Fabrication of high dielectric permittivity polymer composites by architecting aligned micro-enhanced-zones of ultralow content graphene using electric fields

High dielectric permittivity flexible composites have long been desired for enhancing the performance of embedded capacitors. One of the most promising approaches to improve the dielectric permittivity of flexible polymer is the addition of fillers with specific nanostructures. Previous reports revealed that nanocomposites with aligned 10 wt% barium titanate particles showed substantially enhanced dielectric permittivity in the thickness direction. Herein, one facile strategy toward ultralow addition of graphene (≤1‰) to architect Micro-Enhanced-Zones in poly(dimethylsiloxane) (PDMS) induced by an external alternating-current (AC) electric field is presented. The dielectric permittivity of graphene/PDMS was dramatically enhanced as compared to those of the nanocomposites containing the same particle loading without Micro-Enhanced-Zones formed by electrical field. With only 0.5 wt‰ graphene loading, 8 times higher dielectric permittivity was achieved at 10−2 Hz after Micro-Enhanced-Zones formed by electrical field. As the graphene loading increases to 1 wt‰, the nanocomposites with Micro-Enhanced-Zones inside exhibit dielectric permittivity as high as 59.7 at 10−2 Hz, which is 18 times the dielectric permittivity of the nanocomposites containing the same loading with graphene randomly dispersed. The effect of different micromorphology of Micro-Enhanced-Zones on dielectric permittivity and dielectric loss were discussed. The more order pattern formed, the higher dielectric permittivity achieved, and the dielectric loss is more sensitive to high frequency. The kinetics and formation of Micro-Enhanced-Zones of graphene is studied by optical microscope and scanning electron microscope during electric field application. It was demonstrated that this facile strategy of applying an AC electric field can be a very effective approach for tailoring the dielectric permittivity of polymer composite for more specific use by architecting different micromorphology.