Synthesis and properties of thermally stable polyimides bearing pendent fluorene moieties

A new diamine monomer containing fluorene unit, 3,5-diamino-N-(9H-fluoren-2-yl)benzamide was successfully synthesized via the condensation of 2-aminofluorene and 3,5-dinitrobenzoyl chloride and subsequent reduction of the dinitro compound. A series of novel aromatic polyimides having pendent fluorenamide moieties were prepared from the reaction of the diamine monomer and various tetracarboxylic dianhydrides by a conventional two-step polymerization process. The polyimides were obtained in quantitative yields with inherent viscosities of 0.33–0.44 dl/g. The resulting polymers dissolved in N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. The glass transition temperature of these polymers was in the range of 261–289°C. They were fairly stable up to a temperature around 450°C and lost 10% weight in the range of 498–556°C in nitrogen. The UV–vis absorption spectra showed that all of the polymers had absorption maxima around 320 nm. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.3 V. Copyright © 2014 John Wiley & Sons, Ltd.