Metal compounds in free-radical processes. III. Polymerization of acrylonitrile initiated by copper (II) nitrate in presence or absence of triphenylphosphine

The bulk polymerization of acrylonitrile (AN) initiated by copper (II) nitrate, Cu(II), in the absence of light has been studied. The rate of the AN polymerization may be expressed in the Cu(II) concentration range from 5 × 10^?4 to 1 × 10^?1 mole 1.^?1 by the equation, R_p = k₅Cu(II)]^0.68, where k₅ = K_ANAN]/(1 + K_ANAN]). From the spectrophotometric measurements the values of 0.70 l./mole and 0.08 l, mole were obtained for the equilibrium constant at 20 and 60°C, respectively, K_AN = C]/AN]-Cu(II)], corresponding to the formation of the complex C from acrylonitrile and copper (II) nitrate. An addition of triphenylphosphine (C₆H₅)₃P into the polymerization system reduces R_p, and no polymerization takes place at all provided (C₆H₅)₃P]/Cu-(II)] ≧ 5. The retardation effect of (C₆H₅)₃P on the polymerization of AN initiated by Cu(II) is attributed to a competitive reaction of Cu(II) with (C₆H₅)₃P in which Cu(II) is reduced and the product of this reduction CuNO₃·2(C₆H₅)₃P is inactive with respect to the polymerization of AN.