Effect of defect-healing in graphene nanosheets on the mechanical properties of polyimide nanocomposites

We report an effective method for fabricating graphene-based multifunctional polyimide (PI) nanocomposites via in situ polymerization, by the chemical defect-healing of pyridine functionalized reduced graphene oxide (H-Py-RGO). H-Py-RGO was successfully obtained through intramolecular cross-dehydrogenative coupling (ICDC). The mechanical properties, and thermal stability of the PI/H-Py-RGO nanocomposites were significantly improved compared with those of pristine PI film due to the restoration of the defect sites on the graphene surface, and the resulting high compatibility between the H-Py-RGO and the PI matrix. The tensile strength and modulus of the PI/H-Py-RGO nanocomposites with 1 wt% of added H-Py-RGO were increased by about 598% (883.5 MPa) and 535% (39.4 GPa) compared to those of pristine PI, respectively. Furthermore, 5 wt% H-Py-RGO loading resulted in a 91% reduction in the coefficient of thermal expansion (CTE) of the PI/H-Py-RGO nanocomposite.