Dielectric analysis of the [Bmim][PF6]/TX-100/ethyleneglycol nonaqueous microemulsions: Microstructures and percolation

Abstract

The ternary system consisting of ethyleneglycol (EG), an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, [Bmim][PF6]) and a nonionic surfactant (p-(1,1,3,3-tetramethylbutyl)phenoxypolyoxyethyleneglycol, TX-100) was studied by dielectric measurements in the frequency range from 40Hz to 110MHz. A remarkable dielectric relaxations caused by interfacial polarization was observed around 10MHz. The dielectric intensity Δɛ and the relaxation time τ could be obtained by fitting the experimental data using the Cole–Cole equation with one dispersion terms. The regions of EG-in-IL (EG/IL), bicontinuous phase (B.C.), IL-in-EG (IL/EG) microemulsions and dilute solution were identified by the dependence of direct current (dc) conductivity on the content of EG, where the dc conductivity was obtained from the total dielectric loss spectra. The scaling relation between conductivity and the content of EG was compared with the predictions of scaling theories. In the IL/EG micro-region, Hanai theory was used to calculate the phase parameters of the constituent phases. The trends of calculated relaxation time τMW and τ as a function of EG content in the IL/EG micro-region were almost the same, inferring that the dielectric relaxation probably arose from the interfacial polarization. In short, this work is helpful to understand the microstructures of different regions and percolation phenomenon in nonaqueous microemulsions.