Electrochemical Synthesis of Optically Active Polyaniline Films

Abstract Polyaniline (PANI) thin films with high optical activity are prepared electrochemically on indium tin oxide (ITO) substrates by polymerizing aniline in the presence of aniline oligomers and optically active camphor sulfonic acid (CSA). These optimized PANI chiral thin films have an anisotropic factor of 0.03 and an estimated molar ellipticity of 8.8 × 10 5 deg cm 2 dmol –1 , ∼ 25 % higher than our previously synthesized chiral PANI nanofibers that were prepared using the chemical method. The thin film prepared without aniline oligomers is basically achiral. The electrochemical method does not require an oxidizing agent and allows control of the rate of polymerization reaction by varying the oxidation potential. The electrochemical polymerization also ensures that the initiation occurs solely with the oligomers. Varying the experimental parameters, such as oxidation potential and the choice of oligomers, allows tuning of optical activity, adsorption properties, crystallinity, and morphology of the PANI thin films.