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Influence of the anion on ionic liquids mixtures properties: A molecular dynamics study

Abstract

Mixing of ionic liquids provides new opportunities for their tuning, enabling the applications of ionic liquids mixtures to expand. At the same time, the genesis of the fundamental properties of ionic liquids mixtures is still poorly understood. In this study we carried out a molecular dynamics simulation of binary mixtures of 1-buthyl-3-methylimidazolium hexafluorophosphate, 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-buthyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate ([C4mim][PF6] + [C4mim][NTf2], [C4mim][PF6] + [C4mim][FAP], [C4mim][FAP] + [C4mim][NTf2]) in wide concentration range at 303.15 K and complemented it with quantum mechanical calculations. Three pure ionic liquids underwent the same kind of analysis for comparison purposes. We found, that the addition of [FAP]--anion to a mixture enhances the non-polar domains segregations and weakens the hydrogen-bond network. The H-bonds in the studied mixtures are rather weak, as it follows from QTAIM analysis, with the rarest occurrence for [FAP]--anion. The competition of two anions in the mixtures for the most acidic hydrogen of the 1-butyl-3-methylimidazolium cation is reported. In most of the cases, the smaller anion ([PF6]- or [NTf2]-) with stronger charge concentration displaces the bigger one ([NTf2]- or [FAP]-) from the preferred coordination site. The existing nano-segregation in some mixtures notably slows down ion diffusion. Our results show that the difference in anion size, shape and nature are the main reasons for nano-segregation and the non-ideal behavior of ionic liquids mixtures.

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Publication details

The article was received on 08 Mar 2018, accepted on 08 May 2018 and first published on 17 May 2018


Article type: Paper
DOI: 10.1039/C8CP01541D
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Influence of the anion on ionic liquids mixtures properties: A molecular dynamics study

    I. Voroshylova, E. S. C. Ferreira, M. Malček, R. Costa, C. M. Pereira and M. N. D. S. Cordeiro, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP01541D

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