The synthesis of organic-modified rectorite (OREC)/polymethyl methacrylate (PMMA) nanocomposite gel polymer electrolyte (NGPE) via in situ polymerization was investigated using free radical initiator in an solution, in which organic plasticizer, propylene carbonate(PC) acted as a solvent. A serious of NGPE membranes with different OREC content were prepared and characterized. The dispersion and exfoliation statuses of the OREC in the prepared NGPE membranes were analyzed through X-ray diffraction (XRD) and transmission electron microscope (TEM), and the results indicated that for the NGPE with 5 wt% OREC membrane, OREC was partly exfoliated and well dispersed in the gel polymer electrolyte system. The electrochemical properties of the NGPE were determined by alternating current (AC) impedance spectroscopy, which illustrated that the ionic conductivity of the nanocomposite gel polymer electrolyte firstly increased and then decreased with increasing OREC content. Meanwhile, the maximum value of ionic conductivity for nanocomposite gel polymer electrolytes was obtained when organic clay amount was 5 wt%. The interactions among the components of the NGPE were investigated by Fourier transform infrared (FTIR) spectroscopy. It was shown that there were specific interactions between OREC and the other components, which may influence the conductivity and the stability of GPEs. Finally, an thermal stability enhancement was presented by NGPE with 5 wt% OREC compared with GPE, which was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114:2632-2638, 2009