As a probe of local structure, the vibrational properties of the 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF 4 ] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim] + conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim] + conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim] + conformers and the [bmim] + − [BF 4 ] − interactions to the vibrational spectra are discussed.
Conductivity and viscosity measurements have been made for poly(propylene glycol)-MCF3SO3 (M=Li, Na) complexes in order to examine more closely the Vogel–Tammann–Fulcher (VTF) empirical relationship which has been found in previous reports to provide a good fit to the experimental data. Further, a dynamic bond percolation model of ion conduction in polymer electrolytes has predicted VTF behavior and an inverse relationship between molar conductivity and viscosity or Walden ‘‘rule’’ behavior. We find that deviations occur from both the VTF and Walden empirical relationships and propose a modest alteration in the form of the dynamic percolation model for ions moving in polyether systems.
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