Nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) percolating composites with low‐percolation binary functional phases and negative permittivity

Abstract Polymer percolating composites with negative permittivity via the construction of percolating structures are of great interest in electromagnetism. In this study, nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) (CP‐MWCNTs/PVDF) composites comprising binary functional phases CP‐MWCNTs were fabricated using hot‐pressing method. The composites achieved both low percolation threshold and tunable negative permittivity properties across the entire frequency range of testing. Percolation phenomenon was observed as functional phases content reaching 5 wt%, which was reflected as the establishment of percolation network and the occurrence of electrical percolation, resulting in a shift toward metal‐like conduction mechanism. Additionally, the notably low percolation threshold can be ascribed to the synergistic effect between the binary functional phases. The plasma oscillation of free electrons within conductive percolation network plays a crucial role in achieving negative permittivity, a phenomenon that can be elucidated using the Drude model from the free electron theory. Furthermore, analyses of the impedance and equivalent circuit illuminate the connection between percolation phenomenon and dielectric behavior. These findings further reveal the influence of functional phases' morphology and composition on percolation behavior and negative permittivity properties, while expanding the application of polymer‐based percolating composites in electromagnetic devices. Highlights Tunable negative permittivity related to plasma oscillation is achieved. Binary functional phases exhibit a low percolation threshold. Synergistic effect of functional phases leads to low percolation threshold.