How mixing tetraglyme with the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide changes volumetric and transport properties: An experimental and computational study

A Sharma and Y Zhang and T Gohndrone and S Oh and JF Brennecke and MJ McCready and EJ Maginn, CHEMICAL ENGINEERING SCIENCE, 159, 43-57 (2017).

DOI: 10.1016/j.ces.2016.05.006

The viscosity and density of the ionic liquid (IL) 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C(6)mim NTf2), the molecular solvent tetraethylene glycol dimethyl ether (tetraglyme or G4) and their binary mixtures were measured experimentally as a function of temperature. The same systems were also studied using classical molecular dynamics (MD) simulations. The viscosities of the C(6)mim NTf2/G4 mixtures decrease with increasing G4 concentration, though not as much as an ideal mixing model would predict. Detailed analysis of the MD results reveals that G4 preferentially solvates cations, leading to a reduction in the interaction energy between cations and anions and a subsequent enhancement in anion mobility. A similar effect has been reported when glymes are mixed with salts containing alkali metal cations, with the resulting mixtures being called "solvate" ionic liquids. The simulations predict that the ionic conductivity will be maximized when the G4 mole fraction is around 10-20%. The ability of G4 to effectively solvate the cations stems from localized charges on the oxygen. The simulations predict that solvents having large localized positive charges would preferentially solvate anions, leading to enhanced cation mobility. (C) 2016 Elsevier Ltd. All rights reserved.

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