Highly stable polymers based on poly(m-carboranyi-siloxane) elastomers

Poly(m-carboranyl-siloxane) elastomers containing a mixture of di-metbyl- and methyl(phenyl)-silyl units were synthesised using the Ferric Chloride catalysed condensation reaction between di-chloro-di-organosilane and 1,7-bis(di-methyl(methoxy)silyl)-ni-carborane. These prepared polymers were aged either by heating in air at elevated temperature or by gamma-irradiation from a Co source. Multinuclear (H-1, C-13 and B-11) solid and solution state nuclear magnetic resonance was used to evaluate degradation. gamma-irradiation doses to 1 MGy were found to induce only a small reduction in elastomer properties as evidenced by a reduction in segmental chain dynamics. Ageing at temperatures below 350 degrees C similarly displayed a small reduction in segmental chain dynamics together and a concomitant weight loss as measured by differential scanning calorimetry. Above 350 degrees C degradation of the elastomer was dramatic with a decreased segmental chain dynamics and oxidation of the carborane cage, vide infra.