Macromolecules, Vol.52, No.19, 7379-7385, 2019
Electrical Conductivity of Graphene-Polymer Composite Foams: A Computational Study
We use a combination of the coarse-grained molecular dynamics simulations and finite difference method calculations to study electromechanical coupling in composite polymer/graphene foams. In these foams, graphene sheets (G-sheets) cover the surface of the foam cells resulting in a percolating network of graphene sheets. Our simulations have shown that upon uniaxial deformation or under foam swelling conditions, the percolating network of the G-sheets breaks down. This breakdown is manifested as an increase of the foam's electrical resistance. The disruption of the graphene networks occurs through crack formation of the G-shells covering the surfaces of the polymeric foam cells. These cracks are responsible for the hysteresis in electromechanical foam properties observed during loading-unloading cycles. In particular, for uniaxial foam deformations, it requires the application of a compressive stress for the foam to retain its initial dimensions. Comparison between uniaxial and swelling foam deformations shows that there is a stronger variation in the foam resistance under uniaxial deformation conditions.