PMMA brush-modified graphene for flexible energy storage PVDF dielectric films

Flexible dielectric materials are highly desirable in many electric/electronic devices for energy harvesting applications, but they usually suffer from the paradox of high dielectric constant and large breakdown strength , thereby reducing the overall energy storage capacity and mechanical strength with large filler loadings. In this work, poly(methyl methacrylate) (PMMA) brush-modified graphene (rGO-g-PMMA) was successfully introduced into poly(vinylidene fluoride) (PVDF) matrix via solution casting method. The PMMA brush-modified graphene for one thing promoted graphene distribution in the PVDF matrix, for another, it effectively limited carrier leakage of conductive graphene by forming a thin insulating PMMA layer. Therefore, the dielectric constant of rGO-g-PMMA/PVDF films was obviously increased, while the dielectric loss was distinctly suppressed with a small addition of the “core-shell” like rGO-g-PMMA. What's more, the breakdown strength of composites increased with rGO-g-PMMA loadings up to 0.2 wt%, accompanied by a 157% increase in energy density of FGM-0.2 composite to that of neat PVDF. In addition, the obtained rGO-g-PMMA/PVDF dielectric films possessed improved thermal stability and mechanical strength due to the homogeneous dispersion and good interfacial adhesion of rGO-g-PMMA within PVDF matrix. Such study provided a new strategy in obtaining flexible, high strength and large energy storage dielectric films.