How graphene crumples are stabilized?

Forced crumpling of graphene and graphene oxides sheets and their reversibilities are explored here by performing molecular dynamics (MD) simulations, with focus on the stabilizing mechanisms and properties of crumples. We find that to balance strain energy stored in crumpled sheets, dangling bonds in graphene show significant chemical activity in forming covalent crosslinks. Interlayer van der Waals cohesion helps also to maintain the crumpled conformation after the compressive load is released. A distinct size-dependent behavior of the process is observed, implying competition between these driven forces. These results suggest possibilities in controlling the reversibility in crumpling graphene sheets into nanoparticles and highlight the effects of chemically active graphene edges, defective sites, van der Waals and hydrogen-bond cohesion in defining microstructures of graphene-based materials.