Influence of hydration on dynamical properties of reverse micelles

We performed dielectric measurements on sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles in CCl ₄ as a function of the molar ratio W=[D ₂O]/[AOT], for a small amount of deuterated water (0.2< W<10). The investigation revealed a relaxation process whose behaviour as a function of the hydration degree can be interpreted in terms of increasing mobility of AOT head groups. Such a phenomenon reflects complex intrinsic dynamics of the reverse micelle, which can be activated above a threshold W value. The data were compared with recent elastic neutron scattering measurements performed on the same system, that indicate an increase of the local mobility of hydrocarbon tails in the AOT molecule above a defined threshold in the hydration degree.