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Various organic reactions were explored to develop novel ordered mesoporous organosilicas (OMOs) by employment of two different synthesis strategies involving: (i) transformation of organic groups in organosilica frameworks, and (ii) formation of new organic groups during the self-assembly process carried out the presence of reactive precursors.An illustration of the first strategy is the synthesis of mesoporous organosilica materials with a hydrophilic bridging group, 1,2-dihydroxyethane, by using triblock copolymer as structure directing agent and ethylene-bridged organosilane as an initial precursor. Cetyl-trimethylammonium permanganate was used to transform ethylene bridge to 1,2-dihydroxyethane and to obtain a new OMO material with high specific surface area (reaching 660 m2/g), large pore size, and significant secondary mesoporosity.The major part of this dissertation is devoted to the development of ordered silica-based mesostructures with different organic groups such as N-hydroxyurea and boron-containing groups, which are relevant to biological and environmental applications. These materials were prepared by the self-assembly of a bridged organosilane (framework building precursor) and a block copolymer (soft template) in the presence of reactive precursors able to form new organic functionalities. This strategy was used to obtain a series of ordered mesoporous ethane-silica samples with N-hydroxyurea groups by using 3-isocyanato-propyltriethoxysilane and hydroxylamine hydrochloride salt as reactive precursors. The latter played a double role: (1) pH adjustor (no acid was used in this synthesis) and (2) reactive precursor needed for the formation of a new pendant organic group, N-hydroxyurea. In addition to N-hydroxyurea group, mercaptopropyl and ureidopropyl groups were introduced too in order to improve the adsorption affinity of the resulting OMOs towards metal ions. In addition, organosilica mesostructures with both basic and acidic groups were studied; namely, one mesoporous organosilica with biologically relevant hanging group, 1-amino-1,1-bisphosphonate, was synthesized and characterized. |
