The combination of π-π interaction and covalent bonding can synergistically strengthen the flexible electrical insulating nanocomposites with well adhesive properties and thermal conductivity

Adding thermal conductive filler is an effective method to improve the thermal conductivity of polymer matrix. In this research, we demonstrated that the polymer composites with much improved thermal conductivity while maintaining low electrical conductivity, which could be achieved via using hybrid 2D stacked filler and controlling the alignment of the filler in polymer matrix. In order to do this, the graphene oxide (GO) was prepared and simultaneously reduced/functionalized by diethylenetriamine (DETA) to obtain NH2-functionalized graphene (NfG) which designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via pi-pi stacking interaction. In this situation, since the NfG sheets were fixed on the surface of h-BN, the NfG sheets were well separated from each other and participated in the resin curing process. Hence, not only significantly enhanced thermal conductivity (similar to 3.409 W/m.K, in-plane direction) was obtained, but also a very low electrical conductivity was achieved. The low electrical conductivity was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated NfG sheets via pi-pi stacking interaction. In addition, the nanocomposites also exhibited good thermal stability and adhesive properties. We believed that this special structure will provide a new thought for fabricating thermal interface materials (TIMs) with much high thermal conductivity as well as low electrical conductivity. (C) 2017 Published by Elsevier Ltd.