Silicon oligomers

Newer silicone adhesives having solids levels up to 97% are also commercially available [109]. Instead of using silanol condensation reactions, they rely on addition chemistry between vinyl functional silicone oligomers and silicon hydride terminated silicones. This addition reaction is typically facilitated with platinum derived catalysts. This hydrosilation process can be run at reduced oven temperatures, but the finished products typically do not yield the same balance of properties as seen for condensation cure materials. 

Plugging Material with 2-Furaldehyde-Acetone Monomer and Silicone Oligomers... 

A plugging material with 2-furaldehyde-acetone monomer and silicone oligomers has been described [1099]. The components for this material are shown in Table 18-1. The 2-furaldehyde-acetone monomer can contain mono-furfurylidene-acetone and difurfurylidene-acetone. The hardener can be iron chloride, benzene-sulfonic acid, hexamethylene diamine, or polyethylene polyamine. The plugging stone has improved strength, elastic-deformation, and anticorrosion and adhesion properties. 

Results of 29Si NMR spectroscopy of the Ti-Beta precursor gels are shown in Figure 1. The spectra exhibit peaks that belong to four major types of silica species, Q°, Q1, Q2, and Q3. Here Q" denotes a silicon environment with n Si-O-Si bonds. By comparison of the measured spectra with the 29Si NMR spectra found in the literature [4, 5] we were able to determine that the peak with the chemical shift of -72.9 ppm corresponds to Si monomer Q°, while the peaks at -80.9 ppm and -81.4 ppm are the peaks of Q1 linear trimer and dimer, respectively. The peaks from -83 ppm to -89.8 ppm were contributed to Q2 silicon oligomers, while the peaks at the chemical shifts from -90.3 ppm to -102 ppm were denoted as the part of the Q3 silica species. 

Si NMR spectroscopy reveals that the silicon monomers and dimers start to bind into higher silicon oligomers at the very beginning of the Ti-Beta synthesis procedure. After... 

The example of the first category is the formation of alkyl- and arylchlorosilanes in the so-called direct process (DP). The process was discovered over 60 years ago by Rochow in the United States, and, independently, by Muller in Germany, and it is still the most important reaction in organosilicon chemistry. In fact, it is at the very basis of the silicone industry, being the primary source of organochlorosilane precursors (mostly methylchlorosilanes, comprising over 90% of the total) in the production of silicone oligomers and polymers. 

Corey, Joyce Y., Dehydrocoupling of Hydrosilanes to Polysilanes and Silicon Oligomers A... 

Harrod s most recent mechanistic proposal for cation-like silylzirco-nocenes is the redox mechanism, one variation of which is shown in Fig. 5.3d>60>81>83 jn caSes where Zr(IV) is not reduced to Zr(III), c-bond metathesis is likely. However, if Zr(III) is produced, Harrod favored generation of silyl radicals through a Zr(III)/Zr(IV) redox cycle and subsequent coupling of silyl radicals produced the silicon oligomer or polymer. Additional arguments for possible radical processes will be provided in a later section. 

Monomer silicone compounds, especially organochlorosilanes, hydroxyor-ganosilanes, alkylalkoxysilanes with amide groups in the alkyl radical, and acyloxyorganosilanes, have recently found an independent practical application, but their role as parent substances for the production of silicone oligomers and polymers is particularly important. 

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