Design, Synthesis, and Properties of Donor–Acceptor–Donor′ Asymmetric Structured Electrochromic Polymers Based on Fluorenone as Acceptor Units

Abstract

Two novel conjugated polymers based on a donor–acceptor–donor′ (D–A–D′) asymmetric structure, using fluorenone as the acceptor unit linked with different donor units on both sides, were designed and synthesized, namely poly2-(2,3-dihydrothieno­[3,4-b]­[1,4]­dioxin-5-yl)-7-(thiophen-2-yl)-9H-fluoren-9-one (PSWE) and poly2-(4-(diphenylamino)­phenyl)-7-(thiophen-2-yl)-9H-fluoren-9-one (PSWT). Compared with the symmetrical structure polymer poly­(2,7-dithiophen-2-yl)-fluoren-9-one (PSWS), the asymmetric structure polymers exhibit lower redox potentials and bandgap values and more redox peaks and thus showed a richer variety of colors. Moreover, the introduction of 3,4-ethylenedioxythiophene improved PSWE’s response speed under the near-infrared–visible band and enhanced its optical contrast in the near-ultraviolet spectrum. The introduction of triphenylamine improved PSWT’s optical contrast in the near-infrared and visible spectra. It could be inferred that the polymers with asymmetric structure (D–A–D′) exhibit more redox sites and metastable states with respect to the symmetrical structure (D–A–D), which was attributed to the change in the distribution of the electronic cloud by replacing one donor (D) with another (D′) in the polymer monomer, and the electrochromic properties of the polymers were improved.

High‐Density Optophysiology Platform for Recording Intracellular and Extracellular Signals across the Brain of Free‐Moving Animals

“…Raman responses were influenced by the change of bond polarity, which were related to the changes in electron distribution. C=O has a strong electron absorption effect and ESP distribution showed that the conjugate structure was favorable for the flow of electrons to C=O, [20] and which was proved by our calculation of Mulliken atomic charges (Table S1, Supporting Information). Furthermore, it was found from theory calculations that the extension of the conjugated molecules with chain length longer than 3 had no obvious gain for C=O local charge distribution.…”

Influence of Cross-Link Density on Electrochromic Properties of Conjugated Polymer

“…For the six conjugated polymers, the good linear relationship between current densities and potential scan rates is observed, which indicates their redox process are nondiffusion-controlled. 43,44 Also, the redox properties of these conjugated polymers were measured under the same conditions at low potential scan rate of 50 mV s −1 (Figure 4c). For poly(ProDOT-Me), the slight oxidation signal could be observed at −0.2 V; however, the obvious oxidation signal appears at about 0.35 V. The result is ascribed to that the surface of poly(ProDOT-Me) could be oxidized at low potential and achieved full oxidation at high potential.…”

Toward High-Performance Electrochromic Conjugated Polymers: Influence of Local Chemical Environment and Side-Chain Engineering

“…Reynolds et al reported a dual n-and p-type electrochromic device based on poly-(bisEDOT-PyrPyr-Hx2) that was extremely stable [ 29 ]. Zhang and colleagues synthesized two donor–acceptor–donor′ (D–A–D′) asymmetric ECPs, PSWE and PSWT, that outperformed symmetrical D–A–D PSWS in terms of optical contrast, response time, and coloration efficiency [ 30 ]. Toppare et al presented asymmetric thiophene−benzothiadiazole−3, 4-ethylenedioxythiophene type ECP with a 1.18 eV bandgap, exhibiting p- and n-type doping superior to that with symmetrical analogues [ 31 ].…”