Novel triphenylamine polyazomethines bearing carbazole and trifluoromethyl substituents: Preparation and electrochromic behavior

Abstract

A series of novel polyazomethines (PAMs) were successfully synthesised as reported herein. In particular, a new electroactive diamine 3″-trifluoromethyl-4, 4′-diamino-4″-N-carbazolyl triphenylamine (IV) underwent direct polycondensation reactions with various dialdehydes, such as terephthalaldehyde (Va), 1, 3-isophthalaldehyde (Vb), o-phthalaldehyde (Vc) and 4, 4′-diformyltriphenylamine (Vd) to yield a sequence of novel PAMs: VIa-VId. These polymers were tested via differential scanning calorimetry (DSC) to have very high glass transition temperatures (Tgs, 237–271 °C). Meanwhile, thermogravimetric analysis (TGA) indicated that all of the PAMs in these series were stable with a 5% weight loss in nitrogen atmosphere (444–483 °C). These PAMs films were tested via cyclic voltammetry (CV) and calculated to have HOMO levels between −5.09 and −5.29 eV, LUMO levels between −2.47 and −3.18 eV (relative to vacuum levels). The color of the PAMs films can be changed from yellow in the initial neutral state to red via electrooxidation during the period of 0.0–1.3 V, and then becomes purple as the voltage rises to 1.5 V. A variety of pH- and chemical doping-responsive color changes were also observed. Taking into account the sensitive properties of PAMs, this PAMs will have broad application prospects, such as chemical sensors, OLEDs and solar cells.