Effect of short-range attractive interactions on the low-frequency electrical conductivity of water-in-oil microemulsions

Abstract

In this paper we report on low-frequency electrical conductivity measurements in water-in-oil micro-emulsion systems, formed using four different organic solvents (n-pentane, n-octane, n-decane and carbon tetrachloride) at different water-to-surfactant molar ratios W, in the temperature range 5-60 °C (up to the stability limit of the single phase system). To evaluate the effects of short-range attractive interactions between surfactant-coated water droplets, the composition of the microemulsion has been appropriately adjusted by maintaining the distance between two adjacent droplets constant. The experimental data have been analyzed considering the currently stated charge fluctuation theories; the excess free energy associated with the whole charging process has been evaluated for the different solvents investigated. The results presented here give further support to the theory that inter-droplet interactions are due to the interdigitation of the surfactant tails and solvent phase molecules.