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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.

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Currently, a growing number of biomaterials have been evaluated to be beneficial to the application of neural tissue engineering. However, their deficient mechanical and electrical properties limit their further application, especially for nerve regeneration. Therefore, the combination of biological matrix and conductive materials has been applied to meet the requirements for nerve tissue engineering. In this work, conductive collagen (COL)/multiwalled carbon nanotube (MWNT) composite films with different MWNT concentrations were developed by the solvent–evaporation method. The effects of rigid MWNT on the structure, mechanical, thermal, and electrical properties of the flexible COL-based film were evaluated. The evaluation of mechanical properties revealed that the tensile strength of the COL/MWNT composite films was almost eight times as high as that of the pure COL film. The electrical property assessment demonstrated that the electrical conductivity of COL/MWNT-0.25% reached 0.45 S/cm, meeting the electrical stimulation conditions required for nerve growth. Furthermore, the cell viability assays revealed that the COL/MWNT composite films were non-cytotoxic and appropriate for cell growth. Our work proved that the conductive COL/MWNT composite films exhibited great potential for nerve tissue engineering application, which provided a novel self-electrical stimulated platform for the treatment of neural injuries.