Carbon nanotube/polyvinylidene fluoride flexible composite material with low percolation threshold and adjustable negative permittivity

In the interdisciplinary fields of materials science, electromagnetics, and optics, the negative dielectric constant, as a unique physical property, is gradually attracting widespread attention from the academic and industrial communities. Materials with negative dielectric constant impose strict requirements on the value and flexibility of the negative dielectric constant in today's diverse development. In this study, a flexible carbon nanotube (CNTs)/polyvinylidene fluoride (PVDF) composite film with a low percolation threshold of negative dielectric constant was prepared using a casting method, with a percolation threshold of only 9 wt%. By varying the CNTs content, the intensity of both positive and negative dielectric constant responses can be tuned. The research revealed that the conduction mechanism involves both hopping conduction and metal-like conduction. Notably, at the CNTs content of 11 wt%, a negative dielectric constant was observed across the entire frequency range, showing a Drude-Lorentz-type dispersion. The composite materials with lower CNTs content exhibited dielectric loss primarily at low frequencies, while those with higher CNTs content showed dielectric loss across the full frequency range. This work demonstrates a cost-effective and straightforward approach for controlling negative dielectric constants, which holds promise for applications in electronic devices and electromagnetic shielding.