KINETICS OF IONIC PROCESSES IN RADIOLYSIS OF LIQUIDS .V. CATIONIC POLYMERIZATION OF ISOBUTYLENE UNDER ANHYDROUS CONDITIONS

By resorting to a rigorous experimental technique, it has been shown that the rate of the radiation-induced polymerization of isobutylene under anhydrous conditions is proportional to the 0.55 power of dose rate. In these circumstances, the kinetic chain lengths are extremely large with G(– m) values exceeding 108 molecules/100eV at the lowest dose rate. These results are perfectly explicable on the basis of polymerization by free ions. The rate of polymerization is almost independent of temperature between 40 and –78°, and the rate constant for propagation at 0° is estimated to be 1.5 X 108 M-1 sec-1. Chain transfer to monomer governs the molecular weight of the polymer which decreases as the polymerization temperature is raised. The results of this work cast considerable doubt on the interpretation of previous studies on the radiation-induced polymerization in the presence of solid additives. © 1969, American Chemical Society. All rights reserved.