Preparation of organo‐soluble co‐polyimides using N‐methyl‐2‐pyrrolidone as the solvent via one‐pot high‐temperature polymerization

A series of organo‐soluble co‐polyimides (co‐PIs) were successfully synthesized from 3,3′,4,4′‐benzophenonetetracarboxylic‐dianhydride (BTDA), 1,4‐bis‐(4‐amino‐2‐trifluoromethyl‐phemoxy)‐benzene (p‐6FAPB) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA) via the one‐pot high‐temperature polymerization using N‐methyl‐2‐pyrrolidone (NMP) as the solvent. The imidization reaction of poly(amic acid)s in solution state was discussed in detail by attenuated total reflectance‐Fourier transform infrared spectra (ATR‐FTIR), and the results illustrate that the introduced benzimidazole moiety has a catalytic activity on the imidization process. The number‐average molecular weights and polydispersity index of these PIs measured by gel permeation chromatography range from 1.11 × 10⁵ to 2.20 × 10⁵ and 1.82 to 3.84, respectively. The prepared co‐PIs exhibit sufficient solubility in some polar solvents and high optical transparency. Meanwhile, these co‐PI films show good mechanical performances, and the strength and modulus of the sample with the molar ratio of p‐6FAPB/BIA = 5/5 reach 183 MPa and 4.71 GPa, respectively. Moreover, the obtained co‐PIs possess high glass transition temperatures (T_g) (above 260 °C) and good thermal stability with 5% weight loss temperature in the range of 502–531 °C in the nitrogen atmosphere. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45497.