Conducting and Magnetic Composites Polypyrrole Nanotubes/Magnetite Nanoparticles: Application in Magnetorheology

The study aims at the design of nanostructured hybrid materials that are both conducting and magnetic. Conducting polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride stimulated by the organic dye, methyl orange. The excess of oxidant involved in the synthesis was used for the in situ generation of magnetite nanoparticles after addition of ammonia that coated the polypyrrole nanotubes. The resulting composites of varying composition were characterized with respect to the specific surface area and by X-ray diffraction and FTIR spectroscopy. The conductivity measurements revealed that polypyrrole nanotubes had a conductivity of ≈20 S cm–1 and the composites with magnetite nanoparticles ≈1 S cm–1 virtually independent of the composition. While polypyrrole nanotubes had marginal magnetic properties, the saturation magnetization of composites reached ≈50 emu g–1, close to that of neat magnetite. The reprotonation of polypyrrole in composites increased the conductivity to ≈5 S cm–1 at the expense of reduction of magnetic properties. The magnetorheological analysis was performed to illustrate their possible application exploiting the nanotubular morphology and requiring a magnetic response.