Carbazole-Functionalized Poly(phenyl isocyanide)s: Synergistic Electrochromic Behaviors in the Visible Light Near-Infrared Region

Since the discovery of the fact that the electrochromic (EC) behavior of polyisocyanides (PICs) can be achieved without the restriction of EC groups in 2018, a new chapter of electrochromic PICs has been opened. However, the synergistic electrochromic behaviors of both PICs and EC groups have not been reported until now. Herein, a series of novel EC poly(phenyl isocyanide) helix cross-conjugated polymers (PICz) containing a strong donor (carbazole)-weak acceptor (phenyl isocyanide) structure feature are synthesized through living polymerization. As a p-type electrochromic polymer, PICz polymer films exhibit good electrochromic abilities, such as easily observed color changes (from orange-yellow to light gray), low onset potentials (0.78-0.80 V), fast switching time ((2.1-2.4)/(1.0-1.1) s for the electrochromic process), and high coloration efficiency (165.54-431.52 cm(2) C-1). It is worth noting that besides the EC behavior from carbazole groups, the strong absorption in the near-infrared region (780-1800) is attributed to the EC behavior of the electrochemically doped PIC structures, which is beneficial to its further application in many military and civilian uses. In addition, PICz polymers can achieve higher switching cycling stability in solution (over 100 cycles) than that in a solid-state thin film (1 cycle), due to the remarkable switching of the polymer structure from the neutral state to the doped state, which is a unique feature compared with the other EC polymers.

Automated summary

A new chapter of electrochromic PICs has been opened with the synthesis of novel EC poly(phenyl isocyanide) helix cross-conjugated polymers (PICz) containing a strong donor-weak acceptor structure. These PICz polymer films exhibit good electrochromic abilities with easily observed color changes, low onset potentials, fast switching time, and high coloration efficiency. The strong absorption in the near-infrared region and higher switching cycling stability in solution make PICz polymers promising for military and civilian applications.