Silicon-containing polymers oxide formation

Three contributions from the groups of G. Roewer, H. Griitzmacher, and R. Nesper cover the formation of various novel BCCSi-substituted borazines and synthetic approaches to the functionalization of silicon-based non-oxidic ceramics, and papers from W. Mitzel, U. Klingebiel, H. Karsch, M. Driess, and A. Bauer deal with the chemistry of aminosilanes and a possible transfer into application, e.g., the formation of Si-N-containing polymers and ceramics. 

A new convenient polymer modification for synthesis of silanol-containing polymer was developed by the selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone. The oxyfunctionalization of the silane precursor polymers can be utilized to synthesize a wide variety of silanol-containing polymers. Control over the properties of these silanol polymers, such as stability and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom. The miscibility in either polymer blends or polymeric hybrids was achieved by the formation of strong inter-polymer hydrogen bonds between the... 

In the following sections some examples are given of the ways in which these principles have been utilized. The first example is the use of these techniques for the low temperature preparation of oxide ceramics such as silica. This process can also be used to produce alumina, titanium oxide, or other metal oxides. The second example describes the conversion of organic polymers to carbon fiber, a process that was probably the inspiration for the later development of routes to a range of non-oxide ceramics. Following this are brief reviews of processes that lead to the formation of silicon carbide, silicon nitride, boron nitride, and aluminum nitride, plus an introduction to the synthesis of other ceramics such as phosphorus nitride, nitrogen-phosphorus-boron materials, and an example of a transition metal-containing ceramic material. 

The determination of dissolved silicon compounds in natural waters is based on the formation of a yellow silicomolybdic acid when an acid sample is treated with a molybdate solution, According to Chow and Robinson (1953), all soluble silicates in seawater can be determined in this manner, even those with sodium oxide/silicon dioxide ratios of less than one. Colloidal silicic acid in seawater quickly changes from its colloidal state and is detectable spectrophotometrically. Only long chain polymers containing three or more silicic acid units do not react at any appreciable speed. 

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