| Popis |
Since the discovery of new synthetic strategies leading to mesoporous materials, supramolecular templating, these materials attract immense attention of many scientists. This new approach is based on the presence of surfactants in a solution. Surfactants can associate into supramolecular arrays, micelles, and therefore can be employed as structure-directing agents for the formation of the inorganic mesostructure from the solubilized inorganic precursors. From the mesostructured material, the surfactant is then removed usually by calcination, alternatively by solvent extraction or ozone treatment. Mesoporous materials are high surface area amorphous solids (up to 1400 m2g-1) characterized by monosized cylindrical pores, ranging from 2 to 50 nm in diameter, with long-range ordering of the packing of pores. Three mesostructure types are studied most frequently: hexagonal, lamellar, and cubic. For the synthesis new mesostructured materials we used as template either a geminal anionic surfactant C12H25OPO(OH)(OCH2CH2)3OPO(OH)OC12H25, prepared by the reaction POCl3 with triethylene glycol followed by the substitution of chlorine atoms by dodecanolate and hydroxyl group, or an anionic surfactant CH3(CH2)11N[CH2P(O)(OH)2]2, prepared by the Mannich reaction of primary dodecylamine with formaldehyde and phosphonic acid. These surfactants were characterized by 1H, 31P, 13C-NMR spectroscopy, X-ray powder diffraction, thermal and elemental analyses, mass spectrometry and IR spectroscopy. By evaluating the surface tension dependence on the concentration of surfactants, we have also determined their critical micellar concentration. Homogenous precipitation method using urea4 served us to prepare aluminium, zirconium, chromium, copper, cobalt and nickel mesostructured materials which were characterized by X-ray powder diffraction, IR spectroscopy, thermal and elemental analyses, 27Al and 31P MAS-NMR spectroscopy. However, we have not yet been able to find applicable method for surfactant removal from mesostructured materials without the collapse of the inorganic mesostructures.
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