S-Phenyl thiobenzoate derivatives are a new class of photoinitiator with high efficiency of photoinitiation for polymerization of vinyl monomers. The photolytic products of the title compounds included thiophenol, diphenyldisulphide, diphenylsulphide, benzoylbenzaldehyde and benzil. Cleavage of the C-S bond occurs under irradiation, resulting in the formation of free radicals. The substitution position of the compounds has a significant influence on the yield of photolytic products. The rate of photopolymerization also depends strongly on the position of the substiuents, the results are consistent with those obtained from the time-resolved laser spectroscopy. The order of rate of polymerization initiated by the title compounds with different substituted benzoyl is as follows: para-＞meta-≈ortho-.

Key words: BENZENECARBOTHIOIC ACID P, PHENYLESTER, INITIATOR, PHOTO POLYMERIZATION, FLASH PHOTOLYSIS, LASER, METHYLMETHACRYLATE