Synthesis and characterization of a novel alginate–poly(ethylene glycol) graft copolymer

Sodium alginate grafted with low molecular weight polyethylene glycol (PEG) was prepared by reacting a mono-carboxyl terminated PEG with a sodium alginate modified by inserting a given amount of amine functionalities. The coupling between PEG and alginate was carried out using carbodiimide chemistry in aqueous solutions. Significant reduction of the molecular weight of alginate is recorded, as expected from literature reports. The chosen strategy allowed to graft significant amounts of PEG saving the carboxylic functionalities of alginate, necessary for the cross-linking of the polysaccharide. The chemical structure and chemical–physical properties of alginate derivatives were characterized by FTIR, 1H and 13C NMR, DSC, TGA and wide angle X-ray analysis.