title: Revised and Extended Values for Self-Diffusion Coefficients of 1-Alkyl-3-methylimidazolium Tetrafluoroborates and Hexafluorophosphates: Relations between the Transport Properties.
abstract: Earlier measurements of the self-diffusion coefficients of 1-alkyl-3-methylimidazolium (or [RMIM], R = alkyl) tetrafluoroborates and hexafluorophosphates have been revised and extended to 90 °C. The main changes are to DS+and DS-for [HMIM][PF6] ([C6C1Im][PF6]) and DS-for [OMIM][BF4] ([C8C1Im][BF4]). New atmospheric pressure self-diffusion, density, and conductivity data are provided for [HMIM][BF4] ([C6C1Im][BF4]). Velocity cross-correlation, distinct diffusion, and Laity resistance coefficients have been calculated. There is no evidence for ion association. A new relation between the Nernst-Einstein deviation parameter (Δ) and resistance coefficients (rij) is derived; Δ tends toward 0.5 when the like-ion riiare much smaller than the unlike-ion rij, i.e., when the counterion interactions dominate. [OMIM]+ion salts approach this limit. Stokes-Einstein-Sutherland and Walden plots overlap almost quantitatively for [BF4]-, [PF6]-, and Cl-salts with a common [RMIM]+cation. That is, in thermodynamic states that have the same viscosity, the salt molar conductivities and hence ionic electrical mobilities of, say, [BMIM][BF4] and [BMIM][PF6] are almost equal, as are the corresponding Brownian or diffusive mobilities, (DSi/RT), for the cation, and also for these three small anions.
authors.affiliation: School of Physical, Environmental and Mathematical Sciences, University of New South Wales , P.O. Box 7916, Canberra BC, ACT 2610, Australia.
authors.forename: Kenneth R
authors.identifier: 0000-0001-6732-0488
authors.initials: KR
authors.lastname: Harris
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , 4-2-1 Nigatake, Miyagino-ku, Sendai 983-8551, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kanakubo