Radiation‐induced polymerization at high dose rate. II. α‐Methylstyrene in bulk

Abstract Bulk polymerization of α‐methylstyrene was carried out in a wide dose rate range, 7.6–256 rad/sec by γ rays and 8.5 × 103–2.1 × 105 rad/sec by electron beams. At high dose rate by electron beams, cationic polymerization took place along with formation of oligomeric product of DPn = ∼4. At low dose rate by γ rays, radical polymerization was found to occur in water‐saturated monomer. The cationic polymerization at high dose rate proceeds with essentially the same mechanism as was already known in γ‐ray polymerization of dry monomers. Relatively low reaction rate of the cationic polymerization compared with that of styrene is explained with the fact that the propagation of α‐methylstyrene is much more easily inhibited by a slight amount of water.