Coarse-grained potentials to perform large scale molecular dynamics simulations of graphene sheets self-assembling at the water-oil interface

Water-oil interfaces provide excellent templates to synthesize networks of graphene flakes, only up to a few layers thick. To simulate and study such systems using particle based simulations, we derive force-fields for particle-liquid interactions relying on the wetting coefficient (ω) as the parameter to provide the criterion. Using molecular dynamics, we simulate a composite system containing water-n-hexane interface and a graphene sheet at various values of ω to evaluate the boundaries for which the particle adsorbs at the interface. At the two resolutions studied (atomistic and coarse-grained) we observe that the boundaries for values of ω that allow monolayer graphene to adsorb at the interface are very consistent with the predictions made for thick macroscopic particles. We confirm our results by evaluating potentials of mean force of the system as a function of the particle’s separation from the interface. Further, we illustrate the applicability of method by simulating a relatively large water-oil interface with many graphene particles adsorbing at the interface using the derived coarse-grained model. The method might find applications in multi-scale modeling of polymer nanocomposites where a great deal of solid-liquid interface is to be modelled accurately.