Semi-interpenetrating polymer network (semi-IPN) hydrogel membranes composed of beta-chitin and poly(ethylene glycol) (PEG) diacrylate macromer were synthesized and characterized for future biomedical application. PEG macromer/beta-chitin dissolved in formic acid was cast to prepare films, followed by subsequent crosslinking with 2,2-dimethoxy-2-phenylacetophenone by u.v. irradiation. Photocrosslinked hydrogels exhibited relatively high equilibrium water content in the range of 60-81%. The crystallinity, thermal properties and mechanical properties of semi-IPN hydrogel membranes were studied. All the crosslinked membranes revealed a remarkable decrease in crystallinity. Their glass transition temperatures increased with increasing beta-chitin content. The tensile strengths of semi-IPNs in the swollen state range between 1.35 and 2.41 MPa; these are the highest values reported to date for crosslinked hydrogels.