Relationship between photo-induced scission of cellulose chains and graft copolymerization

Abstract

Studies were carried out on the relationship between the scission of cellulose chains and the initiation of photo-induced graft copolymerization of methyl methacrylate. The photo-induced scission of cellulose chains was sharply accelerated by the application of irradiation with light shorter than 300 nm, the use of photosensitizer such as ferric ion, the swelling of cellulose samples, and so on. On the other hand, the scission reaction was markedly suppressed by blocking the carbonyl groups contained in the samples by oximation. A linear increase in the number of grafts was indicated with the number of scissions of cellulose chains in the graft copolymerization. However, a number of scissions not contributing to any formation of grafts was also noticed during the induction period of copolymerization. The factors such as short wavelength light, photosensitizer, and swelling, which contribute to the rises in the rate of graft formation and the scission of cellulose chains, worked also to shorten the induction period. As might be expected, appreciable increases of per cent grafting and shortening of induction period were achieved by preirradiation the cellulose samples with light. From the above, it was concluded that the scission of cellulose chains should be a main factor for the initiation of graft copolymerization in the system.