Fluorine-Free, Thermally Resistant, and Superhydrophobic Nanofibrous Skins with Biomimetic Micro/Nanostructure for Waterproofness and Breathability

Fluorine-free, thermally resistant, waterproof and breathable (W&B) membranes are crucial for personal protection, especially in firefighting and high-temperature industrial applications. However, conventional membranes often fail in high-temperature environments and generally rely on fluorinated compounds for waterproofness. Herein, a biomimetic and fluorine-free polyimide (PI) nanofibrous skin is fabricated on an electrospun nanofibrous membrane via a facile stepwise strategy combining electrospraying and electrospinning. The resulting nanofibrous skin exhibits a rice-leaf-like micro/nanostructured surface, demonstrating remarkable superhydrophobicity (152°) and notable self-cleaning performance due to the synergistic effect of hierarchical micro/nanostructure and a hydrophobic polymer matrix. This ultrathin, highly porous, and micro/nanostructured surface layer enables the PI composite membrane to achieve excellent W&B performance with remarkable hydrostatic pressure resistance (55 kPa) and superior water vapor transport (3537 g m–2 d–1). Importantly, these performance advantages are relied on without the incorporation of any fluorine-containing chemicals. Moreover, after continuous exposure at 320 °C for 6 h, the membrane maintains robust mechanical strength (27.1 MPa), structural integrity, and surface functionality. This work provides a feasible, environmentally friendly, and durable strategy for the development of next-generation high-temperature protective materials.