STRUCTURE AND PROPERTIES OF AOT REVERSED MICELLES AS STUDIED BY THE FLUORESCENCE PROBE TECHNIQUE

The microviscosity in the water pool of Aerosol OT (AOT) reversed mice lles was estimated with the fluorescence yield of a viscosity-sensitiv e fluorescence probe, auramine O (AuO), and the steady-state fluoresce nce depolarization of xanthene dyes solubilized in the micellar core. The fluorescence yield measurement of AuO showed that the microviscosi ty eta(W) at the vicinity of the AOT anionic head groups falls abruptl y up to R(W) ([H2O]/[AOT])=10 and then gradually decreases until the u pper limit of the water solubilization. The eta(W)-T-W curve almost co incides with the curve obtained from the steady-state fluorescence dep olarization of RhB. Thus, the availability of the AuO method was confi rmed. Fluorescence depolarization of xanthene dyes with different ioni c characters evidently demonstrated the heterogeneity of the water poo l. The effects of temperature, surfactant concentration, solvent, and counterion on the microviscosity were examined to obtain a more detail ed picture of the static structure of AOT reversed micelles. In additi on, the fluorescence depolarization of a solubilized dye demonstrated that dynamic fluctuation occurs at the vicinity of the phase separatio n in the cooling process. Finally, the intermicellar aggregation state was studied by utilizing the excitation energy transfer phenomenon. A suitable combination of donor and acceptor molecules solubilized in t he water pool illustrates that AOT reversed micelles are not randomly dispersed in an isolated state in a nonpolar medium, but are clustered through intermicellar coagulation.