276305 Molecular Dynamics Simulation Study of Tris(pentafluoroethyl)Trifluorophosphate-Based Ionic Liquid and Small Molecules Mixtures

Monday, October 29, 2012
Hall B (Convention Center )
Xiaochun Zhang1, Zhiping Liu2, Xiaomin Liu1 and Suojiang Zhang3, (1)State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China, (2)Division of Molecular and Materials Simulation, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing, China, (3)Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China

As a new type of green solvents with many unique properties, ionic liquids have been paid much attention all over the world. Recently, tris(pentafluoroethyl)trifluorophosphate ([FEP])-based ionic liquids have been widely studied due to their excellent properties, such as hydrolytic stability, low viscosity, high electrochemical and thermal stability [1]. However, there is little report about the structure and properties of [FEP]-based ionic liquids from microcosmic view. To understand the properties of [FEP]-based ionic liquids, we studied the solvation properties of water (H2O), methanol (CH3OH) and dimethyl ether (CH3OCH3) in 1-hexyl-3-methylimidazolium ([hmim])[FEP] by molecular dynamics simulation.

Based on the simulation results, the excess molar volume (VE) and excess molar enthalpy (HE) were calculated for mixtures of H2O- [hmim][FEP], CH3OH-[hmim][FEP] and CH3OCH3-hmim][FEP]. The values of VEand HE are negative for the three mixtures, and the negative values follow the order of CH3OCH3 > CH3OH > H2O. The radial distribution functions (RDF) of solute-solute of the three mixtures were investigated, which show that some H2O/CH3OH molecules aggregate in [hmim][FEP]. For comparison, the same RDFs for the three solutes in [hmim] hexafluorophosphate ([PF6]) were also analyzed. It is found that [hmim][FEP] is much more hydrophobic than [hmim][PF6], which is consistent with the experimental result in the literature [1].

Reference

[1].  NV. Ignat'ev, U. Welz-Biermann, A. Kucheryna, G. Bissky, H .Willner. New ionic liquids with tris(perfluoroalkyl)trifluorophosphate (FAP) anions. J Fluor Chem, 2005, 126: 1150-1159.

Acknowledgment

This work was supported by the National Natural Scientific Fund of China (21106146, 20976004, 20903098).


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