Group transfer polymerization (GTP) is a "quasi-living" polymerization technique discovered in the 1980s. It allows for the polymerization of methacrylates and acrylates at room temperature using silyl ketene acetal initiators and Lewis acid catalysts. GTP offers excellent control over polymer architecture, producing block copolymers and star polymers with low polydispersity. Recent work has applied GTP to polymerize biobased monomers like itaconic acid esters. N-heterocyclic carbene catalysts have also shown potential as alternatives to traditional bifluoride catalysts for GTP.

1. Group Transfer
Polymerization
(GTP)
Sujoy Saha (20101095)
Nikhil Y. L. K. (2009004)

2. Brief Overview
• Introduction
• Discovery of Method
• Synthetic Routes
• Mechanisms:
Then and Now
• Applications
• Pros and Cons
• Paper (2)
• Conclusion

3. 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

4. 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 !!!

5. •“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

6. Synthetic Routes
• Always start with conjugate addition of silyl ketene acetal initiators
• Monomer: Methacrylates, Acrylates, Ketones, Nitriles, Carboxamides
-Nucleophilic Anions
KHF2
TASHF2
Bu4NF
TASCN
Et4NCN
TASN3
-Lewis Acids
ZnBr2
ZnI2
ZnCl2
(i-Bu2Al)2O
i-Bu2AlCl
Et2AlCl
Webster et al., J. Am. Chem. Soc. 1983, 105, 5706-5708
Sogah et al., Macromolecules, Vol. 20, No. 7, 1987
• Catalysts: Two choices

7. Mechanisms

8. 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

9. Spinelli, H.J. Prog. Org. Coat. 1996, 27, 255-260
Applications
• Pigment Dispersant
• Emulsion Stabilizers
• AB block co-polymer
A = Hydrophilic Block
B = Hydrophobic Block
H2O
H2O
H2O
H2O

10. Spinelli, H.J. Prog. Org. Coat. 1996, 27, 255-260
Applications
• Pigment Dispersant
• Emulsion Stabilizers
• AB block co-polymer
A = Hydrophilic Block
B = Hydrophobic Block
H2O
H2O
H2O
H2O

11. 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

12. Conc: NHCs demonstrate equivalent activity and superior control in comparison
to bifluoride-catalyzed systems.
Results

13. 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.

14. 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.

15. 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.

16. • 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

17. 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