Onset of Droplet Aggregation from Self-Diffusion Measurements in Microemulsions

Abstract

We report the first self-diffusion measurements of water-in-oil microemulsions done with fringe-pattern photobleaching-recovery techniques. These measurements give evidence of the onset of droplet aggregation which can be fairly distinct from the percolation threshold where an infinite aggregate is formed. Our results show that in some cases spherical droplets may not exist even at very low water-volume fractions. Above the observed onset, the self-diffusion coefficient reaches a nonzero limit value, reflecting the dynamical aspect of aggregation in these media.