S-PHENYL THIOBENZOATE AS A NEW SULFUR-CONTAINING PHOTOINITIATOR - A PRODUCT, LASER FLASH-PHOTOLYSIS AND PHOTOPOLYMERIZATION STUDY

Photolysis of the title compound (1) in benzene gives benzaldehyde, diphenylsulphide and biphenyl; these are formed from α fission of the excited triplet state of 1 which yields benzoyl and thiyl radicals. The aryl substituent has a significant influence on the efficiency of photocleavage. The benzoyl radical is detected by time-resolved laser spectroscopy and the results of kinetic analysis are in complete agreement with those obtained from the product investigation. Photopolymerization of phenyldiethyleneglycol acrylate in the presence of 1 results in the formation of a polymer whose yield is roughly correlated with the photoreactivity of 1. The effect of initiator concentration on the photopolymerization efficiency suggests that 1 acts as an iniferter (initiator-transfer agent-terminator), with the benzoyl radical as initiator and the thiyl radical as terminator. © 1990.