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Linear D2‐m‐carborane‐siloxanes with one, two, and three trifluoropropyl moieties per repeat unit were prepared by the condensation reaction between bisureidosilanes and carborane disilanol. Molecular weights between 100,000 and 220,000 were obtained. Compared to fluorosilicones, the trifluoropropyl‐modified carborane‐siloxanes exhibited greater thermal and oxidative stability and in certain cases comparable solvent resistance. The swelling index for carborane‐siloxane elastomers decreased with increasing trifluoropropyl content, although this fluorocarbon moiety did compromise the thermal stability of the carborane system.

SynopsisA D2-rn-dodecacarboranesiloxane containing alternating block copolymer +A-B+n was prepared by the reaction of a ureidosilane-terminated polysulfone hard block with a carboranesilanol-terminated carboranesiloxane oligomer. The resulting block copolymer exhibited thermoplastic elastomeric behavior. This unique polymer had excellent thermal stability up to 400°C.

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Ferric oxide produced from iron pentacarbonyl was evaluated as an oxidative stabilizer in D2-m-carborane-siloxane and polydimethylsiloxane vulcanizates. The results indicate a significant improvement in efficiency compared to powdered ferric oxide. Thus a carborane-siloxane vulcanizate retained elastomeric properties after 1000 hours in air at 315°C. The practical upper use temperature for carborane-siloxane vulcanizates were evaluated by heat aging samples at 340° and 370°C.