Vibrational Spectroscopic Studies on Interactions in PEO−NaSCN−Urea Composites

Abstract

FT-Raman (Fourier transform Raman) and FTIR (Fourier transform infrared) studies, along with DTA (differential thermal analysis) and XRD (X-ray diffraction) measurements, were performed on PEO−NaSCN−urea/thiourea solid polymer electrolytes (SPEs) at room temperature, and the interactions of urea/thiourea with NaSCN, PEO, and PEO−NaSCN were analyzed respectively. It is shown that the eutectic molten salt of urea−NaSCN occurs because of the interaction of sulfur in SCN- with the complex cation formed by the coordination of the N atom in urea with Na+. Urea and thiourea can form complexes with PEO by hydrogen bonds. When urea is added to PEO−NaSCN SPEs, the formation of such hydrogen bonds and the molten salt of urea−NaSCN causes crystalline PEO and the P(EO)3NaSCN complex to break up and results in significant changes of the ion association components. In contrast with urea−NaSCN mixtures, the formation of molten salt in thiourea−NaSCN mixtures was not observed and the interactions of thiourea with NaSCN we...