Graft copolymers of starch–polyacrylonitrile prepared by ferrous ion–hydrogen peroxide initiation

The effect of concentration, reactant ratios, temperature, and starch pretreatment on grafting of acrylonitrile onto starch were studied. Grafting was efficient at high concentrations (8–12% starch) when granular starch was used. The molecular weights for grafted polyacrylonitrile (PAN) were higher when gelatinized starch was used, but grafting efficiencies (grafted PAN/total PAN) were much lower. The molecular weight of the grafted side chain increased with increased concentration of reactants. The grafting frequency was highest when the reaction mixture was kept at 5°C and decreased with increased swelling of the starch. The starch–polyacrylonitrile graft copolymers were saponified and dried to give products which absorbed 75–440 ml H₂O per gram and 20–70 ml synthetic urine per gram.