Swelling equilibria for weakly ionizable, temperature-sensitive hydrogels

Swelling equilibria in aqueous citrate-phosphate buffer solutions are reported for thermally-sensitive poly-N-isopropylacrylamide hydrogels containing weakly ionizable groups.The comonomers containing these groups were sodium acrylate and 2dimethylaminoethyl methacrylate to produce gels with, respectively, acidic and basic character.Gel swelling was measured as a function of pH, ionic strength, and temperature.With increasing ionization, the temperature range over which the gel volume change is greatest becomes larger and shifts to higher temperatures.