Trialkoxysilyl groups

The preparation of monocomponent hybrid materials is determined by the chemistry of the building block. To prepare them, the first condition is the presence of hydrolysable-function groups in the building block in order to form the oxide matrix by hydrolytic polycondensation. The trialkoxysilyl groups —Si(OR)3 (R=Et, Me, i-Pr) is the most commonly used among possible (—SiX3) groups. 

No separation of the various adducts was possible and, therefore, route b was prefered. Indeed, grafting of CPS on the silica surface prior to modification by ephedrine is supposed to protect the trialkoxysilyl groups and consequently, to limit such cyclization reactions. 

Cocondensation of macromers containing trialkoxysilyl groups with modified polystyrene (PS), polyoxazoline, polyimide, polyethylene glycol (PEG), polyether-ketones, polymethyl methacrylate, and derivatives of polytetramethylene oxide was established as convenient procedure for the preparation of telechelic polymer net-... 

The hydrosilylation of unsaturated polymers (e.g, polybutadiene, polyiso-prene, polyesters, polyenes, and polycarbonates) with a silane having hydrolyzable substituents at silicon atoms leads to polymeric systems with enhanced activity toward mineral fillers (32). Such process also offers a useful and convenient method for preparing silane-modified polymers that may find potential applications as rubber materials, adhesives, and drug delivery agents. Both >C=C< as well >C=0 bonds are capable of hydrosilylation. This modification is connected with a reversed use of the silane (siloxane) coupling agents. Trialkoxysilyl groups are commonly incorporated onto the polymers by Pt-catalyzed hydrosilylation... 

The introduction of trialkoxysilyl groups into an ENPCAF-type structure (SILCAF) has produced a system of coupling natural rubber to siliceous materials such as fine silicas and china clays. Initial studies indicate the system is superior in many respects to conventional silane coupling agents (Dawes and Rowley, 1977, 1978). 

The case of chemically grafted cations is by far the most studied form of ionosilicas [76]. This is due to the chemical versatility of the cationic precursors that are most often derived from imidazolium, ammonium, pyridinium, or phospho-nium compounds. Due to their ease of derivatization, in most cases the cationic substructure is functionalized with hydrolyzable trialkoxysilyl groups. As ionosilicas are often inspired with ionic liquids, imidazolium-containing ionosilicas have an outstanding position in this field. 

The final end group addressed was the attachment of the trialkoxysilyl group via a methylene bridge. PI-ATES (Figure IIII) contains such a methyl-... 

Most immobilization methods require modification of the ligands for anchoring to the support by introducing functional groups such as vinyl, trialkoxysilyl, sulfonic acid, and amino groups. The consequence is often a more elaborate synthesis of the ligand, which adds to the costs of an immobilized catalyst. However, two interesting approaches were developed in recent years, when unmodi-... 

Telechelic polymers usually bear monofunctional groups at each of their extremities. However, sometimes each end-group is bifunctional, such as in a, co-bis-unsaturated telechelics, or trifunctional as in a, co-bis(trialkoxysilyl) telechelics wherein they participate in crosslinking by the sol-gel reactions (hydrolysis and condensation of alkoxysilane groups). 

FIGURE 4. Di- and trialkoxysilyl derivatives with various functional organic groups... 

Reagents like NH2—R —Si(OR)3 are useful for the synthesis of functional precursors with an imido group. This is possibly achieved by reacting the alkyl(trialkoxysilyl)amine with at least three types of substrates (1) with a suitable carboxylic acid chloride114,116120, (2) by transimidation of bisimides, e.g. in the preparation of 52 according to equation 13115, and (3) by the imidization of an anhydride as in the preparation of 53 (equation 14)112. 

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