Dynamics of water-containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles: A high-frequency dielectric study

The high-frequency dielectric response of AOT reverse micelles in n-heptane and ${\mathrm{CCl}}_4$ has been measured in the range 0.01-20 GHz as a function of the water-surfactant ratio (W). A relaxation phenomenon has been observed which is connected to the single particle dynamics. This dielectric relaxation depends on surfactant hydration and is markedly affected by interparticle interactions. At low values of the volume fraction φ of dispersed matter (water + AOT), interparticle interactions are negligible and the behavior of the dielectric relaxation vs W has been interpreted in terms of two coexisting diffusion mechanisms: the reorientation of the whole micelle and the ‘‘free’’ diffusion of the completely hydrated AOT ion pairs. As φ is increased, interparticle interactions start to play a role and the dielectric relaxation is considerably affected by the nature of the external oil and by the addition of small amounts of electrolyte. © 1996 The American Physical Society.