Addition-fragmentation chain transfer to polymer in the free radical ring-opening polymerization of an eight-membered cyclic allylic sulfide monomer

Department of Applied and Bioapplied Chemistry, Faculty of Engineering, Osaka City. A detailed investigation of chain transfer to polymer during free radical ring-opening polymerization of the eight-membered disulfide monomer 2-methyl-7-methylene-1,5-dithiacyclooctane (MDTO) is presented, It bas been shown that extensive chain transfer to polymer occurs involving both poly(MDTO) radicals and cyanoisopropyl radicals. Significant decreases in molecular weight were observed when cyanoisopropyl radicals wore generated in the presence of poly(MDTO) in the absence of monomer. The molecular weight distribution (MDTO) obtained from polymerization of MDTO in the presence of pre-added poly(MDTO) was markedly different from that obtained without pre-added polymer. A kinetic model was constructed in an attempt to quantitatively describe the chain transfer to polymer process based on the addition fragmentation chain transfer mechanism. It was found however that the simulated MWDs were considerably broader than the experimental MWDs, which were similar to the Schulz-Flory distribution.