Boron nitride–Ag NWs/polyvinyl alcohol films with high thermal conductivity and excellent mechanical properties prepared via air/water interfacial assembly†

The construction of heat transfer channels based on highly thermally conductive fillers in a polymer matrix is important for improving the thermal conductivity of thermal management materials (TMMs). However, owing to the inhomogeneity of filler distribution and the limitation of the mechanical properties of polymers, it is a great challenge to achieve both high thermal conductivity and excellent mechanical properties. In this work, a simple air/water interfacial (AWI) assembly was implemented for the preparation of boron nitride–silver nanowires/polyvinyl alcohol (BN–Ag NWs/PVA) films. BN–Ag NW hybrid fillers were obtained through the ultrasonic treatment of amino-functionalized BN flakes with an Ag NW solution, followed by drying. BN–Ag NWs/PVA composite films were prepared via AWI assembly on the surface of a saturated sodium sulphate solution based on the salting-out effect. BN flakes tended to be oriented and aligned along the in-plane direction, and Ag NWs could bridge different BN flakes to form thermal conductivity pathways. The in-plane thermal conductivity of the BN–Ag NWs/PVA film was 1.24 W m⁻¹ K⁻¹ at a filler content of 25 wt%, which was about 4.8 times higher than that of a pure PVA film. Meanwhile, the tensile strength of the BN–Ag NWs/PVA film could reach 54.3 MPa owing to the regular distribution of hybrid fillers. The simultaneous improvement of thermal conductivity and mechanical properties was beneficial for the practical application of BN–Ag NWs/PVA films.