Sequential Photodecomposition of Bisacylgermane Type Photoinitiator: Synthesis of Block Copolymers by Combination of Free Radical Promoted Cationic and Free Radical Polymerization Mechanisms

A block copolymer of cyclohexene oxide (CHO) and styrene (St) was prepared by using bifunctional visible light photoinitiator dibenzoyldiethylgermane (DBDEG) via a two-step procedure. The bifunctionality of the photoinitiator pertains to the sequential photodecomposition of DBDEG through acyl germane bonds. In the first step, photoinitiated free radical promoted cationic polymerization of CHO using DBDEG in the presence of dipbenyhodonium hexafluorophosphate (Ph2I(+)PF6(-)) was carried out to yield polymers with photoactive monobenzoyl germane end groups. These poly(cyclohexene oxide) (PCHO) prepolymers were used to induce photoinitiated free radical polymerization of styrene (St) resulting in the formation of poly(cyclohexene oxide-block-styrene) (P(CHO-b-St)). Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as NMR, IR, and DSC spectral measurements. (C) 2009 Wiley Periodicals, Inc. J Polyro Sci Part A: Polym Chem 47: 4793-4799, 2009