Vibrational Spectroscopic Studies of Interactions in PEO−NaSCN−Montmorillonite Electrolytes

Abstract

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)20NaSCN−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.