Electrical Conductivity of Seven Binary Systems Containing 1-Ethyl-3-methyl Imidazolium Alkyl Sulfate Ionic Liquids with Water or Ethanol at Four Temperatures

Abstract

We present experimental measurements of specific electrical (or ionic) conductivity of seven binary systems of 1-ethyl-3-methyl imidazolium alkyl sulfate (EMIM-C(n)S) with water or ethanol. Electrical conductivity was measured at 298.15 K in all ranges of concentrations and selected mixtures also at 288.15, 308.15, and 318.15 K. The alkyl chains of the anions used are ethyl (EMIM-ES), butyl (EMIM-BS), hexyl (EMIM-HS), and, only for mixtures with ethanol, octyl (EMIM-OS). Let us note that the four ionic liquids (ILs) measured are miscible in water and ethanol at those temperatures and atmospheric pressure in all ranges of concentrations, but EMIM-OS jellifies for a given range of concentration with water. We compare the measured data in terms of the alkyl chain length and solvent nature. Data are compared with previously scarce results for these same systems and also for other aqueous and ethanol mixtures with ILs. In addition, we verify that our data fit the universal theoretical expression with no fitting parameters given by the pseudolattice-based Bahe-Varela model, except for IL concentrated mixtures. To fit well all ranges of concentrations, we add to the original equation two phenomenological terms with one fitting parameter each. Finally, we calculate the molar conductivity and fit it successfully with an expression derived from Onsager theory.

The properties of residual water molecules in ionic liquids: a comparison between direct and inverse Kirkwood–Buff approaches

“…This finding becomes even more important in terms of computer simulations, which showed the formation of apolar and polar regions in neat dialkylimidazolium ILs with long alkyl chains 34 . Other simulation results revealed the perturbation of the apolar domains by water molecules for the full range of water mole fractions 13 , which was confirmed by experiments, such that the diffusivity and ionic conductivity [35][36][37] , as well as the viscosity of the IL solution changes when compared to pure ILs 38 . Additional outcomes of simulations also indicated the change of interactions between IL species and solvent molecules for low mole fractions of ILs 39 .…”

Transport properties and intermolecular interactions in binary mixtures based on the protic ionic liquid ethylimidazolium triflate and ethylene glycol

“…This nonmonotonic behaviour is rationalised by a competition between dissociation, concentration and mobility of the charge carriers, and has previously been observed for several imidazolium based ionic liquids upon addition of water or ethanol. 7 However, the extent by which the conductivity of C 2 HImTfO is increased by EG is markedly lower than observed by adding water, 8 which results in a more than tenfold increase with a maximum at w E 0.9 (see Fig. S2, ESI †).…”

“…In this context, PIL/water binary mixtures have been studied to measure changes in thermodynamic properties such as phase transition temperatures, density, and viscosity. 5,6 Some efforts have also been spent to understand how added water affects the ionic conductivity or the self-diffusion of the ions in the PIL, 7,8 but considerably fewer studies have been focused on explaining these effects in terms of intermolecular interactions. 9 In some recent works we have shown that the extent by which ionic mobility and ionicity in imidazolium based PILs such as C 2 HImTFSI and C 2 HImTfO are enhanced by added water very much depends on the way water coordinates to the ions.…”

Properties for binary mixtures of (acetamide + KSCN) eutectic ionic liquid with ethanol at several temperatures

“…The relationship between the conductivity of the mixtures and the mole fraction of alcohol had been described by a pseudolattice-based Bahe-Varela model [42], a classical polynomial equation [41] and a Castell-Amis equation [43]. Here, the ethanol fraction dependent conductivity is well fitted by the empirical Castell-Amis equation over the temperature range studied.…”