Stably anodic green electrochromic aromatic poly(amine–amide–imide)s: Synthesis and electrochromic properties

A series of new poly(amine–amide–imide)s with pendent 4-methoxy-substituted triphenylamine (TPA) units having inherent viscosities of 0.35–0.45 dL/g were prepared from various aromatic bis(trimellitimide)s and the 4-methoxy-substituted triphenylamine-based aromatic diamine, 4,4′-diamino-4″-methoxytriphenylamine (I), by direct polycondensation. All the polymers are readily soluble in polar organic solvents. Flexible and amorphous films of these poly(amine–amide–imide)s could be obtained by solution-casting, and showed excellent thermal stability, 10% weight-loss temperatures in excess of 515 °C, and char yields at 800 °C in nitrogen higher than 58% associated with high glass-transition temperatures (297–305 °C). These polymers exhibited a maximum UV–vis absorption at 302–304 nm with fluorescence emission maxima around 360–376 nm in N-methyl-2-pyrrolidinone (NMP) solution. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine–amide–imide) films cast onto an indium–tin oxide (ITO)-coated glass substrate exhibit a reversible oxidation at 0.79–0.80 V vs. Ag/AgCl in acetonitrile solution, and reveal good stability of electrochromic characteristics with a color change from yellow to green at applied potentials ranging from 0.00 to 0.95 V. These anodically polymeric electrochromic materials not only showed excellent reversible electrochromic stability with good green coloration efficiency (CE = 395 cm2/C) but also exhibited high contrast of optical transmittance change (ΔT%) up to 78% in 768 nm. After over 100 cyclic switches, the polymer films still exhibited stable electrochromic characteristics.