Polymer electrolytes based on the copolymer of N-vinylimidazolium tetrafluoroborate (VyImBF(4)) and poly (ethylene glycol) dimethacrylate (PEGDMA) have been prepared. Ethylene carbonate (EC) and LiClO4 are added to form gel polymer electrolytes. The chemical structure of the samples and the interactions between the various constituents are studied by FT-IR. TGA results show that these polymer electrolytes have acceptable thermal stability, are stable up to 155 degrees C. Measurements of conductivity are carried out as a function of temperature, VyImBF(4) content in poly(VyImBF(4)-co-PEGDMA), and the concentration of EC and LiClO4. The conductivity increases with PEGDMA and EC content. The highest conductivity is obtained with a value of 2.90 x 10(-6) S cm(-1) at room temperature for VP1/EC(25 wt.%)-LiClO4 system, corresponding to the LiClO4 concentration of 0.70 mol kg(-1) polymer. (C) 2008 Elsevier B.V. All rights reserved.