Ionic liquid-polymer gels were prepared by incorporating N-butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide (Mor(1.4)TFSI) and poly(vinylidene fluoride)-hexafluoropropylene copolymer (PVdF(HFP)) using three different methods in order to observe the variation of ionic conductivities according to the presence of propylene carbonate (PC) and various weight ratios between Mor(1.4)TFSI and gel polymer electrolyte (GPE). Ionic conductivities for each gel polymer electrolyte were measured with increasing temperature. Ionic conductivities of the GPEs increased with increasing temperature and weight ratio of Mor(1.4)TFSI. In addition, the addition of PC into GPE led to the improvement of ionic conductivities. Thermogravimetric analysis (TGA) showed the suggested gel polymer electrolytes composed of only ionic liquid and polymer were stable up to approximately 400 degrees C. TGA and infrared spectroscopy data indicated that residual PC remains after evaporating PC in a vacuum oven, which did not affect the ionic conductivities. The GPEs containing PC displayed high conductivity (ca. 10(-2) S cm(-1)) at 60 degrees C. (C) 2005 Elsevier Ltd. All rights reserved.