Reversible and irreversible inhibition in free-radical polymerization of methyl methacrylate mediated by 2,2,6,6-tetramethyl-1-piperidinyloxylстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Местоположение издательства:Road Town, United Kingdom
Первая страница:526
Последняя страница:535
Аннотация:It was shown that the interaction of MMA propagating radicals with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) may occur either reversibly to give rise to living PMMA-TEMPO adducts or irreversibly through disproportionation to yield the dead polymer and hydroxylamine. In the homopolymerization of MMA, the reaction predominantly proceeds via irreversible inhibition. Using ESR, gel permeation chromatography, quantitative chemical analysis, competitive inhibition, and radioactive label introduction techniques, the basic quantitative characteristics of the free-radical polymerization of MMA mediated by TEMPO were evaluated, namely, changes in the ratio of living and dead chains, in the concentration of free TEMPO in the course of reaction, and in the constants of dissociation of living PMMA-TEMPO adducts and interaction of a PMMA radical with TEMPO; the role of secondary inhibition in this process was estimated. On the basis of the data obtained, it was predicted and experimentally verified that the copolymerization of MMA with styrene predominantly proceeds according to the pseudoliving mechanism.