Experimental and molecular modeling study on the binary mixtures of [EMIM][BF4] and [EMIM][TFSI] ionic liquids

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.