Polymers anionic grafting

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). 

Anionic grafting methods (vide infra) can be applied to the synthesis of comb-shaped polymers. As an example, a polystyrene backbone is partially chloromethylated (under mild conditions) and used as an electrophilic deactivator for a living polystyrene 89). The grafting onto process yields well defined species that have been characterized accurately. The branches are distributed randomly along the backbone 90). 

Gauthier, M. and Mdller, M. Uniform highly branched polymers hy anionic grafting Arborescent graft polymers. Macromolecules, 24, 4548, 1991. 

A Cationic Graft Copolymer of Lignin. The applications of the anionic graft copolymers described above are many but the negative charge on the polymer or the behavior of the anionic polymer under application conditions often limit the utility of these materials. 

Zilkha, A., B. A. Feit, and A. Bar-Nun Anionic graft copolymerization of vinyl monomers on natural polyhydroxy compounds, their derivatives, and on synthetic polyhydroxy polymers. Israeli Pat. 15 962, Oct. 1962 C. A. 58, 5803 (1963). 

Polyvinylchloride can also be anionically grafted. With this method the chain breaking property of alkyl halides is utilised whereby the active anionic polymer is terminated with the alkyl group in the case of PVC the anionically synthesised polymer becomes the grafted chain 21). Hereafter, this review will be concerned only with those grafting methods involving azo functions. 

Fibrous anion exchangers were prepared from polypropylene staple fibres 22 mcm in diameter by radiation grafting of polystyrene followed by chloromethylation and amination of the grafted polymer. The grafting was... 

Ionic routes such as formation of the polymer anion by reaction with a strong base or the direct reaction of a polyamide with sodium are less likely to be used in reactive processing than is free-radical initiation. The process of self-graft polymerization by chain transfer to polymer, when it occurs in a single monomer/polymer system during polymerization, is an example of chain branching that is discussed in the next section. 

Copolymers containing the isoelectronic Si-0 backbone grafted to the P-N backbone were obtained by using the polyphosphazene anion to open the ring in hexamethylcyclotrisiloxane (23, 24). To avoid crosslinking reactions, a THF solution of the polymer anion at -78 0 was treated with [Me2SiO]3 and the resulting mixture was warmed to room temperature and stirred for two hours. 

The grafting onto, although offering unlimited chance for various architeaures, suffers from stria reaction conditions, which are almost similar to those used in the anionic polymerization process. The highly aaive polymer anion has less tolerance to functional groups for further chemical reaaion or modification. Click chemistry may overcome this shortcoming, but there is still no efficient method to attach long side chains to the backbone. 

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