Dielectric polyimide composites with enhanced thermal conductivity and excellent electrical insulation properties by constructing 3D oriented heat transfer network

With the continuous development of electronic technology, polymer-based thermal management materials (TMMs) with insulation, high thermal conductivity (TC), and low dielectric performance are urgently needed for electronic devices. Nevertheless, balancing above expected properties is still a daunting challenge because of phonon scattering and interfacial polarization. Here we put forward a simple and useful method for preparing polyimide (PI) composites. First, the alignment of modified boron nitride nanosheet (MBN) along the fiber was controlled by electrospinning, while silver nanowire (AgNW) was utilized for electrostatic spraying to overlap the AgNW with MBN. Finally, a hybrid network oriented along the horizontal direction was formed by hot-pressing. The in-plane TC of the PI composites was up to 8.38 W/mK due to the formation of thermal conduction pathways along the hybrid network. The PI composites also had a series of merits, such as electrical insulation of over 2.40 × 1014 Ω cm, low dielectric constant (3.84), low dielectric loss (<0.01) at 106 Hz, excellent thermal stability (THRI = 299.3 °C), and heat dissipation capability. These PI composites with satisfactory comprehensive properties have great application potential in electronic devices, particularly in flexible electronic devices or circuits that demand electrical insulation and high TC.