Carborane-siloxane-acetylenic polymers

High temperature thermosets and ceramics have been synthesized by heat treatment of various blends of poly (siloxane-acetylene) and poly (carborane-siloxane-acetylene). The polymeric blends give high char yields on pyrolysis, and the resultant chars show excellent oxidative stability to at least 1500 °C. The thermosets and ceramic chars show similar oxidative stability to previously studied copolymers containing varying amounts of siloxane, carborane, and acetylene units within the backbone. It has been determined that only a small percentage of carborane is necessary to provide this oxidation protection. Thus, these precursor linear hybrid polymers are more cost-effective than previous polymers which contained carborane in each repeating unit. 

The major advantage of our approach is that the desirable features of inorganics and organics such as high thermal and oxidative stability and processability are incorporated into the same polymeric chain. The siloxane units provide thermal and chain flexibility to polymeric materials. Siloxane-acetylenic polymers have also been made but lack the thermal and oxidative stability that the carborane units possess. The chemistry involved in synthesizing poly(siloxane) and poly(carborane-siloxane) has been modified to accommodate the inclusion of an acetylenic unit in the backbone. The novel linear... 

A linear carborane-siloxane-acetylenic hybrid polymer has been synthesized and characterized. The poly (carborane-siloxane-acetylene) is a viscous liquid at room temperature and can be easily processed to a high temperature polymeric thermoset under either thermal or photochemical conditions. Thermal curing of the linear polymer to the thermoset is accomplished above 150 C. This novel thermosetting polymer is readily converted into a ceramic material by heating to 1000 C under inert or oxidative conditions. The tfaermoset and ceramic material are stable in air at elevated temperatures. 

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