Effects of cupric salts on the polymerization of acrylonitrile in aqueous solution

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Abstract
The polymerization of acrylonitrile in aqueous solution initiated by ammonium persulfate in the presence of cupric salts was studied by a dilatometric method. The presence of cupric sulfate, nitrate, or acetate has a pronounced effect on polymerization, leading to an increase in the rate, and both cupric chloride and bromide retard or inhibit polymerization beyond certain salt concentrations. The increased rate is explainable by the following reactions: equation image The polymerization of acrylonitrile can be initiated by an oxidizing agent such as cupric sulfate, ferric sulfate, stannic chloride, nitric acid, or periodic acid. The decreased rate can be explained by assuming that the complexes of Cu+ ion with a halide ion X− such as CuX2−, CuX3=, CuX4≡, or Cu2X3− shows lower reactivity in the reaction with S2O8=. The cupric‐terminated reaction depends on the coexisting anion. The effect of sulfate, nitrate, acetate, phosphate, chlorate, or fluoride anions is negligible, while that of the chloride is marked, and that of the bromide is overwhelming. The CuX+(X = Cl, Br) ion appears to terminate polymer chains more efficiently than does Cuaq++. Apparent transfer constants of cupric sulfate in the presence of sodium chloride or bromide and the transfer constant of CuCl+ are given. It is suggested that the possibility of the termination reactions by halogen atom transfer is large under conditions of high halide ion concentration: magnified image and magnified image

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