Synthesis of cross-linked conducting copolymers containing twisted spirobifluorene units via direct arylation random copolymerization for electrochromic applications

Two cross-linked copolymers containing twisted spirobifluorene (SBF) units are successfully synthesized via direct arylation polymerization (DArP) with a low reaction temperature and catalyst addition. The resultant polymers are fully characterized by H Nuclear magnetic resonance (HNMR), gel permeation chromatography (GPC), thermo gravimetric analysis (TGA), Fourier Transform infrared spectroscopy (FTIR), Cyclic voltammo-gram (CV). Spectroelectrochemical measurements indicate the synthesized polymers possess wide band gap and red color in their neutral state. After applying an oxidized potential, the polymer films are highly transparent in their oxidized state. Additionally, two electrochromic devices are assembled based on these two copolymers, which demonstrate good optical contrast, fast switching response and good stability, indicating the incorporation of SBF units into the poly(3,4-alkyldioxythiophene) mainchain can induce the synthesis of high-performance red -to-transparent electrochromic polymers.