AgNFs/PVDF Composites With Adjustable Negative Permittivity Toward Electromagnetic Shielding at Radio Frequency

According to the Hagen–Rubens relationship, negative permittivity is an intrinsic characteristic of metals at optical frequencies. However, in the radio frequency, metals typically exhibit conductive properties rather than a plasma state, and negative permittivity inherently faces challenges at low frequencies. In this study, polyvinylidene fluoride (PVDF) matrix percolation composites filled with silver nanoflowers (AgNFs) were fabricated via a hot‐pressing process, which induced the α‐phase to β‐phase transformation of the PVDF matrix as confirmed by XRD and FTIR. The microstructure and interfacial characteristics were systematically characterized by SEM and TEM. The percolation threshold was determined to be approximately 46.98 wt% through conductivity analysis, and the formation of the conductive network was directly visualized by cross‐sectional SEM and COMSOL simulations. Above the percolation threshold, benefiting from the enhanced dipolar polarization of β‐phase PVDF and abundant heterogeneous interfaces, the composites exhibited a low negative permittivity (approximately −26.42) at 1 MHz. Furthermore, COMSOL simulations demonstrate that the shielding performance gradually improves as the permittivity decreases, especially after it turns negative, highlighting the application prospects of negative permittivity materials for radio‐frequency electromagnetic shielding and their promise as a guiding parameter for EMI shielding design.