A work was carried out on a solid polymeric electrolyte system comprising blends of poly (vinyl chloride) and liquid 50% epoxidized natural rubber (LENR50) as a polymer host with LiClO4 as a salt and prepared by solution casting technique. In this paper, the main study was the effect of LiClO4 salt concentration on the electrolyte properties. The effect of the salt on the electrolyte properties was characterized and analyzed with impedance spectroscopy (EIS), X-ray diffraction (XRD), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). The EIS result showed that highest ionic conductivity was obtained at 30 wt % salt with a value of 2.3 x 10(-8) S cm-1. The XRD results revealed that the LiClO4 salt was fully complexed within the polymer host as no sharp peaks were observed. However, above 30 wt % of salt, some sharp peaks were observed. This phenomenon was caused by the association of ions. Meanwhile, DSC analysis showed that Tg increased as the salt content increased. This implied that LiClO4 salt had interaction with polymer host by forming coordination bond. The morphologies' studies showed that good homogeneity and compatibility of the electrolyte were achieved. Upon the addition of the salt, formation of micropores occurred. It was noted that micropores which aid in mobility of ions in the electrolyte system has increased the ionic conductivity. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012