Diffusion-influenced deactivation of excited species in AOT microemulsions below, at, and above the percolation threshold

Abstract
The deactivation of long-lived excited states by diffusive quenching has been examined for a microemulsion system, composed of small water droplets dispersed in an alkane solvent by means of the surfactant AOT. The reactants were confined to the water droplets, but with a possibility to exchange between the droplets - probably by the fusion and fission of individual droplets - giving rise to a slow deactivation process, following the initial fast deactivation frome droplets which contained quenchers initially. From measurements using probes of different lifetime, and by varying the quencher concentration, it is possible to determine an average droplet size, to get some information about the polydispersity, to estimate the size and polydispersity of small clusters of micelles formed in dilute systems at low temperatures, and to determine the rate and character of the exchange processes between micelles in large and small clusters. In the interpretation of the decay data pertaining to the exchange between droplets in a cluster of droplets, the process was looked upon as a randon walk over the cluster, leading to fractal type of decay for long walks over a loose cluster close to the percolaton threshold, but to exponential decays both for the compact clusters at high water content, and for the short walks at high quencher concentration.