Polypyridylruthenium(II) persulphate as photoinitiator in the grafting of vinyl monomers onto cellulose acetate

Abstract

The use of tris(2,2′-bipyridyl)ruthenium(II) and tris(1,10-phenanthroline)ruthenium(II) to photoinitiate the grafting of vinyl monomers onto cellulose triacetate in the presence of persulphate ion is described. IR spectra and gravimetric studies of the product, after separation of homopolymer, confirm that grafting occurs when acrylamide, acrylic acid, acrylonitrile, methyl acrylate, methacrylamide and glycidyl methacrylate are used as monomers. With maleic acid, there is no evidence of grafting. Photolysis can be carried out using mercury or tungsten lamps, sunlight or an argon ion laser. For acrylamide, acrylic acid, acrylonitrile and methyl acrylate, the effects of monomer and persulphate concentration and irradiation time on the yield of grafting were studied. Luminescence quenching studies suggest that reaction involves the formation of SO 4 − by interaction between persulphate and excited ruthenium(II) complexes. These then form radicals with the cellulose derivative, which react with vinyl monomers to yield, eventually, graft copolymer. With poly(methyl acrylate) copolymer, the graft, after hydrolysis of cellulose triacetate, has a molecular weight of 40 000. No ruthenium(III) species is present in the final product, showing that the photoinitiation is catalytic. The graft copolymer with poly(glycidyl methacrylate) can be used to immobilize the enzyme trypsin.