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.

柔性介电材料在许多用于能量收集应用的电气/电子设备中是非常理想的，但它们通常会遇到高介电常数和大击穿强度的矛盾，从而降低整体储能容量和大填料负载的机械强度。在这项工作中，聚（甲基丙烯酸甲酯）（PMMA）刷改性石墨烯（rGO-g-PMMA）通过溶液浇铸法成功地引入到聚（偏二氟乙烯）（PVDF）基质中。PMMA 刷改性石墨烯一方面促进了石墨烯在 PVDF 基体中的分布，另一方面，它通过形成薄的绝缘 PMMA 层有效地限制了导电石墨烯的载流子泄漏。因此，rGO-g-PMMA/PVDF 薄膜的介电常数明显增加，而通过少量添加“核壳”（如 rGO-g-PMMA）可以明显抑制介电损耗。更重要的是，复合材料的击穿强度随着 rGO-g-PMMA 负载量增加至 0.2 wt% 而增加，同时 FGM-0.2 复合材料的能量密度比纯 PVDF 增加 157%。此外，由于 rGO-g-PMMA 在 PVDF 基质中的均匀分散和良好的界面粘附，所获得的 rGO-g-PMMA/PVDF 介电薄膜具有更高的热稳定性和机械强度。该研究为获得柔性、高强度、大储能介电薄膜提供了新的策略。伴随着 FGM-0.2 复合材料的能量密度比纯 PVDF 增加了 157%。此外，由于 rGO-g-PMMA 在 PVDF 基质中的均匀分散和良好的界面粘附，所获得的 rGO-g-PMMA/PVDF 介电薄膜具有更高的热稳定性和机械强度。该研究为获得柔性、高强度、大储能介电薄膜提供了新的策略。伴随着 FGM-0.2 复合材料的能量密度比纯 PVDF 增加了 157%。此外，由于 rGO-g-PMMA 在 PVDF 基质中的均匀分散和良好的界面粘附，所获得的 rGO-g-PMMA/PVDF 介电薄膜具有更高的热稳定性和机械强度。该研究为获得柔性、高强度、大储能介电薄膜提供了新的策略。