SWELLING BEHAVIOR OF AMPHOTERIC GEL AND THE VOLUME PHASE-TRANSITION

An amphoteric gel (trimethyl(N-acryloyl-3-aminopropyl)ammonium chloride/sodium acrylate/acrylamide/N,N'-methylenebisacrylamide copolymer gel) immersed in distilled water underwent linear volume changes upon changes in concentration of the constituent ionic groups. This was due to a specific binding between the constituent anionic and cationic groups. The amphoteric gel immersed in acetone-water mixtures exhibited a volume phase transition which could be characterized by the effective residual ionic density after forming the specific binding. On the other hand, the amphoteric gels also exhibited a thermoshrinking volume behavior. However, it is suggested that the thermoshrinking character might not originate from the amphoteric property of the gel.