Polymer Films with Metal‐Like Thermal Conductivity, Excellent Stability, and Flame Retardancy

Abstract Polymers often have thermal conductivities that are too low to be used directly in thermal management applications. In this study, a poly(p‐phenylene‐2,6‐benzobisoxazole) (PBO) film is prepared through a sol–gel‐film conversion and annealing method that utilizes PBO nanofibers as building blocks. The polymer film shows an in‐plane thermal conductivity of 36.7 W mK −1 , which is two orders of magnitude higher than those of most polymers (<0.5 W mK −1 ) and 2.4 times that of 304‐stainless steel. The high thermal conductivity is attributed to the highly oriented 3D interconnected nanofiber network resulting from the fine‐tuning sol‐gel‐film conversion, and the annealing that further enhances the ordering of the PBO chains and the interactions between the nanofibers. Moreover, the PBO films exhibit excellent mechanical strength, thermal/chemical stability, electrical insulation, flame retardance, and improved UV resistance. The lightweight, robust, and easily processed PBO film with a metal‐like thermal conductivity has promising potential thermal management applications.