Application of dip-coating process for depositing conducting polypyrrole films

The formation and electrical properties of vapour phase polymerised polypyrrole films on dip-coated polyethylene oxide (PEO)-cupric chloride substrates have been studied with respect to different deposition parameters. The substrate speed (U) during the dip-coating process affects the film thickness (d) and a relationship of the type d alpha U-n with n = 0.27 is followed. The X-ray diffraction studies reveal a distinct formation of ordered polypyrrole moieties but these are very small in size/number. The conductivity of the films increases very rapidly with the exposure time to pyrrole vapours as well as the concentration of the cupric chloride used in the complex. A sharp variation of conductivity with film thickness is also observed for thicknesses lower than 5 mu m. These various results have been explained on the basis of formation of conducting polypyrrole domains in the crystalline regions of the polyethylene oxide complex giving rise to a composite type material in which the concentration and packing of the conducting moieties depend on the different deposition parameters used. (C) 1997 Elsevier Science S.A.