Electrochemical polymerization of triphenylamine end-capped dendron: Electrochromic and electrofluorochromic switching behaviors

Triphenylamine unit containing two electroactive end-capped dendritic macromolecules Benz-3TPA and Benz-3CNTPA have been rationally designed and successfully synthesized with good yield. Their structures contain benzene moieties as part of the core. Both dendrons have formed the polymers (p-Benz-3TPA and p-Benz-3CNTPA) through the oxidative electrochemical polymerization and also are capable of showing simultaneous operation in electrochromic (EC) and electrofluorochromic (EFC) properties. These two polymer films have exhibited stable reversible multi-color electrochromic changes with high coloration efficiency and contrast ratio upon electro-oxidation. These electrochromic polymers have not only produced EC properties with high optical contrast (ΔT% = 65–71%) but also exhibited high contrast ratio (Ion/Ioff = 179, Ion = fluorescence on (neutral state) and Ioff = fluorescence off (oxidized state)) EFC properties at low working voltage. Both have still showed excellent electro-switching stability even after hundredth cycles. Solid state electrochromic devices (ECD) using both the polymers have been fabricated and its color and fluorescent state are simultaneously switched by an applied potential, making the polymer a unique candidate for electrochemical fluorescence and electrochromic applications in future.