Novel high-Tg poly(amine-imide)s bearing pendent N-phenylcarbazole units: synthesis and photophysical, electrochemical and electrochromic properties

Abstract

A new carbazole-derived, triphenylamine-containing aromatic diamine monomer, 4,4′-diamino-4″-N-carbazolyltriphenylamine, was successfully synthesized by the caesium fluoride-mediated condensation of N-(4-aminophenyl)carbazole with 4-fluoronitrobenzene, followed by palladium-catalyzed hydrazine reduction. A series of novel poly(amine-imide)s 6a–6g with pendent N-phenylcarbazole units having inherent viscosities of 0.17–0.56 dL g⁻¹ were prepared from the newly synthesized diamine monomer and seven commercially available tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical or thermal cyclodehydration. The polymers of the series were amorphous and most of them could afford flexible, transparent, and tough films with good mechanical properties. All the poly(amine-imide)s had useful levels of thermal stability associated with high glass-transition temperatures (303–371 °C), 10% weight-loss temperatures in excess of 543 °C, and char yields at 800 °C in nitrogen higher than 60%. The poly(amine-imide)s 6e–6g exhibited a UV-vis absorption maximum at around 300 nm in NMP solution. The poly(amine-imide) 6g derived from an aliphatic dianhydride was optically transparent in the visible region and fluoresced violet–blue at 403 nm in NMP with 4.54% quantum yield higher than the wholly aromatic 6e and 6f. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-imide) films on an indium-tin oxide (ITO)-coated glass substrate exhibited a reversible oxidation wave at 1.05 V and an additional irreversible oxidation wave at 1.39 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from neutral pale yellowish to green doped form at applied potentials ranging from 0.00 to 1.15 V.