Composites with aligned and plasma-surface-modified graphene nanoplatelets and high dielectric constants

•A method is developed for the design of high dielectric constant polymer and graphene nanoplatelet (GNP) composites.•The GNPs are dispersed and aligned by plasma surface modification and application of an electric field.•The composite shows high dielectric constant over a wide range of GNP contents. We have developed a method for designing polymer and graphene nanoplatelet (GNP) composites that show high dielectric constants over a wide range of GNP contents. GNPs are dispersed in the composites through plasma-surface modification and aligned by applying an electric field (EF). This creates a large number of microcapacitor structures of GNPs separated by the polymer. The maximum dielectric constant of the sample to which the EF is applied is approximately twice that of the sample to which the EF is not applied. Furthermore, the maximum dielectric constants of the samples with plasma-surface modified GNPs are higher than those of the samples with unmodified GNPs. The composites show high dielectric constants (∼500 at 100 Hz) over a wide range of GNP contents (6 ∼ 10 wt%) while maintaining mechanical flexibility (Young’s modulus:12 ± 4 MPa).