Crosslinking and Oxidation of 1, 2-Polybutadiene by UV Irradiation

Abstract

Abstract Photoinduced crosslinking and oxidation of 1, 2-poly-butadiene film were carried out with UV irradiation in vacuo and in air. A small amount of the structures of trans-vinylene, diene, and triene were observed in the infrared spectrum of the nonirradiated film, and bands attributable to conjugated double bond (230, 280 nm) were also observed in ultraviolet spectrum. In the film irradiated in vacuo, intensities of the bands assigned to trans-vinylene, methylene, and methyl groups increased with the increase in irradiation time, but the intensity of the band of pendent vinyl group decreased. With irradiation in air, the formation of carbonyl and hydroxyl groups and ether linkages was observed. Formation of H2 with the irradiation in vacuo and of H2 O with the irradiation in air was observed. The gel fraction increased with an increase in irradiation time in the absence and presence of oxygen. The gel fraction and the formation of carbonyl groups were markedly accelerated by irradiation with UV rays of wavelength near 280 nm and increased with decreasing concentration of pendent vinyl groups. Postreaction of the irradiated film took place in the dark. The gel fraction and the intensity of the carbonyl group increased by radical reaction with α, α'-azobisisobutyronitrile. On the basis of these results, mechanisms of photoinduced crosslinking and oxidation of 1, 2-polybutadiene were discussed.