MICELLAR INTERACTIONS IN WATER-IN-OIL MICROEMULSIONS

The dielectric properties of sodium bis(2-ethylhexyl) sulfosuccinate ( AOT) reverse micelles in CCl4 and n-heptane have been measured in the frequency range 0.02-20 GHz as a function of W = [H2O]/[AOT]. A relaxa tion phenomenon has been observed reflecting some properties inherent the single particle dynamics. This dielectric relaxation has been foun d to be markedly affected by interparticle interactions. Our data, acc ording to previous results, show that interactions in these systems de pend on the oil chain length, on the molar ratio W and are significant ly affected by the addition of small amounts of electrolyte. In order to achieve a deeper insight into the microscopic origin of these inter actions, IR absorptions in the C=O stretching region of AOT molecules have been recorded to give information on the relative population of d ifferent AOT rotational isomers in the various examined systems. The d ata show a clear correlation between the presence of attractive intera ctions and the composition of AOT rotamers, supporting the hypothesis that the intermicellar interactions are favored by a particular orient ation and packing of non-polar tails of AOT molecules in the micellar microaggregate.