Preparation of poly(amic acid) and polyimide derived from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride with different diamines by microwave irradiation

Polycondensation‐type poly(amic acid) (PAA) was synthesized with 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride as a dianhydride monomer and 4,4′‐diaminodiphenylmethane and 4,4′‐oxydianiline as diamine monomers under microwave irradiation in dimethylformamide. Then, PAA was used to make polyimide (PI) by imidization at a low temperature. The structure and performance of the polymers were characterized with Fourier transform infrared (FTIR), proton nuclear magnetic resonance ( 1 H‐NMR), viscosity, X‐ray diffraction (XRD), and thermogravimetry (TG) curve analyses. The FTIR spectra of the polymers showed characteristic peaks of PI around 1779 and 1717 cm −1 . The 1 H‐NMR spectrum of PAA indicated a singlet at 6.55 ppm assigned to NHCO and a singlet at 10.27 ppm assigned to carboxylic acid protons. The XRD spectrum demonstrated that the obtained PI had a low‐order aggregation structure with a d ‐spacing of 0.5453 nm. The TG results revealed that the PI was thermally stable with 10% weight loss at 565°C in an N 2 atmosphere. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008