The fabrication and dielectric properties of a novel multi-component high-k composite system consisting of poly(vinylidene fluoride), surface-functionalized graphene nanosheets and BT nanoparticles (fRGO–BT/PVDF) were investigated. The fRGO nanosheets were prepared through the π–π stacking of polyaniline and GO following in situ hydrazine reduction. The fRGO–BT/PVDF nanocomposites were fabricated by a solution casting and hot-pressing approach. SEM results confirm that fRGO and BT are well dispersed within the PVDF matrix. The dielectric properties of the binary fRGO/PVDF nanocomposites exhibit a typical percolation transition with the percolation threshold of 1.49 vol%. This type of nanocomposite, co-filled with conductive graphene nanosheets and high-k ceramics, shows a high k_r (65) and a relatively low dielectric loss (tan δ = 0.35) at a high frequency of 1 MHz. Meanwhile, the dielectric properties of the fRGO–BT/PVDF nanocomposites show temperature independent behavior over a wide temperature range. These flexible, high-k fRGO–BT/PVDF nanocomposites are potential flexible dielectric materials for use in high-frequency capacitors and electronic devices.

Piezoresistive nanocomposites using alkyl-functionalized graphene (G-ODA) as a conducting filler and polydimethylsilicone (PDMS) as the polymer matrix were prepared and their piezoresistivity behavior was investigated. One-pot synthesis of G-ODA from graphite oxide and octadecylamine improved its dispersion in nonpolar xylene and PDMS with low surface free energy. Results show that the graphene nanosheets were homogeneously dispersed in the PDMS matrix and an ultra-low percolation threshold (0.63 vol%) of the composites was obtained. The G-ODA/PDMS composites with 1.19 vol% content of G-ODA show a remarkable positive piezoresistivity of high sensitivity (R/R₀ > 400 under the pressure of 1.2 MPa), excellent repeatability, small hysteresis, and long-term durability. Under uniaxial compression, the resistance of the composites exponentially increased with the pressure. The resistance–pressure curves remain nearly unchanged after 1000 loading–unloading cycles. The results suggest that the G-ODA/PDMS nanocomposites provide a new route toward fabrication of soft piezoresistive sensors with high performance.