Adjustable and weak negative permittivity behavior in carbon nanofiber/poly(vinylidene fluoride) metacomposites

Abstract Metacomposites with negative permittivity have advanced significantly in recent years, and yet the weak negative permittivity behavior is still not easily adjusted, which obstructs the advancement of metacomposites in electronic devices. Herein, poly(vinylidene fluoride) (PVDF) composites with different carbon nanofiber (CNF) contents were prepared to explore regulatory mechanism of weak negative permittivity behavior. As the CNF contents were low, the long‐range isolated nanofibers endowed the composites with hopping conductance, capacitance characteristic and positive permittivity. When the CNF contents reached the percolation threshold, many nanofibers were in close contact and enough conductive network was formed to generate metal‐like conductivity, inductance characteristic and negative permittivity. Interestingly, a weak negative permittivity behavior could be realized the composites with high CNF contents (5.94 ~ 17.48 wt%), and its magnitude could be precisely adjusted (−60 ~ −538). The weak negative permittivity behavior was imputed to the suppressed low‐frequency plasma state of free electron in the sparse CNF network. The PVDF could impede the formation of nanofiber network and tunneling effect between adjacent nanofibers, and thus the negative permittivity was weakly dependent on the CNF content. These findings suggested that the negative permittivity could be affected by the synergistic effect of both conductive filler and insulating matrix, offering a new thread of researches in adjusting weak negative permittivity behavior. Highlights The weak negative permittivity behavior was observed in CNF/PVDF composites. The magnitude of negative permittivity could be precisely adjusted. Adjustable negative permittivity could be well explained by Drude model. The synergistic effect of both CNF and PVDF affected negative permittivity.