SOL-GEL DERIVED TIO2 MICROEMULSION GELS AND COATINGS

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 microenviromnent 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 TiO2 absorption. X-ray analysis of films heated to 400-500-degrees-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.