Similar products but different mechanisms in thermal and photodegradation of vinyl polyperoxides

Vinyl polyperoxides degrade through two competing reactions, they pyrolyze unimolecularly through a chain unzipping process but they photolyze mainly through a disproportionation mechanism involving hydrogen transfer process. Surprisingly, in dilute solutions, we have observed that vinyl polyperoxid es such as poly(styreneperoxide), poly(methylmethaclate peroxide), poly(alp ha-methylstyreneperoxide) and poly(alpha-phenylstyrene peroxide) photolyze to give the same products which are obtained through the chain unzipping pr ocess. Still, the photodegradation mechanism seems to be different than the thermal degradation. While thermal degradation is controlled by the dissoc iation of the O-O bonds, the photodegradation depends upon the stability of the bialkoxy radicals. The poly(alpha-phenylstyrene peroxide), however, sh ows unusual thermal and photostability which has been explained from stable crystalline structure and retarding effect of the degradation product, res pectively. (C) 2000 Elsevier Science Ltd. All rights reserved.