COMPARISON BETWEEN MICROVISCOSITIES OF WA TER POOL IN SODIUM AND BIVALENT-METAL SALTS OF 1,2-BIS(2-ETHYLHEXYLOXYCARBONYL)ETHANESULFONIC ACID REVERSED MICELLAR CORES DETERMINED WITH A FLUORESCENCE PROBE

Microviscosity of water-pool, eta(W), in reversed micellar cores of so dium 1,2-bis(2-ethylhexyloxycarbonyl) ethanesulfonate (AOT) and metal 1,2-bis (3-ethylheptanoyl)ethanesulfonic acid (MOT) was determined wit h a viscosity-sensitive probe, Auramine O (AuO). AuO aqueous solutions were solubilized in AOT or MOT reversed micelles. The eta(W), detemin ed by the measurement of the fluorescence intensity and absorbance of the solutions was depicted as a function of R(W,A),A (=[H2O]/[AOT]) an d Rw,M (= [H2O]/n[MOT], in which the number n shows metal valence). Th e relation between eta(W), and R(W) M for MOT solutions coincided with that for AOT solutions. With the increase in R, (R(W), A and R(W), M) , the eta(W), rapidly decreased in the region of R < 10, and leveled o ff at about R=20. The level off values of eta(W), were higher than the value of bulk water. This shows the localization of AuO molecules in the vicinity of anionic polar head of AOT or MOT surfactant molecules.