Synthesis and study of water-soluble chitosan-O-poly(ethylene glycol) graft copolymers

Novel chitosan-O-poly(ethylene glycol) graft copolymers were synthesized. Etherification of N-phthaloyl chitosan by poly(ethylene glycol) monomethyl ether (MPEG) iodide was carried out in dimethylformamide in the presence of silver oxide. Varying the ratio of MPEG iodide to chitosan, different degree of O-substitution of MPEG to monosaccharide residue of chitosan (5–197%) was obtained. Chemical structure of the new chitosan derivatives was confirmed using FTIR spectroscopy and analysis of functional groups. O-PEGylated chitosans are soluble in water and aqueous solutions of wide pH range. Reduced viscosity of aqueous solutions of the graft copolymers is extremely low and similar to that of MPEG-2000.