Anodic deposition of compact, freely-standing or microporous polypyrrole films from aqueous methanesulphonic acid

Abstract

Freely-standing and flexible films (0.075 to 9 μm in thickness) of electrically conducting polypyrrole were synthesised via anodic electrodeposition onto a stainless steel substrate from methanesulphonic acid under stirred conditions at 295 K. Cyclic voltammetry was used to study the effect of pyrrole monomer concentration (0.01 to 1.0 mol dm⁻³) and methanesulphonic acid level (1.0 to 6.0 mol dm⁻³) on the formation of polypyrrole films. The films were prepared for deposition times of 30–240 s at constant current densities of 1 to 15 mA cm⁻². The ionic conductivity of freely-standing polypyrrole membranes in aqueous methanesulphonic acid was studied. Scanning electron microscopy was used to image the surface microstructure. The polypyrrole films, which were prepared in the oxidised (methanesulphonate doped), conductive state, showed an ionic area resistance as low as 10 ohm cm². The films were readily doped with the methanesulphonate anion and the membrane ionic conductivity was dependent on the electrolyte composition used for their deposition. In the presence of anodic oxygen evolution, the films showed a ‘template-free’ porosity due to film growth around the bubbles.

Keywords:

• Conducting polymer
• Methanesulphonic acid
• Microporosity
• Polypyrrole
• Templating