Amorphous organosilicas

Phenylene-bridged periodic mesoporous organosilicas, with both amorphous and crystal-like walls, (referred to in the following as AW-Ph-HMM and CW-Ph-HMM, respectively) were synthesized and characterized as previously reported [6,7]. BTEB was used as a precursor for both solids the surfactant was Brij-76 (Ci8H37(OCH2CH2)nOH) in acidic media for AW-Ph-HMM and octadecyl-trimethylammonium bromide(ODTMA) in basic media for CW-Ph-HMM. A purely siliceous MCM-41 sample was also synthesised, the first step being the solution of octadecyltrimethylammonium bromide in a basic aqueous solution (NH3), kept a 333 K. Tetraethyl orthosilicate (TEOS) was then added in all cases dropwise, and the mixture stirred for 24h at room temperature (H20 34.2 g/ NH3 (15%) 8.52 g/ ODTMA 0.73 g TEOS 3.24 g). After further 24 hours in hydrothermal conditions at 368 K, the sample... 

Again, summarizing what has been extensively described elsewhere, the two main techniques to prepare sol-gel microparticles start either from W/0 or from oil-in-water (0/W) emulsions to entrap, respectively, hydrophilic or lipophilic ingredients inside the spherical shell of amorphous silica or organosilica. 

It is also relevant that silica microspheres being readily biodegradable and of no toxicity, they will not contaminate the environment as the cmrent commercial trend in their use continues, production of increasing quantities of sol-gel-derived silica-based fimctional materials will inevitably result in the introduction of granules and microparticles made of amorphous silica (or organosilica) in environmental matrices and in the biosphere (Table 18.2). 

Periodic Mesoporous Organosilicas with Amorphous Wall Structure... 

Fluorescence emission fi om 2,6-naphthylene-bridged mesoporous organosilicas with an amorphous or crystal-like framework. Chem. Eur. J, 15, 219-226. 

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