Tailoring multifunctional polyimide fabrics: Sustainable dyeing with supercritical carbon dioxide for improved hydrophobicity and thermal insulation

Polyimide (PI) fabrics, next-generation aerospace/advanced protective core materials, are inherently recalcitrant to conventional dyeing due to their rigid, non-polar backbones, making coloration of high-performance garments a critical unmet challenge. While supercritical carbon dioxide (scCO₂) water-free dyeing technology is validated for chemical fibers, PI-focused studies are sparse, and scCO₂- in-situ functionalization coupling remains unexplored. Herein, a single-scCO₂-step “ in-situ functional dyeing” strategy for simultaneous PI coloration and functionalization is proposed. A sublimable anthraquinone disperse dye, Disperse Blue 359 (DB359), was selected as both the chromophore and the hydrophobic/thermal-insulating modifier; its low-surface-energy backbone and π-conjugated structure integrate coloration and functionality without the need for any post-treatment. After systematic optimization of temperature, pressure, and time, the optimal protocol was determined as 200 °C, 20 MPa, and 3 h. Under these conditions, the dyed PI fabric exhibited a K/S value of 12.38 ± 0.6, wash and rub fastness ratings of 4–5, a water contact angle (WCA) of 139.6° ± 1.4°, and a thermal conductivity as low as 0.0778 W · m⁻¹ · K⁻¹. This work achieves the synchronous coloration and multifunctional integration of high-performance PI textiles, thereby providing a platform for the design of colored and functional PI fabrics.