Kinetics of polymerization reaction of α,α + ′-bis(tetrahydrothiophenio)-p-xylene dichloride

Polymerization reactions of α,α + ′-bis(tetrahydrothiophenio)-p-xylene dichlorides with OH in H₂O have been studied kinetically. The reactions proceeded via the α-tetrahydrothiophenio-p-xylylene intermediates. Results of the H-D exchange experiments and kinetic studies reveal that the 1,6-elimination forming the intermediates proceeds reversibly via the ylide intermediate. The observed rate of disappearance of the intermediate was increased by the addition of OH^-, tetrahydrothiophene, and S₂O₈^2- as well as by the photoirradiation with a tungsten lamp in the presence of Rose Bengal and was inhibited by TEMPO. However, the rate was found to be independent of ylide concentration. From these results, an elimination-free radical polymerization mechanism is proposed. The microscopic rate constants for each step of this mechanism were calculated from the change in the intermediate concentration with time. All of the rate data showed excellent correlations with the substituent constants in the Hammett plot.