Down-Top Strategy Engineered Large-Scale Fluorographene/PBO Nanofibers Composite Papers with Excellent Wave-Transparent Performance and Thermal Conductivity

With the miniaturization and high-frequency evolution of antennas in 5G/6G communications, aerospace, and transportation, polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed. Herein, a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole) precursor nanofibers (prePNF). The prePNF was then uniformly mixed with fluorinated graphene (FG) to fabricate FG/PNF composite papers through consecutively suction filtration, hot-pressing, and thermal annealing. The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion, while the increased π-π interactions between PNF and FG after annealing improved their compatibility. The preparation time and cost of PNF paper was significantly reduced when applying this strategy, which enabled its large-scale production. Furthermore, the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity. When the mass fraction of FG was 40 wt%, the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient (|T|²) of 96.3% under 10 GHz, in-plane thermal conductivity (λ_∥) of 7.13 W m⁻¹ K⁻¹, and through-plane thermal conductivity (λ_⊥) of 0.67 W m⁻¹ K⁻¹, outperforming FG/PNF composite paper prepared by the top-down strategy (|T|² = 95.9%, λ_∥ = 5.52 W m⁻¹ K⁻¹, λ_⊥ = 0.52 W m⁻¹ K⁻¹) and pure PNF paper (|T|² = 94.7%, λ_∥ = 3.04 W m⁻¹ K⁻¹, λ_⊥ = 0.24 W m⁻¹ K⁻¹). Meanwhile, FG/PNF composite paper (with 40 wt% FG) through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m⁻³, respectively.