Interlayer spacing effect of alkylammonium-modified montmorillonite on conducting and mechanical behaviors of polymer composite electrolytes

Polymer composite electrolytes (PCE) based on poly(ethylene oxide) (PEO) and alkylammonium-functionalized clay materials were fabricated. Structural modification and the electrochemical properties were investigated in order to understand the effects of organically modified montmorillonite (OMMT) in the polymer matrix on the ion conductivity. Nanosize layer-structured clay fillers were used having an organic modifier with different alkyl lengths and positions. The X-ray diffraction (XRD) results revealed that the interlayer spacing (2.55 nm) for MMT-20A was increased compared with that (1.16 nm) for Na-MMT. Both the XRD and the thermal analysis results indicated that the PCE showed reduced crystallinity after the introduction of the OMMT fillers. From the ion-conductivity results, the PCE containing MMT-20A showed higher conductivity (6.1 × 10^-4   S / cm) than that containing Na-MMT (2.2 × 10^-4   S / cm). This indicated that the improved ion conductivity was dependent on the reduced crystallinity that was correlated with the d-spacing of the MMT. Furthermore, the PCE/OMMT showed improved tensile strength. Finally, it was shown that the conducting and mechanical properties were dependent on the interlayer spacing of the modified clays.