A dynamic transition at the percolation threshold of a three-component microemulsion

Abstract

We report on a series of static and dynamic light-scattering experiments performed in a three-component water-in-oil microemulsion consisting of water/decane/AOT (sodium-di-2-ethyl hexyl sulfosuccinate). The measurements have been done throughout the isotropic one-phase region, in a large domain of volume fractions, as a function of temperature and scattering wave vector. For volume fractions φ > 0.42 the long-time tail of the droplet density correlation function S(Q t) is not an exponential, but tends toward a stretched exponential. The temperature and wave vector dependences of the first cumulant K ₁, and of the average relaxation time have bene investigated. These parameters change abruptly when crossing the well-defined electrical percolation locus. A theoretical model based on the aggregation of polydispersed fractal clusters of fractal dimension d=2, is in agreement with the experimental results.