Reswelling transition of poly(sodium acrylate) gels due to destruction of hydrogen bonds observed by ATR FTIR spectroscopy

Abstract

AbstractWe report the reswelling transition of a physically crosslinked polyelectrolyte hydrogel in water, which was prepared using poly(sodium acrylate) as the main constituent and Al ions as the crosslinker. The nonmonotonic swelling behavior was observed at room temperature (25°C) under the continuous exchange of water; an as‐prepared gel swelled at the first stage (the swelling process) and then shrunk very slowly at the second stage (deswelling process). In the deswelling process, the water exchange was stopped and the diameter of the gel in a limited amount of water was measured as a function of the temperature. The gels reswelled at different transition temperatures in the heating processes, which depended on the initial diameter at 25°C (resulting from the different numbers of water exchange). The reswollen state was stable at 25°C and could shrink again as a result of successive water exchanges at 25°C. In the following temperature increase in the closed system, the reswelling phenomenon was observed again. The destruction of the hydrogen bonds introduced by the water exchange was confirmed by the attenuated total refraction Fourier transform infrared measurements. The reversible transition behavior between the deswollen and the reswollen states is discussed in terms of the formation and destruction of the hydrogen bonds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007