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Microemulsion gels and coatings have been obtained by the sol-gel method using titanium(IV) isopropoxide. Three types of fine water dispersions have been used as the basis sol: reverse Triton X-100 micelles in cyclohexane; quaternary water-in-oil microemulsions containing cyclohexane, 1-pentanol, sodium dodecyl sulfate, and water; and dispersions of water in pentanol in the presence of sodium dodecyl sulfate. Titanium(IV) isopropoxide was dissolved in the continuous phase and hydrolyzed by the dispersed water. Gelation occurred in a few hours in the case of cyclohexane, as the solvent of the continuous phase, and in few days in the case of pentanol. The gelation processes and the obtained microenvironment were probed with fluorescent probes. Films of thickness of the order of a hundred nanometers can be obtained by dipping glass, plastic, or aluminum plates into the solutions at their early stage of gelation. The absorption spectra of the films were characteristic of TK>2 absorption. X-ray analysis of films heated to 400-500 °C revealed a rutile structure. Films on glass substrates analyzed with a scanning electron microscope revealed a partial coverage of the substrate surface with a rather interesting geometry which depended mainly on the extent of gelation and secondarily on the type of the solution used.

Water-in-oil microemulsions compoaed of cyclohexane or toluene, sodium dodecyl sulfate, 1-pentanol, and water have been prepared by chooaing compositions close to the demixion line in the pseudoternary phase diagrams. The microemulsions were either in the electric nonpercolating or in the electric percolating domain. Their properties were studied by luminescence probing, quasi-elastic light scattering, and electrical conductivity measurements both in the absence and in the presence of a-hydro-w-hydroxypoly(o.y-1,2-ethanediyl), MW 6QQQ. Cyclohexane and toluene microemulsions behave in a similar manner, with differences only in the absolute values of the observed parameters. In the presence of polymer, the number of droplets decreases, their size increases, the apparent hydrodynamic radius increaees, and the electric conductivity decreases. Due to the decrease of the number of droplets, the probability of an immediate encounter between a luminophore and a quencher increases in the presence of polymer. However, the overall quenching efficiency then decreases, due to a partial immobilization of the reactants by the polymer. In other words, the diffusion of the reactants is reduced in the presence of polymer.

Thin surfactant films have been formed by dip-coating glass slides in a solution of reversed micelles containing titanium isopropoxide. The alkoxide is slowly hydrolyzed in the presence of reversed micelles since hydrolysis competes with hydration of surfactant polar groups. Adhesion of the surfactant on the glass slide is assisted by incompletely hydrolyzed alkoxide through the following possible mechanism: the alkoxide adheres by -Si-0-Ti-bonds and the surfactant follows by hydrophobic attraction to the isopropyl groups. The films are transparent and visually uniform. Three surfactants, forming reversed micelles, have been investigated: one nonionic, Triton X-100; one anionic, AOT; and one cationic, hexadecyldimethylbenzylammonium chloride. The environment provided by the surfactant film has been studied by fluorescence probing. In particular, we have analyzed pyrene excimer formation as well as energy transfer between pyrene, acting as donor, and coumarin-153 or N-n-heptyl-4-(((dimethylamino)phenyl)ethenyl)-pyridinium bromide, acting as acceptor. In Triton and hexadecyldimethylbenzylammonium chloride films, pyrene excimer formation is diffusion-controlled while in AOT films excimer largely comes from pyrene aggregation. Pyrene excimer formation capacity decreases in the presence of cosulubilized poly(viny1 methyl ether) chains. Energy transfer data indicate that coumarin-153 is randomly distributed in the films, but N-n-heptyl-4-(((dimethylamino)phenyl)ethenyl)pyridinium bromide is not randomly distributed but shows a tendency to aggregate. Generally speaking, the benzyl-group-bearing surfactants form fluid structures while AOT may provide a restricted low dimensional environment.