High-performance triarylamine-based electrochromic aramids incorporating electron-withdrawing fluorine substituents
Journal
Materials Today Chemistry
Journal Volume
49
Start Page
103044
ISSN
24685194
Date Issued
2025-10
Author(s)
Abstract
Two novel electrochromic polyamides (PAs) with dual electroactive nitrogen sites, IA and IB, were synthesized from 4,4′-dicarboxydiphenyl ether and two new diamines with para-methylphenyl and para-fluorophenyl substituents, respectively. IA and IB demonstrated superior electrochromic performances, including multiple color changes, high contrast in optical transmittance change, and high electrochromic stability, with only 2.78 % and 6.94 % decay of their coloration efficiency (CE) at 1040 nm and 964 nm, respectively, after 5000 switching cycles at first oxidation stage, compared to all other triarylamine-based polymers to date. IB contains strong electron-withdrawing fluorine substituents, which are generally thought to destabilize the cation radicals. Surprisingly, IA and IB exhibited similar electrochromic switching stability. Our study discovered that the unshared electron pair of an existing phenyl ring substituent, like fluorine, could resonate with the nitrogen electroactive site through the benzene ring, thereby surprisingly stabilizing cation radicals and enhancing electrochromic stability. Notably, IB film changed from colorless in the neutral state to bright green and dark blue in the first and second oxidation states. In addition, these PAs were highly soluble in many organic solvents and exhibited high glass-transition temperatures and thermal stability. Moreover, IA and IB exhibit strong absorption properties in both the near-infrared (NIR) and visible light regions, indicating their substantial potential as dual-band electrochromic materials.
Subjects
Fluorine atom
High stability
Polyamide
Resonance effect
Triphenylamine
SDGs
Publisher
Elsevier Ltd
Type
journal article