Impedance spectra analysis of a thermoresponsive poly(acryloyl-(L)-proline methyl ester) (poly(A-ProOMe)) hydrogel membranes in an aqueous solution of LiCl was carried out using a simple equivalent model. The hydrogel membrane was synthesized by gamma-radiation-induced polymerization and crosslinking of A-ProOMe monomer aqueous solution in a glass-cast. By means of the impedance spectra analysis, a novel method for the calculation of the ionic conductivity of the hydrogel membranes in LiCl solution was proposed. The calculated ionic conductivity was in agreement with the determined value. In addition, effects of temperature and LiCl concentration on the impedance spectra and ionic conductivity of the gel membrane were analyzed. Results indicated that the impedance spectra analysis is a very useful tool for evaluating the electric properties of gel membranes in an electrolyte solution. The poly (A-ProOMe) gel membrane in 1.0 M LiCl solution showed a high ionic conductivity of about 0.2 S/cm at 14 degrees C. The temperature-dependence of the ionic conductivity was a complex nonlinear form due to the volume phase transition of the thermoresponsive poly(A-ProOMe) gel membrane, and the volume phase transition temperature appeared to be decreased with the increase in the LiCl concentration. (c) 2005 Wiley Periodicals, Inc.