Effects of salts of metals on vinyl polymerization. Part 5.—Polymerization of methacrylonitrile in the presence of cupric chloride

Abstract

The polymerization of methacrylonitrile in 20 % by volume dimethylformamide, initiated with (1,1′)azo-bis-isobutylnitrile, and inhibited by cupric chloride has been studied at 50, 60 and 70°C. Cupric chloride behaves as an ideal inhibitor of this polymerization. The product of the inhibition reaction, which is most probably the cuprous salt, is inert and produces none of the retardation phenomena observed in the cupric-chloride-inhibited polymerization of acrylonitrile in DMF. Rates of initiation at the three temperatures quoted have been determined from inhibition period against inhibitor concentration plots. These results give values for the rate constant for initiation of 4.12 × 10^–6, 1.82 × 10^–5 and 6.94 × 10^–5 sec^–1 at 50, 60 and 70°C respectively. The activation energy for the initiation reaction is 31 kcal/mole. Measurement of reduced rates during the acceleration period following inhibition has led to values of the ratio k_x/k_p where k_x is the rate constant for the reaction between polymethacrylonitrile radicals and the cupric species; k_x thus obtained at 60°C is 9 × 10⁵ M^–1 sec^–1, i.e., ca. 3000 times greater than for the corresponding reaction with ferric chloride in DMF.