Substituent effect on the cationic ring-opening polymerization of acyloxymethyl five-member cyclic dithiocarbonates

Abstract

Five-member cyclic dithiocarbonates were synthesized by the reactions of carbon disulfide with benzoic, p-anisic, p-chlorobenzoic, 1-naphthalenecarboxylic, p-nitrobenzoic, and p-(tert-butyl)benzoic glycidyl esters, and their cationic ring-opening polymerizations were carried out with methyl trifluoromethane sulfonate and trifluoromethane sulfonic acid as initiators at room temperature to 80°C. Polymers with number-average molecular weights of 3400-24,900 were obtained in high yields, and their structures were estimated by NMR and IR spectroscopy. The monomers showed a clear difference in the polymerization rate according to the substituents. The rate of polymerization decreased in the order of p-chlorobenzoic ≥ benzoic > 1-naphthalenecarboxylic > p-nitro-benzoic > p-tert-butylbenzoic > p-anisic. The data of the reaction kinetics, NMR studies, and molecular orbital calculations proved a plausible mechanism involving the participation ofp-substituted benzoyloxymethyl groups to stabilize the cationic propagating end. The polymers showed decomposition temperatures with 5% weight loss ranging from 200 to 260 °C. No glass-transition temperatures for the polymers were observed below 200 °C by differential scanning calorimetry.