Photopolymerization of styrene in the presence of oxygen. Role of the charge-transfer complex

Abstract

Ultraviolet absorption spectra of several monomers such as styrene, α-methylstyrene, isoprene, vinyl acetate, etc., were measured in nitrogen and oxygen atmospheres by bubbling the respective gases into the monomers at room temperature. The extra absorptions due to the oxygen which could be ascribed to contact charge-transfer complexes between monomers and oxygen with oxygen as an electron acceptor was found. The photopolymerization of styrene was carried out to investigate the role of the charge-transfer complex in it and was found to proceed several orders of magnitude faster in the presence of small amounts of oxygen than in its abscence. On thebasis of polymer composition, viscosity measurement, the wavelength dependence of polymerization, and the ability of initial product to initiate polymerization, these facts could be explained as follows. Polystyrene peroxideis formed by photoirradiation of the charge-transfer complex between styrene and oxygen in the initial stage of the polymerization and the photoinduced decomposition of the polystyrene peroxide initiates the polymerization of the styrene. Some contribution from the exciplex between oxygen and excited singlet styrene to the formation of the alternating copolymer was also suggested on the basis of measurements of the fluorescence spectra of styrene. © 1973, The Society of Polymer Science, Japan. All rights reserved.