Dielectric study of percolation in an oil–continuous microemulsion

Abstract

Measurements of the electrical conductivity and the complex permittivity near a percolation threshold in the ternary microemulsion system composed of water, iso-octane, and AOT are reported. It is shown that the electrical conductivity, which implies charge transfer process, is well described by a dynamic percolation model. The frequency dependence of the dielectric constant and the behavior of the relaxation frequency are also found to be in close agreement with the scaling power laws of the dynamic percolation model.

Percolating Microemulsions of Nonionic Surfactants Probed by Dielectric Spectroscopy

“…These features are typical for percolation phenomena. [5,7,9,10,13] For "doted" nonionic microemulsions, where the ions essentially reside within the water droplets, the percolation-induced rise of conductivity was already reported previously. [11,22] Far below the percolation threshold isolated reverse micelles dominate in these systems.…”

“…[11,12] Investigations of the conductivity, s, and the dielectric relaxation (via probing the total complex permittivity, ĥ (n) = e'(n)Ài[e''(n) + s/(2pne 0 )] of the sample as a function of frequency n; e 0 is the electric field constant) of ionic W/O microemulsions not only revealed a marked rise of s, when the percolation limit of the reverse micelles is approached, but also related maxima in the principle relaxation time t [associated with the peak frequency of the dielectric loss, e''(n)] and of the static permittivity, e = lim n!0 -e'(n). [5,7,9,10,13] These effects are generally assigned to the exchange of charges between the reverse micelles, which is strongly facilitated when the droplets start to aggregate to loose clusters that continue to grow until the percolation limit is reached. Charge carriers in these systems are the surfactant ion, such as AOT À , and the usually much smaller and more mobile counterion, for example, Na + .…”

Percolation Behavior in W/O Emulsions Stabilized by Interfacially Active Fractions from Crude Oils in High External Electric Fields

“…Two distinctly different types of reads (4,9) coalescence were identified and were ascribed to differences in water-crude oil interfacial rheological properties, one f r Ç (f p 0 f) s/t , [9] where incompressible interfacial films lead to an increase in the emulsion conductivity due to droplet chain formation (type I) and one where mobile interfacial films lead to low where f r is the critical frequency, and is valid when f is near f p . From linear regression analysis of our results emulsion conductivity due to immediate droplet-droplet coalescence (type II).…”

Study of Ionic Liquid Microemulsions: Ethylammonium Nitrate/TritonX-100/Cyclohexane

“…A static percolation model has been developed to describe the percolation mechanism in traditional microemulsions; this mechanism attributes percolation to the generation of a bicontinuous water structure. The open water channel is presumably responsible for electrical conduction [27,28]. In addition, a dynamic percolation model has been established based on the unique interactions among water droplets or micelles [28].…”

“…The open water channel is presumably responsible for electrical conduction [27,28]. In addition, a dynamic percolation model has been established based on the unique interactions among water droplets or micelles [28]. From this perspective, these interactions between water globules may facilitate the formation of percolation clusters.…”