Weakly negative permittivity with an extremely low plasma frequency in polyvinyl alcohol/graphene membranous metacomposites

Although the metacomposites with tunable negative permittivity response have recently attracted more attention in electromagnetic wave absorber and electronic devices, the scientific explanation of metacomposites with a weakly negative permittivity and an extremely plasma frequency ( $${f}_{\text{p}}$$ ) at kHz has not been systematically investigated. Herein, the polyvinylpyrrolidone (PVP)-modified polyvinyl alcohol/graphene (PVA/GR) membranous composites were prepared to exploit those performances at the radio frequency. When the content of GR material was below the percolation threshold ( $${f}_{\text{c}}$$ ), the enhancement of positive permittivity was attributed to interfacial polarization, while when its content exceeded the $${f}_{\text{c}}$$ , the negative permittivity response was observed, which was owing to the plasma oscillation of delocalized electrons within GR frameworks. Moreover, with the carrier concentration of GR material effectively diluted by introducing PVA matrix, an extremely low $${f}_{\text{p}}$$ $$\sim$$ 160 kHz and absolute negative permittivity value $$\sim$$ − 180 were observed. Besides, the regulation mechanism of impedance and ac conductivity were explored to support essential insights into negative permittivity behavior. Furthermore, because of the construction of percolative GR pathways, the conductivity mechanism fundamentally turned into metal-like conduction and the resulting composites exhibited an inductive character. Briefly, the PVA/GR membranous metacomposites with a weakly negative permittivity and an extremely low $${f}_{\text{p}}$$ can contribute to the development of flexible metamaterials in the field of novel capacitor and wearable cloaking.