Nanocomposite polymer electrolytes consisting of low molecular weight poly(ethylene oxide) (PEO), iodine salt MI (M = K+, imidazolium(+)), and fumed silica nanoparticles have been prepared and characterized. The effect of terminal group in PEO, i.e., hydroxyl (-OH) and methyl (CH3) using poly(ethylene glycol) (PEG) and PEO dimethyl ether (PEODME), respectively, was investigated on the interactions, structures, and ionic conductivities of polymer electrolytes. Wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC, and complex viscosity measurements clearly showed that the gelation of PEG electrolytes occurred more effectively than that of PEODME electrolytes. It was attributed to the fact that the hydroxyl groups of PEG participated in the hydrogen-bonding interaction between silica nanoparticles, and consequently helped to accelerate the gelation reaction, as confirmed by FTIR spectroscopy. Because of its interaction, the ionic conductivities of PEG electrolytes (maximum value similar to 6.9 x 10(-4) S/cm) were lower than that of PEODME electrolytes (2.3 x 10(-3) S/cm).