Preparation and property modulation of modified-SiO₂-KH570/styrene-ethylene-butylene-styrene superhydrophobic coatings with stretching-induced micro-nano-structure optimization

To address the issue of superhydrophobic coatings on flexible/stretchable substrates failing under strain and friction conditions, this paper proposes a fluorine-free, stretchable composite method: First, γ-Methacryloxypropyl trimethoxysilane (KH-570) modifies the surface of SiO₂ nanoparticles to enhance interfacial compatibility with the organic phase. This modified surface is then blended with the thermoplastic elastomer SEBS and sprayed onto a chloroprene rubber (CR) substrate. Stretching induces controlled micro/nano-scale roughness evolution. Results indicate that at SiO₂-KH570:SEBS of 1:1, the coating exhibits surface roughness Ra≈5.12 μm, an initial water contact angle (WCA) of 157.5 ± 1.5°, and a rolling angle (SA) of 7.4 ± 1.5°. At 100% tensile strain, the WCA further increased to approximately 161 ± 1.5° while maintaining low adhesion, and superhydrophobicity persisted even at 150% strain. After durability testing (tape stripping, sandpaper abrasion, water jet impact, sand impact), both 1:1 and 1:2 ratio samples retained high hydrophobicity overall. Electrochemical impedance spectroscopy (3.5   wt% NaCl) and 500   h neutral salt spray testing showed: the 1:1 sample exhibited optimal initial shielding performance, while the 1:2 sample demonstrated slightly superior long-term immersion durability. Mechanistically, KH-570 endows the interface with low surface energy, SEBS provides stress buffering and elastic rebound, and stretching creates hierarchical structures in surface wrinkles/pores. This stabilizes the Cassie-Baxter state and reduces the actual solid-liquid contact area. This work provides a concise, scalable route for durable superhydrophobic/anti-fouling self-cleaning surfaces on stretchable substrates.