Tetramethoxysilane

Redistilled tetraethoxysilane containing less than 1 ppm chloride added to neutral 18 x 10 H water purged with nitrogen ia fluorocarbon bottles does not hydroly2e to a gel for over 6 months (10). Without special precautions, tetraethoxysilane hydroly2es to a gel ia - 10 d tetramethoxysilane... 

Glass Frosting. Deposition of siUcon dioxide is used to impart a translucent coating on glass (qv) (50). The surfaces are either exposed to tetraethoxysilane or tetramethoxysilane under high moisture conditions, or the alkoxysilanes are ignited and the resulting powder is appHed to the surface. 

Gas phase production of flue SiOi particles from tetramethoxysilane... 

In our previous paper [6], the authors have demonstrated that production of fine silica powder is possible by phase hydrolpis of tetramethoxysilane fTEMS). In this communication, we report the effect of the shape of reactor and operational condition, especially mixing condition on conversion of the reaction and properties especially diameter of produced silica fines. 

Further examination has shown that the acid content should be small in order for the solution to become spinnable in the course of hydrolysis and polycondensation. It has been found (4 ) that very large concentrations at more than 0.15 in the [HCl]/[Metal alkoxide] ratio of acid catalyst produce round-shaped particles in the tetra-ethoxysilane (7) and tetramethoxysilane solutions, and so no spinnability appears. 

During the preparation of the hexamethoxides of rhenium, molybdenum and tungsten by co-condensation with excess tetramethoxysilane on a cold surface, simultaneous co-condensation is necessary to avoid the danger of explosion present when sequential condensation of the reactants is employed. In the latter case, the high concentrations of hexafluoride at the interface leads to violent reaction with the silane. 

See Tetramethoxysilane Metal hexafluorides See other METAL ALKOXIDES... 

In a related approach, alginate beads were modified with aminopropyl-silicate membrane (derived from APTS and tetramethoxysilane). The amino groups remaining on the surface are favorable for the anchoring of biomolecules [84],... 

The sol-gel process involves the preparation of inorganic matrices via three steps. Components of the sol-gel cocktail are the sol-gel precursor (e.g. tetramethoxysilane), water, a catalyst (acids or bases), the indicator chemistry and a solvent such as ethanol. Mixing these components causes hydrolysis of the ester, silanol-ester condensation, and silanol-silanol condensation of the precursors ... 

For silica, much of the work in this area was carried out in the 1980s and the reader is referred to the series of proceedings volumes from the Materials Research Society entitled Better Ceramics through Chemistry. 63 To illustrate typical precursor structures, and the role of reaction chemistry on precursor structure, Fig. 2.3 presents capillary gas chromatography results for the hydrolysis of tetramethoxysilane [TMOS Si(OCH3)4].72 Typical polymeric species formed (Fig. 2.3a) include linear and cyclic structures. 

The trend was studied and verified, for instance, for reactions catalysed by transition metal, organo- and enzyme catalysts entrapped in ORMOSIL prepared by copolymerization of tetramethoxysilane (TMOS) and the modifying co-precursor methyltrimethoxysilane (MTMS). It has been correlated with the encapsulation itself but also with the structure of the sol-gel matrix, namely the hydrophobicity-lipophilicity balance (HLB) and the textural properties of the materials.9... 

The 3,5-diphenylmorpholine-2-one 161 was used to prepare bicyclic lactams 162 by reaction with the cesium fluoride/tetramethoxysilane system and different Michael acceptors. The adducts were rapidly obtained as a mixture of diastereoisomers that could be separated by column chromatography just after TFA-mediated cyclization to the 8-substituted-4,8a-diphenyltetrahydro-l//-pyrrolo[2,l-r1[l,4]oxazine-l,6(7//)-diones 62 and 163 <1997SL935>. These compounds were then reduced to give substituted prolines as described in Section 11.11.6.1. 

Tang et al. used columns packed with a slurry of beads suspended in supercritical C02. This packed column was filled with a dilute sol solution prepared by hydrolysis and polycondensation of tetramethoxysilane and ethyltri-methoxysilane precursors. The column was dried using supercritical C02 and heated first to 120 °C for 5 h followed by another 5 h at a temperature of 250 °C [108-110]. Column efficiencies of 127,000 and 410,000 plates/m were reported... 

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