High‐temperature elastomers: A systematic series of linear poly(carborane‐siloxane)s containing icosahedral (CB 10 H 10 C) cages. I. Thermomechanical behavior in nitrogen

An extensive study of structure–bulk property relations 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 iswhere (1) x = 1, 3, 4, 5, ∞; (2) A = endgroups (reactive and inert); (3) Z = meta‐, para ‐carborane (for x = 3); (4) R = CH 3 , R = C 2 H 4 CF 3 (for x = 3), one in five R = C 6 H 5 with the remainder ∼CH 3 (for x = 4, randomly and regularly substituted); (5) molecular weight = ∼10,000, ∼50,000 (for x = 3). Thermomechanical spectra (∼1 cps) from −180°C to 625°C to −180°C in nitrogen at 3.6°C/min and thermogravimetric data from 25°C to 800°C in argon are presented. Physical transitions ( T g , T m , T crys , T sec ) are discussed, including a correlation of T g data with structure (for x = 1, 2, 3, 4, 5, ∞) using a copolymer equation. Thermostability is also discussed in terms of structure.