Durable superhydrophobic coating with a self-replacing mechanism of surface roughness based on multiple Pickering emulsion templating

Abstract

Superhydrophobic coatings have remarkable potential for applications in different fields. With the availability of either nano-structural templates or simple methodology, the search for superhydrophobic coatings that are easy to prepare and durable remains challenging for both academia and industry. This study presents a novel durable superhydrophobic coating formulation based on oil-in-oil-in-oil (O/O/O) multiple Pickering emulsions. After applying the emulsions on a polypropylene surface, a hierarchical structure is formed, leading to superhydrophobicity. The resulting hierarchical surface morphology leads to a self-replacing mechanism of the coating’s surface roughness and unique structure of the multiple Pickering emulsion templates, which restores its superhydrophobicity during abrasion. This self-replacing mechanism leads to highly durable superhydrophobic coatings. The structural complexity of the multiple emulsions is translated to a complex hierarchical structure of the coating, which involves the formation of concave compartments with spherical/deflated structures lying inside them. During abrasion, the concave structure will be removed at the first stage, exposing the deflated structure, which is the new rough surface geometry that will maintain the superhydrophobicity. The multiple O/O/O Pickering emulsions developed in this study are composed of acetone-in-mineral oil-in-acetone (A/MO/A), mineral oil-in-acetone-in-mineral oil (MO/A/MO), acetone-in-mineral oil (A/MO), and mineral oil-in-acetone (MO/A). The studied multiple emulsions were prepared by a one-step procedure. Multi-functional silica nanoparticles were used as stabilizers in all these emulsions with both alkane and PTFE functional groups. Before emulsification, polyacrylate/polyvinyl chloride (PA/PVC) was dissolved in the acetone phase. This rapid simple technique is easy to apply and yields a multi-functional surface with self-replacing superhydrophobic properties that have great potential for many applications in diverse fields.