Self-networking of graphene in epoxy resin based on thermal induced dynamic chemical network

Graphene is widely incorporated into thermosetting resins as a nanofiller to improve the conductive performance of resins for its excellent electrical conductivity. However, the effective dispersion of graphene and the construction of conductive percolation networks in resin matrices cannot be easily achieved due to the strong tendency of graphene to agglomerate and the decreased chain mobility of thermosetting resins during curing. Herein, a conductive DA-epoxy/graphene nanocomposite was prepared with graphene as nanofiller and epoxy resin vitrimer based on dynamic Diels-Alder bond (DA-epoxy) as matrix. The reversible transition of vitrimer from crosslinked networks to uncrosslinked molecular segments under heat treatment enhanced the mobility of both graphene and the epoxy molecular segment, which consequently induced the "self-networking" of graphene to form a conductive percolation network. In the case of DA-epoxy/graphene nanocomposites with 1 wt% graphene contents, the electrical conductivity increased exponentially from 10−5 S/m before heat treatment to 10−1 S/m after heat treatment. More interestingly, by taking advantage of the in-situ photothermal conversion of graphene, the formation of conductive percolation networks could be regionally controlled under near infrared light irradiation. Thus, the DA-epoxy/graphene nanocomposites with enhanced mechanical properties and electrical conductivity were facilely prepared without any chemical modifications to graphene.