Conducting polypyrrole composite thin films chemically prepared by spreading on surface of aqueous solution containing oxidizing agent

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Abstract
Polypyrrole–PMMA composite films have been prepared with the chemical oxidative polymerization by spreading the water‐insoluble solvent solution of pyrrole and PMMA mixture on the surface of the aqueous solution containing K2S2O8, the oxidizing agent. The conductivity of the films increases rapidly, passes through a plateau, and then decreases gradually as the reaction time increases. The conductivity of the oxidized side of the film is higher by over 1 order of magnitude than that of the evaporated side. It is due to the fact that the former is rich in polypyrrole while the latter is rich in PMMA. The thickness of the films can be controlled by adjusting the PMMA concentration. However, the lower limit of the film thickness is practically in submicron order. The relationship between the transmittance and the logarithm of the conductivity of the films gives a straight line with a gradient, ca. −8. The conductivity of the films is stable on silicagels in a desiccator over 2000 h at 25°C. The conductivity of the film is, however, very sensitive to the moisture in atmosphere and gives rise to decrease with humidity.