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Abstract: The polymer–ammonium complexes are an important class of proton conducting polymer electrolytes. In this work, poly(ethylene oxide) (PEO)–NH4SCN electrolytes were prepared over a large range of the salt content, and their FT-IR spectra were measured at room temperature. Based on the assignments of each band in the spectral envelope of SCN−1, their relative intensities are determined by the use of FT-IR technique. Following the experimental results and spectral analyses, this paper reports the interactions, the various ionic associations, the changes of the ionic association with NH4SCN content, and the characteristics of structure in PEO–NH4SCN electrolytes. It is shown that the hydrogen bonds of PEO and NH4SCN exert the great effect to the ionic association, the interactions of PEO with NH4SCN, and PEO crystallinity, in particular, under the condition of high NH4SCN content. In addition, the differences of ionic association among PEO–NaSCN, PEO–KSCN and NH4SCN electrolytes are also compared in this paper. [Copyright &y& Elsevier]

Abstract: The polymeric conformations can provide insight into the structure and the mechanism of ion transport in solid polymer electrolytes. In this work, the FT-IR spectra of PEO–NaSCN complexes were measured at room temperature, and the solvation of NaSCN in PEO was revealed by the conformational changes of PEO with NaSCN content. It is suggested that the complexation of PEO with NaSCN can occur through three modes: trans-coordination, gauche-coordination, and cryptande-coordination, depending on the conformation and the flexibility of PEO backbone. The trans-coordination is a weak solvation and can cause the interchain crosslinking and the reduction of segmental motion. The gauche-coordination is a strong complexation and can form complexes in which Na+ is wrapped by the PEO helix. The cryptandes result from the internal rotation of the flexible PEO backbone and can interact directly with NaSCN to form triple ion aggregations, especially when the salt content is low in PEO. In addition, the effect of PEO crystallinity on solvation and the solvating ability of PEO with different molecular weight are discussed also in this paper. [Copyright &y& Elsevier]

Abstract: Solid polymer electrolytes are potentially useful electrolytes to be applied in high-energy batteries. In the present work, a novel polymer electrolyte, polyethylene oxide (PEO)–NaSCN–AlCl3, was prepared and investigated by FT-IR spectroscopic techniques. Based on the FT-IR data, the bands in the CN stretching envelope have been assigned and the effect of AlCl3 on ion–ion and ion–polymer interactions in the polymer electrolyte has been examined. It is shown that the Lewis acid–base interaction of AlCl3 with SCN1− leads to the formation of the complex anions AlCl3SCN− and Al2Cl6SCN−, depending on the content of AlCl3 and/or NaSCN in PEO; the preferential interactions of AlCl3 with crystal complex P(EO)3NaSCN occur in PEO–NaSCN–AlCl3 electrolytes; the AlCl3–NaSCN complex anions can play a plasticization role in PEO–NaSCN–AlCl3 electrolyte, and are expected to be a important factor to improve the conductivity and to enhance the cation transference number. In addition, the interactions between AlCl3 and ether oxygen of PEO were analyzed, and their effect on ionic association was also discussed. [Copyright &y& Elsevier]

The blend-based electrolyte, polyethylene oxide (PEO)–poly(vinylidene fluoride) (PVdF)–NaSCN, was prepared and characterized by FT-IR, X-ray diffraction (XRD) and differential thermal analysis (DTA) measurements at room temperature, and the effect of PVdF content on solvation and ion association was discussed over the content of 5–95%. It is shown that PEO has much stronger ability of solvation to NaSCN than PVdF does, indicating that the polymeric donor number is more important than its dielectric constant in solvating effect of polymer. However, PVdF can keep its semicrystalline nature and form microporous structure in blend-based electrolytes. These characters make PVdF not only enhance the mechanical stability of the electrolyte thin films, but also transform PEO crystalline phase into fully amorphous phase. Although PVdF can effectively disrupt the crystalline complex P(EO)3NaSCN, it does not affect the component of triple aggregations. In addition, the effect of PVdF content on ion association is also discussed in PEO–NaSCN electrolytes. [Copyright &y& Elsevier]

FT-IR spectra of P(EO)nMSCN polymer electrolytes have been recorded at room temperature from n=6–80. The peaks located at ∼2037 and ∼2043 cm−1 were respectively assigned to SCN− stretching mode in crystalline complex and contact ion-pair dimer of NaSCN. It was shown that the free SCN− and the crystalline complex were formed in PEO–NaSCN, but they were not observed in PEO–KSCN system. The PEO–KSCN electrolytes exhibit the amorphous characteristics, which make the contact ion pairs, and the solvent-separated dimers are main ion species in this system. The contact ion-pair dimers can be formed in both systems as the ability of PEO chain to wrap cation is reduced with increase salt content. These conclusions are used to explain the experimental results of conductivity for PEO–MSCN polymer electrolytes. [Copyright &y& Elsevier]