THEORY AND EXPERIMENT OF ELECTRICAL-CONDUCTIVITY AND PERCOLATION LOCUS IN WATER-IN-OIL MICROEMULSIONS

An extensive set of measurements of low-frequency conductivity of a three-component microemulsion system, sodium-di-2-ethyl-hexylsulfosuccinate (AOT)-water-decane, as a function of temperature (T from 10 to 50°C) and volume fraction of the dispersed phase (from 0.098 to 0.65) has been made. The measurements were made at a fixed value of the water-to-surfactant molar ratio equal to 40.8, where the microemulsion consists of AOT-coated water droplets, 85 in radius, dispersed in oil. can be quantitatively calculated at low by means of a charge fluctuation model of Eicke et al., while it can be interpreted for higher vlaues of in terms of power-law behavior with indices related to the dynamic percolation picture below the threshold and the static one above it. The percolation locus in -T plane has been determined starting from the vicinity of the lower consolute point up to =0.65. This line can be successfully interpreted in terms of a modified version of the analytical theory of percolation given by Xu and Stell. © 1990 The American Physical Society.