Electrochromic behavior of poly(amine-amide) with pendant N-phenylcarbazole and triphenylamine units and its composite with multiwalled carbon nanotubes

•Electrochromic behavior of poly(amine-amide) with pendent N-phenylcarbazole and triphenylamine units showed four redox processes.•Only first two reactions are reversible and correspond to coloring film from the colorless neutral state to green and blue.•IR-spectra analysis of polymer before and after electrochemical measurements indicates changes in the polymer structure.•The introduction of MWCNTs in the polymer films led to a decrease in switching times between color states. Electrochromic behavior of poly(amine-amide) with pendant N-phenylcarbazole and triphenylamine units (A1) and its composites with multiwalled carbon nanotubes (MWCNTs) were investigated. Cyclic voltammetry showed four separate redox processes with oxidation peaks at Eox1 = 720 mV, Eox2 = 1070 mV, Eox3 = 1295 mV and Eox4 = 1730 mV vs Ag/Ag+. The first two reactions are reversible and spectroelectrochemical analysis demonstrated color changes. A1 exhibits a colorless initial state, a green radical cation state, and a blue dication state. The polymer exhibits a good stability during the electrochromic tests in the range of -400 to 1100 mV with minimal loss of the transmittance during 30 cycles. The potential increasing above 1100 mV induces the third and fourth redox reactions and results to coloring film to deep blue. However, these redox processes are chemically and electrochemically irreversible. Detailed calorimetric study and FTIR-spectra analysis of polymer before and after electrochemical measurements show change of the macromolecular structure induced by the redox processes at potentials above 1100 mV. The introduction of MWCNTs in the polymer films improves the kinetics of switching between the A1 color states while a slight decrease in the optical contrast. The FTIR spectroscopy, TG and DSC results of A1/MWCNT composites (in the range of the studied component composition) before and after electrochemical tests practically coincide with the data for pristine polymer and indicate a change in the polymer structure in the third and fourth redox reactions. Thus, the introduction of MWCNTs leads to an improvement in electrochromic characteristics during reversible redox reactions, but does not affect the destructive processes induced by the third and fourth oxidative reactions.