Ultrahigh Thermal Conductive Graphite Films Derived From Poly(p‐Phenylene‐1,3,4‐Oxadiazole) Precursor Copolymerized With 2,6‐Naphthalenedicarboxylic Acid

Efficient thermal management materials are indispensable for next‐generation electronic devices with ever‐increasing power densities. However, the thermal conductivity of artificial graphite films remains far below the theoretical limit of graphene because abundant structural defects generated during carbonization and graphitization severely impede phonon transport. Herein, a pre‐fused aromatization strategy is proposed to regulate the microstructural evolution of graphite films by introducing 2,6‐naphthalenedicarboxylic acid (2,6‐NDA) into a poly(p‐phenylene‐1,3,4‐oxadiazole) (POD) precursor through copolymerization. The pyrolysis behavior of the copolymers was systematically investigated, revealing that the rigid fused naphthalene units promote the formation of enlarged conjugated aromatic domains during thermal decomposition, thereby facilitating the growth of highly ordered graphitic crystallites while suppressing defect generation during subsequent graphitization. Consequently, a graphite film with a thickness of 35 µm was successfully fabricated, exhibiting an ultrahigh in‐plane thermal conductivity of 1820 ± 20 W m − 1 K − 1 . Meanwhile, the incorporation of 2,6‐NDA significantly increased the carbon residue ratio owing to its superior thermal stability. This work demonstrates that molecular‐level pre‐fused aromatization effectively tailors the graphitization pathway and provides a scalable strategy for producing low‐defect, highly graphitized graphite films for advanced thermal management applications.