Photochemical reactions of high polymers. XIII. Photografting of methyl methacrylate onto the polymers bearing thiosulfate groups

Abstract

AbstractPolymers bearing pendent thiosulfate groups, that is, sodium poly(vinyl benzyl thiosulfate) (PVBB) and the sodium salt of poly(vinyl hydrothiosulfatoacetate)(PV AcB), were prepared. The photograft polymerization of methyl methacrylate onto these polymers was carried out. The relationships between irradiation time and conversion, degree of grafting, and grafting efficiency were investigated in the photograft polymerization. It was ascertained that the pendent thiosulfate groups acted as effective initiators for the graft polymerization. From the number of endgroups in the homopolymer formed along with the graft polymer, the mechanism of the graft polymerization was discussed and it was verified that the graft polymerization was initiated by the thiyl radical formed by scission of the sulfur–sulfur bond of the pendent thiosulfate group. An unusually high degree of grafting and extremely rapid polymerization rate observed in the graft polymerization suggested the dual functions of thiosulfate‐bearing polymer as initiator and emulsifier. It was found that addition of FeCl2 to this polymerization system increased the rate of polymerization and the degree of grafting but decreased the grafting efficiency. The effect of FeCl2 was interpreted by assumption of a photo‐redox reaction between thiosulfate group and Fe2+.