Abstract
The properties of [EMIM][BF4] + [EMIM][TFSI] double salt ionic liquid (DSIL) were studied as a function of mixtures composition and temperature. Experimental physicochemical properties combined with molecular simulation (quantum chemistry and classical molecular dynamics) were considered, thus providing a micro and macroscopic characterization of fluids’ structuring, intermolecular forces and molecular aggregation. The results were analysed in thermodynamics terms considering deviations of ideality and mixing properties as well as from the solvation and interaction between the involved ionic liquids by the developed complex hydrogen bonding networks. Likewise, liquid [EMIM][BF4] + [EMIM][TFSI] interfaces (x[EMIM][BF4] = x[EMIM][TFSI] = 0.5) were also studied using molecular dynamics methods to examine the diffusion of [BF4]- and [TFSI]- anions in the [EMIM][BF4] + [EMIM][TFSI] liquid interface, and the mechanism of interface crossing. The results allow a multiscale characterization of the considered ionic liquid mixtures thus providing another way of designing IL-type solvents for specific applications, by choosing not only the ion identity but also the ion ratio.
Highlights
Ionic liquids (ILs) have attracted great attention because of their properties such us negligible vapor pressure [1], stability [2] or solvency power for different types of molecules [3,4], which combined with the variety of cation–anion combinations available (1018 possible mixed ILs [5]) show the possibility of considering ILs as designer solvents for process specific requirements [6]
molecular dynamics simulations (MD) simulations on [EMIM][BF4] + [EMIM][TFSI] interfaces (x[EMIM][BF4] = x[EMIM][TFSI] = 0.5) were carried out, inferring the diffusion of [BF4]- and [TFSI]- anions across the interface and the behaviour at [EMIM][BF4] + [EMIM][TFSI] liquid interfaces.The selection of these ILs was done considering that the available literature have showed minor deviations from ideality for alkylimidazolium – based cations but the nanoscopic behaviour of these systems is not clarified, neither in the evolution of excess and mixing properties nor in the changes in intermolecular forces upon mixing and the local composition effects
Experimental density and viscosity data for the studied IL mixtures are reported in Table S5 (Supplementary Information) as well as the derived VE and Dg
Summary
Ionic liquids (ILs) have attracted great attention because of their properties such us negligible vapor pressure [1], stability [2] or solvency power for different types of molecules [3,4], which combined with the variety of cation–anion combinations available (1018 possible mixed ILs [5]) show the possibility of considering ILs as designer solvents for process specific requirements [6]. In this work a study of 1-ethyl-3-methylimidazolium coupled with tetrafluoroborate and bistriflimide ([EMIM][BF4] and [EMIM] [TFSI]) ILs and their binary mixtures containing a common cation (DSILs) has been reported in the full composition range as a function of temperature For these systems, microstructuring and characterization of intermolecular forces is not available in the literature. MD simulations on [EMIM][BF4] + [EMIM][TFSI] interfaces (x[EMIM][BF4] = x[EMIM][TFSI] = 0.5) were carried out, inferring the diffusion of [BF4]- and [TFSI]- anions across the interface and the behaviour at [EMIM][BF4] + [EMIM][TFSI] liquid interfaces.The selection of these ILs was done considering that the available literature have showed minor deviations from ideality for alkylimidazolium – based cations but the nanoscopic behaviour of these systems is not clarified, neither in the evolution of excess and mixing properties nor in the changes in intermolecular forces upon mixing and the local composition effects. The main novelty of this work stands on the combination of highly accurate thermophysical studies with molecular modelling, as a function of composition and temperature, which may led to the required insights into the mixtures properties
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