(147g) Multicomponent Effects in the Diffusion of Hydrophobic Solutes in Microemulsions

A major motivation for the use of microemulsions in food and medical applications is to alter the rate at which valuable solutes are delivered or released.  In microemulsions, solute transport is often characterized with a single, effective diffusion coefficient.  In this presentation, we show how this approach breaks down when concentrations are not dilute.  Holographic interferometry was used to monitor transport of hydrophobic solutes within microemulsions.  Transport is driven by concentration differences across the sample, either in the solute (at constant [surfactant]), or in the surfactant (at constant [solute]).  Especially for more hydrophobic solutes, the transport kinetics cannot be interpreted by straightforward application of Fick's second law.  Multicomponent interaction effects must be taken into account to interpret qualitative changes in the interference fringes, even at particle concentrations as low as 5%.  Furthermore, the off-diagonal terms in the diffusion matrix are not generally small relative to the diagonal terms.  By incorporating multicomponent effects into the analysis of the interference fringes, their importance can be demonstrated and measured.