Oxidative (co)polymerization of dithiarubicene derivatives and electrochromic properties of narrow-bandgap conjugated polymers

• Published in: Polymer journal 2022-09, Vol.54 (9), p.1055-1062
• Main Authors: Takagi, Koji, Yamamori, Takeru, Tsukamoto, Kenji
• Format: Article
• Language: English
• Subjects: 119/118; 140/131; 639/638/298/917; 639/638/455/954; Absorption spectra; Biomaterials; Bioorganic Chemistry; Charge transfer; Chemical reactions; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Chloroform; Color; Cross coupling; Electrochromism; Energy gap; Ferric chloride; Original Article; Oxidation; Polymer films; Polymer Sciences; Polymerization; Polymers; Surfaces and Interfaces; Thin Films
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-022-00655-7

EDOTDTR with a dithiarubicene (DTR) core and 3,4-ethylenedioxythiophene (EDOT) flanking group was synthesized by a Migita-Kosugi-Stille cross-coupling reaction. The EDOTDTR exhibited long-wavelength absorption at 822 nm and a narrow electrical bandgap energy ( E g elect  = 1.32 eV) due to its efficient intramolecular charge transfer. Chemical polymerization by FeCl 3 in CHCl 3 solution and electropolymerization on an ITO electrode yielded the conjugated polymers polyDTR chem and polyEDOTDTR elect , respectively. CV measurements revealed that the redox processes of the polymer films were reversible and not diffusion-limited. Both conjugated polymers exhibited an absorption band at 480 nm, indicating that their π-π* transitions were not much influenced by polymerization. The absorption edge of the polyEDOTDTR elect film extended into the near-infrared region ( λ onset  > 1000 nm), implying effective intra- and intermolecular charge transfer interactions between the DTR and EDOT segments. The polyDTR chem and polyEDOTDTR elect were electrochromic active, and the corresponding color changes were brought about by applying both positive and negative potentials. In particular, both polymer films showed good switching stabilities at the oxidation potential, as confirmed by spectroelectrochemistry. The following diagram is the form for Graphical Abstract. The use of color to enhance quality and appearance is encouraged. The graphics should be EPS, PS, CDX, PPT, and TIFF formats at 300 dpi for color and 1200 dpi for black and white.