Cationic polymerization of cyclic sulphides. I. Kinetic study of the polymerization of 3.3‐dimethylthietane initiated by triethyloxonium tetrafluoroborate

The kinetics of the cationic polymerization of 3,3‐dimethylthietane with triethyloxonium tetrafluoroborate in methylene chloride at 20°C have been studied. The polymerization is characterized by a very fast initiation reaction. The propagation occurs most probably via cyclic sulphonium ions. The existence of a termination by reaction of the growing chains with sulphur atoms of the polymer chain was demonstrated by kinetic and molecular weight measurements. The propagation constants kp and termination constants kt at different temperatures were calculated. The enthalpies of activation for the propagation and termination reactions are, respectively, ΔH≠p = 12.5 kcal mole−1, ΔH≠t = 7.4 kcal mole−1, and the corresponding entropies of activation are ΔS≠p = ‐26 cal deg−1 mole−1, ΔS≠t = ‐49 cal deg−1 mole−1.