Proton conduction induced weak negative permittivity and low frequency dispersion in activated carbon felt-polyaniline metacomposites

High negative permittivity of most metacomposites has significant limitations for various applications, so design of novel metacomposites with weakly negative dielectric constants still is a critical challenge. In this work, activated carbon felt-polyaniline (ACF-PANI) metacomposites with high compressibility have been prepared through in-situ polymerization of PANI on ACF, and the effect of PANI polymerization on the dielectric properties of the ACF-PANI metacomposites has been investigated. Adjusting the in-situ polymerization time can precisely control the loading of PANI on ACF, thereby achieving controllable negative permittivity. By optimizing the polymerization time to 240 min, we have successfully achieved a weak negative permittivity of approximately −30 from 50 kHz to 1 MHz, and the dispersion of ACF-PANI 240 is only 26. This is attributed to the unique protonic conduction of PANI, which dilutes the carrier concentration in the metacomposite material and enhances the carrier mass, thereby suppressing plasma the oscillations. Moreover, the negative permittivity of the compressible ACF-PANI metacomposites could be dynamically tuned based on its deformation, and the change in negative permittivity (Δε’/ε’) exhibits a clear linear correlation with the strain. This work provides a novel approach for the fabrication of low frequency dispersion and weak negative permittivity metacomposites.