Langmuir-Blodgett manipulation of poly(3-alkylthiophenes)

Langmuir-Blodgett (LB) multilayer thin films were fabricated from mixed monolayers containing stearic acid and various poly(3-alkylthiophenes). It has been found that mixed LB films containing as much as 80 mol % of poly(3-alkylthiophenes) form stable monolayers at the air-water interface that can be deposited onto solid substrates as Y-type films by the vertical lifting method. The LB films exhibit well-defined layered structures as determined by optical, capacitance, and x-ray diffraction measurements. Multilayer thin films containing highly ordered domains of cadmium stearate can be formed with polythiophenes substituted with alkyl chain lengths ranging from 4 to 18 carbon atoms. The molecular organization and the electrical and optical properties of the films depend on the length of the alkyl chain of the polythiophene backbone. All of these LB films can be rendered electrically conductive by doping with strong oxidizing agents.