High-Loading Boron Nitride-Based Bio-Inspired Paper with Plastic-like Ductility and Metal-like Thermal Conductivity.

Although desirable in next-generation flexible electronics, fabricating hybrid film materials with excellent integration of mechanical and thermally conductive yet electrically insulating properties is still a challenge. In mollusk nacre, a small volume of the chitin nanofiber framework hosts 95 vol % CaCO3 microplatelets, enabling the high-loading natural composites to exhibit a ductile deformation behavior. Inspired by this, we fabricate a large-area, boron nitride-based bio-inspired paper using a facile sol-gel-film conversion approach, in which BN microplatelets with a loading of 40-80 wt % are embedded into a 3D poly(p-phenylene benzobisoxazole) nanofiber framework. Because of the vital role of the 3D nanofiber framework, the BN-based paper exhibits plastic-like ductility (38-80%), ultrahigh toughness (10-100 MJ m-3), and good folding endurance. The high-loading BN platelets form an oriented, percolative network and endow the paper with outstanding in-plane thermal conductivity (77.1-214.2 W m-1 K-1) comparable to that of some metals, such as aluminum alloys (108-230 W m-1 K-1). Using the electrically insulating BN-based paper as a flexible substrate, we demonstrate its promising application for lowering the temperature of electronic devices.