Amidation reaction to derive waterborne, tolerant, and optically transparent solid slippery and superhydrophobic coatings

Abstract

Separate and lubrication-free association of low surface energy with hierarchically featured and highly smooth interfaces yield two distinct and prospective bio-inspired wettability—superhydrophobicity and solid slippery properties, respectively. However, the derivation of such bio-inspired wettability with high optical transparency—following a simple, completely waterborne, non-fluorinated and scalable fabrication approach is an extremely challenging task to achieve. Here, a simple amidation reaction between thioester and amine groups is rationally extended for aqueous processing of strategically selected small molecules to attend desired outputs through formation of nanoparticles. An aqueous reaction mixture of selected non-fluorinated small molecules provided a stable (for 30 days) dispersion of nanoparticles (size ∼210 nm). While the ‘in-situ’ deposition of the reaction mixture yielded completely waterborne, optically transparent, physically and chemically durable lubrication-free solid slippery coating on a planar substrate, a highly deformable superhydrophobic coating on porous and fibrous substrates was obtained following a rapid and facile post-deposition of the prepared nanoparticles. The prepared solid slippery coating remained efficient in sliding the beaded droplets of various (e.g., polar and non-polar) liquids having a wide range (70.2 mN/m to 22.3 mN/m) of surface tension. The embedded slippery property remained unaltered even after exposure of prepared coating to extremes of temperatures and severe abrasive conditions—including continuous drop of 250 g of sand, sandpaper abrasion with a distance of 500 cm under an applied load of 25 KPa, adhesive tape peeling for 500 cycles, pencil (6H) & knife scratching, and prolonged (15 days) treatments of extremes of pH, seawater, river water, etc. The synthesized superhydrophobic coating on porous and fibrous-substrate remained efficient in sustaining repetitive and large physical deformations and other relevant abrasive exposures.