Inherently Superoleophobic Nanocomposite Coatings by Spray Atomization

We describe a technique to fabricate, for the first time, superoleophobic coatings by spray casting nanoparticle-polymer suspensions. The method involves the use of ZnO nanoparticles blended with a waterborne perfluoroacrylic polymer emulsion using cosolvents. Acetone is shown to be an effective compatibilizing cosolvent to produce self-assembling nanocomposite slurries that form hierarchical nanotextured morphology upon curing. Fabricated coating surface morphology is investigated with an environmental scanning electron microscope (ESEM), and surface wettability is characterized by static and dynamic contact angle measurements. The coatings can be applied to large and/or flexible substrates by spray coating with ease and require no additional surface treatments of commonly used hydrophobic molecules such as fluorosilanes; i.e., the nanocomposites are inherently superoleophobic. The superoleophobic nature of the coatings is also discussed within the framework of Cassie-Baxter and Wenzel wetting theories.