Effects of salts of metals on vinyl polymerization. Part 3.—Polymerization of acrylonitrile in presence of cupric chloride

Abstract

The homogeneous polymerization of acrylonitrile initiated with 1,1′-azo-bis-isobutyronitrile and inhibited with cupric chloride in dimethylformamide solution has been studied at 60°C. The rate of polymerization following the inhibition period was invariably less than the rate obtained in the absence of cupric chloride, and varied inversely with the initial cupric chloride concentration for concentrations >3 × 10^–3 M. The corrected value of the rate constant for the initiation reaction obtained from the inhibition against time plot was 1.51 × 10^–5 sec^–1. The plot of the final retarded rate of polymerization against the reciprocal of the initial cupric chloride concentration gave a corrected value of 5.7 for k_y/k_p where k_y is the rate constant for the reaction between growing polymer radicals and the inhibition product (presumably cuprous chloride). The value of k_x/k_p, where k_x is the rate constant for the reaction between polyacrylonitrile radicals and cupric chloride, was determined from the period of acceleration following complete inhibition, and had a mean value of 100 at 60°C. Using a value of 1930 l. mole^–1 sec^–1 for k_p at 60°C we obtain values of 1.93 × 10⁵ and 1.1 × 10⁴ l. mole^–1 sec^–1 for k_x and k_y respectively. The value of k_x is much greater than the corresponding value obtained with ferric chloride, and is approaching the order of magnitude of rate constants for radical-radical interactions as for methyl methacrylate polymerization.