Blended polymer electrolytes with poly(vinyl chloride) (PVC)- poly(acrylonitrile) (PAN) were prepared with different plasticizer concentrations and constant lithium perchlorate (LiClO4) ratio by the solution-casting technique. The structure and complexation of the prepared films were studied by X-ray diffraction and Fourier transform infrared spectroscopy. The effect of the plasticizer on the ionic conduction in these electrolytes was investigated using alternating current impedance measurement and discussed. The temperature-dependant ionic conductivity was carried out in the range 302-373 K. The prepared films were also examined by thermogravimetry/differential thermal analysis to determine their thermal stability. © 2007 Springer-Verlag.