Thermoreversible hydrogels: 3. Synthesis and swelling behavior of the (N-isopropylacrylamide-co-trimethylacrylamidopropyl ammonium iodide) copolymeric hydrogels

In this study, a series of N-isopropylacrylamide/trimethyl acrylamidopropyl ammonium iodide (NIPAAm/TMAAI) copolymeric gels were prepared from the various molar ratios of NIPAAm, cationic monomer TMAAI, and N,N'-methylene bisacrylamide (NMBA). The influences of the amount of the cationic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures were investigated. Results showed that the swelling ratios of copolymeric gels were significantly larger than those of pure homopolymer NIPAAm gels, and the more the TMAAI content, the higher the gel transition temperature. In the saline solution, results showed that the swelling ratio of pure NIPAAm gel did not significantly change with an increase of the salt concentration until the salt concentration was greater than 0.1 M. The swelling ratios for the copolymeric gels NIPAAm/TMAAI were decreased with increasing of the salt concentration. In various saline solutions, results showed that the anionic effects were greater than cationic effects in the presence of common anion, different cations and common cation, different anions for these hydrogels. (C) 1998 Elsevier Science Ltd. All rights reserved.