Chitosan-O-dextran graft copolymers with the degree of substitution (DS) of chitosan varying from 25 to 90% were synthesized using dextran with the molecular weight 1500 and 6000. Grafting of dextran on the C-6 position of glucosamine residues of chitosan was achieved by protecting amino functionality by phthaloylation and “activating” primary hydroxyl groups of chitosan by tosylation. The chemical structure of the chitosan derivatives was confirmed by FT‑IR and ¹H NMR spectroscopy, the DS of chitosan in its derivatives was determined from the content of nitrogen in the products. Chitosan-O-dextran graft copolymers were hydrophilic products soluble in aqueous solutions in a wide pH range and exhibited an apparent polyelectrolytic effect. The intrinsic viscosity of these chitosan derivatives was relatively low, especially of those containing dextran-6000 grafts. Attachment of dextran at the C-6 position of glucosamine residues significantly enhanced the breakdown of the chitosan backbone during the amino group protection–deprotection procedure using N-phthaloylation.

Keywords: chitosan, dextran, graft copolymer, phthaloylation, tosylation, polyelectrolyte