▎ 摘　　要

Incorporating graphene into epoxy composites is a facile strategy to improve their mechanical performances. However, the uniform and reliable dispersion of graphene within epoxy matrix remains a large challenge owing to the intrinsic difference in chemical properties. Here, pyrene-functionalized polyethylene glycol (Py-PEG-Py) was easily synthesized and utilized as a dispersant to homogenize graphene. The effect of graphene loading on mechanical performances of reinforced epoxy composites was also investigated. As 0.01 to 0.05 wt% of graphene were incorporated in epoxy resin, the resulted composites exhibited excellent improvement in flexural strength and fracture toughness compared with neat epoxy. Typically, the flexural strength increased from 63.57 +/- 1.5 MPa for neat epoxy to 108.36 +/- 1.9 MPa (about 70.5%) for composite, and the fracture toughness (K-IC) increased from 1.25 MPa m(1/2) for neat epoxy to 2.15 MPa m(1/2) (around 72%) for composite modified with only 0.04 wt% of graphene and 4 wt% of Py-PEG-Py. Crack pinning caused by well dispersed graphene was contributed to enhancement of the fracture toughness. This work reveals a tiny amount graphene can also largely improve the mechanical properties of composites, providing a feasible approach to disperse graphene and fabricate high performance graphene composites.