Synthesis and properties of polyimides derived from a new phthalonitrile-containing diamine with high polyaddition reactivity

A new phthalonitrile-containing diamine, 1,3-bis(4-aminophenoxy)-5-(3,4-dicyanophenoxy)benzene (CN-APB), was readily synthesized via a three-step route. The key intermediate, 3,5-bis(4-nitrophenoxy)-phenol (compound 1), was synthesized by carefully controlling the molar ratio of phloroglucin to 1-chloro-4-nitrobenzene, which is a key to minimize the production of undesirable byproducts. FTIR and 1H NMR techniques were used to fully verify the proposed structure of this new phthalonitrile-containing diamine. The polyimides were prepared from such new diamine and commercial dianhydrides by low-temperature polyaddition and subsequent chemical imidization. The inherent viscosities of all polymers were over 0.50 dL/g due to the relatively high reactivity of this new diamine. The organosolubility and thermal properties of these polymers were investigated.