Graft copolymerization of methyl methacrylate onto curdlan was first investigated. In the graft copolymerization initiated by ammonium persulfate (APS) in DMSO under a homogeneous condition, the resulting graft copolymers had low molecular weights and low grafting percentages. However, the initiation by APS in water gave graft copolymers having relatively higher molecular weight ((M) over bar(n) = 17.7 x 10(4)) and higher grafting percentage (548%) than those copolymers obtained by the homogeneous condition. When the graft copolymerization was carried out by cerium (IV) ammonium nitrate-HNO3 initiation, the graft copolymer had the highest grafting percentage of 1620% without degradation of the curdlan backbone. The resulting graft copolymers were soluble in DMSO. The graft copolymers obtained by the cerium salt had narrow molecular weight distributions ((M) over bar(w)/(M) over bar(n)) compared with those by the APS catalyst in DMSO or water. The graft copolymers decomposed with sulfuric acid to isolate PMMAs, which molecular weights were larger than that of the corresponding homo-PMMAs. The structure of the grafted copolymers was characterized by IR, C-13 NMR, DSC, and SEM. It was found that the graft copolymers exhibited the glass transition temperature (T-g), though curdlan had no T-g. As the grafting percentage increased, the T-g increased to reach 270 degrees C, which was higher than the decomposition temperature of curdlan. The surface image of the grafted copolymers observed by SEM, showed smoothless compared with that of curdlan. It was also revealed that the graft copolymers having the grafting percentage of 1620% swelled in common organic solvents up to 4.5 times of the weight of the dry graft copolymer to form gels.