Hierarchical dual-sized film surface morphologies self-generated from fluorinated binary latex blends boost hydrophobicity and lipophobicity

Latex films with controlled dual-level nanorough surfaces were obtained by casting from binary blends of fluorinated copolymer particles with a nanostructured core-shell morphology, narrow size dispersity and large size ratios. For this purpose, particles with different size, a common unfluorinated acrylic core copolymer of the self-crosslinking trimethoxysilylpropyl methacrylate (TSPMA) and a hard shell copolymer of either 2,2,2-trifluoroethyl methacrylate (TFEMA) or 1H,1H,2H,2H-heptadecafluorodecyl methacrylate (FMA) were synthesized by multistage emulsion polymerization. The FMA-based particles showed patchy morphologies dictated by the type of β-cyclodextrin used as FMA phase carrier in their synthesis. Four series of binary blends of either TFEMA or FMA copolymer particles with large (3-4 diameters) size ratios were cast into latex films with controlled hydrophobicity and lipophobicity. AFM and electron microscopy results indicate that addition of the small particles disrupts the hexagonal compact packed 3D organization of the large particles, resulting in dual-level nanorough surfaces and high water contact angles (up to θ(w)=127° in the as cast films, and θ(w)=135° upon aging or thermal annealing causing surface restructuring and TSPMA sol-gel condensation) with respect to the parent single component films. The proposed approach provides a straightforward route for the fabrication of robust coatings and films with tunable lipophobic and highly hydrophobic surfaces.