New triphenylamine-based poly(amine-imide)s with carbazole-substituents for electrochromic applications

Abstract

A new carbazole-derived triphenylamine-containing diimide-diacid monomer (5), 4,4′-bis(trimellitimido)-4″-N-carbazolytriphenylamine, is prepared by the condensation of 4,4′-diamino-4″-N-carbazolytriphenylamine (4) and two molar equivalents of trimellitic anhydride (TMA). A series of new poly(amide-imide)s (PAIs) 7a–7d with carbazole-substituted triphenylamine units are prepared by direct polymerization from the new diimide-diacid (5) and various aromatic diamines (6a–6d). The PAIs shows high glass transition temperature between 269 and 297°C, and high 5% weight loss temperature between 526 and 561°C under nitrogen environment. Cyclic voltammograms of the PAIs films, which are casted onto the indium–tin oxide (ITO)-coated glass substrate, exhibit two reversible oxidation redox couples at 1.05–1.08V and 1.38–1.46V under an anodic sweep. The PAI-7a film reveals excellent stability of electrochromic characteristics for the radical cations generated, changing color from original pale yellowish neutral form to the green and then to dark blue oxidized forms. Furthermore, the anodically coloring of PAI-7a shows high coloration efficiency (CE=205cm2/C), high contrast of optical transmittance change (ΔT=80% at 776nm) and long-term redox reversibility.