Carbon nanotube composites with high dielectric constant at low percolation threshold

Abstract

In this letter, the dielectric properties of the untreated multiwall carbon-nanotubes∕poly(vinylidene fluoride) (MWNT∕PVDF) composites are studied. Towards low frequencies, the dielectric constant of a composite with about $2.0\mathrm{vol}\%$ of MWNT increases rapidly and the value of the dielectric constant is as high as 300. However, by a calculation, the percolation threshold of the MWNT∕PVDF composites is only $1.61\mathrm{vol}\%$ (0.0161 volume fraction) of MWNT. Both the large aspect ratio and the high conductivity of the MWNT may lead to the low percolation threshold of the MWNT∕PVDF composites. For the percolation composite, the dielectric loss value is always less than 0.4, irrespective of the frequency. Therefore, the experimental results suggest that the dielectric properties of MWNT∕PVDF composites may be improved significantly without the chemical functionalization to carbon nanotubes.