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Abstract

A series of nanocomposites of polyaniline-montmorillonite have been prepared in which polyaniline is present within the interlayers as well as adsorbed onto the external surfaces of the clay particles (i.e., emeraldine salt-montmorillonite, ES-MMT series). The composite materials show uniform texture as revealed by scanning electron microscopy. The ES-MMT members show high electronic conductivities. Under the identical conditions of sample preparation, the d-spacing enhancement upon the polymer intercallation is the same regardless of whether the polymer is present only within intergalleries or both inside and outside the intergalleries. The FTIR studies reveal that the OH stretching in the Al-Mg-OH infrared band appearing at 840cm^-1 disappears upon polymer loading. Since the OH in Al-Mg-OH moieties are directed outward from the hexagonal cavities, this effect may be attributed to the interaction between the clay particles and the polymer that is present adsorbed to clay surfaces. The polymer present within the intergalleries influences strongly on the 0-H vibrations, which are directing inward to the intergalleries. Cyclic voltammetric studies reveal that the electroactivity of the composite material is limited by the accessibility of solution species into the intergalleries in a diffusion-controlled manner. The electrochemical impedance spectroscopic (EIS) studies reveal that the ES-MMT members have both electronic and ionic conductivities with similar transport numbers even when the polymer is in its fully electronically conducting state. Four different and mutually independent techniques used to characterize the composites give strong evidence to confirm that there is a limit to the repetitive polymer loading within the intergalleries of the clay particles. The limited interspacing with all repeated polymer loading may be due to the saturation of all ion-exchangeable sites of montmorillonite by the cations of the polymer.

Keywords

electrochemical impedance spectroscopy polyaniline-montmorillo-nite intercalates electronic and ionic conductance

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Electrochemical Impedance Spectroscopic and Other Studies of Polyaniline-Montmorillonite Intercalates

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