Polyimide (PI) aerogels containing rigid-rod biphenyl, benzimidazole, and triphenylpyridine moieties have been developed. The flexible PI aerogels exhibited excellent thermal stability with glass-transition temperatures (Tg) higher than 350 °C. Initial porous structures in the PI aerogels could be maintained even after isothermal aging at 300 °C for 24 h in nitrogen. Furthermore, the weight losses of the aerogels after isothermal aging at 300 and 400 °C for 24 h in nitrogen were below 5 and 10 wt %, respectively.

Polyimide aerogel with an intrinsically hydrophobic nature and a dielectric constant as low as 1.19 at a frequency of 2.75 GHz was synthesized by the polycondensation of an alicyclic dianhydride, an aromatic fluorinated diamine, and an amino-substituted polyhedral oligomeric silsesquioxane (POSS) end-capper, followed by a supercritical carbon dioxide drying procedure.

A novel phosphorous‐silicone‐nitrogen ternary flame retardant (FR), [(1,1,3,3‐tetramethyl‐1,3‐disilazanediyl)di‐2,1‐ethanediyl]bis(diphenylphosphine oxide) (PSiN) was synthesized with high yield via a one‐step procedure by the reaction of diphenylphosphine oxide and vinyl‐terminated silazane with triethylborane as the catalyst. The chemical structure of the target compound was confirmed by nuclear magnetic resonances, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and Flourier transform infrared measurements. The developed PSiN FR was applied in the flame retardancy of o‐cresol novolac epoxy (CNE)/phenolic novolac (PN) hardener system. Effects of PSiN on the processability, thermal properties, especially the flame retardancy properties of the composites were investigated. Experimental results revealed that addition of PSiN improved the flowability of the CNE/PN systems, while the thermal stability of the epoxy thermosets was maintained. Meanwhile, the incorporation of PSiN was in favor of the formation of char during the thermal degradation process of the epoxy thermosets. The limited oxygen index of the epoxy system increased along with the PSiN content. An UL 94 V‐0 FR rating was achieved when the weight content of PSiN in the epoxy composites reached 20 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40412.