The mechanical and electrochemical properties of gel electrolytes, formed by immobilizing ethylene carbonate (EC)-propylene carbonate (PC)/lithium Perchlorate (LiClO4) solutions in a polyacrylonitrile (PAN) matrix, were investigated by oscillating theological experiments, conductivity measurements and H-1-NMR spectroscopy. The gel's theological behaviour showed two thermoreversible structural transitions in the temperature range 25-120 degreesC independent from the salt content in the membranes but can be attributed to the only polymeric matrix. In this paper, we also report a study of the EC-PC/LiClO4 solutions in a wide concentration range performed by pulsed gradient spin-echo NMR (PGSE-NMR) technique. The solvent self-diffusion coefficient measurements have allowed elaborating a model to describe the solvation mechanism of the lithium ions in these solutions. (C) 2003 Elsevier B.V. All rights reserved.