Dry reverse micelles of the anionic twin-tailed surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) dissolved in nonpolar solvents form an organogel when p-chlorophenol is added in a 1:1 AOT:phenol molar ratio. The proposed microstructure of the gel is based on strands of stacked phenols linked to AOT through hydrogen bonding. Small-angle x-ray scattering (SAXS) spectra of the organogels suggest a characteristic length scale for these phenol-AOT strands that is independent of concentration but dependent on the chemical nature of the non-polar solvent used. Correlation lengths determined from the SAXS spectra indicate that the strands self-assemble into fibers. Direct visualization of the gel in its native state is accomplished by using tapping mode atomic force microscopy (AFM). It is shown that these organogels consist of extended fiber bundle assemblies. The SAXS and AFM data reinforce the theory of a molecular architecture consisting of three length scales-AOT/phenolic strands (ca. 2 nm in diameter) that self-assemble into fibers (ca. 10 nm in diameter), which then aggregate into fiber bundles (ca. 20–100 nm in diameter) and form the organogel. Ferrite and cadmium sulfide nanoparticles have been synthesized in AOT reverse micelles, and the preferential incorporation of these ferrite nanoparticles along the organogel fibers is observed via AFM.; The addition of lecithin (phosphatidylcholine) to AOT water-in-oil microemulsions leads to a dramatic increase in viscosity and the formation of an isotropic rigid bicontinuous mesophase as the water content is increased above a specific threshold. Characterization of this phase transition behavior through electrical conductivity measurements, NMR, and rheology indicates a shift to a percolating aqueous network upon the formation of the rigid mesophase. This rigid mesophase possesses equal volumes of the organic and aqueous phases at the percolation threshold. Small angle neutron scattering experiments show a pronounced peak with a characteristic d-spacing that is a function of the system water content. At elevated temperatures these rigid mesophases undergo a phase transition back to the liquid phase and are thermoreversible in nature. The SANS profiles demonstrate that the rigid mesophases possess a high degree of ordering, and modeling of the SANS data indicate that the rigid mesophases have an ordered bicontinuous microstructure. A novel system that undergoes a phase transition from a liquid to a rigid mesophase upon an increase in temperature also exhibits thermoreversible behavior.; An exciting extension of this rigid mesophase is the formation of mixed AOT + lecithin reverse micelles (water-in-oil microemulsions) at low concentrations. AOT tends to form spherical reverse micelles spontaneously in solution once above the critical micelle concentration (c.m.c). SANS profiles indicate that as lecithin is added to an AOT water-in-oil microemulsion a deformation of this spherical geometry occurs. Cadmium sulfide nanoparticles were then synthesized in this system in order to observe any differences in particle morphology utilizing transmission electron microscopy (TEM). In typical spherical AOT reverse micelles, the CdS obtained is spherical and relatively monodisperse in terms of size. In an equimolar mix of AOT and lecithin, CdS needles are obtained with aspect ratios ranging from 12–36. It is hypothesized that this change in morphology can be related to the shape of the reverse micelle in which the CdS is synthesized, and may be direct evidence of surfactant templating.
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