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from 4/2/2013

Maro Encyclopedia


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Polysilazane Applications



“Polysilazanes are polymers in which silicon and nitrogen atoms alternate to form the basic backbone. Since each silicon atom is bound to two separate nitrogen atoms and each nitrogen atom to two silicon atoms, both chains and rings of the formula [R1R2Si–NR3]n occur. R1-R3 can be hydrogen atoms or organic substituents. If all substituents R are H atoms, the polymer is designated as Perhydropolysilazane, Polyperhydridosilazane or Inorganic Polysilazane ([H2Si–NH]n). If hydrocarbon substituents are bound to the silicon atoms, the polymers are designated as Organopolysilazanes. Molecularly, polysilazanes [R1R2Si–NH]n are isoelectronic with and close relatives to Polysiloxanes [R1R2Si–O]n

The synthesis of polyorganosilazanes was first described in 1964 by Krüger and Rochow. By reacting ammonia with chlorosilanes (ammonolysis), trimeric or tetrameric cyclosilazanes were formed initially and further reacted at high temperatures with a catalyst to yield higher molecular weight polymers. Ammonolysis of chlorosilanes still represents the most important synthetic pathway to polysilazanes. The industrial manufacture of chlorosilanes using the Müller-Rochow process, first reported in the 1940s, served as the cornerstone for the development of silazane chemistry. In the 1960s, the first attempts to transform organosilicon polymers into quasi-ceramic materials were described. At this time, suitable (“pre-ceramic”) polymers heated to 1000°C or higher were shown to split off organic groups and hydrogen and, in the process, the molecular network is rearranged to form amorphous inorganic materials that show both unique chemical and physical properties. Using polymer derived ceramics (PDCs), new application areas can be opened, especially in the area of high performance materials. The most important pre-ceramic polymers are polysilanes [R1R2Si–R1R2Si]n, polycarbosilanes [R1R2Si–CH2]n, polysiloxanes [R1R2Si–O]n and polysilazanes [R1R2Si–NR3]n.”

(Polysilazanes, Wikipedia, 4/2/2013)


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(RDC 6/5/2012)


Roger D. Corneliussen

Maro Polymer Links
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Copyright 2013 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 4/2/2013.