Synthesis and electrochromic performance of a novel polymer based on an oxidative polymer derived from carbazole and thiophene

A polymer derived from poly-9-bis[4-(thiophen-3,4-yloxy)biphenyl)]-9H-carbazole containing a carbazole and thiophene group, abbreviated as B2, was synthesized via the oxidation method by using FeCl₃ as an oxidant. Additionally, the electrochemical polymer of B2 was synthesized and coated onto an ITO–glass surface via electrochemical oxidative polymerization. The electrochemical synthesis of the polymer was performed in 0.05 M AN/LiClO₄ solvent/electrolyte solution containing 0.1 M concentration of B2 between +0.3 and +1.4 V potentials. The compounds were characterized by FT-IR, NMR, and elemental analysis techniques. The spectroelectrochemical and electrochromic properties of this polymer were also investigated in 0.05 M AN/LiClO₄ solvent/electrolyte solution for 200 s and at a constant potential of +1.4 V. Switching ability of this polymer was measured as the percent transmittance (∆T%) at its changing point of maximum contrast. Additionally, the scan rate study was performed at different scan rates: 400, 300, 200, 100, 50, 20 mV/s. According to the electrochromic measurements, the synthesized polymer had a light blue color when it was oxidized, and when it was reduced, it had a transparent color. As a result, the synthesized polymer P(B2) can be used to produce new polymeric electrochromic devices, and it can be considered a good candidate for applications of electrochromic devices (ECDs) because of its short response time of 3.5 s.