Group Transfer Polymerisation (GTP)

Group Transfer

Polymerization

(GTP)

Sujoy Saha (20101095)

Nikhil Y. L. K. (2009004)

Brief Overview

• Introduction• Discovery of Method• Synthetic Routes• Mechanisms:

Then and Now• Applications• Pros and Cons • Paper (2)• Conclusion

Introduction

• conjugate addition of silyl ketene acetals to α,β‐unsaturated carbonyl compounds

Organic Chemistry, Clayden, p-755

• Applied to alkylated methacrylate monomers and the initiator is a silyl ketene acetal.

• New monomer adds to the initiator and to the active growing chain in a Michael rxn.

• Discovered over 30 years ago at

• Anionic living polymerization- but active chain end is covalent

Discovery- A Story

Webster et al at DuPont’s Central R&D

• Methacrylate block polymers useful in automobile

finishes.

• at -80°C by sequential polymerization of different

methacrylate monomers under “living” anionic

conditions.

• maintaining reactors at -80°C !!!

•“living” anionic polymerization of methyl methacrylate with a 1,1-

diphenylhexyl anion containing a silyl protected –OH.

• trimethylsilyl ketene acetal could react with MMA to give polymer by a repetitive

Mukiayama reaction…..

• few unsuccessful reactions with Lewis acids such as BF3 etherate

• First production of PMMA by group transfer polymerization with ZnBr2 catalyst

• Name suggested by Trost

Discovery- A Story

Synthetic Routes

• Always start with conjugate addition of silyl ketene acetal initiators

• Monomer: Methacrylates, Acrylates, Ketones, Nitriles, Carboxamides

-Nucleophilic Anions

KHF2

TASHF2Bu4NF

TASCN

Et4NCN

TASN3

-Lewis Acids

ZnBr2ZnI2ZnCl2(i-Bu2Al)2O

i-Bu2AlCl

Et2AlClWebster et al., J. Am. Chem. Soc. 1983, 105, 5706-5708

Sogah et al., Macromolecules, Vol. 20, No. 7, 1987

• Catalysts: Two choices

Mechanisms

Pros and Cons

• Advantages

1. Good for making blocks of

acrylates and methacrylates

2. Can be done at RT and

elevated T

3. Excellent architectural control

(stars, blocks, etc.)

4. Low PDIs (can get down to

1.03!)

5. No metallic or halide impurities

left over

6. No bad odors!

• Disadvantages

1. Cannot be done in presence of

water

2. Initiator still costly

3. Cannot use monomers with

acidic or active hydrogen

functional groups

Spinelli, H.J. Prog. Org. Coat. 1996, 27, 255-260

Applications

• Pigment Dispersant

• Emulsion Stabilizers

• AB block co-polymerA = Hydrophilic BlockB = Hydrophobic Block

H2O

H2O

H2O

H2O

Spinelli, H.J. Prog. Org. Coat. 1996, 27, 255-260

Applications

• Pigment Dispersant

• Emulsion Stabilizers

• AB block co-polymerA = Hydrophilic BlockB = Hydrophobic Block

H2O

H2O

H2O

H2O

Group Transfer Polymerization of Acrylates and Methacrylates

using N-hetereocyclic Carbene Catalysts

- Scholten et al., Polymer Preprints 2007, 48(2),167

N-heterocyclic carbenes (NHCs) as potent catalysts

for GTP of methyl methacrylate and tert-butyl acrylate

Conc: NHCs demonstrate equivalent activity and superior control in comparison

to bifluoride-catalyzed systems.

Results

Group transfer polymerization of biobased unsaturated esters

-E. Kassi et al./ European Polymer Journal 49 (2013) 761–767

•(As the fossil resources dwindle) concerned with organic synthetic building blocks.

Group transfer polymerization of biobased unsaturated esters

-E. Kassi et al./European Polymer Journal 49 (2013) 761–767

•(As the fossil resources dwindle) concerned with organic synthetic building blocks.

Polymerization of Itaconic Acid esters

• can be obtained from “distillation” of citric acid.

• Attempted random block copolymerization of the pairs di(n-butyl)itaconate

(DBI) with methyl methacrylate (DBI-MMA) and 2-(dimethylamino)ethyl

methacrylate (DBI-MAEMA)

• Products were just DBI oligomers, whereas MMA and DMAEMA were not consumed.

• This indicated the greater reactivity of DBI compared to the methacrylates.

• attachment of 1–2 DBI units to the second short block of DMAEMA

• DMAEMA-DBI combination corresponds to amphiphilic block

copolymers capable of forming micelles in water

Conc: nature designed unsaturated compounds are not inert

Polymerization of Itaconic Acid esters

Conclusion

• Relatively new ‘quasi- living’ oxyanionic polymerization technique,

capable of the rapid, room-temperature polymerization of

α,β-unsaturated carbonyl compounds.

• Full of potential, still room for improvement

• Best method around for block polymers of methacrylate derivatives