Polymer composites filled with core-shell structured nanofillers: effects of shell thickness on dielectric and thermal properties of composites

In this study, we explore poly(vinylidene fluoride) (PVDF) filled with the core-shell nanofillers of silicon dioxide-coated beta-silicon carbide whisker (beta-SiCw@SiO2), and investigate the effects of core-shell structure and shell thickness on the composite thermal and dielectric properties. The formation of an insulating SiO2 layer can not only substantially reduce the dielectric loss of polymer composites but also suppress their dielectric constant (k). Further increasing shell thickness continues inhibiting the dielectric loss while rendering the k nearly unaffected. We attribute the underlying mechanism to the different effects of shell thickness on long-range and short-range charge migration. In addition to the constraint on charge transport, the SiO2 shell improves the filler-polymer interfacial compatibility and therefore leads to a large improvement in the thermal conductivity (TC) of the composites. The synthesized core-shell fillers afford high k and enhanced TC as well as low loss in the composites, which would enable a wide range of applications in dielectric and electrical fields.