Design of Fluoro-Free Surfaces Super-Repellent to Low Surface Tension Liquids.

Super liquid repellent surfaces feature high liquid contact angles and low sliding angles, finding key applications in anti-fouling and self-cleaning. While repellency for water is easily achieved with hydrocarbon functionalities, repellency for many low surface tension liquids (down to 30 mN/m) still requires perfluoroalkyls (a persistent environmental pollutant and bioaccumulation hazard). Here, we investigate the scalable room-temperature synthesis of stochastic nanoparticle surfaces with fluoro-free moieties. Silicone (dimethyl and monomethyl) and hydrocarbon surface chemistries are benchmarked against perfluoroalkyls, assessed using model low surface tension liquids (aqueous-based ethanol-water mixtures). We discover that both hydrocarbon- and dimethyl silicone- based functionalization can achieve super liquid repellency down to 40-41 mN/m and 32-33 mN/m, respectively (versus 27-32 mN/m for perfluoroalkyls). The dimethyl silicone variant demonstrates superior fluoro-free liquid repellency likely due to its denser dimethyl molecular configuration. We show that perfluoroalkyls are not necessary for many real-world scenarios requiring super liquid repellency. Effective super-repellency of different surface chemistries against different liquids can be adequately predicted using empirically verified phase diagrams. Our findings encourage a liquid-centric design, i.e., tailoring surfaces for target liquid properties. Herein, we provide key guidelines towards achieving functional yet sustainably designed super liquid repellency. This article is protected by copyright. All rights reserved.