Swelling of Composite Graphene/Polymer Foams*

Composite graphene/polymer foams, made through templated polymerization of the continuous monomer phase in graphene stabilized monomer/water emulsions, have unique solvent selectivity and displays electrical conductivity that is sensitive to deformation. We use a combination of the experimental techniques and coarse-grained molecular dynamics simulations to elucidate factors influencing foam selectivity and dynamics of the swelling process. In particular, we have studied swelling ability of the composite graphene poly(butyl acrylate) foams in 17 different solvents. Analysis of the swelling data shows direct correlation between solubility parameter and degree of the foam swelling. The equilibrium swelling ratio of the foam changes with the degree of crosslinking as expected for swelling of the polymer networks in selective solvents. MD simulations of the composite graphene/polymer foams indicate that the capillary forces first drive the liquid to fill up the foam cells which is followed by swelling of the surrounding polymer network. This swelling process changes overlap between graphene sheets coating the foam cell. This rearrangement of sheets manifests itself in change of the foam conductivity upon swelling.