Vibrational spectroscopic studies of interactions in PEO-NaSCN-montmorillonite electrolytes

Mixtures of NaSCN-montmorillonite (MMT) and the electrolytes of both poly(ethylene oxide) (PEO)-MMT and PEO-NaSCN-MMT were prepared, and the MMT interfacial effect and the interactions of PEO with MMT and NaSCN were investigated by FT-IR and X-ray diffraction measurements at room temperature. It is shown from these experimental results that MMT surface possesses Lewis acid centers, and the interactions of MMT with PEO and PEO-NaSCN can occur several ways, including PEO intercalation, the solvation of PEO toward the interlayer cations, the grain boundary effect, Lewis acid-base interactions, and the epitaxial effect. When Na+-MMT content is high enough, the epitaxial effect cannot be observed in P(EO)(20)NaSCN-Na+-MMT electrolytes, whereas such effect occurs significantly in PEO-Na+-MMT electrolytes. The Lewis acid-base interactions between PEO and Na+-MMT are the main interactions in the electrolytes with high Na+-MMT content. The grain boundary effect and the intercalation of PEO in MMT galleries become the dominant interactions in the electrolytes in which Na+-MMT content is less than 5%. Moreover, the effect of these interactions on the PEO conformation and the electrolytic performances is also analyzed in this paper.