Electrochromic Properties of Electrochemically‐Deposited Copolymers Based on Edot, Bithiophene, and Thiophene–Benzothiadiazole: Binary and Ternary Systems

Abstract 3,4‐ethylenedioxythiophene ( EDOT ) and 2,2′‐thiophene ( bith ) are mostly used units in conjugated polymer synthesis. These electron‐donor materials have a good partnership with the electron‐acceptor units for donor–acceptor–donor type (DAD) conjugated polymers. Numerous studies including these units have been published so far. This study aims to investigate the electrochromic properties of the combination of these units in the same polymer backbone via electrosynthesis. Moreover, a thiophene–benzothiadiazole‐based DAD type conjugated unit, 4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole, ( thBth ) has also contributed to the study for better comparison of these materials. In summary, the present work includes the aforementioned homopolymers and their electrosynthesized copolymers of EDOT‐bith , EDOT‐thBth , bith‐thBth, and EDOT‐bith‐thBth units with varying monomer feed ratios. The electrochromic properties of resulting copolymers are elucidated via cyclic voltammetry and UV–vis spectrometry. Each copolymer exhibited different colors and optical behaviors than their parent homopolymers. However, EDOT containing copolymers showed better optical properties. As a final study, dual type electrochromic devices were constructed using copolymers in order to show the practical application of the copolymers.