High Tg and Thermo‐Oxidatively Stable Thermosetting Polyimides Derived from a Carborane‐Containing Diamine

To provide high‐temperature polyimide matrix resins, novel carborane‐containing thermosetting polyimides are presented. First, the low‐viscosity carborane‐containing imide oligomers are synthesized using newly designed 1‐(3‐amino‐4‐tolyl)‐2‐(4‐aminophenyl)‐o‐carborane and aromatic dianhydride as monomers, 4‐phenylethynyl phthalic anhydride as the end‐capping reagent. Followed by thermal curing, the resulting polyimides show high Tg (≥500 °C) and above 92.1% char yield at 800 °C both in nitrogen and air atmosphere due to the incorporation of the bulky carborane cages. Aging studies, performed at 400 and 500 °C for 5 h in air on a carborane‐containing polyimide and a carborane‐free polyimide, show that the polyimide with carborane groups possesses excellent thermo‐oxidative stability. Moreover, the novel polyimides exhibit constant and relatively low coefficient of thermal expansion values over a wide range of temperature, indicative of a remarkable dimensional stability. Thus, this study clearly demonstrates the viability of the incorporation of carborane cages to access polyimide thermosets with ultrahigh Tg and thermo‐oxidative stability. High Tg and thermo‐oxidatively stable thermosetting polyimides (PIs) are produced from the novel carborane‐containing diamine. The resulting PIs exhibit high Tg (≥500 °C) and thermal stability. Aging studies display the carborane‐containing polyimides with excellent thermo‐oxidative stability. These PIs with promising properties offer a convincing proof that incorporation of carborane into PIs can be beneficial for high‐performance matrix resins.