Aromatic Polyimides Containing Cyano Substituents for High Performance Applications

Aromatic polyimides containing cyano groups have been synthesized by solution polycondensation reaction of an aromatic diamine having cyano group, namely 2,6-bis(m-aminophenoxy)benzonitrile, with certain aromatic dianhydrides, such as benzophenonetetracarboxylic dianhydride, biphenyl-tetracarboxylic dianhydride, hexafluoroisopropylidene bis(phthalic anhydride) or pyromellitic dianhydride. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidinone, N,N-dimethylacetamide and N,N-dimethyl-formamide, and some of them exhibited remarkable film forming ability. The thin films prepared by casting polymer solutions onto glass plates were transparent and flexible. All the polymers showed high thermal stability, with decomposition temperature above 400degC and glass transition above 200degC. They exhibited a reasonable interval between glass transition and decomposition, which can be advantageous for their processing.