Preparation, characterization and conductivity study of polypyrrole-pillared clay nanocomposites

Polypyrrole-aluminum pillared montmorillonite (PPy-Al-PMMT) clay composites were prepared by in-situ polymerization of pyrrole in aqueous dispersion of aluminum pillared montmorillonite (Al-PMMT) clay using FeCl(3.6)H(2)O as an oxidant. Various composite samples with varying amounts of (Al-PMMT) clay from 0.2 wt% to about 25 wt% were prepared and were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). XRD results revealed that for very low concentration of Al-PMMT, PPy was intercalated in the interlamellar region of PMMT replacing the aluminum pillars. With the increase of Al-PMMT concentration above 1wt% the level of intercalation decreased. Room temperature DC conductivity of PPy-Al-PMMT composites was measured using standard Four Point Probe technique and AC conductivity was measured in the frequency range 100 Hz to 1 MHz. using an LCR meter. DC conductivity values slightly increased with the increase of clay content in the samples due to the effect of intercalation of PPy in the interlamellar galleries of PMMT. For upto 1% Al-PMMT the DC conductivity increased rapidly with Al-PMMT content but for higher concentrations this increase was not so rapid. AC conductivities of the (PPy- Al-PMMT) clay composites were considerably high as compared to the AC conductivity of pure PPy and this also increased with the content of Al-PMMT in the composites. At low frequencies the AC conductivities of pure PPy and its composites remained constant with the increase of frequency and increased rapidly with the increase of frequency at high frequencies. The slope of frequency dependence curves at high frequencies did not change with the Al-PMMT content and was found to be the same in pure PPy as well as in all the composite samples studied. The onset of rapid increase of AC conductivity, however, shifted to a higher frequency value on addition of Al-PMMT in PPy.