The effect of plasticizer (PC) on the conductivity and chemical interaction of polymer electrolyte of MG49–PC–LiClO4–TiO2 has been investigated. The electrolyte films were successfully prepared by solution casting technique. Alternating current electrochemical impedance spectroscopy was employed to investigate the ionic conductivity of the electrolyte films at 25 °C, and the analysis showed that the addition of propylene carbonate (PC) plasticizer has increased the ionic conductivity of the electrolyte up to its optimum level. The highest conductivity of 2.54×10−4 Scm−1 was obtained at 30 wt.% of PC. Fourier transform infrared spectroscopy measurement was employed to study the interactions between lithium ions and oxygen atoms that occurred at carbonyl (C=O) and ether (C-O-C) groups. XRD pattern showed that the crystallinity phase was reduced at the highest conductivity.