Polyacrylonitrile In-Situ reinforced polyimide superhydrophobic porous fibers: A miraculous thermal insulation and flame-retardant material

In response to the demand for safety protective textiles suitable for extreme conditions such as intense heat and humidity, we have innovatively developed a novel approach using polyacrylonitrile (PAN) in-situ reinforced polyimide (PI) superhydrophobic porous fibers. We blended fluorinated polyamic acid (PAA) with PAN and prepared PI/pre-oxidized fiber (panof) porous fibers using a process that includes wet phase separation spinning and integrated synchronous imidization/pre-oxidation. Special emphasis was placed on the chemical mechanisms during the heat treatment stage of the preparation process. The uncapped PAA underwent imidization reactions and also facilitated PAN's pre-oxidation, which notably enhanced the structural stability of the PI porous fibers. This novel enhancement mechanism effectively addresses the challenges of structural collapse and volume shrinkage encountered in the preparation of traditional PI porous fibers. In addition, our investigation into the impact of thermal imidization temperature on the structure of porous fibers led to the evaluation of PI/panof porous fibers. The PI/panof-320 porous fibers, produced by the combined enhancement effect of fluorinated PI and PAN, showcased exceptional features: superhydrophobicity (water contact angle = 168.9°), low density (0.078 g/cm3), reduced thermal conductivity (0.0251 W/(m·K)), high strength (22.18 MPa), outstanding flexibility (bend radius = 205 μm), and superior flame retardancy and insulation. The outstanding performance of these composite porous fibers paves the way for innovative, comfortable, and safe wearable devices in high heat and humidity environments, highlighting their extensive applicability and potential.