Functional alkoxysilane precursors

Table 6.1 Selected examples of commercially available functional alkoxysilane precursors.

Inorganic phase - silica network, was formed by sol-gel process from alkoxysilane precursors - TEOS or alkoxysilane-endcapped prepolymer SED2000. This endcapped prepolymer was prepared by alkoxy functionalization of oligomer D2000 with (3-glycidyloxypropyl)trimethoxysilane (GTMS). 

In method (a) of Fig. 18, the alkoxysilane-functionalized ligand is first used to functionalize a silica surface. The modified material is then mixed with a metal precursor to generate the desired supported complex. 

According to studies on the loealization of metal particles in cogelled catalysts [32, 33, 39, 40, 109, 149-152], the small metal particles are located inside silica particles or aggregates and new results from 3D-TEM studies conducted for the moment confirm such a localization. Small metal particles would be located inside silica particles because of a role of nucleation agent played by the alkoxysilane-functionalized complex in the sol-gel process [32, 35, 151, 152, 156, 181]. Briefly, if the alkoxysilane-functionalized ligand used for metal complexation is more reactive towards hydrolysis and condensation than the main silica precursor, which has... 

Organofunctional alkoxides of the type (RO)nE-X-A in which the two reactive centers, the functional organic group A and E(OR)n, are connected by a hydrolytically stable spacer X have found wide-spread applications, mainly for E = Si (3). One of the many possible functions of A js that of binding metal ions (M ) to give the complexes [(RO)nE-X-A]yM " ". Suitable groups A are, for example, NH2, NHCH2CH2NH2, CN or CH(COMe)2. In alkoxysilane chemistry a variety of precursors of this type, particularly (RO)3Si(CH2)n re commercially available or can be easily prepared. 

These alkoxysilanes are useful for making five-membered rings via a 5-enufo-trigonal radical cyclization from a selenide precursor (eq 2). It was observed that the (di-r-butyl)silyl group may be difficult to cleave in the absence of an adjacent oxygen functionality. 

Contrarily, the sol-gel process is a wet chemical approach carried out mostly at ambient temperature for the production of nanopartides. As such, the formed particles contain many silanol groups on their surface, which can be easily functionalized, for example, with various chlorosilanes or alkoxysilanes [9]. In addition, the silica-based sol-gel process often produces stable suspensions that can be stored for a long time [10]. The precursors of the sol-gel materials can be easily prepared and purified therefore, very pure silica particles are produced, which is important for applications in electronics and the biomedical field. Due to its ability to control the particle size, size distribution, and morphology through systematic monitoring of reaction parameters, the sol-gel process is ideally suited for many different applications. 

Precursors, which generally are di- and trifunctional silanes, span a wide range of sizes, chemical reactivities and functionalities. The use of precursors containing non-hydrolyzable SiC bonds, such as bifunctional or/and trifunctional alkoxysilanes (R Si(OR), n = 1 to 3, R = alkyl, R = organic group), allows introduction of organic groups directly bonded to the polymerlike silica network. Trifunctional alkoxysilanes... 

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