Heat-resistant polymers containing the low molecular weight closo-carboranes. II. Thermal behavior of polycarboranesiloxane SiB-1 elastomers from C₂B₅H₇

Unmodified 5-SiB-1 polymers have been found to be virtually equivalent to their 10-SiB-1 counterparts with respect to thermal stability. The 5-SiB-1 polymers, however, are substantially more amenable to conversion into elastomers. The introduction of 15 to 20 mole-% of m-C₂B₁₀ into the 5-SiB-1 backbone results in elastomers whose thermal stability, although less than that of the parent homopolymer, is nevertheless substantially in excess of the published values for the higher SiB polymers. The crystallization of the 5-SiB-1 copolymer containing 15 mole-% C₂B₁₀ was inhibited by irradiation with 50 megarads of 3 MeV betas. The 5-SiB-1 copolymer containing 20 mole-% C₂B₁₀, on the other hand, remained a rubber at room temperature.