Coordination-Assembled Liquid Metal–Carbon Dot Nanofillers Improve Thermal Conductivity and Fire Safety of Epoxy Adhesives

In the era of high-power electronics, simultaneously achieving efficient heat dissipation, mechanical robustness, and reduced fire hazard is highly desirable for epoxy-based bonding and encapsulation materials. Herein, coordination-assembled liquid metal/carbon dot hybrid fillers (LM@CD) were successfully fabricated via a coordination-driven interfacial assembly strategy. Specifically, N, B, and P codoped carbon dots (CDs) act as interfacial linkers to anchor onto the liquid metal (LM) surface and improve the dispersion stability and functional utilization of LM in the epoxy matrix. Benefiting from this interfacial design, the optimized composite achieves a thermal conductivity of 1.90 W·m –1 ·K –1 at a total filler loading of 70 wt %, representing a 728.82% increase over neat epoxy and significantly outperforming the CD-only control composite (0.52 W·m –1 ·K –1 ), while maintaining a relatively low density of 1.51 g·cm –3 and improved overall mechanical performance. In addition, although the increase in limiting oxygen index is limited, the LM-containing composites exhibit markedly reduced heat release and form a more continuous and graphitized protective char structure, indicating a predominantly condensed-phase fire-hazard-reduction mechanism. The composite achieves a UL-94 vertical burning V-0 rating. This work provides an interfacial design strategy for multifunctional epoxy composites intended for thermal-management bonding/encapsulation applications requiring balanced thermal transport, mechanical integrity, and fire safety.