Translational Diffusion in Mixtures of Imidazolium ILs with Polar Aprotic Molecular Solvents

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• 作者：Bogdan A. Marekha ; Oleg N. Kalugin ; Marc Bria ; Richard Buchner ; Abdenacer Idrissi
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：May 22, 2014
• 年：2014
• 卷：118
• 期：20
• 页码：5509-5517
• 全文大小：375K
• 年卷期：v.118,no.20(May 22, 2014)
• ISSN：1520-5207

文摘

Self-diffusion coefficients of cations and solvent molecules were determined with ¹H NMR in mixtures of 1-n-butyl-3-methylimidazolium (Bmim⁺) tetrafluoroborate (BF₄^{鈥?/sup>), hexafluorophosphate (PF₆鈥?/sup>), trifluoromethanesulfonate (TfO鈥?/sup>), and bis(trifluoromethylsulfonyl)imide (TFSI鈥?/sup>) with acetonitrile (AN), 纬-butyrolactone (纬-BL), and propylene carbonate (PC) over the entire composition range at 300 K. The relative diffusivities of solvent molecules to cations as a function of concentration were found to depend on the solvent but not on the anion (i.e., IL). In all cases the values exhibit a plateau at low IL content (x_IL < 0.2) and then increase steeply (AN), moderately (纬-BL), or negligibly (PC) at higher IL concentrations. This behavior was related to the different solvation patterns in the employed solvents. In BmimPF₆-based systems, anionic diffusivities were followed via 31P nuclei and found to be higher than the corresponding cation values in IL-poor systems and lower in the IL-rich region. The inversion point of relative ionic diffusivities was found around equimolar composition and does not depend on the solvent. At this point, a distinct change in the ion-diffusion mechanism appears to take place.}