Grafting of vinyl acetate onto chitosan and biocidal activity of the graft copolymers

Modification of chitosan by grafting with vinyl acetate (VAc) was carried out using potassium persulfate, and sodium bisulfite as redox initiators. The effect of monomer, initiator concentration, time, and temperature was studied. The grafted samples were subjected to alkaline hydrolysis and the polyvinyl acetate (PVAc) branches were consequently partially converted into polyvinyl alcohol (PVAl) graft, which showed enhanced swelling in water. The graft copolymers showed a better dye uptake for both acidic and basic dyes. Chitosan/VAc and chitosan/VAl copolymers were both subjected to reaction with dimethyl sulfate in alkaline medium to yield quaternized copolymers. The antifungal behavior of chitosan and its graft copolymers was investigated in vitro on the mycelial growth, sporulation, and germination of conidia or sclerotia of the following sugarbeet: Beta vulgaris pathogens isolated in Egypt, Rhizoctonia solani Kuhn (AG(2-2)) Sclerotium rolfsii Sacc. and Fusarium solani (Mart.) Sacc. These polymers were also screened against several fungi and it has been found that grafting with polyvinyl alcohol branches enhances the antifungal activity dramatically. (c) 2006 Wiley Periodicals, Inc.