▎ 摘　　要

Graphene/polymer nanocomposites (GPNCs) have gained intense research interest in recent years. Graphene can improve the properties of the nanocomposites at low loadings, but usually causes sudden drops in the mechanical properties of the nanocomposites at similarly low loadings, risking the performance, reproducibility, and batch stability of the nanocomposites. This problem has been troubling the GPNCs field for years, but it is difficult to solve mainly because the mechanism of the sudden mechanical property drops has not been well documented yet. Here, we present a systematic study on this problem. At first, a statistical study was made to provide an overview of the sudden mechanical property drops. It was found that the sudden mechanical property drops were almost independent of the surface modification of graphene, and the in situ polymerization method sometimes leads to lower critical concentration than the solvent blending and melt blending methods. Then, we demonstrated a cutting-off mechanism which unveiled that the formation of a continuous or semicontinuous network of graphene throughout the polymeric matrix was the main cause of the sudden mechanical property drops, and the low critical concentration of the sudden mechanical property drops was mainly due to the large aspect ratio of graphene. Finally, future research prospects were proposed. Overall, our work has provided new understandings and insights to the mechanical properties of GPNCs.