Exfoliated clay/polyaniline nanocomposites through tandem diazonium cation exchange reactions and in situ oxidative polymerization of aniline

Abstract

Robust, conductive clay/polyaniline nanocomposites were prepared through a simple approach which consists of in situ polymerizing aniline, in the presence of the 4-diphenylamine diazonium-modified bentonite. XPS measurements indicate that clay experiences a cation exchange of sodium by the diazonium, and the polyaniline is present in large amounts at the nanocomposite surface. As judged by XRD, the clay basal distance increased from 13.7 to 16.2 Å after diazonium modification, whilst, after the in situ polymerization of aniline, the clay characteristic peak at low angle (<8°) has vanished showing the exfoliation of the resulting nanocomposites. However, the nanocomposite prepared with unmodified clay was also found to be a polyaniline-rich surface but without any sign of exfoliation. In addition, the composite morphology, imaged by electron microscopy (SEM) and (TEM), differs significantly from that of pristine clay and shows twisted layers with an inter-distance which increases with the mass loading of the diazonium salt and PANI therefore leading to the exfoliation of the clay. Furthermore, this diazonium modification resulted in a quantum jump of the conductivity of the nanocomposites compared to bentonite, ca. 6 orders of magnitude, whereas the deposition of PANI on pristine clay induced a marginal increase of conductivity from 10⁻⁹ to 2 × 10⁻⁸ S cm⁻¹ due to an uneven coating of the conjugated polymer.