Two-stage thiol-ene click reaction for fluorine-free superhydrophobic fabrics with buoyancy boost and drag reduction

Superhydrophobic fabrics suggest tremendous potential in some emerging fields such as electronic skin, bioelectronic sensors and special clothing due to their excellent liquid repellency and self-cleaning properties. However, currently reported superhydrophobic materials are usually prepared using biologically toxic fluorinated compounds, which severely restricts their practical applications. Herein, we propose a two-step thiol-ene click reaction strategy to fabricate fluorine-free superhydrophobic cotton fibers (Fabric-SH-PB-SiO2). The 1,2-polybutadiene (1,2-PB) with flexible rubber molecular chains and low surface energy was coated by cotton fiber through thiol-ene click reaction. Subsequently, based on this reaction, the coated cotton fiber was used to establish chemical bonds with hydrophobic silica. The Fabric-SH-PB-SiO2 possesses a rich multi-level micro-nano structure that can form stable air layer on the surface of the fabric, which showed a high hydrophobic angle of 156° and exhibited some distinct advantages such as anti-fouling and self-cleaning characteristics, high buoyancy, and reduced drag. More remarkably, the Fabric-SH-PB-SiO2 could float on the water surface after carrying 34 times its weight. Compared with unmodified fabrics, the Fabric-SH-PB-SiO2 demonstrated a high drag reduction rate of up to 102 %, among the highest values for the reported hydrophobic materials. The strategy developed here provides insights towards fabricating high-buoyancy fluorine-free superhydrophobic cotton fibers