Living radical polymerizations in homogeneous solution by using organic sulfides as photoiniferters

Abstract

Some examples for living radical polymerization in homogeneous solution by four organic sulfides as photoiniferters have been proposed. In the photopolymerization of styrene (St) with diphenyl disulfide (DPD), tetraethyl thiuram disulfide (TD), benzyl diethyldithiocarbamate (BDC) and 2-phenylethyl diethyldithiocarbamate (PEDC), both the yields and the average-molecular weights of the polymers were found to increase as a function of the reaction time. The results obtained suggested that these polymerizations proceeded via a living radical mechanism. When these photoiniferters except DPD were used, the propagating polymer chain end was confirmed to be always the diethyldithiocarbamate [(C2 H5)2NCSS] group, which can further photodissociate into a reactive propagating radical and a less reactive small radical[(C2H5)2NCSS·] in order to result in successive insertion of monomer molecules into the dissociated bond.