Silicon organofunctional silanes

The synthesis of organosilicones and organosilicone surfactants has been well described elsewhere [36-39] and hence only a brief review is given here. Industrially the manufacture of silicones is performed stepwise via the alkylchlorosilanes, produced through the reaction of elemental silicon with methyl chloride (the Muller—Rochow Process) [40,41]. Inclusion of HC1 and/or H2(g) into the reaction mixture, as in Eq. (1.2), yields CH3HSiCl2, the precursor to the organofunctional silanes, and therefore the silicone surfactants ... 

Aliphatic organofunctional silanes recommended as coupling agents for glass-reinforced polyesters, epoxies, or phenolics have heat stabilities of typical aliphatic organic chemicals and are not at all comparable to the methyl or phenyl silicones found in silicone polymers and resins. 

In this review, we will briefly discuss selected literature on hydrolysis and condensation reactions at silicon which are relevant to organofunctional silanes. Some studies will involve simpler (lower functionality) models some may involve related chemical reaction classes illustrating a mechanistic point. We will then discuss selected references focused on silanes of the types used as coupling agents and crosslinkers. Finally, some reactions at the interface will be mentioned. 

A critical concern in the use of organofunctional silanes is the effects that the organofunctional groups and the silane ester groups have on the hydrolysis reactions occurring at silicon. 

Trichlorosilane is particularly important as a starting material for organofunctional silanes, it is produced by reacting silicon with hydrogen chloride. 

Organofunctional silane.s have silicon atoms linked to an organic group with reactive groups... 

Organofunctional silanes with hydroxy-, epoxy-, acryl-, ester- and carboxy-functions are produced industrially. They are in particular utilized as additives for modification of polymers and for functionalizing silicones for different application sectors. Most of these compounds are manufactured by the addition of appropriately functionalized alkenyl-compounds. 

Organofunctional silanes as shown in Fig. 1 have at least one organic group and at least one alkoxy function directly attached to the silicon. However, the vast majority of organofunctional silanes used in industry — and the ones discussed in this paper — have three identical alkoxy groups, i.e., R = r" = OR. 

The versatility of organofunctional silanes is due to their unique combination of organic activity and silicon reactivity (see Fig. 3) the latter is due the hydrolyzable alkoxy groups. 

The best surface treatments for mica are the organofunctional silanes made by PCR Inc., by Witco s OSi Silicones Division, and the proprietary material made... 

Researchers discovered that antimicrobial organofunctional silanes could be chemically bound to receptive substrates by what were believed to be Si-0 linkages. The method was described as orienting the organofunctional silane in such a way that hydrolyzable groups on the silicon atom were hydrolyzed to the silanols and formed chemical bonds with each other and to the substrate. The resultant surface modification, when an antimicrobial moiety such as a quaternary nitrogen was included, provided for the antimicrobial group to be oriented away from the surface. ... 

The most common sol—gel system that has been electrochemically deposited is based on silane, although electrochemical deposition of non-silicon sol-gel films from metal alkoxides has also been reported [3-6]. Early studies mainly dealt with the electrochemical deposition behavior of different silanes and their mixtures. The silanes include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and organofunctional silanes such as 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyltrimethoxysilane (MPTMS). The electrochemically deposited silane films find applications in electroanalysis, corrosion... 

Just as the hydrosilylation reaction is important in the synthesis of silanes, so it also serves as a useful route to functional polysiloxanes. The same variety of chemistry as previously described for silanes is available and two further examples are given in equations 82 and 83. One of the main advantages of this route is that the silicon hydride prepolymers are well characterized and readily available materials, which in turn leads to well-defined organofunctional products. A disadvantage is the low efficiency in the use of the precious metal catalyst and the difficulty of its recovery. This is particularly true for systems containing a low level of functionality but this can be partially overcome by using recyclable platinum catalysts on solid supports216,217. 

The properties and effects of silanes are defined by their molecular structure. The silicon at the center is combined with two different functional groups an organofunctional group Y and a silicon-functional group OR ... 

Organofunctional polysiloxanes with silanol groups can be cross-linked at low temperatures with tetrabutyl titanium, methyl triacetoxy-silane, and similar compounds and are thus used as cold vulcanization materials. In contrast, hot vulcanizable silicones possess one vinyl group in about 500-1000 monomeric units and can be cross-linked with peroxides. All silicon rubbers are filled with highly dispersed silica since the unfilled rubber is practically a useless elastomer. 

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