Exfoliated graphene reinforced polybenzimidazole nanocomposites with high dielectric permittivity at low percolation threshold

Abstract

The present article reports the dielectric performances of exfoliated graphene (xGnP) reinforced polybenzimidazole (PBI) nanocomposites, which were prepared through in-situ chemical polymerization, using xGnP-methanesulfonic acid solution as a reaction medium. FTIR and X-ray diffraction (XRD) studies confirmed the existence of non-covalent π-π stacking interactions between xGnP basal plan and PBI backbone chains. Morphological analysis of nanocomposite by FE-SEM and TEM demonstrated a uniform dispersion of xGnP nanosheets into PBI matrix as well as the formation PBI layer on individual xGnP nanosheet that imparted huge improvement in dielectric permittivity. The PBI nanocomposite with 2.5 wt% xGnP loading exhibits five times enhancement in the dielectric permittivity at low percolation threshold (0.52 vol%) together with low dielectric loss at room temperature. The results could be ascribed to Maxwell-Wagner-Sillars (MWS) effects based on the π-π stacking interactions between conjugated PBI chains and xGnP. The dielectric permittivity of the nanocomposite is appeared to be nearly stable up to 200 °C followed by small enhancement at higher temperature (up to 300 °C), which make this nanocomposite potential candidate for high-performance embedded capacitors.