The sulfinic acid‐initiated polymerization of methyl methacrylate

Abstract

Abstract The rate of polymerization of methyl methacrylate initiated by p ‐methoxybenzenesulfinic acid, benzenesulfinic acid, and p ‐trifluoromethylbenzenesulfinic acid in the absence of oxygen was studied. The p ‐methoxy substituent accelerated the rate while the p ‐trifluoromethyl substituent acted as a retarder. The order of the rate with respect to sulfinic acid concentration varied between 1 and 3/2; this is consistent with an initiation process of kinetic order between 2 and 3. Dilution of the monomer with benzene in an attempt to determine the order of the rate of polymerization with respect to monomer unexpectedly resulted in an increase in rate. Mixtures of p ‐methoxybenzenesulfinic acid and p ‐trifluoromethylbenzenesulfinic acid did not give an acceleration in rate. The rate of polymerization was accelerated by sulfonic acid, benzoyl peroxide, dicumyl peroxide, and di‐ n ‐butylamine hydrochloride. Decomposition of the very unstable 2,2′‐biphenyldisulfinic acid by disproportionation to the intramolecular sulfonic acid‐sulfenic acid was shown to be incompatible with the yield and rate of formation of the thiolsulfonate. The gross features of a mechanism consistent with the polymerization data is proposed.