Zusammenfassung
Self-diffusion coeffs. of cations and solvent mols. were detd. with 1H NMR in mixts. of 1-n-butyl-3-methylimidazolium (Bmim+) tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), trifluoromethanesulfonate (TfO-), and bis(trifluoromethylsulfonyl)imide (TFSI-) with acetonitrile (AN), γ-butyrolactone (γ-BL), and propylene carbonate (PC) over the entire compn. range at 300 K. The ...
Zusammenfassung
Self-diffusion coeffs. of cations and solvent mols. were detd. with 1H NMR in mixts. of 1-n-butyl-3-methylimidazolium (Bmim+) tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), trifluoromethanesulfonate (TfO-), and bis(trifluoromethylsulfonyl)imide (TFSI-) with acetonitrile (AN), γ-butyrolactone (γ-BL), and propylene carbonate (PC) over the entire compn. range at 300 K. The relative diffusivities of solvent mols. to cations as a function of concn. 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 (xIL < 0.2) and then increase steeply (AN), moderately (γ-BL), or negligibly (PC) at higher IL concns. 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 compn. and does not depend on the solvent. At this point, a distinct change in the ion-diffusion mechanism appears to take place.
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