High Contrast Ratio and Rapid Switching Electrochromic Polymeric Films Based on 4-(Dimethylamino)triphenylamine-Functionalized Aromatic Polyamides

A series of electroactive aromatic polyamides with 4-(dimethylamino)triphenylamine [(NMe2)TPA] units in the backbone were prepared from a newly synthesized diamine monomer, 4,4′-diamino-4′′-(dimethylamino)triphenylamine, and various aromatic dicarboxylic acids via the phophorylation polyamidation reaction. These polyamides are readily soluble in many organic solvents and can be solution-cast into tough and amorphous films. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (277–298 °C), 10% weight loss temperatures in excess of 500 °C, and char yields at 800 °C in nitrogen higher than 67%. The polymer films showed reversible electrochemical oxidation accompanied by strong color changes with high coloration efficiency, high contrast ratio, and rapid switching time. The optical transmittance change (∆%T) at 640 nm between the neutral state and the fully oxidized state is up to 88%, and the coloration efficiency is as high as ca. 261 cm2/C with high optical density change (δOD) up to 0.94. The polymers also displayed low ionization potentials as a result of their (NMe2)TPA moieties. Cyclic voltammograms of the polyamide films on the indium-tin oxide (ITO)-coated glass substrate exhibited a pair of reversible oxidation waves with very low onset potential of 0.35 V (vs Ag/AgCl) in acetonitrile solution.