Polyoxometalate additives were entrapped in the poly(methyl methacrylate) (PMMA) and poly (glycidyl methacrylate) (PGMA) swollen with polar aprotic solvents. Conductivities of 3 x 10(-3) S cm(-1) at 25 degreesC and 5.6 x 10(-3) S cm(-1) at 90 degreesC were measured, making the resulting electrolytes useful materials for application in electrochemical devices. Properties of these gel electrolytes, such as transparency, conductivity and thermal stability depend both on the type of plasticizing solvent and the heteropolyacid content. Interactions between get components were studied using FT-IR and Raman spectroscopies. (C) 2003 Elsevier Science Ltd. All rights reserved.