Conductometric and Volumetric Studies on the Inonization, Hydration, Aggregation, and Coagulation of AOT in Dodecane

Abstract

For the sodium l,2-bis(2-ethylhexyloxycarbonyl)ethanesulfonate (AOT)/water/dodecane system, the conductivity (κ) of the solution as well as the partial molar volume of water was determined at 25 °C as a function of the water concentration (CW) at a given concentration of AOT (CA). The value of (κ) increased stepwise through 2 peaks before water-phase separation. Each step was assigned as follows. Upon the initial additions of water at all of the CA’s studied (CA < 0.2 mol kg−1 (dodecane)), κ remained zero, indicating the formation of unionized hydrate, AOT(H2O)2. The critical composition of the solution for reversed micelle formation was estimated to be CA = ca. 0.02 and CW = ca. 0.04 mol kg−1 (dodecane). After hydrate formation, micelles were formed in equilibrium with the hydrate, at which point κ increased abruptly to the 1st peak. Coagulation of the micelles occurred above another critical composition (CA = 0.120 and CW = 0.612 mol kg−1), at which point κ increased with a steep slope up to the 2nd peak. The partial molar volume of water in the same system also indicated the formation of AOT(H2O)2.

Intermicellar Material Exchange and Droplet Clustering in AOT Reverse Micellar Systems. A Pulse Radiolysis Study of (SCN)2•- Radical Anion Spectra and Decay

“…In our case, for AOT reverse micelles in n -heptane at w 0 = 20 the above suggested critical concentration falls in the range between 0.1 and 0.2 M. Note that Manabe et al. have found 0.12 M AOT in dodecane at w 0 ≅ 5 to be a critical composition above which coagulation of micelles occurs …”

Study on Percolation of Mixed Reverse Micelles

“…Among these methods, conductivity measurements are very useful for the reason that electrical conductivity is very sensitive to the microstructure of reverse micelles [4]. Although there still exists controversy about the conducting mechanism, investigations on the structures and properties of reverse micelles by conductivity measurements have been widely carried out [5][6][7][8][9]. Eicke et al [S] explained the conductivity of reverse micelles quantitatively on the basis of the charge fluctuation model by taking into account the Born energy of charging the droplets in a dielectric medium, in which the conductivity was interpreted by the migration of the charged water droplets in the electric field.…”

Clustering of Aerosol OT Reversed Micelles As Studied by Nonradiative Energy Transfer of Solubilized Probes

“…For the AOT/dodecane reversed micellar system, Manabe et al. obtained a phase diagram composed of five realms on the basis of the electric conductivity as functions of [H 2 O] and [AOT]. The four regions appeared in a [H 2 O]−[AOT] diagram plotted on the basis of the inflection points in the conductivity curves.…”