Scanning force microscope studies of Langmuir-Blodgett polyaniline thin films

Abstract

Thin films of electrically conductive polyaniline were prepared using the Langmuir-Blodgett (LB) technique. Both single-layer and multilayer films were prepared using various surface pressures and dipping speeds. The resulting film microstructures were then studied using scanning force microscopy. Z-type deposition was observed, with high-quality single layers of flat polyaniline platelets being formed at dipping speeds of 1 mm min −1 and surface pressures near 10 mN m −1. Lower surface pressures resulted in incomplete layers, while much higher surface pressures resulted in clumps of polyaniline bundles in the finished films. The fabrication of polyaniline films composed of flat platelets using the Langmuir-Blodgett technique as opposed to films composed of the more common clumped bundles as seen in chemically cast or evaporated films, results in finished films of much greater smoothness and structural homogeneity. In all cases, the conductivity of protonated LB films was lower than free-standing films cast from polyaniline-NMP solutions.