Progress Towards the Fabrication of Langmuir-Blodgett Thin Films of Conducting Polymers

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Abstract The molecular organizations and electrical properties of multilayer LB films fabricated from monolayers comprised of a mixture of conjugated polymer chains and surface active molecules have been examined. LB films created from electrically conductive polypyrrole-based monolayers were found to consist of well ordered domains of the surface active component (3-octadecanoyl pyrrole) and partially oriented polymer chains. The multilayer films of this system were found to exhibit very large dielectric constants (> 100) at low frequencies and enormous conductivity anisotropies. These unusual electrical properties can be directly attributed to the supermolecular organization of the film which consists of polypyrrole chains sandwiched between well ordered layers of the 3-octadecanoyl pyrrole molecules. LB films created from poly(3-alkyl thiophene)-based monolayers were found to be comprised of poorly ordered polymer domains randomly dispersed throughout a well ordered matrix of the surface active component (cadmium stearate). The level of conductivity reached by chemical oxidation and the magnitude of the resultant conductivity anisotropy were found to be strongly influenced by the type of dopant used and the manner in which it was introduced into the film. Doping from the solution phase produced the most highly conducting thin films but also dramatically altered the molecular organization of the film. Gas phase doping, on the other hand, could be accomplished without major modifications of the original heterogeneous structure of the film thus creating more anisotropic electrical properties.