Preparation of polyphenylsiloxanes and polyphenylsiloxane varnishes

Polyphenylsiloxanes are produced from alkoxyphenylsilanes, triacetoxy-phenylsilane, pure phenyltrichlorosilane or undistilled phenylchlorosilanes. Depending on the functionality of the parent monomer and the preparation technique, polyphenylsiloxanes can be branched or ladder. Often, to improve the properties of polyphenylsiloxanes, they are modified with various organic substances (by mechanical mixing or chemically). 

Alkoxyphenylsilanes, which are used as raw stock in the production of polyphenylsiloxanes and polyphenylsiloxane varnishes, can be produced by the Grignard technique and etherification of phenyltrichlorosilane with alcohol. 

However, the phenylation of tetraethoxysilane is a complicated process, which forms not only phenyltriethoxysilane, but also diphenyldiethoxysi-lane and triphenylethoxysilane. The products of phenylation also include unreacted tetraethoxysilane and diphenyl, which is formed due to the byinteraction of chlorobenzene with magnesium. 

The hydrolytic condensation of phenylethoxysilanes is carried out in butyl alcohol that is why at this stage we observe a partial re-etherification of phenylethoxysilanes with butyl alcohol and partial condensation of the re-etherification products. Generally, the process can be described by the following scheme  

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