Further, we observe a split of the imide N-H stretch at 3300 cm -1 that is caused by heterogeneously intercalated ions that break the symmetry of the material. The UV-Raman spectrum of PTI-LiBr shows only two distinctive features at 1629 and 982 cm -1 . The 1629 cm -1 band is interpreted as C=N ring-stretches, also referred to as G band, while the band at 982 cm -1 represents the C3N3 breathing mode. The ring mode in PTI-LiBr has a shoulder towards higher wavenumbers. The aloof-EELS phonon spectrum of PTI-LiBr shows a broad feature reminiscent of the CN-stretches in the FT-IR spectrum. Additionally, the ring mode at around 800 cm -1 can be picked up with this technique. The vibrational modes in PTI-IF are better resolved than in PTI-LiBr (Figure , Figure ). DFT calculations predict the main four bands in the aloof-EELS and FT-IR spectra of PTI-IF observed between 980-1620 cm -1 (Figure ). However, the intensity of the ring modes at 642 and 802 cm -1 is drastically underestimated in the phonon calculation. The ring mode of PTI-IF at 990 cm -1 in the Raman spectrum has a higher intensity and no shoulder compared to PTI-LiBr.