Poly( <i>p</i> -phenylene benzobisoxazole) Nanofiber-Bridged Hexagonal Boron Nitride Microsheets as Thermally Conductive Flame-Retardant Films

The rapid advancement of high-power integrated electronics has generated an urgent demand for high-performance thermal management materials. Hexagonal boron nitride (h-BN) has been widely explored for efficient thermal management. However, voids within the h-BN films compromise their thermal conduction and mechanical performance. Herein, we employed poly(p-phenylene benzobisoxazole) nanofiber (PBONF) as a polymer matrix to bridge unmodified h-BN microsheets. Highly compact nacre-like structures with enhanced interfacial interaction were obtained via a combination of blend exfoliation, filtration self-assembly, hot pressing, and thermal cross-linking. Remarkably, the films containing only 5 wt % PBONF achieved superior thermal conductivity (46.11 W/mK in-plane and 6.53 W/mK through-plane), alongside outstanding mechanical strength, thermal stability, and flame retardancy. These exceptional properties make the composite a promising candidate for application in extreme environments and next-generation thermal management solutions.