Integration of acrylate polymer in sol-gel silica depending on their molecular weightsfhvjck/Solgel_files/Slides/18_4... · 2013-06-13 · How cross linking acrylate polymers are

Integration of acrylate polymer in sol-gel silicadepending on their molecular weight

Anthony Maçon1

1Imperial College of London, UK

Confidential :)

Anthony Maçon (PhD) Integration of synthetic polymer in sol gel silica matrix Sol gel meeting 1 / 17

Outline

1 IntroductionAims and Objectives

2 Polymer synthesis and characterisation

3 Polymer Characterisation


introduction

Acrylate polymer can have different chemical properties andarchitecture

Monomer organisation Polymer Architecture Homopolymer Statistical Copolymer Block Copolymer

Brush

Star Branched


Aim & objectives

AimHow cross linking acrylate polymers are integrated in the silica matrix

depending on their molecular weightobjectives

Use the Regulated free radical polymerizationCharacterised the polymerisation reactionCharacterise the hybrid


Tageted Mw DPni R0 (x10�3)30kDa 120 8.315kDa 60 16.67.5kDa 30 33.12.5KDa 10 99.4

Cmonomer =1mol.L�1

C0= ninitiatornmonomer

= 1.5%R0= nCTA

nmonomer= variable

T0= ntrioxanenmonomer

= 5%Anthony Maçon (PhD) Integration of synthetic polymer in sol gel silica matrix Sol gel meeting 5 / 17

Chain Transfer constant

(1

DPn)i = CT

[T ]

[M]=

d [T ]

d [M]


Chemical Structure : NMR

NMR

1H ppm

13C

pp

m

0.511.522.533.54

0

15

30

45

60

75


Chemical Structure : NMR

0.511.522.533.54

30kDa

15kDa

7.5kDa

2.5kDa

1H NMR (ppm)

Inte

nsi

ty (

a.u

.)

Atatic (mr) / Syndiotatic (rr)

Tageted Mw tacticity (rr/mr)30kDa 1.85/115kDa 1.80/17.5kDa 1.70/12.5KDa 1.44/1

An increase of the tacticity of the polymer is observed with theincrease of the molecular weight.


Chemical Structure : FTIR

6508501050125014501650Wavenumber (cm

!1)

Ab

sorb

an

ce

(a

.u.)

1725

C=O

1466

C−H

2 sci

ssor

ben

d

1400

C−H

3 sym

ben

d

1270

C−O

stre

ch o

ut o

f pha

se12

39 s

trech

C−O

in p

hase

11

90 S

i−O

CH

311

40 C−O

+ s

kele

tal C−C

1070

Si−

OC

H3

981

CH 3 ro

ckin

g

845

Si−C

791

CH 3 ro

ckin

g

30kDa

15kDa

7.5kDa

2.5kDa

10001500200025003000

30kDa

15kDa

7.5kDa

2.5kDa

Wavenumber (cm!1

)A

bso

rba

nc

e (

a.u

.)


Size of the polymer : GPC & Dynamic Light Scattering


Synthesis method : Inorganic weight percentThe mass of the polymer mPoly is known. The mass of TEOS, mTEOS , used, is calculated to get a final Inorganic weight percentof Iw .

Inorganic Weight %

Iw =mSiO2

+mSiO1.5mSiO2

+mSiO1.5+mOrganic

) nTEOS =

Iw1�Iw

.nPolymer .Mw.Organic�nPolymer .Mw.SiO1.5Mw.SiO2

1 mol of TEOS gives 1 mol of SiO2 and 1 mol of polymer gives 1 mol of SiO1.5


Synthesis method : Ratio

The classical definition of the R ratio can’t be used in the study. Network precursors are also introduced by the polymer whichcounts only 3 alkoxy groups where TEOS has 4. Therefore, H2O and the catalyst are introduced relatively to the number of moleof alkoxy group.

Ratio definition

nAlkoxy = 3.nPolymer + 4.nTEOS

RH2O =nH2O

nAlkoxy; RCatalyst =

nCatalystnAlkoxy

; REtOH =nEtOHnAlkoxy

Table : Reagent which is needed for 1g of polymer and RH2O=1, RCatalyst =0.01, REtOH =1

Reagent Mw (g.mol�1) D (g.mL�1) n (mmol) V (mL)Ethanol 46.07 0.789 32.2 1.88

H2O 18.01 1 14.3 0.258HCL 1M 1 0.32 0.322

TEOS 208.33 0.933 5 1.123Alkoxy group - - 32.2 -


Chemical Structure : FTIR

6508501050125014501650Wavenumber (cm−1)

Absorbance (a.u.)

30kDa15kDa7.5kDa2.5kDa

6508501050125014501650Wavenumber (cm−1)

Abs

orba

nce

(a.u

.)

30kDa15kDa7.5kDa2.5kDa


Thermoanalysis

125 250 375 500 625 7500

102030405060708090

100

Temperature (oC)

Mas

s los

s (%

)

2.5kDa7.5kDa15kDa

125 250 375 500 625 7500

2

4

6

8

10

12

Temperature (oC)

DSC

(mW

.mg−

1 ) −−>

exo

2.5kDa7.5kDa15kDa

Composition TGA DSC Residual massinflection pt (oC) exothermic peaks(oC) (%)

2.5kDa 366.8 377.2 &394.5 28.9I29 7.5kDa 368.8 313.8 & 365 31.6

15kDa 363.2 302.7 & 368.2 29.52.5kDa 349.3 359 & 377.5 48.5

I50 7.5kDa 336.4 310.9 & 336.4 50.715kDa 302.1 296.2 & 315.1 52.5


Thermoanalysis

0 50 100 1500

10

20

30

40

50

60

70

Time (min)

[Si]

(µg.

ml−

1 )


Mechanical properties

Nonoindentation using berckvich indenter.

2.5KDa 15KDa 3

3.5

4

4.5

5

Redu

ced

youn

g m

odul

us (G

Pa)

50% inorganic

0 500 1000 1500 2000 25000

10

20

30

40

50

60

Displacement (nm)

Forc

e (m

N)

50% inorganic, 2.5kDa50% inorganic, 15kDa


The end

Thanks for your attention


1

Silica – polysaccharide hybrids for bone tissue regeneration

Sol-gel meeting

18th April 2013

Yuliya Vueva

Intra-European Fellowship for career development (IEF) - Marie Curie

2

Objectives

The aim of the project is to create new bioactive porous hybrid scaffolds that fulfil all the criteria of a scaffold for bone regeneration

Preparation and characterization of hybrids by incorporating in the sol-gel process natural polysaccharide polymers

(Carrageenans, Alginates, Celluloses)

naturally occurring, biodegradable, nontoxic

used in the food industry and in medic, in the field of drug delivery

provide an alternative and novel method for introducing calcium into the hybrids

The principle challenge will be to produce hybrid materials with covalent bond between the organic (polysaccharide) and inorganic (silica) part of the hybrid with controllable degradation and mechanical properties matching the host bone

IEF Marie Curie – HABER

Carrageenans

Carrageenans are sulphated linear polysaccharides of D-galactose and 3,6-anhydro-D-galactose extracted from certain red seaweeds

Iota -carrageenan

Interesting for hybrids application

•  Iota-carrageenan produces soft and elastic gels •  Carrageenans are anionic polyelectrolytes which gives the posibility of Ca2+ to be incorporated in the hybrid network Carrageenan Issues

•  Solubility problems - soluble only in water at 70oC; depending on the molecular weight; 10 mg/ml maximum •  Viscosity of solution - difficult to obtain homogenous gels

•  Modification with Si coupling agents is difficult due to the solubility issues -  modification with GPTMS could be performed only in heterogenous conditions -  the resultant product is insoluble

50.00 µm

Si+MC: 201; TC: 1.217e+007

200

190

180

170

50.00 µm

Ca+MC: 982; TC: 6.293e+007

980

970

960

950

940

930

920

0 200 400 600 800 1000

0

500000

1000000

1500000

2000000

2500000

3000000

Inte

nsity

(cou

nts)

Data points

Si+ (27.9915) Ca+ (39.9852) total (Intensity (Raw))


SIMS

40 %CAR 60 %SiO2Ca2+

Hybrids with alginates

4

Guluronic acid

Mannuronic acid

•  Anionic polysaccharides derived from seaweeds •  In presence of Ca2+ form gels crosslinked by complexation with Ca2+

•  Contain carboxylic functional groups - Good potential for modification •  Potential to produce hybrids with double crosslinking (chemical and physical ionic crosslinking)

Alginate

Crosslinking of alginate with Ca2+

5

Alginate modification with GPTMS

Fictionalisation reaction

Alginate

ester

Guluronic acid

Mannuronic acid

30 mg/ml Alginate in 0.01 M HCl

RSH > RNH2 > R2NH > RCOOH > SiOH >> ROH > H2O

Relative reaction rates of different functional groups toward epoxy groups


R

O

O O Si

OH

OH

OHOH

e’’

f’’

1H NMR

GPTMS + Alg 12h

GPTMS + Alg 3 days

Alginate

GPTMS in D2O/DCl

Alg

Alg Alg

Alg Alg

Alg

Alg Alg

Alg

f1 f2

O SiOH

OH

OHOH

OH a

b

c d' e’

f’ diol

MeOH c

Courtesy of Louise

d

O Si

O

O

OO

CH3

CH3

CH3a

b c d e

f GPTMS Functionalised GPTMS

pH ~ 5

Dioxane Diol PEO

Dioxane Diol PEO

f1

f2

Epoxide opening versus silica condensation during sol-gel hybrid biomaterial synthesis, Luca Gabrielli, Laura Russo, Ana Poveda, Julian R. Jones, et. DOI: 10.1002/chem.200

HSQC of functionalised with GPTMS Alginate

3 days functionalisation

e

a

b

f1 f2

MeOH

12 h functionalisation

c

??

O SiOH

OH

OHOH

OH a

b

c d' e’

f’ Diol

R

O

O O Si

OH

OH

OHOHe’’

f’’ e f’

e’ d1 d’ d2

a

b

f2 f1

MeOH

e f’ e’ d1

c

d’ d2

Alg

Functionalised GPTMS

8

Issues and conclusions

•  Polymer concentration is not high enough to achieve suitable 1H and 13C NMR signals

•  This is not clear if the covalent linkages are lost in the background along with the polymer signal or is no covalent coupling occurring

•  The epoxy ring is not fully opened during fictionalisation of alginate at pH 5. The main compounds detected are diol, dioxane and PEO.


Dissolution study of alginate-silica hybrids

Dissolution study in Tris

0

20

40

60

80

100

120

140

160

0 50 100 150 200 250 300 350

µg/m

l

Time (h)

Si release

Alg2 Alg5 Alg10

Alg15 Alg0 300 500 700 900 1100 1300 1500 1700 Wavenumbers, cm-1

Alg0 0h

Alg0 672h

COO- C=O

300 500 700 900 1100 1300 1500 1700 1900 Wavenumbers, cm-1

Alg2 672 h

Alg2 0h

C=O$COO%$

Sample$with$GPTMS$GC2$$$

Sample$without$GPTMS$

•  Early&release&of&silica&is&rapid&when&alginate&is&not&coupled&with&GPTMS.&&

•  No alginate after 4 weeks in TRIS for the sample without GPTMS

•  The samples coupled with GPTMS showed very weak bands corresponding to carboxylic groups of alginate

•  Most of the polymer had dissolved after 4 weeks in Tris


Modification of Alginate with APTES

Reaction utilizing carbodiimide chemistry

H2N C2H5

C2H5 C2H5

N H

3C2H5OH EDC/NHS

amide bond


1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride

EDC NHS

N-Hydroxysuccinimide

ATR-FTIR of alginate modified with APTES

1900 1800 1700 1600 1500 1400 1300

NH2

NHC=O (amide)

C=O COO-

COO-COO-

Alginate

APTES + Alginate

Abs

orba

nce

a.u.

Wavenumbers, cm-1

APTES

C=O

NHS

Formation of amide bond

Preliminary study of the reaction of APTES with Alginate

pH = 6

After dialysis of Alginate-APTES solutions the APTES is still present in the solution. – Functionalised Alginate

Further work

•  Optimization of reaction conditions for modification of Alginate with APTES

•  Evaluation of substitution degree by ICP and NMR

•  Optimization Alginate-silica hybrid synthesis

Documents

Integration of acrylate polymer in sol-gel silica depending on their molecular weightsfhvjck/Solgel_files/Slides/18_4... · 2013-06-13 · How cross linking acrylate polymers are