Group Transfer Polymerization GTP

GTP produces a living polymer, such that each chain is terminated by a silyl ketene acetal that will be stable once all monomer is exhausted. Thus, all the advantages of living poly- 

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The anionic polymerization of methacrylates using a silyl ketene acetal initiator has been termed group-transfer polymerization (GTP). First reported by Du Pont researchers in 1983 (100), group-transfer polymerization allows the control of methacrylate molecular stmcture typical of living polymers, but can be conveniendy mn at room temperature and above. The use of GTP to prepare block polymers, comb-graft polymers, loop polymers, star polymers, and functional polymers has been reported (100,101). 

These TMS-carbamate-mediated NCA polymerizations resemble to some extent the group-transfer polymerization (GTP) of acrylic monomers initiated by organo-silicon compounds [40]. Unlike GTPs that typically require Lewis acid activators or nucelophilic catalysts to facilitate the polymerization [41], TMS-carbamate-mediated NCA polymerizations do not appear to require any additional catalysts or activators. However, it is still unclear whether the TMS transfer proceeds through an anionic process as in GTP [41] or through a concerted process as illustrated in Scheme 14. 

Synthesis of Block Copolymers by Group Transfer Polymerization, GTP... 

Group transfer polymerization (GTP) requires either a nucleophilic or Lewis acid catalyst. Bifluoride (HF2) and fluoride ions, supplied by soluble reagents such as tris(dimethylamino)-sulfonium bifluoride, [(CH3)2N]3SHF2, and (w-C NF, are the most effective nucleophilic catalysts, although other nucleophiles (CN , acetate, p-nitrophenolate) are also useful. Zinc... 

Based on evidence available at the time, the DuPont workers proposed that the trimethylsilyl group was transferring to monomer as it was adding to the polymer chain ends and thus named the new procedure Group Transfer Polymerization (GTP). Based on all the evidence now available this mechanism is almost certainly wrong but the name should remain since it is firmly imbedded in the chemical literature. 

Group transfer polymerization (GTP) must be co-initiated by bases or acids. Nucleophilic compounds are preferred because only a small amount is needed, only about 0.1 % with respect to the initiator which most often is... 

The most thorough mechanistic investigation which supports an intramolecular silyl group migration has been carried out in connection with the method known as group transfer polymerization (GTP), f6r the polymerization of acrylic monomers182. This involves a catalysed Michael addition of silyl ketene acetals 89 to a,/ -unsaturated esters,... 

Zirconocenes and lanthanocenes active for olefin polymerization do, in fact, carry out well-controlled homopolymerizations of (meth)acrylic monomers, but polymerization takes place by an enolate mechanism in which the conjugated carbonyl group plays a crucial role in stabilizing the active center. Both monometallic and bimetallic mechanisms have been documented. Collins and co-workers developed a zirconocene group-transfer polymerization (GTP) technique for the polymerization of methyl methacrylate (MMA) which utilizes a neutral zirconocene enolate as an initiator and the conjugate zirconocene cation as a catalyst (Scheme 3). ... 

SCLCPs have also been prepared by group transfer polymerization (GTP) of mesogenic methacrylates are room temperature [47, 48]. The livingness of the nucleophilic catalyzed GTP was originally attributed to a new mechanism (Eq. 12), in-... 

Group-transfer polymerization (GTP) was discovered by scientists at DuPont and involves the conjugate Michael addition of an enol silane or related compound to acrylate or methacrylate monomers under the influence of an activator. The process is related to anionic polymerization but the species involved are believed to feature a high degree of covalent character in the transition state for chain growth. 

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