Self-Diffusion Coefficients and Related Transport Properties for a Number of Fragile Ionic Liquids

详细信息    查看全文

• 作者：Kenneth R. Harris ; Mitsuhiro Kanakubo
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：61
• 期：7
• 页码：2399-2411
• 全文大小：612K
• 年卷期：0
• ISSN：1520-5134

文摘

Ion self-diffusion coefficients (D_Si) for [EMIM][CF₃SO₃] and [chol][Tf₂N] and cation self-diffusion coefficients for [CH₃SO₃]⁻, [TCB]⁻, and [FAP]⁻ salts of [EMIM]⁺ are reported together with ancillary data allowing calculation of velocity cross-correlation (VCC or f_ij), distinct diffusion (D^d_ij) and Laity resistance coefficients (r_ij). Comparison of ion Stokes–Einstein–Sutherland (SES) exponents is a useful test of experimental consistency. New analysis shows the viscosity (η) and molar conductivity (Λ) of [EMIM][CH₃SO₃] and [EMIM][TCB] do not show the dynamic crossovers previously reported. Nor do D_S and η for the comparison substance propylene carbonate. For all the ionic liquids, D_S+ > D_S-. Data show fractional SES (D_Si-η, D^d_ij-η) and Walden (Λ–η) plots. The Nernst–Einstein parameter, Δ, for [EMIM][FAP] is approximately zero, implying the relative velocity of any ion pair selected randomly is uncorrelated with those of other distinct pairs. For the other ionic liquids, the relative pair velocities are anticorrelated. VCC values for the [EMIM]⁺ salts except [EMIM][FAP] lie in the order |f_+–| < |f₊₊| < |f_––|; that is, the anticorrelation is smallest for the unlike ion interactions: correspondingly, r₊₊ < r_–– < r_+–. For [EMIM][FAP], |f₊₊| < |f_+–| < |f_––|, with f_+– ∼ (f₊₊ + f_––)/2 and r_+–² ∼r₊₊ r_––, consistent with Δ ∼ 0.