▎ 摘　　要

To take full advantage of the potential of graphene nanosheets as reinforcing agents for polymer nanocomposites, good exfoliation, homogenous dispersion, and strong affinity of graphene nanosheets in a polymer matrix are needed. In this research, homogeneous dispersion of graphene nanosheets in epoxy is achieved via chemical functionalization of graphene oxide with 4-nitrobenzenediazonium salt. Optical microscopy and transmission electron microscopy demonstrate that graphene nanosheets are well exfoliated in organic solvents and in epoxy. While only a marginal increase in Young's modulus is observed, significant improvements in tensile strength (>30%) and elongation at break (>50%) for epoxy nanocomposites with a graphene concentration of 0.8 wt.% are achieved. The thermal conductivity of an epoxy nanocomposite with modified graphene nanosheets at 5 wt.% increases to 0.56 W/mK, approximately 2.5 times that of the neat epoxy. The possible mechanisms that account for the observed improvements in tensile properties and thermal conductivity are discussed. (C) 2017 Elsevier Ltd. All rights reserved.