Electrochemical and electrochromic properties of aromatic polyamides and polyimides with phenothiazine-based multiple triphenylamine cores

Abstract

A new diamine monomer derived from phenothiazine, named 3,7-bis[(4-aminophenyl)(4-methoxyphenyl) amino]-10-(4-methoxyphenyl) phenothiazine, was successfully synthesized, leading to the development of new electroactive aromatic polyamides and polyimides. The resulting polymers demonstrated high solubility in polar organic solvents and formed strong, flexible films through solution casting. They exhibited high thermal stability, with no notable weight loss observed before 400 °C, and moderately high glass transition temperatures (T_g) ranging from 252 to 282 °C. These polymers displayed a pale orange color change during their first-stage oxidation and a light blue color change during their second-stage oxidation. Cyclic voltammetry results revealed three reversible oxidation redox couples within the potential range of 0–1.3 V, with the first two redox processes occurring at 0.47–0.61 V and 0.73–0.85 V showing high stability. Furthermore, these polymers demonstrated excellent electrochemical and electrochromic stability, along with moderate coloration efficiency and strong absorption in the near-infrared (NIR) region upon oxidation. Simple single-layer electrochromic devices were also fabricated and tested.