Studies on graft copolymerisation of vinyl monomers onto chitosan for biomedical application

Abstract

Biopolymer chitm, the most abundant natural ammo polysaccharide, newlineand its most important derivative, chitosan, are recently considered as the newlinesubjects for extensive worldwide academic and industrial research. In spite newlineof potential applications of chitin and chitosan, it is necessary to establish newlineefficient appropriate modifications to explore fully their high potential. newlineA variety of chemical modifications are employed to modify these newlinecarbohydrate polymers. The present article provides a comprehensive review newlineon one of the most promising approaches to modify chitin and chitosan, i.e., newlinegraft copolymerization, with an emphasis on the synthetic aspects. Both newlinechemically and radiation initiated graft copolymerization of various vinyl newlinemonomers onto the trunk polymers are investigated. Meanwhile, the limited newlinecases of poly-condensation and oxidative coupling are presented as the nonvinyl newlinegraft copolymerization methods. Then, the ring-opening graft newlinecopolymerization is described and the cases of the cyclic monomers newlinea-aminoacid N-carboxyanhydrides and s-caprolactone are investigated. An newlineextensive description of the grafting onto approach is provided. newlinePoly (acrylonitrile) (PAN) and poly (methyl methacrylate) were grafted newlineonto chitosan in acidic medium by using ceric-ammonium-nitrate as newlineinitiator under nitrogen gas atmosphere. The grafting percentage showed newlinedependence on initiator concentration, monomer concentration, acetic acid newlineconcentration, as well as time of the reaction and temperature of the newlinereaction. Extent of grafting, percentage of homopolymer formation, grafting newlineefficiency and total conversion were estimated. The highest percentage of newlinegrafting of acrylonitrile achieved was as high as 23-40% when the optimum newlineconditions were used (cerium ammonium nitrate (CAN) = 0.015 mol. L1, newlineacrylonitrile (AN) = 2.1mol. L1, and acetic acid = 2%, the reaction time = 60 newlineminutes and reaction temperature = 50°C). The maximum percentage of newlinegrafting of methyl methacrylate was 450% when the optimum conditions newlinewere used (ceric ammonium nitr