Phase transition in swollen gels

Summary

The DC conductivity of two networks — a poly(N,N-diethylacrylamide) network (N1) and a network prepared by the copolymerization of N,N-diethylacrylamide with 3 mol.% of sodium methacrylate (N2) — in deionized water in the temperature range 10–55°C was measured. While in the low-temperature range (expanded gel state) the volt-ampere (V-A) behaviour of both networks shows a semiconductive character (conductivity increases with increasing temperature), in the high-temperature range (collapsed gel state) the conductivity of the network N1 rapidly decreases with increasing temperature (metallic character). The presence of charges on the chain raises the conductivity and shifts the temperature of the change in conductivity to higher values. In the collapse region of the ionized network N2 anomalies were observed on the V-A characteristics.