Edge-Hydroxylated Boron Nitride Nanosheets for Simultaneous Improvement of Thermal and Mechanical Properties of Composite Films

With the rapid evolution of high-power electronics driven by advanced communication technologies and artificial intelligence, efficient thermal management has become a critical challenge. Hexagonal boron nitride (h-BN)/polymer composites, which integrate the flexibility of polymers with high thermal conductivity, low dielectric constant, and electrical insulation of inorganic fillers, are promising candidates for electronic packaging and communication systems. However, inefficient micro/nanoscale interfacial heat transport and weak interfacial bonding severely limit simultaneous improvements in thermal conductivity and mechanical robustness. Here, we demonstrate an edge-selective hydroxylation strategy that overcomes this limitation. Edge hydroxyl groups bridge the filler-matrix interface via hydrogen bonding interactions, markedly decreasing interfacial thermal resistance by 24.5%, while reducing the intrinsic thermal conductivity of BNNS by only 4.1%. Both molecular dynamics simulations and experimental results consistently show that the significantly enhanced interfacial coupling enables the edge-hydroxylated boron nitride nanosheets/polyvinyl alcohol (BNNS-OH/PVA) films to achieve a high in-plane thermal conductivity of 45.8 W m-1 K-1 and a tensile strength of 47.2 MPa, while maintaining low dielectric constant and loss for high electromagnetic wave transparency. These findings establish interfacial bridging as an effective route to simultaneously optimize heat transport and mechanical performance, offering a viable pathway for thermal management in next-generation high-power electronics and communication devices.