Adiabatic compressibility of AOT [sodium bis(2-ethylhexyl)sulfosuccinate] reverse micelles:  Analysis of a simple model based on micellar size and volumetric measurements

Abstract

The self-assembly of amphiphilic molecules into supramolecular aggregates involves a number of complex phenomena and forces. Recent developments of highly sensitive, densimetric and acoustic methods on small volume samples have provided novel sensitive probes to explore the physical properties of these complex fluids. We have investigated, by high precision densimetry and ultrasound velocimetry, reverse micelles of [sodium bis(2-ethylhexyl)sulfosuccinate] in oil (isooctane and decane), at increasing water concentration and at variable micellar volume fractions. The size of these spherical micelles has been determined by small angle x-ray scattering. Using these results, in the framework of the effective medium theory, we have developed a simple model of micellar compressibility, allowing the calculation of physical parameters (aggregation number, volume, and compressibility) of the surfactant monomolecular film as well as that of the micellar waters. In particular, we show that the central aqueous core designated as "free" water, located at a distance from the oil-water interacting interface, is twice as compressible as "bulk" water. One notable feature of this work is the influence of the nature of the oil on the above parameters.

Ultrasonic Characterisation of W/O Microemulsions - Structure, Phase Diagrams, State of Water in Nano-Droplets, Encapsulated Proteins, Enzymes

“…The skin depth, T  , for isooctane is shorter than for other common solvents and at 10MHz is about 45 nm. This is comparable with the www.intechopen.com size of droplets of water formed in 0.1M AOT isooctane microemulsion without protein, 5nm at concentration 0.075 (30 molecules of water per one molecule of surfactant) and larger at higher concentrations of water (van Dijk et al, 1989;Amararene et al, 2000). We could expect that a presence of protein molecules increases the size of the droplets.…”

Phyicochemical Processes Controlling Source Term from Tank Residuals

“…This is illustrated in Figure 4 in which the effective diameter calculated by DLS analysis is plotted as a function of W (H 2 O-to-AOT mole ratio). Results from other studies of the pure H 2 O system show that the micelle diameter for scales linearly with W. [8][9][10][11][12] The present results were interpreted in terms of a changing intermicellar potential which DLS also senses. This tuning of the intermicellar potential with changes in solvation is the first report of its kind.…”

“…The solutions of dispersed silver nanoparticles in these systems are highly stable and show no signs of aggregation even after more than a year of storage. The present results represent the first completely green synthesis of metallic nanoparticles Diameters of H 2 O-AOT-isooctane system from ( ) Bohidar and Beboudnia, [9] ( ) Keh and Veleur, [10] (▲) Zulauf and Eicke, [8] (•) Amararene et al, [11] and (▼) Dunn et al [12]. This work has motivated other researchers to take this approach.…”

Protein folding in a reverse micelle environment: The role of confinement and dehydration

“…24 The structure of RMs has been studied with experimental techniques including fluorescence, [25][26][27] NMR, [28][29][30] IR, [31][32][33] and small-angle neutron scattering (SANS)/small-angle x-ray scattering (SAXS). [34][35][36][37][38][39] Scattering studies provide limited insight into the size distribution of the RMs as well as the degree of shape fluctuations. In considering the use of RMs as a confining environment for the study of peptide folding and aggregation, it is important to consider the possible role of RM shape fluctuations in any interpretation of the thermodynamics or kinetics of folding and aggregation.…”