Propylenedioxy and Benzimidazole Based Electrochromic Polymers

In this study, three acceptor units were synthesized by substituting cyclohexane, cycloheptane and cyclooctane rings at 2-C position of benzimidazole. These acceptor units were coupled with dihexyl substituted 3,4-propylenedioxythiophene (PRODOT-C6) donor segments and the resulting donor-acceptor-donor monomers were polymerized via potentiostatic and potentiodynamic methods to obtain their corresponding conjugated polymers (CP). Monomers and their polymers were investigated in terms of the ring size of the substituent on the acceptor unit and their electrochemical and optical behaviors were reported. The monomers exhibited dual absorption bands (at about 310 nm and 520 nm) due to their donor-acceptor pattern. CP films on indium tin oxide conducting substrate were investigated in a monomer free electrolytic solution. The polymer films exhibited quasi-reversible redox behavior due to doping/dedoping which was accompanied by a reversible electrochromic behavior. All three polymer films showed similar multichromic behaviors: green color in the neutral state, gray in the oxidized state, and brick-red in the reduced state. Band gap values (E-g) were elucidated via both electrochemical and optical methods. Moreover, electrochromic device (ECD) was constructed with one of the polymer films (cyclohexane ring bearing benzimidazole and PRODOT-C6 containing polymer) with poly(3,4-ethylenedioxythiophene) (PEDOT). (C) 2016 The Electrochemical Society. All rights reserved.