Ceric ion‐induced redox polymerization of acrylonitrile on cellulose

The ceric ion‐cellulose redox system has been studied for grafting acrylonitrile on cotton fibers. Grafting yields are very high as compared to the persulfate‐thiosulfate redox system reported earlier. Traces of copper sulfate in the reaction mixture do not increase grafting yields, unlike the persulfate‐thiosulfate system. The high polymerization rate on cotton fibers is shown to be due to the reducing action of cellulose and not to the large surface area of cotton fibers. The Ce+4 consumption during grafting is higher than during oxidation of cellulose, indicating formation of homopolymer during the grafting reaction. Studies on the consumption of Ce+4 by model compounds such as D‐glucose and α‐methyl‐D‐glucoside show that the hemiacetal group in D‐glucose is responsible for a faster rate of Ce+4 consumption. Formation of a Ce+4‐alcohol complex also contributes to the initial fast rate of Ce+4 consumption. Studies on the oxidation of cellulose by Ce+4 indicate that the initial oxidative attack occurs on carbon atom 2, with the formation of a >CO group. On further oxidation, cleavage of the C2‐C3 bond occurs as shown by the presence of glycol aldehyde determined chromatographically. Cellulose‐polyacrylonitrile grafts have been isolated by an acetolysis treatment followed by extraction with dimethylformamide. Number‐average molecular weights of the isolated fractions are approximately 50,000–55,000. A theoretical method to calculate the number‐average molecular weights, based on the PAN and the COOH contents of the grafted cellulose, is described.