End-Capping of Living polymeric Anions

A great deal of work most of which was published in patents was carried out along this line. As mentioned already, the basic principle of anionic deactivation is to react a monofunctional living polymer with an unsaturated electrophile. It must be ensured that this deactivation predominates with respect to the attack 

Unsaturated electrophiles that have been employed for the purpose of synthesizing macronomers are compiled in Table 1. 

As already mentioned allyl unsaturation is not very reactive as far as free-radical polymerizations are concerned 

In a recent paper Sharkey et al. 20) have shown that carbanions of lower reactivity such as those originating from methyl methacrylate do react with organic halides such as allyl bromide. The reaction proceeds quantitatively and rapidly at — 78 °C in THF solution. No side reaction has been detected. 

Asami21 studied this reaction. Even in the presence of a tenfold excess of VBC, is the reaction strongly influenced by the nature of the solvent, lithium being the counterion. Asami established that when the reaction medium contains tetrahydro-furan (THF) no side reaction (leading in fine to a molecular weight increase) was detected. The polystyrene obtained contains at its chain end a styryl group. 

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Indirect Methods using End-Capping of Living Polymeric Anions... 

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