Anionic Polymerization of β-Nitrostyrene under the Influence of High Energy Radiation

Abstract

Abstract β-Nitrostyrene (βNS) was polymerized in aprotic solvents. The rate of polymerization increased in the series dimethyl sulfoxide ≈ dimethylformamide < N-methylpyrrolidone < hexamethylphosphoric triamide (HMPT). From copolymerization experiments with α-methylstyrene and methacrylonitrile, evidence for an ionic mechanism was obtained. Electron scavengers inhibited the polymerization. Thus it was concluded that in dilute solution the initiation comprises the thermaliza-tion of electrons which become solvated and react with β NS to form the radical anion βNS. Pulse radiolysis experiments were carried out in HMPT. The spectrum of an intermediate (presumably -βNS−) was recorded. By measuring the rates of the formation of -βNS− and of the decay of solvated electrons the rate constant k e (9 ± 3) × 109 liter/mole-sec was determined. At higher monomer concentrations the polymerization was autoinhibited which is probable due to the fact that direct absorption of radiation by the monomer becomes important.