Enhanced Polarization in a Graphene/Poly(vinylidene fluoride-co-chlorotrifluoroethylene) Nanocomposite with a Hyperbranched Polyethylene-Grafted Poly(methyl methacrylate) Interface

Polymer dielectric materials of film capacitors have been investigated widely for advanced electronics and energy storage systems, in which high discharge energy density and low loss are the key parameters to motivate promising applications. Here, we tailored the miscible segments in a hyperbranched copolymer to suppress the charge carrier in the graphene/poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) nanocomposite with improved energy capability. The hyperbranched copolymer of polyethylene-grafted poly(methyl methacrylate) (HBPE-g-PMMA) was obtained via atom transfer radical polymerization (ATRP) and was then employed as a stabilizer to exfoliate graphene in chloroform. The copolymer was attached on nanosheets through CH−π noncovalent interconnections. The compatibility between graphene and the P(VDF-CTFE) matrix is improved because of the miscibility between PMMA segments and the fluoropolymer matrix. The dielectric constant of the 0.5 wt % nanocomposite is 18 at 102 Hz, and the energy density of the current nanocomposite is 3.3 J/cm3 at 250 MV/m with a charge–discharge efficiency of 64%, which is ascribed to the improved interfacial polarization in the presence of the HBPE-g-PMMA copolymer. The strong interaction at the interface restrains the diffusion activity and suppresses the loss during the electric field on–off cycle. This strategy provides a feasible route for the noncovalent functionalization of graphene in a flexible film capacitor with desirable energy storage capability.