Novel low color poly(ester imides) with triphenylamine and carbazole substituents for electrochromic applications

Autor: Wen-Ze Li, Lian Liu, Yu Liu, Weiyi Zhou, Baoyi Ren, Xiaoyu Zhu
Rok vydání: 2019
Předmět:
Zdroj: Dyes and Pigments. 162:232-242
ISSN: 0143-7208
Popis: A series of novel poly(ester imides) (PEIs, individually denoted as VIIa–VIIe) with triphenylamine and carbazole substituents were prepared herein by direct polymerization of 4, 4′-bis(trimellitimido)-4″-N-carbazolytriphenylamine (V) with various bisphenols (VIa–VIe). All of the PEIs exhibit good solubility in various organic solvents, high glass transition temperatures (Tgs, 245–276 °C) and excellent thermal stability (with only 5% weight loss observed at 478–504 °C under nitrogen protection). The PEI-based films have excellent optical transparency 71–83%, 91–95%, and 94–97% at 450, 550, and 800 nm, and they are paler in color than poly(amine-imide) (PAI) films in the neutral state while also exhibiting better optical transparency. Cyclic voltammetry measurements reveal that the films exhibit two reversible oxidation redox couples at 1.06–1.12 and 1.44–1.79 V under an anodic sweep. Oxidation of the PEI-VIIa film results in the formation of radical cations with outstanding stability, and yields excellent electrochromic properties. In particular, the color of this film changes from pale yellow in the neutral form to green and then to dark blue in the oxidized form. In addition, the anodic coloring of PEI-VIIa displays a high coloration efficiency (CE = 191 cm2/C), dramatic change in optical transmittance (△T = 82% at 760 nm) and long-term redox reversibility.
Databáze: OpenAIRE