*3.4. UV–Vis Spectroscopy*

On the UV-Vis spectrum of PANI solution in DMF, two peaks were visible (Figure 4). The peak at 323 nm was connected with π-π\* excitation, and the peak at 618 nm was connected with the exciton excitation of the quinone rings in the PANI (Figure 4a). The presence of these peaks and the dark blue coloration of the solution were characteristic for the emeraldine base [23]. On the spectrum of the spinning solution containing 1 wt.% of polyacrylonitrile and polyaniline synthesized in DMF, the peak near 320 nm was more visible and shifted in towards the shorter wave (Figure 4b). However, in this spectrum there was no clear peak around 618 nm, which corresponded to the exciton excitation of the quinone rings in the PANI.

**Figure 4.** UV-Vis spectrum: (**a**) polyacrylonitrile (PAN) and PANI powder dissolved in Dimethylformamide (DMF) (blended); (**b**) change in absorbance during the PANI synthesis in DMF (in situ).

The PANI synthesis in the DMF solution containing 1 wt.% of PAN occurred very slowly. In this time, the peak characteristic for PAN disappeared. In contrast, the characteristic peak, corresponding to the π-π\* excitation during synthesis, moved towards the 327 nm band. This can indicate the interaction between PAN and PANI molecules [24].
