Heat-Resistant, Soluble, and Intrinsically Flame-Retardant Poly(aryl sulfone ketone)s Derived from Dibenzothiophene-Bridged Bisphthalazinone Motifs

The development of polymeric materials combining high thermal resistance and solution processability is critical for chemical and energy engineering. Herein, dibenzothiophene-bridged bisphthalazinone (T-BDHPZ) units are incorporated into poly(aryl sulfone ketone)s (PTPSKs) to simultaneously achieve extreme heat resistance, solubility, and intrinsic flame retardancy. The resulting PTPSKs exhibit high glass-transition temperatures (388–404 °C), decomposition temperatures above 500 °C, and char yields exceeding 64%. The noncoplanar heteroaromatic backbone generates substantial free volume and efficient chain disorder, enabling solution fabrication of high-performance films and coatings. The PTPSK films show tensile strengths of 90.5–93.2 MPa, storage moduli of 3.41–3.74 GPa, high modulus retention at 300–350 °C, optical transparency (73–76% at 800 nm), and low dielectric constants (2.95–3.09 at 1 MHz). Notably, PTPSK films achieve UL-94 VTM-0 without additives. The PTPSK coatings also display strong adhesion, high hardness, corrosion resistance up to 450 h, and solvent-based recyclability. These features make PTPSKs promising for high-temperature coatings and electronic insulation.