A novel transition from liquid microemulsions to organogels, and applications of such microstructured media to materials synthesis

In this dissertation, reversed micelles of the surfactant AOT (sodium bis(2-ethylhexyl) sulfosuccinate) have been used for the synthesis of various materials. Peroxidase catalyzed polymerization of 4-hydroxythiophenol was conducted along the lines of poly(4-ethylphenol) synthesis. Polymerization in monophasic dioxane/water system without the surfactant seems to cause oxidation of the sulfhydryl groups producing an extensively crosslinked polymer. Polymerization in reversed micelles produces a soluble polymer that is mostly oxidatively coupled monomer units with minimal thiol oxidation.;A role for the surfactant AOT is demonstrated in the formation of spherical poly(4-ethylphenol) particles when synthesized in AOT reversed micellar systems. Mature polymer can be refolded from solution with the aid of the surfactant and precipitated as spherical particles. The technique seems to be directly applicable to the synthesis of poly(4-ethylphenol): iron oxide nanocomposites.;In nonpolar solvents, dry reversed micelles of AOT transform into a class of organogels upon the addition of suitable phenols. The gels are novel in that they form at very low concentrations of these low molecular weight solutes. Hydrogen-bonding interactions between phenols and the head group of AOT form the basis for such gels. The gel-liquid transition is sharply defined, and occurs over a very narrow temperature range when the gel is warmed or when trace amounts of moisture are absorbed. The underlying molecular architecture of these gels seems to contain strands of stacked and motionally restricted phenol molecules, with the surfactant adsorbed externally. These gels also admit doping with other species leading to the formation of mixed gels. NMR evidence indicates that some of these dopants stack into the gel matrix by "intercalation" into the motionally restricted region of the aromatic strand. Factors such as the molecular shape and proton donor strength (acidity) that determine whether or not a dopant is intercalated are examined.;Cadmium sulfide semiconductor nanoclusters are prepared in AOT/isooctane reversed micelles. The interaction of various ligands with the nanoparticle surface is examined by monitoring changes in the cluster luminescence. Among the quenchers examined, 4-hydroxythiophenol quenches the CdS luminescence most efficiently. The kinetics are modified by the levels of the surfactant by diluting the quencher concentration at the crystallite surface at high micelle concentration. Quenching in the phenolic organogels is slower because both the quencher and the cluster undergo motional and diffusional restrictions.