Fluorine-free superhydrophobic breathable membranes with lotus-leaf/corncob-like composite structure for highly water-resistant fabrics

Waterproof and breathable microporous membranes with superhydrophobic properties have significant applications in numerous fields, including self-cleaning, outdoor protective equipment, and corrosion prevention. However, creating an environmentally friendly, fluorine-free, and waterproof breathable membrane (WBM) that offers excellent water resistance and durable superhydrophobic surfaces without post-coating technology remains a great challenge. Herein, we provide a facile and powerful method to fabricate a superhydrophobic, fluorine-free composite polyurethane (PU) WBM. This WBM is based on a corncob-like substrate membrane combined with a lotus-leaf-like surface layer with differing surface wettability; it is achieved via a two-step electrospinning and heat treatment technique. A corncob-like substrate membrane with excellent water resistance was prepared owing to its improved surface wettability and small pore size. It features a uniform hierarchical rough structure achieved by introducing appropriate SiO 2 nanoparticles (SiO 2 NPs) and two-component liquid silicone rubber (rPDMS) with low surface energy. In addition, a lotus-leaf-like skin layer with the presence of SiO 2 rough microspheres was introduced on a corncob-like membrane’s surface for imparting superhydrophobicity to the double-layer WBM. Importantly, rPDMS not only acted as a hydrophobic agent synergizing with SiO 2 NPs to enhance the wettability of the fiber surface from hydrophobic to superhydrophobic but also served as an adhesive to firmly fix SiO 2 NPs to the fiber surface. The resulting double-layer composite membrane exhibited excellent waterproofness of 93.3 kPa, moderate breathability of 5235 g m −2 d -1 , and durable self-cleaning properties, indicating its great potential for use in protective clothing and other applications.