Highly Ordered BN_⊥–BN_⊥ Stacking Structure for Improved Thermally Conductive Polymer Composites

The substantial heat generation in modern electronic devices is one of the major issues requiring efficient thermal management. This work demonstrates a novel concept for the design of thermally conducting networks inside a polymer matrix for the development of highly thermally conductive composites. Highly ordered hexagonal boron nitride (hBN) structures are obtained utilizing a freeze-casting method. These structures are then thermally sintered to get a continuous network of BN_⊥–BN_⊥ of high thermal conductivity in which a polymer matrix can be impregnated, enabling a directional and thermally conducting composite. The highest achieved thermal conductivity (K) is 4.38 W m⁻¹ K⁻¹ with a BN loading of 32 vol%. The effect of sintering temperatures on the K of the composite is investigated to optimize connectivity and thermal pathways while maintaining an open structure (porosity ≈ 2.7%). The composites also maintain good electrical insulation (volume resistivity ≈ 10¹⁴ Ω cm). This new approach of thermally sintering BN_⊥–BN_⊥ aligned structures opens up a new avenue for the design and preparation of filler alignment in polymer-based composites for improving the thermal conductivity while maintaining high electrical resistance, which is a topic of interest in electronic packaging and power electronics applications.