Montmorillonite/polypyrrole nanocomposites.: The effect of organic modification of clay on the chemical and electrical properties

Montmoritionite/polypyrrole (MMT/PPy) nanocomposites, with 15% mass loading of PPy, were prepared by the in situ polymerization of pyrrole in the presence of montmorillonite (MMT) or organo-modified montmorillonite (oMMT) in aqueous solutions containing an oxidant and an anionic surfactant. The morphology of MMT/PPy nanocomposites distinctly differs from that of the untreated MMT as shown by SEM. X-ray photoelectron spectroscopy showed that the MMT/PPy nanocomposite has an MMT-rich surface, whereas the oMMT/pPy nanocomposite surface has a rather organic nature. Due to the organic modification of MMT by the alkylammonium chloride, polymerization of pyrrole at the surface of oMMT is much more efficient in producing a conductive adlayer resulting in an enhancement of conductivity of the oMMT/PPy nanocomposites (1.1 S cm(-1)) compared to MMT/PPy (3.1 X 10(-2) S cm(-1)). The difference in the behaviour of oMMT/PPy and MMT/PPy is interpreted in terms of surface energy minimization by the alkylammonium ions present at the surface of organo-modified MMT. Indeed, the dispersive contribution to the surface energy (y(s)(d)), as determined by inverse gas chromatography at 150 degrees C, was estimated to be 34.0 mJ/m(2) for oMMT, much lower than the value of 216 mJ/m(2) determined for MMT. (c) 2005 Elsevier B.V. All rights reserved.