Interfacial insight into elevated dielectric properties in graphite nanosheets reinforced PVDF composites via engineering TiO2 shell as an interlayer

Percolating composites present giant dielectric constant (ε′) at the critical filler loading (fc), whereas the accompanied undesirable high loss and leakage current significantly limit their wide applications owing to the deteriorated breakdown strength (Eb). To prohibit the unwished large loss and leakage current of the graphite nanosheets (GNS)/poly(vinylidene fluoride, PVDF) while still keeping a high ε′, the titanium dioxide (TiO2) encapsulated GNS, i.e., GNS@TiO2, were first obtained in this study via a sol-gel technology, and then composited with PVDF to explore the TiO2 shell’s impact and modulation effect on the dielectric properties of the nanocomposites. The findings on the relationship between structure and dielectric parameters reveal that the presence of a TiO2 interlayer not only strengthens the interface interactions, but also remarkably relieves the pronounced interfacial mismatch in both ε′ and electric conductivity between the filler and host matrix, thus leading to boosted Eb of the nanocomposites. Moreover, the dielectric loss and conductivity of the nanocomposites can be significantly suppressed and reduced to rather low levels because of the introduced deep traps resulting from the interlayer frustrating the long-distance electron migration. And the integrated dielectric properties of the GNS@TiO2/PVDF can be effectively regulated by adjusting the GNS@TiO2’s electric resistivity and optimizing the TiO2 shell thickness. This work offers a beneficial strategy for the design of percolating nanodielectrics with high εr and Eb but suppressed loss for prospective applications in microelectronic devices and power equipment.