Graft copolymerization of methacrylonitrile on caesarweed fibers by ceric ion/isopropanol redox pair

Abstract

AbstractThe graft copolymerization of methacrylonitrile to caesarweed fiber and its sodium derivative by ceric ions in the presence of isopropanol was investigated in aqueous media. The percentage graft yield decreased initially and then increased with the concentration of isopropanol, but the graft levels of sodium caesarweed fibers were much lower. The graft reaction in the presence of isopropanol was characterized by the high frequency of grafting, up to 2.81 × 102 Ng/104 anhydroglucose units, and the low molecular weight of the grafted polymer, not higher than 0.94 × 103. The molecular weight of the grafted polymer showed a negative dependence on the concentration of isopropanol, suggesting the involvement of the latter in the transfer reactions with growing grafted polymer chains, which permitted calculation of the transfer constant, kA/kp, for the process: 7.91 × 10−2. The graft yield percent was found to be negatively dependent on the concentration of ceric ions for grafting of methacrylonitrile on sodium caesarweed fibers, but the molecular weight of the grafted polymer showed no clear‐cut trend with ceric ion concentration. The graft yield percent increased with temperature in the range of 30°C–50°C and decreased markedly at 70°C. The calculated activation energy of the graft reaction was 10.5 kcal/mol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 353–358, 2006