The graft copolymerization of butyl acrylate onto chitosan in acetic acid aqueous solution was investigated, using the gamma-ray of Co-60 gamma-irradiation method. Fourier transform infrared spectra analysis, X-ray diffraction analysis, and scanning electron microscopy characterized the graft copolymer. The effect of synthesis variables in the graft copolymerization have been discussed in the light of grafting efficiency, grafting percentage, and homopolymer percentage. Hydrophilicity and impact strength of the films formed from copolymer solution were tested and their feasibility as seed coating was studied. (C) 2003 Wiley Periodicals, Inc.