

ether–polyols based on polyglycerol: polarity design by

block copolymerization with propylene oxide. Macromol-

ecules 2000;33:309–14.

[139] Liu M, Vladimirov N, Frechet JMJ. A new approach to

hyperbranched polymers by ring-opening polymerization of

an AB monomer: 4-(2-hydroxyethyl)-epsilon–caprolactone.


[140] Trollsas M, Lowenhielm P, Lee VY, Moller M, Miller RD,

Hedrick JL. New approach to hyperbranched polyesters: self-

condensing cyclic ester polymerization of bis(hydroxy-

methyl)-substituted 1-caprolactone. Macromolecules 1999;

32:9062–6.

[141] Chang HT, Frechet JMJ. Proton-transfer polymerization: a

new approach to hyperbranched polymers. J Am Chem Soc

1999;121:2313–4.

[142] Gong CG, Frechet JMJ. Proton transfer polymerization in the

preparation of hyperbranched polyesters with epoxide chain-

ends and internal hydroxyl functionalities. Macromolecules

2000;33:4997–9.

[143] Kadokawa J, Kaneko Y, Yamada S, Ikuma K, Tagaya H,

Chiba K. Synthesis of hyperbranched polymers via proton-

transfer polymerization of acrylate monomer containing two

hydroxy groups. Macromol Rapid Commun 2000;21:362–8.

[144] Paulasaari JK, Weber WP. Synthesis of hyperbranched

polysiloxanes by base-catalyzed proton-transfer polymeriz-

ation. Comparison of hyperbranched polymer microstructure

and properties to those of linear analogues prepared by

cationic or anionic ring-opening polymerization. Macromol-

ecules 2000;33:2005–10.

[145] Jikei M, Kakimoto M. Hyperbranched polymers: a promising

new class of materials. Prog Polym Sci 2001;26:1233–85.

[146] Inoue K. Functional dendrimers, hyperbranched and star

polymers. Prog Polym Sci 2000;25:453–571.

[147] Ishizu K, Tsubaki K, Mori A, Uchida S. Architecture of

nanostructured polymers. Prog Polym Sci 2003;28:27–54.

[148] Frechet JMJ, Hawker CJ. Hyperbranched polyphenylene and

hyperbranched polyesters: new soluble, three-dimensional,

reactive polymers. React Funct Polym 1995;26:127–36.

[149] Wei HY, Shi WF. Structural characteristics, syntheses and

applications of hyperbranched polymers. Chem J Chin Univ

2001;22:338–44.

[150] Voit B. New developments in hyperbranched polymers.


[151] Hawker CJ. Dendritic and hyperbranched macromolecules—

precisely controlled macromolecular architectures. Adv

Polym Sci 1999;147:113–60.

[152] Bischoff R, Cray SE. Polysiloxanes in macromolecular

architecture. Prog Polym Sci 1999;24:185–219.

[153] Hult A, Johansson M, Malmstrom E. Hyperbranched

polymers. Adv Polym Sci 1999;143:1–34.

[154] Burchard W. Solution properties of branched macromol-

ecules. Adv Polym Sci 1999;143:113–94.

[155] Kim YH. Hyperbranchecs polymers 10 years after. J Polym



[156] Hobson LJ, Harrison RM. Dendritic and hyperbranched

polymers: advances in synthesis and applications. Curr Opin

Solid State Mater Sci 1997;2(6):683–92.

[157] Malmstrom E, Hult A. Hyperbranched polymers: a review.

J Macromol Sci Rev Macromol Chem Phys 1997;C37(3):

555–79.

[158] Frechet JMJ, Hawker CJ, Gitsov I, Leon JW. Dendrimers and

hyperbranched polymers: two families of three-dimensional

macromolecules with similar but clearly distinct properties.

J Macromol Sci, Pure Appl Chem 1996;A33(10):1399–425.

[159] Jikei M, Chon SH, Kakimoto M, Kawauchi S, Imase T,

Watanabe J. Synthesis of hyperbranched aromatic polyamide

from aromatic diamines and trimesic acid. Macromolecules

1999;32:2061–4.

[160] Emrick T, Chang HT, Frechet JMJ. An A2 þ B3 approach to

hyperbranched aliphatic polyethers containing chain end

epoxy substituents. Macromolecules 1999;32:6380–2.

[161] Yan D, Gao C. Hyperbranched polymers made from A2 and

BB02 type monomers. 1. Polyaddition of 1-(2-aminoethyl)pi-

perazine to divinyl sulfone. Macromolecules 2000;33:

7693–9.

[162] Gao C, Yan D. Hyperbranched polymers made from

commercially available A2 and BB02 type monomers. Chem

Commun 2001;(1):107–8.

[163] Gao C, Yan D. Polyaddition of B2 and BB2 type monomers to

A2 type monomer. 1. Synthesis of highly branched

copoly(sulfone-amine)s. Macromolecules 2001;34:156–61.

[164] Gao C. Molecular design, preparation, characterization and

functionalization of hyperbranched polymers. Doctor Dis-

sertation of Shanghai Jiao Tong University; 2001.

[165] Froehling P, Brackman J. Properties and applications of

poly(propylene imine) dendrimers and poly(esteramide)

hyperbranched polymers. Macromol Symp 2000;151:

581–9.

[166] van Benthem RATM, Meijerink N, Gelade E, de Koster CG,

Muscat D, Froehling PE, Hendriks PHM, Vermeulen CJAA,

Zwartkruis TJG. Synthesis and characterization of bis(2-

hydroxypropyl)amide-based hyperbranched polyestera-

mides. Macromolecules 2001;34:3559–66.

[167] Gao C, Yan DY. The approach to hyperbranched poly-

urethanes with urea units and the prepared hyperbranched

polymers. Chinese Applied Patent 02111580.X; 2002.

[168] Aharoni SM, Edwards SF. Gels of rigid polyamide networks.


[169] Aharoni SM, Murthy NS, Zero K, Edwards SF. Fractal nature

of one-step highly branched rigid rodlike macromolecules

and their gelled-network progenies. Macromolecules 1990;

23:2533–49.

[170] Aharoni SM. Gels of two-step rigid polyamide networks.


[171] Aharoni SM. Gelled networks prepared from rigid fractal

polymers. Macromolecules 1991;24:235–9.

[172] Emrick T, Chang H-T, Frechet JMJ. The preparation of

hyperbranched aromatic and aliphatic polyether epoxies by

chloride-catalyzed proton transfer polymerization from ABn

and A2 þ B3 monomers. J Polym Sci, Part A: Polym Chem

2000;38:4850–69.

[173] Dai L, Winkler B, Dong L, Tong L, Mau AWH. Conjugated

polymers for light-emitting applications. Adv Mater 2001;

13:915–25.

[174] Dai L, Huang S, Lu J, Mau AWH, Zhang F. Conducting

polymers with multi-dimensional structures. Polym Prepr

1998;39(1):171–2.

[175] Lin T, He Q, Bai F, Dai L. Design, synthesis and

photophysical properties of a hyperbranched conjugated

polymer. Thin Solid Films 2000;363:122–5.

[176] Tanaka S, Takeuchi K, Asai M, Iso T, Ueda M. Preparation

of hyperbranched copolymers constituted of triphenylamine

and phenylene units. Synthetic Metals 2001;119:139–40.

[177] Fang J, Kita H, Okamoto K. Hyperbranched polyimides for

gas separation applications. 1. Synthesis and characteriz-

ation. Macromolecules 2000;33(13):4639–46.

[178] Chen H, Yin J. Synthesis and characterization of hyper-

branched polyimides with good organosolubility and thermal

properties based on a new triamine and conventional

dianhydrides. J Polym Sci, Part A: Polym Chem 2002;40:

3804–14.

[179] Chen H, Yin J. Preparation of fully imidized hyperbranched

photosensitive polyimide with excellent organosolubility and

thermal property based on 4,40-(hexafluoroisopropylidene)

diphthalic anhydride (A2) and 1,3,5-tris(4-aminophenoxy)-

benzene (B3). Polym Bull 2003;49:313–20.

[180] Chen H, Yin J, Xu H. Synthesis of arenesulfonated

hyperbranched polyimide from A2 þ B3 monomers. Polym

J 2003;35(3):280–5.

[181] Hao J, Jikei M, Kakimoto M. Preparation of hyperbranched

aromatic polyimides via A2 þ B3 approach. Macromolecules

2002;35(14):5372–81.

[182] Flory PJ. Principles of polymer chemistry. Ithaca, NY:

Cornell University Press; 1953. [chapter 9].

[183] Yan DY, Gao C, Tang W, Zhu XY, Wang ZJ, Zhu PF, Tao P.

Synthesis of hyperbranched polymers from A2 and BB02 type

monomers. Proc CCS Congr 2000 2000;573–4.

[184] Gao C, Yan DY. New strategy for preparation of hyper-

branched polymers. Chem World (Suppl.) 2001;42:229–30.

[185] Gao C, Yan DY, Zhu XY, Huang W. Preparation of water-

soluble hyperbranched poly(sulfone-amine)s by polyaddition

of N-ethylethylenediamine to divinyl sulfone. Polymer 2001;

42:7603–10.

[186] Gao C, Yan DY, Tang W. Hyperbranched polymers made

from A2 and BB02 type monomers. 3. Polyaddition of N-

methyl-1,3-propanediamine to divinyl sulfone. Macromol

Chem Phys 2001;202(12):2623–9.

[187] Holter D, Frey H. Degree of branching in hyperbranched

polymers. 2. Enhancement of the DB: scope and limitations.

Acta Polym 1997;48:298–309.

[188] Holter D, Burgath A, Frey H. Degree of branching in

hyperbranched polymers. Acta Polym 1997;48:30–5.

[189] Gao C, Tang W, Yan DY. Synthesis and characterization of

water-soluble hyperbranched poly(ester amine)s from dia-

crylates and diamines. J Polym Sci, Part A: Polym Chem

2002;40:2340–9.

[190] Nishimura T, Maeda M, Nitadori Y, Tsuruta T. Synthesis and

copolymerization of a polyamine macromer: molecular


design of a new functional graft copolymer. Macromol Chem

1981;183:29–45.

[191] Nitadori Y, Tsuruta T. Lithium alkylamide catalyzed

addition of 1,4-divinylbenzene with N,N0-diethylethylene-

diamine. Macromol Chem 1979;180:1877–90.

[192] Gao C, Yan DY. A2 þ CBn approach to hyperbranched

polymers with alternating ureido and urethano units.

Macromolecules 2003;36(3):613–20.

[193] Gao C, Yan DY. Preparation of hyperbranched poly(urea-

urethane) with hydroxyl end-groups from A2 and CB2 type

monomers. Chem J Chin Univ 2002;23:2202–4.

[194] Gao C, Yan DY. The approach to hyperbranched poly-

urethanes with various of degree of branching and the

prepared hyperbranched polymers. Chinese Applied Patent

02111579.6; 2002.

[195] Gao C, Xu YM, Yan DY, Chen W. Water-soluble degradable

hyperbranched polyesters: novel candidates for drug-deliv-

ery? Biomacromolecules 2003;4:704–12.

[196] Lu Y, Lin D, Wei HY, Shi WF. Synthesis and charaterization

of hyperbranched poly(amine-ester). Acta Polym Sin 2000;

(5):554–8.

[197] Uhrich K. Hyperbranched polymers for drug delivery. Trends

Polym Sci 1997;5:388–93.

[198] Gao C, Xu YM, Zhang HM, Yan DY. AB þ Cn approach to

aliphatic hyperbranched polyamides. Polym Prepr 2003;

44(1):845–6.

[199] Gao C, Yan DY. The approach to water-soluble hyper-

branched polyamides with terminal amino groups and the

prepared hyperbranched polymers. Chinese Applied Patent

02111578.8; 2002.

[200] Gao C, Yan DY. The approach to hyperbranched polyesters

with terminal hydroxyl groups and the prepared hyper-

branched polymers. Chinese Applied Patent 02145097.8;

2002.

[201] Wang KC, Gao C, Huang W, Yan DY. Synthesis and

characterization of hyperbranched polyesters with terminal

hydroxyl groups from Ap and B3 type monomers. Polym

Prepr 2003;44(1):583–4.

[202] Koster S, de Koster CG, van Benthem RATM, Duursma MC,

Boon JJ, Heeren RMA. Structural characterization of

hyperbranched polyesteramides: MSn and the origin of

species. Int J Mass Spectrom 2001;210/211:591–602.

[203] Muscat DM, Henderickx H, Kwakkenbos G, van Benthem R,

de Koster CG, Fokkens R, Nibbering NMM. In-source decay

of hyperbranched polyesteramides in matrix-assisted laser

desorption/ionization time-of-flight mass spectrometry. J Am

Soc Mass Spectrom 2000;11:218–27.

[204] Gao C, Yan DY. The approach to hyperbranched polyesters

and the prepared hyperbranched polymers. Chinese Applied

Patent 02145100.1; 2002.

[205] Wang KC, Gao C, Huang W, Yan DY. Preparation of

hyperbranched polyesters from benzene-1,2-,4-tricarboxylic-

1,2-anhydride and dihydroxy alcohols. Polym Prepr 2003;

44(1):888–9.

[206] Wang KC, Gao C, Huang W, Xu YM, Yan DY. Synthesis

of water-soluble hyperbranched polymer with

alternating amido, tertiary amino and ester units from

benzene-1,2-4-tricarboxylic acid-1,2-anhydride and N-(2-

hydroxyethyl)piperazine. Acta Chim Sin 2003;61(5):

795–9.

[207] Gao C, Yan DY. The approach to hyperbranched poly(amide

ester)s and the prepared hyperbranched polymers. Chinese

Applied Patent 02145101.X; 2002.

[208] Gao C, Tang W, Yan DY, Zhu PF, Tao P. Hyperbranched

polymers made from A2, B2, and BB02 type monomers. 2.

Preparation of hyperbranched copoly(sulfone-amine)s by

polyaddition of N-ethylethylenediamine and piperazine to

divinyl sulfone. Polymer 2001;42:3437–43.

[209] Gao C, Yan DY, Tang W. Hyperbranched polymers made

from A2, B2, and BB02 type monomers. 3. Comparison of

hyperbranched copoly(sulfone-amine)s with 4,40-trimethyle-

nedipiperidine and piperazine units. Macromol Chem Phys

2001;202:3035–42.

[210] Gao C, Tang W, Yan DY, Wang ZJ, Zhu PF, Tao P.

Hyperbranched polymers made from A2, B2, and BB02 type

monomers. 4. Copolymerization of divinyl sulfone with 4,40-

trimethylenedipiperidine and N-ethylethylenediamine. Sci

China, Ser B 2001;44:207–15.

[211] Gong ZH, Leu CM, Wu FI, Shu CF. Hyperbranched

poly(aryl ether oxazole)s: synthesis, characterization, and

modification. Macromolecules 2000;33:8527–33.

[212] Wu FI, Shu CF. Hyperbranched aromatic poly(ether imide)s:

synthesis, characterization, and modification. J Polym Sci,


[213] Cho SY, Chang Y, Kim JS, Lee SC, Kim C. Hyperbranched

poly(ether ketone) analogues with heterocyclic triazine

moiety: synthesis and peripheral functionalization. Macro-

mol Chem Phys 2001;202:263–9.

[214] Schmaljohann D, Haußler L, Potschke P, Voit BI, Loontjens

TJA. Modification with alkyl chains and the influence on

thermal and mechanical properties of aromatic hyperbranched

polyesters. Macromol Chem Phys 2000;201:49–57.

[215] Sunder A, Bauer T, Mulhaupt R, Frey H. Synthesis and

thermal behavior of estified aliphatic hyperbranched poly-

ether polyols. Macromolecules 2000;33:1330–7.

[216] Malmstrom E, Hult A, Gedde UW, Liu F, Boyd RH.

Relaxation processes in hyperbranched polyesters: influence

of terminal groups. Polymer 1997;38:4873–9.

[217] Hanselmann R, Holter D, Frey H. Hyperbranched poly-

mers prepared via the core-dilution slow addition

technique: computer simulation of molecular weight

distribution and degree of branching. Macromolecules

1998;31:3790–801.

[218] Sunder A, Quincy MF, Mulhaupt R, Frey H. Hyperbranched

polyether polyols with liquid crystalline properties. Angew

Chem Int Ed 1999;38:2928–30.

[219] Salazar R, Fomina L, Fomine S. Functionalized poly-

glycidol–CuCl-complexes as catalysts in the oxidative

coupling reaction of terminal acetylenes. Polym Bull 2001;

47:151–8.

[220] Bergenudd H, Eriksson P, DeArmitt C, Stenberg B, Jonsson

EM. Synthesis and evaluation of hyperbranched phenolic

antioxidants of three different generations. Polym Degrad

Stab 2002;76:503–9.


[221] Mueller A, Kowalewski T, Wooley KL. Synthesis, charac-

terization, and derivatization of hyperbranched polyfluori-

nated polymers. Macromolecules 1998;31:776–86.

[222] Miller TM, Neenan TX, Zayas R, Bair HE. Synthesis and

characterization of a series of monodisperse, 1,3,5-phenylene-

based hydrocarbon dendrimers including C276H186 and their

fluorinated analogues. J Am Chem Soc 1992;114:1018–9.

[223] Pitois C, Wiesmann D, Lindgren M, Hult A. Functionalized

fluorinated hyperbranched polymers for optical waveguide

applications. Adv Mater 2001;13:1483–7.

[224] Pitois C, Vestberg R, Rodlert M, Malmstrom E, Hult A,

Lindgren M. Fluorinated dendritic polymers and dendrimers

for waveguide applications. Opt Mater 2002;21:499–506.

[225] Coessens V, Pyun J, Miller PJ, Gaynor SG, Matyjaszewski K.

Functionalization of polymers prepared by ATRP using

radical addition reactions. Macromol Rapid Commun 2000;

21:103–9.

[226] Wang G, Wang X. A novel hyperbranched polyester

functionalized with azo chromophore: synthesis and photo-

responsive properties. Polym Bull 2002;49:1–8.

[227] Haag R, Stumbe JF, Sunder A, Frey H, Hebel A. An approach

to core–shell-type architectures in hyperbranched polygly-

cerols by selective chemical differentiation. Macromolecules

2000;33:8158–66.

[228] Gao C, Yan DY. Preparation of fluorescent hyperbranched

polymer materials by end-capping approach. Chin Sci Bull

2000;45:1760–4.

[229] Gao C, Yan DY, Zhang B, Tang W. Water-soluble

fluorescent hyperbranched polysulfone-amine. Polym Prepr

2001;42(2):538–9.

[230] Gao C, Hou J, Yan DY, Zhang B, Tang W. Fluorescent

hyperbranched polyether with color effect. Polym Prepr

2001;42(2):417–8.

[231] Knischka R, Lutz PJ, Sunder A, Mulhaupt R, Frey H.

Functional poly(ethylene oxide) multiarm star polymers:

core-first synthesis using hyperbranched polyglycerol

initiators. Macromolecules 2000;33:315–20.

[232] Burgath A, Sunder A, Neuner I, Mulhaupt R, Frey H. Multi-

arm star block copolymers based on 1-caprolactone with

hyperbranched polyglycerol core. Macromol Chem Phys

2000;201:792–7.

[233] Frey H, Haag R. Dendritic polyglycerol: a new versatile

biocompatible material. Rev Mol Biotechnol 2002;90:

257–67.

[234] Maier S, Sunder A, Frey H, Mulhaupt R. Synthesis

of poly(glycerol)-block-poly(methyl acrylate) multi-arm

star polymers. Macromol Rapid Commun 2000;21:226–30.

[235] Carlmark A, Vestberg R, Malmstrom E, Jonsson M. Atom

transfer radical polymerization of methyl acrylate from a

multifunctional initiator at ambient temperature. Polymer

2002;43:4237–42.

[236] Ni PH, Cao XP, Yan DY, Hou J, Fu SK. Synthesis of novel

temperature/pH responsive polymer via oxyanionic polym-

erization. Chin Sci Bull 2002;47:280–3.

[237] Hou J, Yan DY. Synthesis of a star-shaped copolymer with a

hyperbranched poly(3-methyl-3-oxetanemethanol) core and

tetrahydrofuran arms by one-pot copolymerization. Macro-

mol Rapid Commun 2002;23:456–9.

[238] Claesson H, Malmstrom E, Jonsson M, Hult A. Synthesis and

characterization of star branched polyesters with dendritic

cores and the effect of structural variations on zero shear rate

viscosity. Polymer 2002;43:3511–8.

[239] Trollsas M, Hawker CJ, Remenar JF, Hedrick JL, Johansson

M, Ihre H, Hult A. Highly branched radical block copolymers

via dendritic initiation of aliphatic polyesters. J Polym Sci,


[240] Weberskirch R, Hettich R, Nuyken O, Schmaljohann D,

Voit B. Synthesis of new amphiphilic star polymers

derived from a hyperbranched macroinitiator by the

cationic grafting from method. Macromol Chem Phys

1999;200:863–73.

[241] Peez RF, Dermody DL, Franchina JG, Jones SJ, Bruening

ML, Bergbreiter DE, Crooks RM. Aqueous solvation and

functionalization of weak-acid polyelectrolyte thin films.

Langmuir 1998;14:4232–7.

[242] Zhou Y, Bruening ML, Liu Y, Crooks RM, Bergbreiter DE.

Synthesis of hyperbranched, hydrophilic fluorinated surface

grafts. Langmuir 1996;12:5519–21.

[243] Zhou Y, Bruening ML, Bergbreiter DE, Crooks RM, Wells M.

Preparation of hyperbranched polymer films grafted on self-

assembled monolayers. J Am Chem Soc 1996;118:3773–4.

[244] Bruening ML, Zhou Y, Aguilar G, Agee R, Bergbreiter DE,

Crooks RM. Synthesis and characterization of surface-

grafted hyperbranched polymer films containing fluoresent,

hypdrophobic, ion-binding, biocompatible, and electroactive

groups. Langmuir 1997;13:770–8.

[245] Zhao M, Zhou Y, Bruening ML, Bergbreiter DE, Crooks RM.

Inhibition of electrochemical reactions at gold surfaces by

grafted, highly fluorinated, hyperbranched polymer films.

Langmuir 1997;13:1388–91.

[246] Lackowski WM, Franchina JG, Bergbreiter DE, Crooks RM.

Atomic force microscopy study of the surface morphology of

hyperbranched poly(acrylic acid) thin films. Adv Mater

1999;11:1368–71.

[247] Nagale M, Kim BY, Bruening ML. Ultrathin, hyperbranched

poly(acrylic acid) membranes on porous alumina supports.

J Am Chem Soc 2000;122:11670–8.

[248] Franchina JG, Lackowski WM, Dermody DL, Crooks RM,

Bergbreiter DE, Sirkar K, Russell RJ, Pishko MV. Electro-

static immobilization of glucose oxidase in a weak acid,

polyeletrolyte hyperbranched ultrathin film on gold: fabrica-

tion, characterization, and enzymatic activity. Anal Chem

1999;71:3133–9.

[249] Bergbreiter DE, Tao G. Chemical modification of hyper-

branched ultrathin films on gold and polyethylene. J Polym


[250] Tsubokawa N, Hayashi S, Nishimura J. Grafting of

hyperbranched polymers onto ultrafine silica: postgraft

polymerization of vinyl monomers initiated by pendant azo

groups of grafted polymer chains on the surface. Prog Org

Coat 2002;44:69–74.

[251] Hayashi S, Fujiki K, Tsubokawa N. Grafting of hyper-

branched polymers onto ultrafine silica: postgraft


polymerization of vinyl monomers initiated by pendant

initiating groups of polymer chains grafted onto the

surface. React Funct Polym 2000;46:193–201.

[252] Fujiki K, Sakamoto M, Sato T, Tsubokawa N. Postgrafting of

hyperbranched dendrtitic polymer from terminal amino

groups of polymer chains grafted onto silica surface.

J Macromol Sci, Pure Appl Chem 2000;A37(4):357–77.

[253] Okazaki M, Murota M, Kawaguchi Y, Tsubokawa N. Curing

of epoxy resin by ultrafine silica modified by grafting of

hyperbranched polyamidoamine using dendrimer synthesis

methodology. J Appl Polym Sci 2001;80:573–9.

[254] Kim HJ, Moon JH, Park JW. A hyperbranhced poly(ethyle-

neimine) growth on surfaces. J Colloid Interface Sci 2000;

227:247–9.

[255] Mori H, Seng DC, Zhang M, Muller AHE. Hybrid

nanoparticles with hyperbranhced polymer shells via self-

condensing atom transfer radical polymerization from silica

surfaces. Langmuir 2002;18:3682–93.

[256] Meszaros R, Thompson L, Bos M, Groot P. Adsorption and

electrokinetic properties of polyethylenimine on silica


[257] Sidorenko A, Zhai XW, Simon F, Pleul D, Tsukruk VV.

Hyperbranched molecules with epoxy-functionalized term-

inal branches: grafting to a solid surface. Macromolecules

2002;35:5131–9.

[258] Sidorenko A, Zhai XW, Greco A, Tsukruk VV. Hyper-

branched polymer layers as multifunctional interfaces.

Langmuir 2002;18:3408–12.

[259] Sidorenko A, Zhai XW, Peleshanko S, Greco A, Shechenko

VV, Tsukruk VV. Hyperbranched polyesters on solid


[260] Mori H, Boker A, Krausch G, Muller AHE. Surface-grafted

hyperbranched polymers via self-condensing atom transfer

radical polymerization from silicon surfaces. Macromol-

ecules 2001;34:6871–82.

[261] Bergbreiter DE, Franchina JG, Kabza K. Hyperbranched

grafting on oxidized polyethylene surfaces. Macromolecules

1999;32:4993–8.

[262] Bergbreiter DE. New chemistry for surface modification of

polyethylene. Polym Prepr 2000;41(2):1927–8.

[263] Liu ML, Tao G, Bergbreiter DE. Thiophene polymerization

in an ultrathin hyperbranched graft on a polyethylene film

substrate. Polym Prepr 2000;41(2):1320–1.

[264] Tao G, Liu ML, Bergbreiter DE. Fluoresence studies of

solvent–polymer interactions at poly(acrylic acid) grafts and

their derivatives on polyethylene films. Polym Prepr 2000;

41(2):1154–5.

[265] Bergbreiter DE, Liu ML. Polythiophene formation within

hyperbranched grafts on polyethylene films. J Polym Sci,


[266] Bergbreiter DE, Tao G, Franchina JG, Sussman L. Polyvalent

hydrogen-bonding functionalization of ultrathin hyper-

branched films on polyethylene and gold. Macromolecules

2001;34:3018–23.

[267] Bergbreiter DE, Tao G, Kippenberger AM. Functionalized

hyperbranched polyethylene powder supports. Org Lett

2000;2:2853–5.

[268] Nakada S, Sawatari C, Tamura K, Yagi T. Hyperbranched

modification of unsaturated side chains of polyethylene

introduced by g-ray irradiation under a 1,3-butadiene

atmosphere. Colloid Polym Sci 2001;279:754–62.

[269] Tao G, Gong A, Lu J, Sue HJ, Bergbreiter DE. Surface

functionalized polypropropylene: synthesis, characterization,

and adhesion properties. Macromolecules 2001;34:7672–9.

[270] Jannerfeldt G, Boogh L, Manson J-AE. Tailored interfacial

properties for immiscible polymers by hyperbranched

polymers. Polymer 2000;41:7627–34.

[271] Tsubokawa N, Takayama T. Surface modification of chitosan

powder by grafting of dendrimer-like hyperbranched poly-

mer onto the surface. React Funct Polym 2000;43:341–50.

[272] Shi B, Lu X, Zou R, Luo J, Chen D, Liang H, Huang L.

Observation of the topography and friction properties of

macromolecular thin films at the nanometer scale. Wear

2001;251:1177–82.

[273] Kuo PL, Ghosh SK, Liang WJ, Hsieh YT. Hyperbranched

polyethyleneimine architecture onto poly(allylamine) by

simple synthetic approach and chelating characters. J Polym


[274] Lach C, Hanselmann RH, Frey H, Mulhaupt R. Hyper-

branched carbosilane oxazoline-macromonomers: polym-

erization and coupling to a trimesic acid core. Macromol

Rapid Commun 1998;19:461–5.

[275] Al-Muallem HA, Knauss DM. Graft copolymers from star-

shaped and hyperbranched polystyrene macromonomers.


[276] He QG, Lin T, Bai FL. Synthesis and photophysical

properties of linear and hyperbranched conjugated polymer.

Chin Sci Bull 2001;46:636–41.

[277] Bai F, Zheng M, Lin T, Yang J, He Q, Li Y, Zhu D. The new

approaches to light emitting conjugated polymers—alternat-

ing copolymers with hole transport chromophores and

hyperbranched polymers. Synth Metals 2001;119:179–80.

[278] Duan L, Qiu Y, He Q, Bai F, Wang L, Hong X. A novel

hyperbranched conjugated polymer for electroluminescence

application. Synth Metals 2001;124:373–7.

[279] Yang J, He Q, Lin H, Fan J, Bai F. Characteristics of twisted

intramolecular charge-transfer state in a hyperbranched

conjugated polymer. Macromol Rapid Commun 2001;22:

1152–7.

[280] He Q, Bai F, Yang J, Lin H, Huang H, Yu G, Li Y. Synthesis

and properties of high efficiency light emitting hyper-

branched conjugated polymers. Thin Solid Films 2002;417:

183–7.

[281] Fomina L, Salcedo R. Synthesis and polymerization of b,

b-dibromo-4-ethynylstyrene: preparation of a new poly-

conjugated, hyperbranched polymer. Polymer 1996;37:

1723–8.

[282] Fomina L, Guadarrama P, Fomine S, Salcedo R, Ogawa T.

Synthesis and characterization of well-defined fully con-

jugated hyperbranched oligomers of b, b-dibromo-4-ethy-

nylstyrene. Polymer 1998;39:2629–35.

[283] Morgenroth F, Mullen K. Dendritic and hyperbranched

polyphenylenes via a simple Diels-Alder route. Tetrahedron

1997;53:15349–66.


[284] Berresheim AJ, Muller M, Mullen K. Polyphenylene

nanostructures. Chem Rev 1999;99:1747–85.

[285] Peng H, Cheng L, Luo J, Xu K, Sun Q, Dong Y, Salhi F, Lee

PPS, Chen J, Tang BZ. Simple synthesis, outstanding tnermal

stability, and tunable light-emitting and optical-limiting

properties of functional hyperbranched polyarylenes. Macro-

molecules 2002;35:5349–51.

[286] Peng H, Luo J, Cheng L, Lam JWY, Xu K, Dong Y, Zhang

D, Huang Y, Xu Z, Tang BZ. Synthesis and optical

properties of hyperbranched polyarylenes. Opt Mater 2002;

21:315–20.

[287] Zhang Y, Wada T, Sasabe H. A new hyperbranched polymer

with polar chromophores for nonlinear optics. Polymer 1997;

38:2893–7.

[288] Zhang Y, Wang L, Wada T, Sasabe H. Synthesis and

characterization of novel hyperbranched polymers with

dipole carbazole moieties for multifunctional materials.


[289] Fomine S, Rivera E, Fomina L, Ortiz A, Ogawa T. Polymers

from coumarines. 4. Design and synthesis of novel

hyperbranched and comb-like coumarin-containing poly-

mers. Polymer 1998;39:3551–8.

[290] Xu MH, Pu L. Novel unsymmetrically hyperbranched

polythiophenes with conjugation gradient. Tetrahedron Lett

2002;43:6347–50.

[291] Yao J, Son DY. Hyperbranched poly(2,5-silylthiophenes).

The possibility of s–p conjugation in three dimensions.

Organometallics 1999;18:1736–40.

[292] Spetseris N, Ward RE, Meyer TY. Linear and hyperbranched

m-polyaniline: synthesis of polymers for the study of

magnetism in organic systems. Macromolecules 1998;31:

3158–61.

[293] Tanaka S, Iso T, Doke Y. Preparation of new branched

poly(triphenylamine). Chem Commun 1997;2063–4.

[294] Leuninger J, Uebe J, Salbeck J, Gherghel L, Wang C, Mullen

K. Poly(phenylene sulfide-phenyleneamine-phenylenea-

mine) (PPSAA): a soluble model for polyaniline. Synth

Metals 1999;100:79–88.

[295] Hawker CJ, Chu F, Pomery PJ, Hill DJT. Hyperbranched

poly(ethylene glycol)s: a new class of ion-conducting

materials. Macromolecules 1996;29:3831–8.

[296] Itoh T, Ikeda M, Hirata N, Moriya Y, Kubo M, Yamamoto O.

Ionic conductivity of the hyperbranched polymer–lithium

metal salt systems. J Power Sources 1999;81/82:824–9.

[297] Itoh T, Ichikawa Y, Hirata N, Uno T, Kubo M, Yamamoto O.

Effect of branching in base polymer on ionic conductivity in

hyperbranched polymer electrolytes. Solid State Ionics 2002;

150:337–45.

[298] Itoh T, Hirata N, Wen Z, Kubo M, Yamamoto O. Polymer

electrolytes based on hyperbranched polymers. J Power

Sources 2001;97/98:637–40.

[299] Wen Z, Itoh T, Ichikawa Y, Kubo M, Yamamoto O. Blend-

based polymer electrolytes of poly(ethylene oxide) and

hyperbranched poly[bis(triethylene glycol)benzoate] with

terminal acetyl groups. Solid State Ionics 2000;134:281–9.

[300] Itoh T, Ichikawa Y, Uno T, Kubo M, Yamamoto O.

Composite polymer electrolytes based on poly(ethylene

oxide), hyperbranched polymer, BaTiO3 and LiN(CF3SO2)2.

Solid State Ionics 2003;156:393–9.

[301] Wen Z, Itoh T, Ikeda M, Hirata N, Kubo M, Yamamoto O.

Characterization of composite electrolytes based on a

hyperbranched polymer. J Power Sources 2000;90:20–6.

[302] Hong L, Cui Y, Wang X, Tang X. Synthesis of a novel one-

pot approach of hyperbranched polyurethanes and their

properties. J Polym Sci, Part A: Polym Chem 2002;40:

344–50.

[303] Wang X, Chen J, Hong L, Tang X. Synthesis and ionic

conductivity of hyperbranched poly(glycidol). J Polym Sci,

Part B: Polym Phys 2001;39:2225–30.

[304] Nishimoto A, Agehara K, Furuya N, Watanabe T, Watanabe

M. High ionic conductivity of polyether-based network

polymer electrolytes with hyperbranched side chains.


[305] Sunder A, Kramer M, Hanselmann R, Mulhaupt R, Frey H.

Molecular nanocapsules based on amphiphilic hyper-

branched polyglycerols. Angew Chem Int Ed 1999;38:

3552–5.

[306] Stiriba SE, Kautz H, Frey H. Hyperbranched molecular

nanocapsules: comparison of the hyperbranched architecture

with the perfect linear analogue. J Am Chem Soc 2002;124:

9698–9.

[307] Slagt MQ, Stiriba SE, Gebbink RJMK, Kautz H, Frey H, von

Koten G. Encapsulation of hydrophilic pincer–platinum(II)

complexes in amphiphilic hyperbranched polyglycerol

nanocapsules. Macromolecules 2002;35:5734–7.

[308] Mecking S, Thomann R, Frey H, Sunder A. Preparation of

catalytically active palladium nanoclusters in compartments

of amphiphilic hyperbranched polyglycerols. Macromol-

ecules 2000;33:3958–60.

[309] Yang J, Lin H, He Q, Ling L, Zhu C, Bai F. Composition of

hyperbranched conjugated polymers with nanosized cad-

mium sulfide particles. Langmuir 2001;17:5978–83.

[310] Plummer CJG, Garamszegi L, Leterrier Y, Rodlert M,

Manson JAE. Hyperbranched polymer layered silicate

nanocomposites. Chem Mater 2002;14:486–8.

[311] Hedrick JL, Hawker CJ, Miller RD, Twieg R, Srinivasan SA,

Trollsas M. Structure control in organic–inorganic hybrids

using hyperbranched high-temperature polymers. Macromol-

ecules 1997;30:7607–10.

[312] Sun Q, Lam JWY, Xu K, Xu H, Cha JAK, Wong PCL, Wen

G, Zhang X, Jing X, Wang F, Tang BZ. Nanocluster-

containing mesoporous magnetoceramics from hyper-

branched organometallic polymer precursors. Chem Mater

2000;12:2617–24.

[313] Sun Q, Xu K, Lam JWY, Cha JAK, Zhang X, Tang BZ.

Nanostructured magnetoceramics from hyperbranched poly-

mer precursors. Mater Sci Engng C 2001;16:107–12.

[314] Nguyen C, Hawker CJ, Miller RD, Huang E, Hedrick JL.

Hyperbranched polyesters as nanoporosity templating agents

for organosilicates. Macromolecules 2000;33:4281–4.

[315] Soraru GD, Liu Q, Interrante LV, Apple T. Role of precursor

molecular structure on the microstructure and high tempera-

ture stability of silicon oxycarbide glasses derived from


methylene-bridged polycarbosilanes. Chem Mater 1998;10:

4047–54.

[316] Lebib A, Natali M, Li SP, Cambril E, Manin L, Chen Y,

Janssen HM, Sijbesma RP. Control of the critical dimension

with a trilayer nanoimprint lithography procedure. Micro-

electron Engng 2001;57/58:411–6.

[317] Lebib A, Chen Y, Cambril E, Youinou P, Studer V, Natali M,

Pepin A, Janssen HM, Sijbesma RP. Room-temperature and

low-pressure nanoimprint lithography. Microelectron Engng

2002;61/62:371–7.

[318] Griebel T, Maier G. Core shell hyperbranched polymers for

molecular imprinting. Polym Prepr 2000;41(1):89–90.

[319] Frey H, Haag R. Dendritic polyglycerol: a new versatile

biocompatible material. Rev Mol Biotechnol 2002;90:

257–67.

[320] Cosulich ME, Russo S, Pasquale S, Mariani A. Performance

evaluation of hyperbranched aramids as potential supports

for protein immobilization. Polymer 2000;41:4951–6.

[321] Lim Y, Kim SM, Lee Y, Lee W, Yang T, Lee M, Suh H, Park

J. Cationic hyperbranched poly(amino ester): a novel calss of

DNA condensing molecule with cationic surface, biodegrad-

able three-dimensional structure, and tertiary amine groups in

the interior. J Am Chem Soc 2001;123:2460–1.

[322] Kadokawa J, Sato M, Karasu M, Tagaya H, Chiba K.

Synthesis of hyperbranched aminopolysaccharides. Angew

Chem Int Ed 1998;37:2373–6.

[323] Tasaka F, Ohya Y, Ouchi T. One-pot synthesis of novel

branched polylactide through the copolymerization of lactide

with mevalonolactone. Macromol Rapid Commun 2001;22:

820–4.

[324] Trollsas M, Atthoff B, Claesson H, Hedrick JL. Hyper-

branched poly(epsilon-caprolactone)s. Macromolecules

1998;31:3439–45.

[325] Trollsas M, Claesson H, Atthoff B, Hedrick JL. Layered

dendritic block copolymers. Angew Chem Int Ed 1998;37:

3132–6.

[326] Zhai J, Li Y, He Q, Jiang L, Bai F. Formation of covalently

linked self-assembled films of a functional hyperbranched

conjugated poly(phenylene vinylene). J Phys Chem B 2001;

105:4094–8.

[327] Zhai J, Bai FL, He QG, Li YS, Jiang L, Lin T. Novel

covalently linked self-assembled films from a functional

hyperbranched conjugated poly(phenylene vinylene). Chin

Chem Lett 2000;11:819–22.

[328] Qiu T, Tang L, Tuo X, Zhang X, Liu D. Study on self-

assembly properties of aryl–alkyl hyperbranched polyesters

with carboxylic end groups. Polym Bull 2001;47:337–42.

[329] Zhang X, Tang L, Qiu T. Synthesis and application of a novel

aromatic hyperbranched polyester. Chem J Chin Univ 2001;

22:1761–3.

[330] Qiu T, Tang L, Tuo X, Zhang X. Studies on the self-assembly

of aliphatic-aromatic hyperbranched polyester with car-

boxylic end-groups. Chem J Chin Univ 2002;23:155–7.

[331] Decher G. Fuzzy nanoassemblies: toward layered polymeric

multicomposites. Science 1997;277:1232–7.

[332] Gao C, Yan DY, Zhang B, Chen W. Fluorescence studies on

the hydrophobic association of pyrene-labeled amphiphilic

hyperbranched poly(sulfone-amine)s. Langmuir 2002;18:

3708–13.

[333] Gao C, Yan DY, Chen W. Self-association and degree of

branching: fluorescence-probe study of hyperbranched poly

(sulfone-amine)s in aqueous solution. Macromol Rapid

Commun 2002;23:465–9.

[334] Gao C, Qian H, Wang SJ, Yan DY, Chen W, Yu GT. Self-

association of hyperbranched poly(sulfone-amine) in water:

studies with pyrene–fluorescence probe and fluorescence

label. Polymer 2003;44:1547–52.

[335] Winnik MA, Bystryak SM, Liu Z, Siddiqui J. Synthesis and

characterization of pyrene-labeled poly(ethylenimine).


[336] Winnik MA, Bystryak SM, Siddiqui J. Interaction of pyrene-

labeled poly(ethylene imine) with sodium dodecyl sulfate in

aqueous solution. Macromolecules 1999;32:624–32.

[337] Huck WTS, Snellink-Ruel BHM, Lichtenbelt JWT, van

Veggel FCJM, Reinhoudt DN. Self-assembly of hyper-

branched spheres: correlation between monomeric synthon

and sphere size. Chem Commun 1997;9–10.

[338] Choi S-H, Lee N-H, Cha SW, Jin J-I. Hyperbranched

thermotropic liquid crystalline polyesters composed of

aromatic ester type mesogens and polymethylene spacers.


[339] Hahn S-W, Yun Y-K, Jin J-I, Han OH. Thermotropic

hyperbranched polyesters prepared from 2-[(10-(4-hydro-

xyphenoxy)decyl)oxy]terephthalic acid and 2-[(10-((40-

hydroxy-1,1(-biphenyl-4-yl)oxy)decyl)oxy]terephthalic

acid. Macromolecules 1998;31:6417–25.

[340] Kricheldorf HR, Stukenbrock T, Friedrich C. New polymer

syntheses. XCVII. Hyperbranched LC-polyesters based on

b-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic

acid. J Polym Sci, Part A: Polym Chem 1998;36:

1397–405.

[341] Reina A, Gerken A, Zemann U, Kricheldorf HR. New

polymer syntheses, 101 Liquid-crystalline hyperbranched

and potentially biodegradable polyesters based on phloretic

acid and gallic acid. Macromol Chem Phys 1999;200:

1784–91.

[342] Monticelli O, Mendichi R, Bisbano S, Mariani A, Russo S.

Synthesis, characterization and properties of a hyper-

branched aromatic polyamide: poly(ABZAIA). Macromol

Chem Phys 2000;201:2123–7.

[343] Crooks RM. Patterning of hyperbranched polymer films.

Chem Phys Chem 2001;2:644–54.

[344] Lackowski WM, Ghosh P, Crooks RM. Micron-scale

patterning of hyperbranched polymer films by micro-contact

printing. J Am Chem Soc 1999;121:1419–20.

[345] Ghosh P, Crooks RM. Covalent grafting of a patterned,

hyperbranched polymer onto a plastic substrate using

microcontact printing. J Am Chem Soc 1999;121:8395–6.

[346] Ghosh P, Amirpour ML, Lackowski WM, Pishko MV,

Crooks RM. A simple lithographilc approach for preparing

patterned, micron-scale corrals for controlling cell growth.

Angew Chem Int Ed 1999;38:1592–5.

[347] Ghosh P, Lackowski WM, Crooks RM. Two new

approaches for patterning polymer films using templates


prepared by microcontact printing. Macromolecules 2001;

34:1230–6.

[348] Rowan B, Wheeler MA, Crooks RM. Patterning bacteria

within hyperbranched polymer film templates. Langmuir

2002;18:9914–7.

[349] Aoki A, Ghosh P, Crooks RM. Micrometer-scale patterning

of multiple dyes on hyperbranched polymer thin films

using photoacid-based lithography. Langmuir 1999;15:

7418–21.

[350] Johansson M, Malmstrom E, Jansson A, Hult A. Novel

concept for low temperature curing powder coatings based on

hyperbranched polyesters. J Coat Technol 2000;72:49–54.

[351] van Benthem RATM. Novel hyperbranched resins for

coating applications. Prog Org Coat 2000;40:203–14.

[352] Mancyzk K, Szewczyk P. Highly branched high solids alkyd

resins. Prog Org Coat 2002;44:99–109.

[353] Zhu SW, Shi WF. Flame retardant mechanism of hyper-

branched polyurethane acrylates used for UV curable flame

retardant coatings. Polym Degrad Stab 2002;75:543–7.

[354] Lange J, Stenroos E, Johansson M, Malmstrom E. Barrier

coatings for flexible packaging based on hyperbranched

resins. Polymer 2001;42:7403–10.

[355] Wan Q, Schricker SR, Culbertson BM. Methacryloyl

derivitized hyperbranched polyester. 1. Synthesis, character-

ization, and copolymerization. J Macromol Sci, Pure Appl

Chem 2000;A37(11):1301–15.

[356] Wan Q, Schricker SR, Culbertson BM. Methacryloyl

derivitized hyperbranched polyester. 2. Photo-polymeriz-

ation and properties for dental resin systems. J Macromol

Sci, Pure Appl Chem 2000;A37(11):1317–31.

[357] Johansson M, Glauser T, Rospo G, Hult A. Radiation curing

of hyperbranched polyester resins. J Appl Polym Sci 2000;

75:612–8.

[358] Claesson H, Malmstrom E, Johansson M, Hult A, Doyle

M, Manson JAE. Rheological behaviour during UV-curing

of a star-branched polyester. Prog Org Coat 2002;44:

63–7.

[359] Staring E, Dias AA, van Benthem RATM. New

challenges for R&D in coating resins. Prog Org Coat

2002;45:101–17.

[360] Wei H, Lu Y, Shi W, Yuan H, Chen Y. UV curing behavior

of methacrylated hyperbranched poly(amine-ester)s. J Appl

Polym Sci 2001;80:51–7.

[361] Mezzenga R, Boogh L, Manson J-AE. A review of dendritic

hyperbranched polymer as modifiers in epoxy composites.

Compos Sci Technol 2001;61:787–95.

[362] Mezzenga R, Plummer CJG, Boogh L, Manson J-AE.

Morphology build-up in dendritic hyperbranched polymer

modified epoxy resins: modeling and characterization.

Polymer 2001;42:305–17.

[363] Xu J, Wu H, Mills OP, Heiden PA. A morphological

investigation of thermosets toughened with

novel thermoplastics. I. Bismaleimide modified with

hyperbranched polyester. J Appl Polym Sci 1999;72:

1065–76.

[364] Gopala A, Wu H, Xu J, Heiden P. Investigation of readily

processable thermoplastic-toughened thermosets. IV. BMIs

toughened with hyperbranched polyester. J Appl Polym Sci

1999;71:1809–17.

[365] Wu H, Xu J, Heiden P. Investigation of readily processable

thermoplastic-toughened thermosets. V. Epoxy resin tough-

ened with hyperbranched polyester. J Appl Polym Sci 1999;

72:151–63.

[366] Mezzenga R, Boogh L, Pettersson B, Manson J-AE.

Chemically induced phase separated morphologies in

epoxy resin-hyperbranched polymer blends. Macromol

Symp 2000;149:17–22.

[367] Boogh L, Pettersson B, Manson J-AE. Dendritic hyper-

branched polymers as tougheners for epoxy resins. Polymer

1999;40:2249–61.

[368] Gryshchuk O, Jost N, Karger-Kocsis J. Toughening of

vinylester–urethane hybrid resins by functional liquid nitrile

rubbers and hyperbranched polymers. Polymer 2002;43:

4763–8.

[369] Gryshchuk O, Jost N, Karger-Kocsis J. Toughening of

vinylester–urethane hybrid resins through functionalized

polymers. J Appl Polym Sci 2002;84:672–80.

[370] Oh JH, Tang J, Lee S-H. Curing behavior of tetrafunctional

epoxy resin/hyperbranched polymer system. Polymer 2001;

42:8339–47.

[371] Emrick T, Chang H-T, Frechet JMJ, Woods J, Baccei L.

Hyperbranched aromatic epoxies in the design of adhesive

materials. Polym Bull 2000;45:1–7.

[372] Liu H, Wilen C-E, Skrifvars M. Reaction of epoxy resin and

hyperbranched polyacids. J Polym Sci, Part A: Polym Chem

2000;38:4457–65.

[373] Burkinshaw SM, Froehling PE, Mignanelli M. The effect of

hyperbranched polymers on the dyeing of polypropylene

fibres. Dyes Pigments 2002;53:229–35.

[374] Schmaljohann D, Potschke P, Hassler R, Voit BI, Froehling

PE, Mostert B, Loontjens JA. Blends of amphiphilic,

hyperbranched polyesters and different polyolefins. Macro-

molecules 1999;32:6333–9.

[375] Jannerfeldt G, Boogh L, Manson J-AE. Influence of

hyperbranched polymers on the interfacial tension of

polypropylene/polyamide-6 blends. J Polym Sci, Part A:

Polym Chem 1999;37:2069–77.

[376] Star A, Stoddart JF. Dispersion and solubilization of single-

walled carbon nanotubes with a hyperbranched polymer.


[377] Hong Y, Cooper-White JJ, Mackay ME, Hawker CJ,

Malmstrom E, Rehnberg N. A novel processing aid for

polymer extrusion: rheology and processing of polyethylene

and hyperbranched polymer blends. J Rheol 1999;43:

781–93.

[378] Hong Y, Coombs SJ, Cooper-White JJ, Mackay ME, Hawker

CJ, Malmstrom E, Rehnberg N. Film blowing of linear low-

density polyethylene blended with a novel hyperbranched

polymer processing aid. Polymer 2000;41:7705–13.

[379] Mulkern TJ, Tan NCB. Processing and characterization of

reactive polystyrene/hyperbranched polyester blends. Poly-

mer 2000;41:3193–203.

[380] Jang J, Oh JH, Moon SI. Crystallization behavior of

poly(ethylene terephthalate) blended with hyperbranched


polymers: the effect of terminal groups and composition of

hyperbranched polymers. Macromolecules 2000;33:

1864–70.

[381] Ratna D, Simon GP. Thermomechanical properties and

morpho-logy of blends of a hydroxy-functionalized hyper-

branched polymer and epoxy resin. Polymer 2001;42:8833–9.

[382] Tang L-M, Qiu T, Tuo X-L, Zhang X-L, Liu D-S. Synthesis,

morphology and application of alkylaryl hyperbranched

polyesters. Polym J 2002;34:112–6.

[383] Baek J-B, Qin H, Mather PT, Tan L-S. A new hyperbranched

poly(arylene–ether–ketone-imide): synthesis, chain-end

functionalization, and blending with a bis(maleimide).


[384] Mezzenga R, Boogh L, Manson J-AE. A thermodynamic

model for thermoset polymer blends with reactive modifiers.


[385] Hsieh T-T, Tiu C, Simon GP. Rheological behavior of

polymer blends containing only hyperbranched polyesters of

varying generation number. Polymer 2001;42:7635–8.

[386] Hsieh T-T, Tiu C, Simon GP. Melt rheology of aliphatic

hyperbranched polyesters with various molecular weight.

Polymer 2001;42:1931–9.

[387] Kharchenko SB, Kannan RM, Cernohous JJ, Venkataramani

S, Babu GN. Unusual contributions of molecular architecture

to rheology and flow birefringence in hyperbranched

polystyrene melts. J Polym Sci, Part A: Polym Chem 2001;

39:2562–71.

[388] Nunez CM, Chiou B-S, Andrady AL, Khan SA. Solution

rheology of hyperbranched polyesters and their blends with

linear polymers. Macromolecules 2000;33:1720–6.

[389] Fang J, Kita H, Okamoto K-I. Gas permeation properties of

hyperbranched polyimide membranes. J Membr Sci 2001;

182:245–56.

[390] Seiler M, Arlt W, Kautz H, Frey H. Experimental data and

theoretical considerations on vapor–liquid and liquid–liquid

equilibra of hyperbranched polyglycerol and PVA solutions.

Fluid Phase Equilib 2002;201:359–79.

[391] Seiler M, Kohler D, Arlt W. Hyperbranched polymers: new

selective solvents for extractive distillation and solvent

extraction. Sep Purif Technol 2002;29:245–63.

[392] Belge G, Beyerlein D, Betsch C, Eichhorn K-J, Gauglitz G,

Grundke K, Voit B. Suitability of hyperbranched polyester

for sensoric applications—investigation with reflectometric

interference spectroscopy. Anal Bioanal Chem 2002;374:

403–11.

[393] Dermody DL, Peez RF, Bergbreiter DE, Crooks RM.

Chemically grafted polymeric filters for chemical sensors:

hyperbranched poly(acrylic acid) films incorporating b-

cyclodextrin receptors and amine-functionalized filter layers.

Langmuir 1999;15:885–90.


Documents

Hyperbrance .pdf