Photoactive allyl ammonium salt (BPEA) containing benzophenone moiety in the structure was synthesized and characterized. Its capability to act as a self-initiating addition fragmentation agent in the photoinitiated cationic polymerization of oxiranes such as cyclohexene oxide and vinyl monomers such as butylvinyl ether was investigated. These monomers turned out to be polymerizable in the presence of BPEA provided free radicals are generated photochemieally at lambda > 300 nm by hydrogen abstraction of excited benzophenone moiety. Accordingly, a free radical adds to the carbon-carbon double bond of a ground state BPEA and fragmentation of the adduct radical results in the formation of reactive ammonium radical cation which is essentially responsible for the initiation. (C) 2002 Elsevier Science Ltd. All rights reserved.