Responsive hydrogels based on N

N-dimethylaminoethyl methacrylate were synthesized in aqueous medium by photopolymerization．H2O2 was used as the photosensitive initiator and N

N-methylene-bis-acrylamide was used as a crosslinker．Effects of the monomer concentration

the initiator concentration

the crosslinker concentration and the radiation time on gel fractions and swelling ratios were investigated．The optimum condition of synthesis was given．The resulting hydrogels were transparent and possessed good elasticity．It WaS found that the gels displayed both thermosensitive and pH-sensitive behaviors．The equilibrium swelling ratios of the hydrogels changed abruptly at 40℃ in water．Swelling ratios would decline abruptly at pH 3．Ionic strength has only a small influence on swelling and the swelling ratio decreased gradually when the ionic strength increased．