title: Translational diffusion in mixtures of imidazolium ILs with polar aprotic molecular solvents.
abstract: Self-diffusion coefficients of cations and solvent molecules were determined with (1)H NMR in mixtures 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 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 (γ-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 (31)P 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.
authors.affiliation: Department of Inorganic Chemistry, V.N. Karazin Kharkiv National University , Svoboda sq., 4, Kharkiv 61022, Ukraine.
authors.forename: Bogdan A
authors.initials: BA
authors.lastname: Marekha
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Kalugin
authors.forename: Marc
authors.initials: M
authors.lastname: Bria
authors.forename: Richard
authors.initials: R
authors.lastname: Buchner
authors.forename: Abdenacer
authors.initials: A
authors.lastname: Idrissi