In the IR spectra of three polyimides, the broad absorption near 3300 cm −1 based on the O-H stretching vibration of carboxyl group was not observed at all. Figure 3 shows the 1 H NMR spectra ...

Stiff and planar NDI derivatives have been used not only as repeating units for polyimides but also as building blocks for supramolecular structures, using CT complex formation with donor ...