Enhanced near-infrared electrochromism in triphenylamine-based aramids bearing phenothiazine redox centers

A series of organosoluble polyamides based on N-phenothiazinylphenyl redox units showing anodically electrochromic characteristics both in the near-infrared (NIR) and visible light regions were prepared from the phosphorylation polyamidation reactions of a newly synthesized diamine monomer, 4,4′-diamino-4′′-N-phenothiazinyltriphenylamine, with various dicarboxylic acids. These polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with relatively high glass-transition temperatures (Tg) (255–277 °C) and high char yields (higher than 67% at 800 °C in nitrogen). In addition, the polymer films showed reversible electrochemical oxidation with enhanced NIR contrast, high coloration efficiency (CE), low switching time, and anodic green/purple electrochromic behaviors.