High dielectric constant and low loss in poly(fluorovinylidene-co-hexafluoropropylene) nanocomposite incorporated with liquid-exfoliated oriented graphene with assistance of hyperbranched polyethylene

Abstract

It is significantly attractive to the development of flexible impulse capacitor with large energy density and charge-discharge efficiency, which is associated with dielectric property of polymer film. The fabrication of polymer dielectrics combining high dielectric constant and low loss is still challenge for now. Here we demonstrate that the dielectric property is enhanced greatly in P(VDF-HFP) nanocomposite incorporated with few-layer graphene, which is exfoliated with assistance of HBPE based on CH-π stacking. The graphene/P(VDF-HFP) nanocomposite was prepared by simple solution casting, and then the arrayed nanosheets was accomplished via uniaxial stretching. The effect of oriented graphene on the conversion of electroactive phase and dielectric property has been investigated systematically. High dielectric performance is obtained in stretched nanocomposite due to the formation of micro-capacitor and large content of electroactive phase, which is attributed to the electrostatic force between matrix and modifier of graphene during the macromolecular re-arrangement. The dielectric constant reaches maximum of 34.2 with low loss as 0.015 at 100 Hz when the orientation angle is 34°. The distribution of graphene is evidenced by the SEM results, which is induced by the combination of viscoelasticity nature in P(VDF-HFP) and the strong interaction with HBPE. The motion of nanosheets is modeled using modified Jeffery equation, and fits well with the experimental SEM images of the graphene/P(VDF-HFP) nanocomposites. This work presents a universal strategy to achieve the tuned orientation of nanosheets and new insight on the mechanism for the improvement of dielectric property in polymer dielectric nanocomposite.