The Effect of Neutral Ion Aggregate Formation on the Electrical Conductivity of an Ionic Liquid and its Mixtures with Chloroform

Authors

  • Dr. Thorsten Köddermann,

    1. Fraunhofer Institute for Algorithms and Scientific Computing (SCAI), Schloss Birlinghoven, 53754 St. Augustin (Germany)
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  • Sandra Klembt,

    1. Abteilung Technische Chemie, Institut für Chemie, Universität Rostock, A.-Einstein-Str. 3a, 18059 Rostock (Germany)
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  • Dagmar Klasen,

    1. Abteilung Physikalische Chemie, Institut für Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock (Germany)
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  • Dr. Dietmar Paschek,

    1. Abteilung Physikalische Chemie, Institut für Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock (Germany)
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  • Prof. Dr. Udo Kragl,

    Corresponding author
    1. Abteilung Technische Chemie, Institut für Chemie, Universität Rostock, A.-Einstein-Str. 3a, 18059 Rostock (Germany)
    2. Leibniz-Institut für Katalyse an der Universität Rostock, A.-Einstein-Str. 29a, 18059 Rostock (Germany)
    • Abteilung Technische Chemie, Institut für Chemie, Universität Rostock, A.-Einstein-Str. 3a, 18059 Rostock (Germany)
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  • Prof. Dr. Ralf Ludwig

    Corresponding author
    1. Abteilung Physikalische Chemie, Institut für Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock (Germany)
    2. Leibniz-Institut für Katalyse an der Universität Rostock, A.-Einstein-Str. 29a, 18059 Rostock (Germany)
    • Abteilung Physikalische Chemie, Institut für Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock (Germany)
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  • Ionic Liquid: 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Abstract

We have studied the electrical conductivity of mixtures of the ionic liquid (IL) [C2mim][NTf2] with chloroform for various concentrations at a temperature of 303 K by both experiments and MD simulations. The molar conductivities exhibit an initial increase with decreasing IL concentration, which again sharply decreases in the region of highly diluted IL concentrations. This behavior is according to a competition between 1) the decreasing viscosity with increasing chloroform concentration due to fluidizing the mixture, and 2) the decreasing amount of charge carriers due to the formation of neutral IL aggregates. The simulated molar conductivities and their concentration dependence are found to be in reasonable agreement with the experimentally determined values, suggesting that essential correlations between the solvated ionic species in the solution are well represented. Both experiments and simulations show that the Nernst–Einstein relation drastically overestimates the conductivity of the solutions at low IL concentrations. According to our MD simulation data, this observation is due to the extensive formation of neutral aggregates in the low-concentration regime.

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