Electrochemistry of polyaniline Langmuir–Blodgett films

Abstract

Langmuir–Blodgett (LB) manipulation of polyaniline has been variously employed to obtain organized assemblies for use in molecule-based electronic devices. However, the electrochemical characteristics of polyaniline LB films which have a direct implication on the proposed device applications have not been given much attention. We report here, electrochemical characterization of multilayer LB films of polyaniline prepared by employing N-methylpyrrolidone as the processing solvent. The films have been transferred onto a variety of substrates such as quartz, platinum, platinum sputtered on quartz, and conducting tin oxide on glass. The electrochemistry of polyaniline LB films has been studied using cyclic voltammetry coupled with a quartz crystal microbalance (QCM). Cyclic voltammograms were obtained for films transferred at different surface pressures, for films containing different number of layers. The electrochemical characteristics of LB multilayers were compared with those of electrochemically deposited films and were used to infer the packing behaviour of polymer chains in the LB film structure. It was found that multilayer LB films are electroactive but the kinetics of counter ion transport in these films is slower than that observed in electrochemically deposited films. The multilayer LB films also show poor electrochromic switching behaviour.