ESR studies of the interaction of propagating radicals with diacetylenes

ESR studies were carried out for the polymerization systems of some vinyl monomers in the presence of diacetylenic compounds in order to determine the nature of interaction between the propagating radicals with the diacetylenes. The systems used in this study were methylmethacrylate, styrene and methylacrylate with diphenylbutadiyne and phenyl-4′-vinylphenylbutadiyne using 2,2′-azobisisobutyronitrile as an initiator. ESR spectra showed a broad triplet for the styrene system, which became exchange narrowed for the methylmethacrylate system. This is explained in terms of increased interaction between the propagating radicals and the diacetylene for methylmethacrylate than styrene. The propagating radicals are considered to be trapped temporalily by the diacetylenes during polymerization, but they do not react until the polymerization system becomes extreemly viscous.