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

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DOI：https://doi.org/10.1021/acsapm.9b00103

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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.