Percolation-Induced Epsilon-Near-Zero Response in Flexible Poly(vinylidene fluoride-hexafluoropropylene)/Acetylene Black Metacomposites

Epsilon-near-zero (ENZ) behavior in the radiofrequency (RF) regime remains challenging, particularly in flexible systems. Here, flexible poly(vinylidene fluoride-hexafluoropropylene)/acetylene black (P(VDF-HFP)/ACET) metacomposites were fabricated via solution casting followed by quenching to achieve a tunable RF ENZ response. By controlling ACET content, a percolation threshold at 5 wt % was identified, where an ENZ transition occurred near 166 MHz. Near this threshold, the ENZ behavior originates from the dielectric resonance associated with interfacial polarization and localized carrier oscillations. Above the percolation threshold, the formation of a continuous conductive network enables plasma oscillations of delocalized electrons, resulting in stable negative permittivity over a broad frequency range. Impedance and dielectric analyses reveal a capacitive-inductive crossover correlated with the ENZ transition. These results establish percolative polymer composites as scalable platforms for flexible RF ENZ materials for impedance matching and RF device applications.