PERCOLATION PHENOMENON IN TERNARY MICROEMULSIONS - THE EFFECT OF PRESSURE

The electrical conductivity sigma and dynamic viscosity eta of water-based water-AOT-undecane [AOT:sodium bis(2-ethylhexyl) sulfosuccinate) microemulsions and waterless glycerol-AOT-isooctane microemulsions were studied as a function of volume fraction phi in dispersed matter (water plus AOT or glycerol plus AOT) and pressure up to 1000 bar. The realm of existence of the single-phase zone was also determined versus pressure P. The curves eta(P) and sigma(P) at constant phi and temperature T, and the curves eta(phi) and sigma(phi) at constant P and T were analyzed within the framework of percolation theory. For water-based microemulsions the percolation threshold phi(c) decreases when P increases, corresponding to an increase in interactions. For waterless microemulsions phi(c) varies very little. The scaling exponents are almost-equal-to 2 above the threshold and almost-equal-to - 1.2 below, whatever the pressure, the system, and the property studied (values which have already between obtained at 1 bar). This corresponds to the fact that these systems belong to the same class of universality.