Effect of silica size and content on superamphiphobic properties of silica-fluoropolymer core-shell coatings

We present a facile approach to fabricate superamphiphobic surfaces by spray coating silica-fluoropolymer core-shell particles without substrate pretreatment with an additional binder resin. A series of SiO₂ @poly(1H,1H,2H,2H-heptadecafluorodecyl methacrylate) (SiO₂ @PFMA) core-shell particles with core particles of different sizes were prepared via thiol-lactam initiated radical polymerization (TLIRP). The surface of each SiO₂ particle with an average particle size of 12, 80, 150, and 350 nm was modified with (3-mercaptopropyl) trimethoxysilane and used as a seed for TLIRP. The SiO₂ @PFMA particles with various SiO₂ sizes and contents were coated on aluminum substrates by a spray gun and then thermally treated to form a stable, rough composite layer. During the spray coating, the core-shell particles were aggregated by rapid evaporation of the solvent and then irregularly adhered to the substrate resulting in hierarchical structures. In the case of SiO₂ @PFMAs with low SiO₂ contents, the roughness created mainly by the polymer shell disappeared during heat treatment. However, the substrates coated with SiO₂ @PFMAs with high SiO₂ contents maintained the roughness even after heat treatment. The core-shell particles prepared with 12 nm SiO₂ formed a stable superamphiphobic surface. The water/hexadecane contact and sliding angles on an aluminum plate coated with SiO₂ @PFMA, prepared using 12 nm silica at 46 wt% silica content (12 nm-SiO₂ (46)@PFMA), were 178.5^◦ /159.2^◦ and 1^◦ /7^◦, respectively. The cross-cut tape test showed that adhesion between the 12nm-SiO₂ (46)@PFMA and the aluminum substrate was classified as 5B. A glass surface spray-coated with the core-shell composite particles exhibited transparent superhydrophobicity and translucent superamphiphobicity by controlling the concentration of the coating solution.