Thermoreversible hydrogels X:: Synthesis and swelling behavior of the (N-isopropylacrylamide-co-sodium 2-acrylamido-2-methylpropyl sulfonate) copolymeric hydrogels

A series of thermosensitive hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm) and sodium-2-acrylamido-2-methylpropyl sulfonate (NaAMPS). Factors such as temperature and initial total monomer concentration and different pH solutions were investigated. Results indicated that the more the NaAMPS content in hydrogel system, the higher the swelling ratio and the gel transition temperature; the higher the initial monomer concentration, the lower the swelling ratio. The result also indicated that the NIPAAm/NaAMPS copolymeric hydrogels had different swelling ratios in various pH environments. The present gels showed a pH-reversible property between pH 3 and pH 10 and thermoreversibility. The swelling ratios of copolymeric gels were lower in a strong alkaline environment because the gels were screened by counterions. Finally, the drug release behavior of these gels was also investigated in this article. (C) 2000 John Wiley & Sons, Inc.