The generation mechanism of negative permittivity in multi-walled carbon nanotubes/polyaniline composites

Abstract

Conductive polymers filled with carbon nanotubes have been proved to have negative permittivity but the mechanism of its strange properties has not been intensively studied. Thus we need to study the mechanism of negative permittivity of conductive polymer metamaterials and reveal the relationship between the permittivity and fillers. Polyaniline (PANI) filled with multi-walled carbon nanotubes (MWCNTs) is chosen as the target to explore the generation mechanism of the negative dielectric properties. PANI with low resistivity (CPA0) and MWCNTs/CPA0 composites synthesized are found to possess negative permittivity. A structure model of “double nano wires” is initially constructed after some structure and properties analysis, and the amplification mechanism of MWCNTs on negative permittivity of CPA0 and the transition phenomenon of permittivity from negative to positive value are correlated with this model. In order to verify the model, PANI with high resistivity (CHK0) and MWCNTs/CHK0 composites are prepared. The surface of MWCNTs is then coated with polyvinylpyrrolidone (PVP). These results further demonstrate the validity of the structure model of “double nano wires” to account for the negative permittivity of MWCNTs/PANI composites. This study provides an experimental basis on further exploration of metamaterials of carbon nanotube/conductive polymer composites.