Electrochemical polymerization of D-A-D type monomers consisting of triphenylamine and benzo[1,2-b:4,5-b′]dipyrazine units for multicolor electrochromism

We developed four donor-acceptor-donor (D-A-D) type monomers (YQ1 ∼ YQ4) with Y-shape configuration consisting of triphenylamine and benzo[1,2-b:4,5-b′]dipyrazine moities, which were further polymerized via electrochemical polymerization for electrochromic applications. The monomers were synthesized facilely from benzene-1,2,4,5-tetraamine tetrahydrochloride by sequential condensation reactions with diketones. The optical properties of these polymers in neutral states can be tuned by variation of the additional substituents on the electron acceptor parts. All these polymers (PYQ1 ∼ PYQ4) exhibited multicolor electrochromism, and appeared similar green color at their second coloration states. Moreover, polymers PYQ1 and PYQ2 with two twisted substituents on the acceptor part showed superior electrochromic performance than the anologues PYQ3 and PYQ4 consisting fused electron acceptor moities with high coplanarity, involving faster response speed, and higher coloration efficiency, which demonstrated that the molecular configuration of monomer was crucial for efficient electrochromic performance.