Nanometer scale multilayers of electroactive polymers: intercalation of polypyrrole in mica-type silicates

Abstract

Intercalative polymerization of pyrrole in the galleries of fluorohectorite, a synthetic mica-type silicate, results in a multilayered structure consisting of single polypyrrole chains alternately stacked with the layers of the silicate host. The multilayered films are characterized by X-ray diffraction, UV-visible, infrared and Raman spectroscopies and electrical conductivity measurements. Upon exposure to I2 vapors, the in-plane electrical conductivity of the polypyrrole-fluorohectorite hybrid increases from 2 × 10−5 to 1.2 × 10−2 S/cm. The conductivity perpendicular to the layers is 3 × 10−6 S/cm corresponding to an electrical anisotropy of 4 × 103. Electrical conductivity measurements as a function of temperature indicate a variable range hopping mechanism, consistent with the current-voltage analysis. The lower conductivity for the intercalated polymer and the shift in the optical absorption bands to higher energies are rationalized in terms of an increased localization of charge carriers due to the molecular confinement of the polymer chains in the host galleries.