Controlled Sol-Gel Processes

Based on the control of sol-gel deposition, hierarchically porous silica-based materials with a bimodal pore system (mesopores/large meso/macropores) and a diversity of dopant elements (Al, Ti, V, and Zr) could be prepared by using a one-pot surfactant-assisted procedure [78]. Another example includes the preparation of nonionically templated [Si]-MSU-X mesoporous silicas with bimodal pore systems by adding dilute electrolytes. 

Qiemically induced liquid-liquid phase separation has been applied to synthesize the siliceous mesoporous materials with co-continuous macropores [79-81]. This phase separation technique is based on the hydrolysis and condensation of inorganic precursors in the aqueous domain, derived from the self-assembly phase of the template used. The phase separation process leads to the formation of a macroporous structure. The walls of the macropores consist of aggregates of silica nanoparticles that give rise to textural mesoporosity in the walls with pore sizes in the 10-20 nm range and a high surface area. 

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The dynamic self-assembly processes of such supramolecular systems undergoing continous reversible exchange between different self-organized entities in solution may in principle be connected to kinetically controled sol-gel process in order to extract and select an amplified supramolecular device under a specific set of experimental conditions. Such dynamic marriage between supramolecular self-assembly and in sol-gel polymerization processes which synergistically might communicate leads to constitutionnal hybrid materials. ... 

Dynamic self-assembly of supramolecular systems prepared under thermodynamic control may in principle be connected to a kinetically controlled sol-gel process in order to extract and select the interpenetrated hybrid networks. Such dynamic convergence between supramolecular self-assembly and inorganic sol— gel processes, which synergistically communicate, leads to higher self-organized hybrid materials with increased micrometric scales. 

L. L. Hench, Use of drying control chemical additives (DCCAs) in controlling sol-gel processing, in L.L. Hench and P. Uhlrich (Eds.), Science cf Ceramic Chemical Processing. Wiley, New York, 1986, pp. 52-65,... 

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