Viscosity-percolation behavior of waterless microemulsions: a curious temperature effect

The dynamic viscosity of the waterless microemulsion glycerol/AOT [sodium bis (2-ethylhexyl)sulfosuccinate]/isooctane has been studied at constant volume fraction φ as a function of temperature. The experimental curves are curious: depending on the value of φ, the viscosity either decrease or goes through a maximum when the temperature increases. The results are interpreted in the framework of the percolation theory. The percolation locus in the φ-T plane has been determined, as well as the cloud-point curve. An approximative model is used in order to fit the percolation line, taking into account the temperature dependence of the interaction strength.