Molecular Organization and Electrical Properties of Mixed Langmuir-Blodgett Multilayer Thin Films of Polypyrrole

Abstract

The molecular organization of Langmuir-Blodgett multilayer thin films containing electrically conductive polypyrrole chains dispersed throughout insulating domains of surface active pyrrole molecules was examined by several thin film spectroscopic techniques. Reflection-absorption FTIR and NEXAFS spectroscopy have revealed that the 3-ODOP (3-octadecanoyl pyrrole) surface active pyrrole molecules are highly oriented within the film with their fully extended hydrocarbon chains tilted away from the surface normal with an unusually large tilt angle of about 55°. Evidence for preferred orientation of the polypyrrole chains was also found. The multilayer films were found to exhibit very large dielectric constants (>100) at low frequencies and enormous conductivity anisotropics. These unusual electrical properties can be directly attributed to the molecular organization of the film which consists of polypyrrole chains sandwiched between well ordered layers of 3-ODOP molecules.