Silica materials, organogels

Fig. 2.18 Schematic representation of the creation of silica structures from the organogel state of 47 (upper), 45 (middle) and 46 (lower) by sol-gel polymerization, (a) gelators, (b) sol-gel polymerization of TEOS and adsorption onto the gelator superstructures and (c) single hollow fiber structure (upper), spherical structure (middle) and lotus-like structure (lower) of the silica materials formed after calcination.

Transcription of Organogel Structure into Silica Materials. 130... 

On the other hand, organogelators are low-weight organic molecules that are able to form thermoreversible physical gels in a variety of solvents and at very low concentrations (< 1 % w/w). The solvent molecules are immobilized, and strongly isotropic structures are formed mainly in the shape of fibers, but also ribbons, platelets, or cylinders. Several examples demonstrate the use of organogels to direct the formation of porous silica and titania fibers (74—76). However, these molecular templates are rarely employed for the preparation of ordered micro- and mesoporous materials. 

Rahman, M.M. Czaun, M. Takafuji, M. Diara, H. Synthesis, self-assembling properties, and atom transfer radical polymerization of an alkylated L-phenylalanine-derived monomeric organogel from silica A new approach to prepare packing materials for high-performance liquid chromatography. Chem. Eur. J. 2008,14, 1312. 

The sol-gel process has been used to produce various amorphous silica structures, such as tubular organogels by molecular imprinting. The use of supramole-cules for the synthesis of crystalline mesoporous materials via sol-gel processing is also well known. Preparation of a silica sol of controlled properties was demonstrated by Stober et al. in 1968 and is discussed here. 

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