Dielectric Insights into the Microcosmic Behavior of Ionic Liquid-Based Self-Assembly—Microemulsions/Micelles

Abstract

Dielectric relaxation spectra of ([Bmim][BF4]/TX-100/ p-xylene) microemulsions and ([Bmim][BF4]/TX-100) micelles were measured. A specific dielectric relaxation changing with the concentration of ionic liquids (ILs) was observed in the range of 106-108 Hz. When dielectric parameters were combined with the Einstein displacement equation and Bruggeman's effective-medium approximation, the interaction between [Bmim][BF4] and p-(1,1,3,3-tetramethylbutyl) phenoxypolyoxyethyleneglycol (TX-100) in microemulsions/micelles was presented: because of the electrostatic interaction and van der Waals force, [Bmim][BF4] is bound around the polyethylene oxide (PEO) chains of TX-100, and once the electric field is added, ions of [Bmim][BF4] will move along the PEO chain. The dependence of dielectric and phase parameters such as relaxation time, permittivity, and volume fraction on the mass fraction of ILs presents an evidence for our proposals about the transition of both systems with the increase of IL content. In addition, it was confirmed that percolation is a unique phenomenon in microemulsions and the percolation mechanism here belongs to static percolation. The transition process of micelles with the change of IL content is presented from the dielectric view.