Polydopamine coating layer on graphene for suppressing loss tangent and enhancing dielectric constant of poly(vinylidene fluoride)/graphene composites

Graphene with polydopamine (PDA) coating layer which displays promoted dispersibility in organic solvent was prepared through self-polymerization of dopamine onto graphene oxide (GO) and subsequent chemical reduction. The PDA coated reduced GO (RDGO) is homogeneously incorporated into poly(vinylidene fluoride) (PVDF) matrix, which exhibit a percolation threshold at 0.643wt%. The dielectric constant of PVDF with 0.70wt% RDGO increases to 176, about 17 times of neat PVDF. Importantly, the loss tangent is suppressed to 0.337 due to reduction of the concentration and mobility of ionizable carboxylic groups by PDA. The enhancement of dielectric constant probably rises from duplex interfacial polarization induced by graphene–semiconductor interface, and semiconductor–insulator interface. The composites displays advantages in excellent dielectric properties and good flexibility and processability guaranteed by low loading of RDGO, which is suitable for the development of dielectric materials for energy storage.