MECHANISTIC AND KINETIC-STUDIES ON THE POLYMERIZATION OF STYRENE INITIATED BY DIMETHYL SULFONIUM 2-PYRIDYL CARBONYL METHYLIDE

Dimethyl sulfonium 2-pyridyl carbonyl methylide (Y(py-s)) initiated radical polymerization of styrene in dimethyl sulfoxide at 85 +/- 0.1-degrees-C for 6 h under a nitrogen blanket using dilatometric techniques has been studied. The initiator and monomer exponent values were calculated to be 0.5 and 1.2, respectively. The system follows ideal radical kinetics with bimolecular termination. The higher monomer exponent value is ascribed to significant solvent effects on the initiation rate. The overall activation energy and average value of k(p)2/k(t) are 52.0 kJ mol-1 and 1.0 x 10(-3) litre mol-1 s-1, respectively. The polymerization was retarded in the presence of hydroquinone or benzene; dimethylformamide, however, enhanced the rate of polymerization. Kinetic data and ESR studies indicate that the overall polymerization takes place via triplet carbene formation which acts as a source of free radicals.