On the copolymerization of acrylonitrile with styrene in the presence of Lewis acid, 3. Photoinitiated copolymerization

Abstract

AbstractThe rate of the acrylonitrile (AN)‐styrene (St) copolymerization (Rp) photoinitiated (λ=365 nm) by the StANZnCl2 complex at 30°C is proportional to the square root of the intensity of radiation. The limiting viscosity number [η] of alternating copolymers increases with the intensity of radiation. The 1/[η] vs. Rp relationship for the StAN copolymers is similar as has been found for the initiation of copolymerization by thermal decomposition of 2,2‐azoisobutyronitrile. Provided benzophenone combined with 2‐propanol is used as a photosensitizer, the rate of the StAN copolymerization in acetone—at constant concentrations of both comonomers, zinc chloride, and benzophenone—decreases with 2‐propanol concentration in the reaction mixture. If benzophenone alone (e.g. without 2‐propanol) is used as a photosensitizer under equal conditions, the observed values of the rate of copolymerization are lower in comparison with the system where the ternary molecular complex is empolyed as a photosensitizer. Moreover, Rp decreases with increasing concentration of benzophenone in the system. These findings are interpreted as a result of the termination reactions of ketyl radicals (hydroxydiphenylmethyl radicals) with macroradicals of copolymer.