The aim of this study was to examine the synthesis of a graft copolymer of chitosan and methacrylic acid (MAA) by free-radical polymerization with a potassium peroxymonosulfate/cyclohexanone (CY) redox system in an inert atmosphere. The optimum reaction conditions affording maximum grafting ratio (%G), grafting efficiency (%E), add on (%A), and conversion (%C) were determined. The grafting parameters were found to increase with increasing concentration of MAA up to 24 x 10(-2) mol/dm(3), but there-after, these parameters decreased. With increasing concentration of peroxymonosulfate from 0.6 x 10(-2) to 1.2 x 10(-2) mol/dm(3), %G, %A, and %E increased continuously. All of these grafting parameters increased with increasing concentration of CY up to 1.2 x 10(-2) mol/dm(3), but beyond this concentration, the grafting parameters decreased. With various concentrations of chitosan from 0.6 to 1.4 g/dm(3), the maximum %G, %A, and %E were obtained at 1.4 g/dm(3). %G, %A, and %C decreased continuously with various concentrations of hydrogen ions from 2 x 10(-3) to 6 x 10(-3) mol/dm(3). The grafting parameters increased with increasing temperature up to 35 degrees C, but thereafter, these parameters decreased. With increasing time period of reaction from 60 to 180 min, %G, %A, and %E increased up to 120 min, but thereafter, these parameters decreased. The graft copolymer was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2429-2439, 2009