Ferric-chloride-photosensitized polymerization of acrylonitrile in N,N-dimethylformamide

Abstract

The ferric-chloride-photosensitized polymerization of acrylonitrile in dimethylformamide solution has been studied. At 25°C, the quantum yield for the formation of primary radicals is 0.088 mole einstein^–1 at 4358 Å. The quantum yield for ferric chloride consumption increases from this value at low concentrations (∼20µM) to 0.176 mole einstein^–1 at high concentrations (∼2000 µM), and the monomer concentration exponent and the rate of initiation exponent in the polymerization rate expression vary from 1.53 to 1.33 and 0.50 to 0.80 respectively. The kinetics of the reaction are discussed in terms of termination by ferric chloride and degradative solvent transfer. The following rate constants in M^–1 sec^–1 are obtained: for the reaction of polyacrylonitrile radicals with FeCl₃, 9.8 × 10²; chain transfer to solvent, 0.19; initiation of polymerization by transfer radicals, 12 (estimated). An allylic type structure is proposed for the solvent transfer radical.