Size-dependent structural behaviors of crumpled graphene sheets

Abstract

Understanding the complex structural behaviors of crumpled graphene at a fundamental level is of critical importance in various engineering and technological applications. Here, we present a coarse-grained molecular dynamics (CG-MD) study for investigating structural behaviors of graphene sheets having varying sizes (or masses) during the crumpling process. The simulation results reveal that larger size graphene sheets at the initial two-dimension (2D) state tends to become more self-adhering and self-folding upon crumpling compared to the smaller ones, before forming a sphere-like highly crumpled structure. The fractal dimension of the crumpled graphene sheets, i.e., a measure of packing efficiency, is predicted to be D=2.395 from our CG modeling, which is largely consistent with previous measurements. Remarkably, the size-dependence of various structural properties of the crumpled graphene sheets, including radius of gyration, hydrodynamic radius, and viscosity radius, can be quantitively described by the power-law scaling relationships during the crumpling process. By systematically evaluating shape descriptors, it is found that the overall crumpling behaviors of graphene sheets can be characterized by three different regimes (i.e., less, intermediate, and highly crumpled states), which are associated with edge-bending, self-adhesion, and further compression mechanisms, respectively. Our study provides fundamental insights into the size-dependent structural behavior of graphene sheets under crumpling, which is crucial to develop the structure-property relationships towards designing and engineering crumpled matter.