Core-shell structured tungsten carbide / polypyrrole metacomposites with tailorable negative permittivity at the radio frequency

Metacomposites which unveil weakly negative permittivity have been regarded as a promising candidate for next-generation electronics. We propose to prepare such metacomposites by developing the core-shell structured WC/PPy composites. The regulation of properties, including reactance, conductivity, and permittivity, has been achieved by controlling the mass ratio of WC in the WC/PPy composite. Conductive networks are constructed when the WC fraction is increased to a certain level, leading to a weakly negative permittivity, which is related to the plasma oscillation of free electrons . Owing to Lorentz dielectric resonance, a frequency-regulated negative permittivity is also realized, which provides an alternative strategy to obtain negative permittivity. This work will push forward further research and applications of metacomposites.