Interface phenomena on conducting polymer films investigated with atomic force spectroscopy

Adsorbed layers of poly(o-ethoxyaniline) (POEA) produced with the layer-by-layer technique have been studied with atomic force spectroscopy (AFS). The films were prepared under different conditions (pH and solution concentration), and measurements were carried out in air and in a liquid cell. Both the doping level and fabrication conditions affect the POEA film morphology and the interactions of the atomic force microscopy (AFM) tip with the polymer molecules. For example, a mapping of the forces indicates the presence of conducting islands surrounded by a less conductive matrix in POEA and PANI films, with the conducting islands being characterized by the presence of double-layer forces. The conducting islands are further visualized via transmission electron microscopy (TEM) pictures. At pH 5, POEA appears completely dedoped where PANI can preserve some of its conducting character, and this is confirmed in electron paramagnetic resonance (EPR) measurements.