Dibenzofuran-Bridged bisphthalazinone architectures enable Solution-Processable, Heat-Resistant, and intrinsically Flame-Retardant Poly(aryl sulfone ketone)s

Achieving a simultaneous enhancement of heat resistance and solubility remains a longstanding challenge for high-performance polyarylethers. Here, we report a molecular-engineering strategy that integrates a rigid and non-coplanar dibenzofuran-bridged bisphthalazinone units into the polymer backbone to create a novel series of poly(aryl sulfone ketone)s (PFPSKs). The introduction of the dibenzofuran-bridged bisphthalazinone units simultaneously enhance backbone rigidity and disrupts dense chain packing, offering a balance between exceptional thermal stability and desirable solubility. The PFPSKs exhibit high glass-transition temperatures ( T g  = 376–391 ℃), excellent thermal resistance ( T d5% above 509 ℃ in N 2 and air), and high storage-modulus retention up to 350 ℃ (57.4%). The polymers dissolve readily in 1,1,2,2-tetrachloroethane and N -methyl-2-pyrrolidone (NMP), enabling the preparation of mechanically robust films with tensile strengths of 93.4–96.1 MPa and moduli of 1.94–2.38 GPa. Concurrently, the PFPSK films exhibit commendable light transmittance (76–78% at 800 nm) and dielectric properties (2.97 to 3.26 at 1 MHz), alongside favourable solution recovery characteristics. Additionally, coatings fabricated by solution spraying display excellent hardness (4H), strong adhesion (5.40–7.20 MPa), good flexibility, and high impact resistance (55 cm), together with outstanding salt-spray durability and closed-loop recyclability. PFPSKs also demonstrate intrinsic flame retardancy, achieving UL-94 V-0 rating without additives. This work establishes a versatile molecular-design platform that overcomes classical trade-offs in polyarylethers and opens pathways toward multifunctional, flame-resistant, and recyclable high-temperature polymers.