Vinyl Copolymerization. II. Copolymerization of Acrylonitrile with Styrene and Vinyl Acetate

Rates of copolymerization of AN-St and VA-AN for various mixing ratios of the two monomers were measured by the thermistor method. The heat of copolymerization, which was obtained by comparing the results of the thermistor method with those of the usual analytical method, agrees very well with Alfrey’s equation. Also, the non-constancy of φ in the AN-St system can be explained by Arlman’s theory; it is concluded that the termination constants for mixed radicals are larger than those for homogeneous radicals and, furthermore, that the ratio of a normal cross-termintion constant to a constant of the cross-termination having a penultimate unit is 20. However, in the VA-NA system, the application of Arlman’s equation was impossible because the large difference between the reactivity ratios of the two monomers causes a large error limit in the calculated values of φ.