Graft Polymerization of Acrylamide from Ultrafine Silica Particles by Use of a Redox System Consisting of Ceric Ion and Reducing Groups on the Surface

Abstract

Radical graft polymerization from ultrafine silica surface was investigated. A redox system consisting of ceric ion and the silica particles carrying reducing groups, such as alcoholic hydroxyl, amino, and mercapto groups, was capable of initiating the radical polymerization of acrylamide (AAm). The introduction of alcoholic hydroxyl groups onto the surface was achieved by the treatment of the silica with 3-glycidoxypropyltrimethoxysilane in acidic condition in water. Amino or mercapto groups were introduced onto the silica by reactions of surface silanol groups with 3-aminopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane, respectively. The initiating ability of the redox system changed, depending on the reducing groups on the silica surface, in the following order: alcoholic hydroxyl group<amino group<mercapto group. In the above redox polymerization, polyacrylamide was grafted onto the silica based on the propagation of the polymer from the radicals formed by the reaction of ceric ion with alcoholic hydroxyl, amino, or mercapto groups. The percentage of grafting onto the silica reached about 25%. The silica obtained from the redox graft polymerization gave a stable colloidal dispersion in water.