Magnetite nanoparticles-catalysed synthesis of conductive polyaniline

Abstract

Nowadays, there is a growing interest to find environmentally-friendly, simple and economical routes for the synthesis of polyaniline (PANI), one of the most important conducting polymers. For the oxidative polymerization approach hydrogen peroxide (H2O2) is highly recommended oxidant due to ecological aspects, since the product of its reduction is only water. However, its usage as an oxidant, aimed to produce conductive PANI with reasonable reaction rate, needs a catalyst. Here we report the preparation of conductive PANI in good yield by the oxidative polymerization of aniline using magnetite nanoparticles (Fe3O4 NPs) as a catalyst and H2O2 as an oxidant, with added very small amount of ammonium peroxydisulfate as the initiator. Synthesized Fe3O4 NPs (size 10–50 nm) were characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). It was found that without Fe3O4 NPs, under otherwise same conditions, the reaction product is not PANI. The effect of mass ratio Fe3O4 NPs/aniline and polymerization time on the structure and physicochemical properties of prepared PANI was studied by various techniques. FTIR, Raman, UV–vis-NIR and electrical conductivity measurements confirmed the existence of conducting emeraldine salt form of PANI. XRPD revealed unchanged crystalline structure of Fe3O4 NPs upon polymerization and semi-crystalline structure of PANI. EPR spectra showed peaks assigned to PANI and Fe3O4 NPs. Described simple, environmentally improved synthetic route opens possibilities for the syntheses of conductive PANI-like polymers from other aromatic amines by using environmentally-friendly oxidant H2O2 and Fe3O4 NPs catalyst which can replace more expensive catalysts such as peroxidase enzymes.