Abstract: Novel anionic thermosensitive hydrogels were prepared by the copolymerization of N-isopropyl acrylamide(NIPA) with 3-sulfopropyl acrylate potassium salt(SPAP) as anionic monomer in the presence of methylene-bisacrylamide(MBA).The hydrogels exhibit excellent thermosensitive behavior and high swelling properites,In the feed ratios varing from 1.0% to 2.0%(molar ratio) SPAPcontent the hydrogels possess the volume ratios of 27～38 and the sensitive temperatures varied from 35℃ to 38℃,which are very close to the human body temperature,and very important for Drug Delivery Systems(DDS).

Key words: Thermosensitive hydrogel, Swelling ratio, N-isopropyl acrylamide