Assessing the role of graphene content in the electromagnetic response of graphene polymer nanocomposites

Abstract

We report experimental results from frequency-domain spectroscopy on graphene (GE) filled polyvinylidene difluoride trifluoroethylene P(VDF-TrFE). The dielectric properties of these polymer nanocomposites (GPN) were investigated over a broad range of frequency (from 102 Hz to a few GHz) and a broad range of temperature (from 150 K to 370 K) by using two measurement techniques: impedance spectroscopy and asymmetrical stripline. Care is needed in relating the GE content to the dielectric properties of GPN since the addition of GE to P(VDF-TrFE) can result in a nonmonotonic permittivity change. At low frequency (<1 MHz) the relaxation spectra is not Debye like but is characterized with a broad relaxation time distribution especially at low temperatures. This effect originates from the freezing process of dipoles and Maxwell-Wagner-Sillars (MWS) interfacial polarization. Additionally, a fit of the effective permittivity versus GE content suggests that our data are in accord with the two-exponent phenomenological percolation equation (TEPPE). These experimental results draw attention to the importance of the large surface area of the GE nanoparticles in controlling the interface between the GE flakes and the polymer phase.