Résumé
Silsesquioxanes are obtained from organotrialkoxysilane precursors, most of which are commercially available. The hydrolysis-condensation of these molecules can lead to well-defined molecular structures including silsesquioxane cages (POSS). According to the type of precursor and to the reaction conditions, several cage compounds can be formed. Thus with p-styryltriethoxysilane T8, T10, T12 and T18 cages could be isolated as pure compounds. These can be postsilylated and hydrolysed leading to POSS units covalently bonded and evenly distributed in a silsesquioxane hybrid network.Moreover bridged silsesquioxanes are available by the hydrolysis of organosilane precursors bearing an organic fragment interconnected to at least two trialkoxysilyl groups. The properties of the resulting hybrid materials can be tuned following the main organic structure (nanostructuring through self-assembly, molecular imprinting/molecular recognition, catalysis, optics, nanomedical applications) and also by the silsesquioxane matrix (periodic and uniform porosity, high surface area, size and shape controlled nano-objects. My presentation will be focused on these two types of silsesquioxane families