Solution-Processable Novel Near-Infrared Electrochromic Aromatic Polyamides Based on Electroactive Tetraphenyl-p-Phenylenediamine Moieties

A series of solution-processable near-infrared (NIR) electrochromic aromatic polyamides with N,N,N′,N′-tetraphenyl-p-phenylenediamine (TPPA) units in the backbone were prepared from the phosphorylation polyamidation reactions of a newly synthesized diamine monomer, N,N′-bis(4-aminophenyl)-N,N′-di(4-methoxylphenyl)-1,4-phenylenediamine, with various aromatic dicarboxylic acids. These polymers were readily soluble in many organic solvents and showed useful levels of thermal stability associated with high glass-transition temperatures (236−246 °C) and high char yields (higher than 58% at 800 °C in nitrogen). The polymer films showed reversible electrochemical oxidation with high contrast ratio both in the visible range and NIR region, which also exhibited high coloration efficiency (CE), low switching time, and the highest stability for long-term electrochromic operation to date. At the first oxidation stage, the polyamide Ib thin film revealed high coloration efficiency in visible (CE = 388 cm2/C) and NIR (CE = 330 cm2/C) region with reversible electroactive stability (over 10000 times within 0.4% loss relative to its initial injected charge). As the dication form of second oxidation stage, the polymer film still exhibited excellent electrochromic/electroactive stability (more than 3000 cyclic switches) with higher CE of 464 cm2/C.