Self‐Doped Oligoaniline Electrochromic Devices: Fabrication and Effect of the Oligoaniline Molecular Architecture

Abstract

A series of self‐doped oligoaniline derivatives, that is, carboxyl‐capped tetraaniline (HOOC‐(Ani)4‐COOH), carboxyl‐capped pentaaniline (HOOC‐(Ani)5‐COOH), carboxyl‐capped hexaaniline (HOOC‐(Ani)6‐COOH), and carboxyl‐capped star‐shaped tetraaniline (Tri‐(Ani)4‐COOH) in leucoemeraldine base state, were synthesized and characterized. The number of the aniline units was varied and a star‐shaped structure was designed to detect the influence of the molecular architecture on the electrochromic properties. The introduction of carboxylic groups into oligoaniline derivatives produced intermolecular hydrogen bonds, which contributed to their self‐doping capability. As a result, these oligoaniline derivatives presented reversible electrochromic properties at pH≥7, which could not be seen in pristine oligoanilines or polyanilines. Then, these oligoaniline derivatives were fabricated into electrochromic devices without an external acid dopant in the assembling process. Comprehensive electrochemical tests were conducted to investigate their electrochromic properties. The resulting devices showed good performances in spectroscopic, electrochemical, and in situ tests. Increasing the chain length contributed to an improved optical contrast, coloration efficiency, response time, and cycling stability. Meanwhile, introducing a star‐shaped structure also led to a better electrochromic performance. Moreover, electrochemical impedance spectroscopy and AFM tests were used to explore the mechanism to understand how the star‐shaped molecule facilitated the redox process.

The Contribution of Density Functional Theory to the Atomistic Knowledge of Electrochromic Processes

“…In recent years, however, the investigation has expanded to other promising organic and inorganic systems including those containing boron [ 41 , 42 , 43 ], quinodimethane derivatives [ 44 , 45 ], metal-phtalocyanine [ 46 ], metal oxides-based film [ 7 , 47 , 48 ], oligoaniline [ 49 ], antracenes [ 50 , 51 ], azacenes [ 52 ], polymethine and polyimides [ 53 , 54 ], and some organometallic complexes [ 55 , 56 ].…”

Electrochromic Conjugated Polymers for Multifunctional Smart Windows with Integrative Functionalities

“…In contrast to PANI, the carboxyl‐substituted aniline shows EC properties at a pH > 7 ( Figure ). [ 46 ]…”

“…b) Transmittance spectra of a) HOOC-(ANI) 4 -COOH, b) HOOC-(ANI) 5 -COOH, c) HOOC-(ANI) 6 -COOH, d) Tri-(ANI)4 -COOH in ECDs at potential of −1.5 V (black) and +1.5 V (red). Reproduced with permission [46]. Copyright 2017, John Wiley & Sons, Inc.…”

Nonlinear Optical and Spectroscopical Properties of Functionalized Oligoanilines

“…The synthetic routes produce functionalized oligoanilines and various block-like structure types having potential applications in organic electronics, sensors and biomaterials interface. [1][2][3][4][5][6][7][8] Several applications of polyaniline (PANI) and hybrid materials have been demonstrated, including electrochromism, [9] supercapacitor, [10] rectifying performance and reversible conductance switching, [11] optical biosensing, [12] and use as sensors, [13][14][15][16] among others. However, oligoanilines present a well-defined and monodisperse molecular structure as well as other useful properties such as solubility and processability in contrast to that observed in the PANI polymer.…”