High-temperature elastomers: A systematic series of linear poly(carborane–siloxane)s containing icosahedral (CB₁₀H₁₀C) cages. II. Thermo-oxidative behavior

A study of oxidative instability versus molecular structure for a systematic series of well-defined linear poly(carborane-siloxane)s is reported. These polymers form the backbone components of the most recently developed high-temperature elastomers. The basic structure is where (1) x = 1, 3, 4, 5, ∞ (2) A = endgroups (reactive and inert); (3) Z = meta-carborane, para-carborane (for x = 3); (4)R = CH₃, R = C₂H₄CF₃ (for x = 3), one in five R's = C₆H₅ with the remainder CH₃ (for x = 4); (5) molecular weight = ∼10,000, ∼50,000 (for x = 3). Thermomechanical spectra in air (∼1 cps) from 130°C → 625°C → 130°C at 3.6°C/min, thermogravimetric data from 25°C → 700°C in air (3.6°C/min), and differential thermal analysis data from 25°C → ∼450°C in air (15°C/min) are presented. Thermo-oxidative stability is discussed in terms of structure, and broad categories of behavior are defined.