Mechanically Strong and Flame-Retardant PBO/BN/MXene Nanocomposite Paper with Low Thermal Expansion Coefficient, for Efficient EMI Shielding and Heat Dissipation

As portable and wearable electronic devices are rapidly developing, there is an urgent need for flexible and robust thermally conductive electromagnetic interference shielding materials to address the associated electromagnetic pollution and overheating issues. Herein, multifunctional poly(p-phenyl-2,6-phenylene bisoxazole) nanofiber/boron nitride nanosheet/Ti3C2Tx MXene nanosheet (PBO/BN/MXene) composite papers are prepared by a gel microparticle-mediated ordered assembly process with the aid of vacuum-assisted filtration. Nacre-like "brick and mortar" structure, segregated structure and sandwich structure are integrated into the composite paper, so that efficient thermally and electrically conductive networks have been established. When the BN and MXene contents are 29.2 wt% and 41.7 wt%, the 13 mu m thick composite paper exhibits an EMI shielding performance of 31.8 dB and a thermal conductivity of 26.1 W/mK, markedly superior to those of the control samples without the ordered structures. Meanwhile, because of the unique architecture and inherent advantages of the building blocks, the composite paper exhibits extremely low coefficient of thermal expansion (similar to 1.43 ppm/K), excellent mechanical properties, and outstanding thermal stability and flame retardance, making it highly advantageous for practical applications in electronic devices. This work offers a promising approach for fabricating high-performance multifunctional composites by constructing efficient filler networks.