Alex van Herk, Hans Heuts, Martin Jung, Syed Imran Ali...

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Multicompartment latex particles design based on possible biomedical and coatings applications

Alex van Herk, Hans Heuts,

Martin Jung, Syed Imran Ali, Dirk-Jan Voorn,

Marshall Ming, Jens Hartig

Emulsion Polymerization Research Group

Eindhoven University of Technology

Berlin July 12 2009

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Molecules Particles

Polymer Colloids

SuprastructuresFunctionalities

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Polymer Colloids = Latex particles are nanosized

polymer particles, colloidally stabilized (usually) in water.

Main production methods: -Emulsion polymerization

-Miniemulsion polymerization (77)

Main applications: -Water-borne Coatings (paper/architectural/car)

-Water-borne Adhesives

100nm1nm

100nm1nm

Polymer Colloids

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Emulsion polymerization

Miniemulsion polymerization

Microemulsion polymerization

Suspension polymerization

μm

nm

μm

nm

nm

Production techniques

6addapted from Mohwald Internet source

Encapsulation in aqueous media

Molecules Particles

LBL Driving force: Charges/Other Emulsion polymerization

Driving force: Water Insolubility

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Release of drugs, crosslinking agents, anti-

corrosive agents etc.

Time Time

Concen

tration

Pulse Pulse

Continuous release,

often based on

(bio)degradation of

polymer.

Pulsatile response,

based on external

trigger pulse, e.g.

pH, Ultrasound,

heat. Release per

pulse not constant.

Time

Pulsatile response,

based on external

trigger pulse, e.g.

pH, Ultrasound,

heat. Release per

pulse constant.

Pulse Pulse

Controlled Release Profiles

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Targeting in the human body

• Targeting particles to enter certain organs in the human body depends on particle size. For example targeting nanoparticles preferable to brain tissue requires particles of 100 nm

• For example, other organs need particles of 50-70 nm

• Preferably narrow particle size distributions because release and degradation will depend on particle size

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Influence of particle size

• Implant too big, molecules on the outside of the

implant will quickly release, molecules on the

inside much slower. It is expected that reducing

particle size will lead to more uniform release

per pulse. Bigger molecules need smaller

particles to be able to diffuse out Ddif

• For targeting also a specific particle size is

needed Dtar Ddif ≠ Dtar

Dtar

Ddif

Multicompartment nanoparticle where

all compartments are the same; Pimple

particle

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Nanobottles

Pulsatile release of substances by a 2

compartment particle where one part is the container

and the other part (the lid) is controlling diffusion out of

the container through external triggering; nanobottle

2-compartment nanoparticle;

Nanobottle

4-compartment nanoparticle;

Vinegar-oil nanobottle

Janus particle

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Vesicles as a route towards multicompartment

nanoparticles

swell bilayer

with monomer polymerize

Jung et al. Langmuir 1997, 13, 6877; Langmuir 2000, 16, 968.

Nanobottles

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application of polymerisable amphiphiles

+ crosslinking amphiphiles

+ styrene

100 nm 100 nm

Influence of initiator.

The “matrioshka” architecture

On the way towards Vinegar-oil nanoparticlesthermal polymerisation at 60°C, V50

100 nm

N NNH

H3N

HN

NH3

ClCl

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Styrene

Vesicle Polymerization…

Some new morphologies.

Nanobottles Pimple particles Pimple particles

Butyl acrylate Butyl methacrylate

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Hybrid multicompartment nanoparticles

Clay/Polymer nanocomposites• Recently clay platelets have been introduced as

nanocontainers for the release of, for example, anticorrosive

agents in paints;M.l. Zheludkevich et al. University of Aveiro, Portugal, CoSi Conference 23-27 june

2008

• Clay platelets can also be regarded as morphology modifiers

• Clay platelets can improve barrier properties of coatings

Why anisotropic composite latex particles?

• Clay encapsulated spherical latex particles can improve material properties

by giving maximum exfoliation and minimum aggregation

Flat

particles

Spherical

particles

• Anisotropic (preferably flat) latex particles can induce anisotropy into the

final film and this would significantly improve the final properties

• For example, barrier properties might be expected to improve because clay

platelets align parallel to the substrate during film formation

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Challenges in Clay encapsulation

through emulsion polymerization

Armoured

latex

particles

Secondary

nucleation

Stacking

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Procedures for clay encapsulation by emulsion

polymerization

Edge modification

Face modification

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Modifications of clay

Face modification through PEO-V+ cation exchange

• PEO-V+ readily exchange with the Na+ stabilizing molecules

Covalent edge modification

• Titanate and siloxane modification of clay by

reaction with OH groups is possible in water,

ethanol and dichloromethane Deuel et al., Helv. Chim. Acta 1950 33(5) 1229-1232

OO

On

O

O

N OO N O

On

Cl

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Face modification of clay platelets

Face modification of the surface with cationic

molecules did not enable polymerization at the surface

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Starved-feed emulsion polymerization of

edge modified MMT

• A feeded addition of monomer is needed to minimize the formation

of “empty” latex particles

• The content of latex particles containing a clay platelet is between

60-70 % (based on counting with TEM)

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Proposed mechanism

Edge modification Initial polymer

formation at the

edge; donut

structure

Engulfing of the

faces, leading to

Dumbbell/Peanut

shape

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Settling of dumbbell shaped nanocomposites shows that

clay is predominantly lying perpendicular to the substrate

Film formation, where is the clay?

Monomer/

Initiator

Polymer Shell

The approach

• Synthesize short anionic amphiphilic random macro-RAFT

copolymers

• Adsorb these macro-RAFT agents onto the oppositely

charged substrate

• Initiate polymerization with a fresh supply of initiator and

desired monomer(s)

Nguyen, D.; Zondanos, H. S.; Farrugia, J. M.; Serelis A. K.; Such C.H.; Hawkett, B. S, Langmuir (2008), 24(5), 2140-2150.

The substrate

•GIBBSITE is chosen because:

•Easy to synthesize

•Particles are monodisperse

•Product easy to image

•Isoelectric point at pH 9 -10

provides ideal working window

for encapsulation

•Encapsulation at pH 7

•Good positive surface charge

for adsorption of negative

macro-RAFT

Synthesis of random RAFT copolymers

2X = 5BA-co-5AA

CH2

CH2S S

S

CH2

XCH2

X S S

S

+ AA/BA =

• In dioxane using AIBN at 70OC

• RAFT agent: Dibenzyl trithiocarbonate (easy to make;

commercially available)

• RAFT/AIBN = 11

Shell thickness can easily be controlled!

50% conversion sample 100% conversion sampleSyed Imran Ali, Johan P.A. Heuts, Brian S. Hawkett and Alex M. van Herk.

Langmuir, Accepted for publication. May, 2009

Gibbsite platelets encapsulated with MMA, grown with the BA/AA

macroRAFT agent 5BA-co-5AA and ABCZ as initiator, 70 C

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4-compartment nanoparticle;

Vinegar-oil nanobottle

2-compartment nanoparticle;

Nanobottle

Janus particle

Pimple particle

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Future research

• Morphology and film formation of latex particles

with clay inside (multiphase particles)

• Actual release experiments with the nanobottles

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Acknowledgements

Prof. Brian Hawkett (University of Sydney)

Dr. Marshall (W.) Ming, Prof. Bert de With (TU Eindhoven)

Foundation Emulsion Polymerization (SEP)

Dutch Polymer Institute (DPI)