Thermophysical properties of [CN − 1C1im][PF6] ionic liquids

M.A. Alves da Rocha, F.M.S. Ribeiro, A.I.M.C. Lobo Ferreira, J.A.P. Coutinho, L.M.N.B.F. Santos

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    Densities, viscosities and refractive index, as a function of temperature, and isobaric thermal expansion coefficient, were determined for 1-alkyl-3-methylimidazolium hexafluorophosphate, [CN − 1C1im][PF6] (where N = 5 to 10) series of ionic liquids. The density presents a regular decrease along the ionic liquid series, with no detectable alkyl chain length dependence of the thermal expansion coefficient. Both the refractive index and viscosity show a trend shift along the series around the [C6C1im][PF6] that could be associated to the impact of the change in the nanostructuration of the ionic liquids. The experimental results are compared with the analogous [CN − 1C1im][NTf2] series and the effect of the anion is analyzed. The sphericity of the [PF6]− anion is reflected in the lower pre-exponential VTF parameter, Aη, and the higher viscosity of the [CN − 1C1im][PF6], when compared with the [CN − 1C1im][NTf2] series, is ruled by the higher energy barriers, which are related with stronger electrostatic interaction due to the low charge dispersion of the [PF6]−.anion.
    Original languageEnglish
    Pages (from-to)196-202
    Number of pages7
    JournalJournal of Molecular Liquids
    Publication statusPublished - 2013


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