Dielectric spectroscopy study on ionic liquid microemulsion composed of water, TX-100, and BmimPF 6

Abstract

We report here a broadband dielectric spectroscopy study on an ionic liquid microemulsion (ILM) composed of water, Triton X-100 (TX-100), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF 6). It is found that the phase behavior of this ILM can be easily identified by its dielectric response. The dielectric behavior of the ILM in the GHz range is consistent with that of TX-100water mixtures with comparable water-to-TX-100 weight ratio. It consists of the relaxations due to ethylene oxide (EO) unit relaxation, hydration water dynamics, andor free water dynamics. The water content dependence of the EO unit relaxation suggests that this relaxation involves dynamics of hydration water molecules. In the IL-in-water microemulsion phase, it is found that bmimPF 6 molecules are preferentially dissolved in water when their concentration in water is lower than the solubility. An additional dielectric relaxation that is absent in the TX-100water mixtures is observed in the frequency range of 10 7-10 8 Hz for this ILM. This low-frequency relaxation is found closely related to the bmimPF 6 molecule and could be attributed to the hopping of its cationsanions between the anioniccationic sites. © 2012 American Institute of Physics.