Dielectric properties of collapsing hydrogels

Dielectric spectra were measured for the polymer gel of N-isopropylacrylami de (NIPA) and copolymer gels of N-isopropylacrylamide and sodium styrenesul fonate (NIPA-SS) in the swollen and collapsing states in the frequency rang e from 100 IrHz to 2 MHz. Dispersions were observed for the NIPA gel in the collapsing state and NIPA-SS gels in both the collapsing and swollen state s. The characteristics of dispersions in the collapsing gels were different from the characteristics in the swollen gels, while the former characteris tics are very similar in NIPA and NIPA-SS. The similarity between dispersio ns observed for NIPA and NIPA-SS gels indicates that counterions of NIAP-SS gels bind tightly to the ionized groups and cannot move freely in the coll apsing gels. The analysis of the dispersions reveals that water molecules i nside the collapsing gels are surrounded by the gel chains and form electri cally disconnected clusters.