Polymerization silicone compounds

The last 15 years have seen great strides made in multiple areas of hydrosilation chemistry, as is evident from the research covered in this review and others. Because of the increasing importance of both small molecule and polymeric silicon compounds in commerce as well as in scientific areas such as in biological fields and emerging materials science research, accelerated scientific and technological growth of catalyzed hydrosilation in the future is clearly foreseeable. 

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

These TMS-carbamate-mediated NCA polymerizations resemble to some extent the group-transfer polymerization (GTP) of acrylic monomers initiated by organo-silicon compounds [40]. Unlike GTPs that typically require Lewis acid activators or nucelophilic catalysts to facilitate the polymerization [41], TMS-carbamate-mediated NCA polymerizations do not appear to require any additional catalysts or activators. However, it is still unclear whether the TMS transfer proceeds through an anionic process as in GTP [41] or through a concerted process as illustrated in Scheme 14. 

In the second, complementary, approach the polycondensation of silica polymer is followed by the formation of an organic network made by cross-linking reaction of monomers covalently bound to silicon compounds (Scheme 4.1) resulting in polymeric materials with outstanding protective abilities, including thermal, mechanical and corrosion resistance. 

Prepoly- merization Silicon compound added in -polymerization Activity ofTi Stereo- regularity... 

As observed by D. Johnson and J. Stiegler, "Polymer-precursor routes lor fabricating ceramics offer one potential means or producing reliable, cost-effective ceramics. Pyrolysis of polymeric metalloorganic compounds can be used to produce a wide variety of ceramic materials." Silicon carbide and silicon oxycarbide fibers have been produced and sol gel methods have been used In prepare line oxide ceramic powders, such as spherical alumina, as well as porous and fully dense monolithic forms. 

Some silicon dioxide ceramics are made by the sol-gel process. In this process, an organic silicon compound is dissolved in water and polymerized into a network structure. As the gel forms, many cross-links are formed. These cross-links form a rigid, strong matrix that is free of... 

Polyolefins are, of course, usually synthesized by the catalyzed polymerization of alkenes. Why is an analogous route, polymerization of disilenes, not employed to prepare polysilanes The reason is paradoxical. The energy barrier to polymerization of doubly bonded silicon compounds is simply too low, so that in most cases they polymerize (or oligomerize) immediately when they are generated ... 

There are some silicon compounds with small Si-Si units linked together by Si-O-Si, Si-NH-Si or similar bond systems. In many cases, such compounds are obtained by the solvolysis of oligosilanes with a subsequent condensation reaction. However, preparation from polymeric starting material is also possible, for instance, the formation of siloxene from calcium silicide. 

Kautsky342) called it siloxene and found the structure to be a polymeric layered compound with six membered silicon-rings linked by oxygen. The... 

Polymeric silicon chlorides One of the first detailed studies of the silicon chlorides was published by Besson and Fournier34) in 1909. The authors found that a compound (SiCl2) was formed during silent electrical discharge in SiHCl3/H2 mixtures. 

Polymeric silicon alkyl compounds Polymeric compounds are often observed in the Wurtz synthesis of dihalodialkyl(aiyl)silanes with metals. The intermediate product is probably a dialkyl(aryl)silylene (see Chapter 7). A polymeric dimethylsilane was found by Burkhard68). A yellow polymeric (SiCH3) was isolated after pyrolysis of SiH4 with ethylene156). 

UAIH4 reacts with (SiBr) to a polymeric silicon hydride267 with the stoichiometric composition (SiH) , and CaBr2. The compound is a brown powder which reacts with water evolving hydrogen, and burns spontaneously in air. The Si-H IR frequency is also extremely low, the value of 2100 cm 1... 

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