Embedded Films of Overlapping Graphene Sheets for Hardened and Electrically Conductive Polymer Surfaces

Abstract We report a one-step, scalable route to polymer films with an embedded, percolating layer of overlapping graphene sheets. Graphite is spread at a water/monomer interface, where it spontaneously exfoliates and self-assembles into a graphene film. Subsequent monomer polymerization locks the film near the polymer surface. Using styrene and methyl methacrylate (MMA), we show that monomer identity affects both the degree of exfoliation suggested by Raman 2D band analysis and the depth at which graphene sits beneath the polymer surface (∼2 Å for styrene, ∼7.5 Å for MMA), as predicted by potential-of-mean-force simulations. A crosslinker (divinylbenzene) is essential; without it, density-driven interfacial curvature during polymerization separates the graphene sheets, rendering the film insulating. With crosslinker, sheet resistance drops by orders of magnitude and PMMA/graphene films reach the static-dissipative regime with much lower variance than polystyrene/graphene films. Nanoindentation shows up to a 60% increase in surface hardness over pure polystyrene. The combination of a self-assembled, in situ deposition step, electrical conductivity, and surface hardening makes these coatings attractive for erosion and static-resistant surfaces.