Polymer films on electrodes. 30. Electrochemistry and scanning electrochemical microscopy characterization of benzimidazolebenzophenanthroline-Type ladder (BBL) and semiladder (BBB) polymer films

Polymer-modified electrodes were obtained by spin-coating solutions of poly(benzobisimidazo-benzophenanthroline) ladder (BBL) and semiladder (BBB) polymers on indium-tin oxide electrodes. An electrochemical study of these films showed reproducible and stable cyclic voltammograms for reduction of the polymer (in the absence of oxygen), the absence of waves for oxidation of the polymer, and brilliant changes in color during the potential scan. Measurements with the scanning electrochemical microscope showed changes in the film conductivity, with the films being more conductive in the reduced form. The potential dependence of the film resistance and atomic force microscopic characterization are also reported. These results confirm the electron transport and electron-accepting nature of both BBL and BBB, which can accept up to two electrons per monomer repeat unit. Although the electrochromic features of BBL and BBB are similar, a significant difference in the film morphologies was observed by atomic force microscopy.