Poly(ethyl methacrylate) (PEMA)- and poly(2-ethoxyethyl methacrylate) (PEOEMA)-based polymer gel electrolytes with entrapped solutions of lithium perchlorate in propylene carbonate (PC) were prepared by direct. UV-initiated polymerization. The electrolytes were Studied using electrochemical methods and they exhibit good ionic conductivity (up to 0.7 mS cm(-1) at 20 degrees C) as well as electrochemical stability up to 2.5 V vs. Cd/Cc(2+) (5.1 V vs. Li/Li(+)) on gold electrode. The electrolytes have thermal stability up to 125 degrees C. The electrolytes were Successfully tested as ionic conductors in the electrochromic device FTO/WO(3)/Li(+)-eIectrolyte/V(2)O(5)/FTO using coupled optoelectrochemical methods to discuss the relationship between the electrolyte composition and parameters such as change of transmittance, response time and stability. The transmittance change Delta tau was found to be 30-45% at 634 nm. (C) 2008 Elsevier B.V. All rights reserved.