On the copolymerization of acrylonitrile with styrene in the presence of Lewis acid, 2. Regulation of molecular weight

The results of the study of the acrylonitrile (AN)‐sytrene (St) copolymerization in the presence of zinc chloride and various hydrogen donors (cyclohexane, octane, isooctane, and decahydronaphthalene) are reported. It was found that the rate of copolymerization (Rp) increases with concentration of the hydrogen donor at constant concentrations of comonomers in acetone in the presence as well as in the absence of a free‐radical source (AIBN). The dependence of the reciprocal value of limiting viscosity number (1/[η]) of the equimolar copolymers on Rp in the system StANZnCl2AIBN is not linear. The position of the minimum on this curve at a given ratio of comonomers depends on the concentration of both zinc chloride and AIBN. The reduction of [η] of the equimolar copolymer attained by the effect of hydrocarbon is relatively small provided the reaction system is homogeneous. On the basis of the results obtained, it may be stated that a change in molecular weight of the copolymer is to be achieved more easily by a change in the rate of copolymerization (effected by AIBN) than by the effect of hydrogen donor (chain transfer).