The complex permittivity of AOT/H₂O/CCl₄ and AOT/H₂O/n-heptane microemulsions has been measured by a frequency domain coaxial technique in the range 0.02 – 20 GHz as a function of the molar ratio W = [H₂O]/[AOT], for small amounts of water added (0.2<W<25). An high frequency dispersion reflecting some properties inherent the single particle dynamics relaxation process has been observed. The hydration of reverse micelles has been also investigated by means of IR spectroscopy. A close connection appears between the behaviour of the relaxation time vs. W and the progressive hydration of AOT polar headgroups.

The results have been interpreted in terms of two coexisting diffusion mechanisms: the reorientation of the whole micellar aggregate and the free rotational diffusion of the completely hydrated AOT ion pairs. As the volume fraction of dispersed phase 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. The data show a clear correlation between the presence of attractive interactions and the composition of AOT rotamers in the microemulsion. These results support the hypotesis that attractive intermicellar interactions are favoured by a particular orientation and packing of non polar tails of AOT molecules in the micellar microaggregate.