Temperature and Pressure Dependence of the Viscosity of the Ionic Liquid 1-Butyl-3-methylimidazolium Acetate

Abstract

Viscosities obtained with a falling-body viscometer are reported at pressures up to 300 MPa, over the temperature range 278–353 K, for 1-butyl-3-methylimidazolium acetate ([BMIM]­[Ac]) samples dried under high vacuum with water content [106 × w(H2O) = 258 and 1180] and ion purity x > 0.992. Atmospheric pressure densities are reported for 273–363 K. Comparison is made with literature viscosities and densities at 0.1 MPa. There is a very large variation in the former, which seems in part due to differences in the purities of the source materials. It is recommended that methanol-free reagents should be used for Karl Fischer water analysis of ionic liquid acetates and that samples used for thermophysical property measurements should be well characterized by spectroscopic methods, not just water content. The proton resonance at the C2 position on the imidazolium ring appears to be a good qualitative indication of the dryness. “Activation” volumes, ΔV ‡, are calculated from the parameters of a fit to a pressure-modified Vogel–Fulcher–Tamman (VFT) equation and compared with those for other 1-butyl-3-methylimidazolium ionic liquids. Thermodynamic or density scaling has been applied to the reduced viscosity as a function of the group (TV γ), γ being the single scaling parameter, equal to 2.02.

Does [Tf2N]− slither? Equivalence of cation and anion self-diffusion activation volumes in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide

“…¶ As in ref. 4 and our other work, 15,16,37 the logarithms of the Rosenfeld reduced quantities were fitted to polynomials in 1/(TV) g for selected values of g with polynomial orders from 2 to 3, depending on the range of available data, with the order being kept as low as needed to give sensible fits commensurate with the experimental precision; g is chosen by iteration to minimize the standard deviation of the fit. Fig.…”

“…In previous studies we have reported on the pressure and temperature dependence of ion self-diffusion coefficients, [1][2][3][4][5][6][7] the electrical conductivity 1,[8][9][10] and the viscosity 2,6,[11][12][13][14][15][16] of a range of ionic liquids. In statistical mechanical Green-Kubo theory, the self-diffusion coefficients and the conductivity can be written in terms of velocity cross-correlation coefficients (VCC) and it has been found that these show, for a given ionic liquid, very similar viscosity dependence for cation-cation, anion-anion, and cationanion interactions.…”

Collectivity in ionic liquids: a temperature dependent, polarizable molecular dynamics study

“…For example, as shown by Cabeza et al, the conductivity of certain 1-ethyl-3methyl-imidazolium based ionic liquids can increase twentyfold in the range of 258.15 to 298.15 K, and up to a factor of 400 when increasing the temperature to 393.15 K. 18 Molten salts are known to form layers of oppositely charged ions around both cations and anions. These cages play a vital role in the evolution of the viscosity and diffusivity of ILs, [19][20][21] slowing down dynamics and reducing conductivity. 18,22,23 Rattling motions within said cages can be assumed to occur at a fast timescale without significant interaction with neighboring like-charged ions.…”

Guanidinium solvents with exceptional hydrogen bond donating abilities

“…32 The viscosities of GuCl : LA and GuCl : LevA are also below that of the common IL [C 4 C 1 im][OAc] (278 mPa s). 33 Hence, these fluids possess improved or comparable viscosities to other, similar non-volatile alternative solvents.…”