Microwave‐Assisted Fabrication of Point‐to‐Plane Bridged Graphene/Copper Hybrid Fillers for High‐Performance Thermal Conductive Polymer Composites

ABSTRACT With the rapid development of hypersonic vehicles and high‐power electronics, lightweight materials with efficient heat dissipation are urgently required. Herein, we propose a microwave‐assisted in situ synthesis strategy that enables the rapid and high‐quality reduction of graphene precursors while simultaneously anchoring of copper nanoparticles onto microwave reduced graphene oxide (mrGO) within an ultrashort reaction time, thereby constructing structurally integrated mrGO‐copper (mrGO@Cu) hybrid thermally conductive fillers. Benefiting from the rapid heating characteristics of microwaves and their selective interfacial coupling effect, this strategy facilitates the formation of a Cu‐graphene interface, thereby enhancing interfacial phonon coupling and phonon‐mediated heat transport. At a low filler loading of only 5 wt.%, the unique point‐to‐plane bridging architecture constructs an effective and continuous thermally conductive network in the epoxy matrix and reduces the interfacial thermal resistance between fillers. Consequently, the composite exhibits a thermal conductivity of 2.63 W·m − 1 ·K − 1 with an effective thermal conductivity enhancement efficiency (TCEF) approaching 208%, while reducing the hotspot temperature of a light‐emitting diode (LED) by 18.4°C. This work provides a rapid, scalable, and effective strategy for the fabrication of graphene‐based thermally conductive fillers and offers a promising route toward the lightweight design of polymer materials for efficient thermal management.