Graft-polymerization of 2-hydroxyethyl acrylate (HEA) onto chitosan (CS) using ammonium persulfate (APS) as an initiator was carried out in an aqueous solution. Evidence of grafting was obtained by comparing H-1 NMR and FT-IR spectra and scanning electron microscopy images of chitosan and the grafted copolymer as well as solubility characteristics of the products. The effects of APS, HEA concentration, reaction temperature and duration of graft-polymerization were studied by determining the grafting parameters, such as grafting percentage and grafting efficiency. The HEA-grafted chitosan product is soluble in a wide pH range, while the original unmodified chitosan is water-soluble only in a narrow pH range. A mechanism for the free-radical grafting was proposed. (c) 2007 Elsevier Ltd. All rights reserved.