Photopolymerization of acrylonitrile in concentrated aqueous zinc halide solutions

Abstract

Crosslinked polyacrylonitrile (PAN) was obtained with a high yield from the photoinduced polymerization of acrylonitrile (AN) in concentrated aqueous zinc chloride solution. It was found that the presence of zinc chloride results in the promotion of the radical generation in the photoinitiation process as well as an increase in the rate of propagation. Any attempt to isolate the polymer from the reaction mixture was not successful due to the insolubility of the polymer to any conventional solvents to polyacrylonitrile (PAN); therefore, the reaction mixtures, consisting of PAN, zinc chloride, and water—which are referred to as the polymer hybrid system—was used without further purification. The effect of other zinc halides on the polymerization such as zinc bromide and zinc iodide was also investigated in connection with the photoinitiation mechanism, which reveals that the complex (Zn++(AN)x(OH−)yCl) is the species that is responsible for the photoinitiation. It was found that the transparent, stretchable polymer hybrid systems are electric conductive and turn to black upon heating to 160°C due to the conversion of the nitrile group of PAN to tetrahydronaphthyridine rings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2588–2594, 2000