Radiation-induced polymerization at high dose rate. IV. Chloroprene in bulk

Bulk polymerization of chloroprene was studied at 25/sup 0/C in a wide dose rate range. Variations of the rate of polymerization (R/sub p/) and molecular weight as a function of dose rate were essentially the same as those in several monomers that are capable of radical and cationic polymerizations. The polymerization proceeds with radical mechanism at low dose rate and with radical and cationic mechanism concurrently at high dose rate. The number-average molecular weight of the high-dose-rate products was ca. 2400. Microstructure of the polymers was mainly of trans-1,4 unit with small fractions of cis-1,4 and 3,4-vinyl unit. Fractions of the vinyl unit and the inverted unit in trans-1,4 sequence which increased at high dose rate reflected the change of dominant mechanism of polymerization. 6 figures, 2 tables.