PHOTOCHEMICALLY AND THERMALLY-INDUCED RADICAL PROMOTED CATIONIC POLYMERIZATION USING AN ALLYLIC SULFONIUM SALT

The photochemically and thermally generated radical promoted cationic polymerization of epoxides such as cyclohexene oxide (CHO) and vinyl m onomers such as n-butyl vinyl ether (EVE) and N-vinyl carbazole (NVC) is reported. This system consists of an allylic sulfonium salt, and ph otochemical and thermal radical initiators. Photoinduced radical gener ation was achieved with benzoin (B) and 2,4,6-trimethylbenzoyl dipheny lacylphosphine oxide (TMDPO) which absorb light at wavelengths where t he sulfonium salt is transparent. A feasible mechanism involves radica l addition to the allylic double bond and subsequent fragmentation to yield reactive species capable of initiating cationic polymerization. An alternative mechanism which involves the oxidation of electron dono r radicals is also discussed. The enhanced activity of the thermal ini tiators, 2,2'-azobisisobutyronitrile (AIBN), benzoyl peroxide (BP) and phenylazotriphenylmethane (PAT) was confirmed in the polymerization o f CHO initiated by the sulfonium salt at 60 degrees C.