Synthesis and properties of poly(m-carborane-siloxane) elastomers

Organic boron polymers are of interest to AWE, and a significant improvement would be to make components from a single phase material that enables the boron content to be maximised and the elastomeric properties to be tuned to requirement. This paper is a summary of the work carried out towards the synthesis and characterisation of poly(m-carborane-siloxane) rubbers. These rubbers have been synthesised by the Ferric Chloride-catalysed condensation reaction between dimethoxy-m-carborane terminated monomer and dichlorodimethylsilane. Phenyl modified and Phenyl-vinyl modified variations have been synthesised in addition to the unmodified poly(m-carborane-siloxane) polymers. The unmodified poly(m-carborane-siloxane) shows some crystallinity but the modified versions are amorphous and have good elastomeric properties. Overall, the measured boron content is in close agreement to that expected from the repeat unit, suggesting the synthesised rubbers have been successfully prepared. It is also demonstrated that the carborane unit offers increased thermal stability and retention of 'rubber-like' properties even after ageing at high temperature.