Tuning the optoelectronic properties of polyfuran by design of furan-EDOT monomers and free-standing films with enhanced redox stability and electrochromic performances

Graphical abstract: - Highlights: • Furan-EDOT monomers were synthesized using Stille coupling. • The electropolymerization of furan-EDOT monomers were reported. • Free-standing furan-EDOT films were electrosynthesized. • Furan-EDOT copolymers show enhanced redox activity and stability. • Furan-EDOT copolymers exhibits improved electrochromic performances. - Abstract: Most recently, conjugated oligo-/polymers containing furan have regained attention due to their unique properties and promising application in organic electronics. Herein, to acquire a thorough fundamental understanding of the electrosynthesis and properties of furan-EDOT copolymers from different initial monomers, the synthesis and electropolymerization performances of furan-EDOT monomers, namely 5-(furan-2-yl)-2,3-dihydrothieno[3,4-b][1,4]dioxin (EDOT-Fu), 5,7-di(furan-2-yl)-2,3-dihydrothieno[3,4-b][1,4]dioxin (Fu-EDOT-Fu), and 2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)furan (EDOT-Fu-EDOT), were comprehensively reported and the effect of different monomers on the structure and properties of the resulting polymers obtained under optimized electrical conditions were systematically evaluated. The monomers exhibit good blue-green photoluminescence with quantum yields ranging from 0.5 to 40%, which may be used as building blocks for rational design of fluorescent conjugated systems. The onset oxidation potential ranged from 0.78 V-0.45 V with the incorporation of EDOT unit in monomer chain, thus leading to the facile electrodeposition of free-standing films with improved optoelectronic properties in comparison with polyfuran. The obtained copolymers featured the advantageous combination of polyfuran and PEDOT, such as higher fluorescence and better planarity of polyfuran, transparency and excellent redox stability of PEDOT. Structure characterization and properties of the as-formed copolymer films from different initiative monomers, including FT-IR, UV-vis, TG, fluorescence, surface morphology and electrochromic properties, etc., were systematically investigated and comparatively discussed