Synthesis of Silica-Based Nanostructured Hybrid via Supramolecular Chemical Approaches

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A variety of ordered hybrid materials have been obtained by self-assembly of designed amphiphilic silicon-based precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. The design of molecules having alkyl chains and large oligosiloxane heads led to the formation of mesophases consisting of cylindrical assemblies, providing a direct pathway to ordered porous silica. We also reported the synthesis of silica-based hybrids with lamellar and wormhole-like mesostructures using of 1-alkynyltrimethoxysilanes. The hybrids with wormhole-like mesostructures, prepared in the presence of TMOS, were converted into mesoporous silica either by chemical treatment or by calcination. Furthermore, we have demonstrated the formation of novel layered materials from alkoxy-derivatives of bis(trichlorosilanes) having methylene, ethylene, and phenylene bridges. On the other hand, we discovered a new class of cage-like oligomers which were selectively formed by hydrolysis and polycondensation of a methylene-bridged bistrialkoxysilane precursor in the presence of tetramethyl-ammonium hydroxide.