Graphene Oxide–Epoxy Composites with Induced Anisotropy of Electrical Properties

At present day, the actual physics behind the polarization mechanism in composite materials remains elusive. In this study, we introduce graphene oxide sheets, decorated with iron oxide nanoparticles (GO-IONP), into epoxy resin, and orient them unidirectionally by using an external magnetic field. The GO-IONP sheets are oriented perpendicular to the magnetic field lines. The as-prepared epoxy/GO-IONP composites possess well-pronounced anisotropy in electric properties: at 0.4% GO, in the direction perpendicular to the GO-IONP planes, permittivity augmentation reaches the value of 17.8, while in the other two orthogonal directions it is ∼6.8. The attained permittivity values at the 0.1–0.4% GO content are the highest ever reported for the epoxy matrix/graphenic filler systems. Such characteristics are due to the fully uniform structure of the composites, where the filler with atomic thickness does not form a distinct phase. The material can be considered as a system, comprising a series of orderly arranged microcapacitors, with the "plates" of atomic thickness, but of a micron-scale lateral size. The data demonstrates that the charge can be stored on a capacitor with the "plates", lacking one dimension. The physics behind electrical conductivity of the composite materials is defined as the interfacial polarization. The developed protocol opens the doors for fabricating anisotropic materials, films, and coatings, which are highly desirable for antennas, radars, vibration sensors, dielectric lenses, etc.