Organically Modified Silane Monoliths

One of the attractive features of the sol-gel process is that it enables the preparation of numerous types of organic-inorganic hybrid materials. Mackenzie and Bescher [68,69] pointed out that there are three ways to prepare such hybrids. The first method involves the dissolution of an organic molecule, such as a dye molecule in a sol-gel solution (alkoxide or alcohol). On gelation the dye molecule is trapped in the porous silica matrix [70]. In this case it is assumed that no 

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In monolith febrication it is required to take into account the influence of the precursor gradient chemical composition on the sol-gel process. Parameters that affect the process are metal alkoxide precursor types, pH effect - type of catalyst used, H2O Si molar ratio (/ ), steric effect of precursor ligand groups, and functionality of organically modified silanes (ORMOSIL). 

The functionality of organically modified silanes influences the fabrication of the monolith in several ways. As already mentioned in Section (10.2.3.4), the size of the organic ligand can induce steric effects and slower reaction time. In addition, less polymerized silanol groups (due to the functional ligand groups) ako lead to slower reaction time. When the reaction time is slower, a monolith can be fabricated more easily. 

Brandhuber, D., Torma, V., Raab, C., Peterlik, H., Kulak, A. and Husing, N. (2005) Glycol-modified silanes in the synthesis of mesoscopically organized silica monoliths with hierarchical porosity. Chemistry of Materials, 17, 4262 1271. 

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