▎ 摘　　要

Recently, graphene has attracted great research interest and produced superior properties for polymer composites at low filler content. However, the lowest filler content is limited because the graphene must provide enough conducting paths to substantially improve the thermal and electrical performances. In this study, three-dimensional interconnected graphene foam (GF) was prepared to overcome the limitation and GF filled poly (methyl methacrylate) (PMMA) composite was fabricated by an in situ polymerization method with an ultralow graphene content of 0.4 wt%. The thermal conductivity of GF/PMMA composite reaches 0.27 W m(-1) K-1 and the electrical conductivity achieves 3.5 x 10(-2) S m(-1), 50% and 8 orders of magnitude higher than that of pure PMMA, respectively. The local mechanical strength of composite is also enhanced by the addition of GF. Furthermore, the composite presents a superior performance in heat dissipation of high power devices and has a stable performance in thermal cycling test. This work provides a method to greatly improve the thermal, electrical and mechanical performances of graphene/polymer composites at an ultralow graphene content and proves that graphene foam filled poly(methyl methacrylate) composite is effective as a thermal interface material (TIM).