A facile method for fabricating robust cellulose nanocrystal/SiO₂ superhydrophobic coatings

A large number of superhydrophobic coatings are prepared using individual particles (especially SiO₂) to build rough surfaces. However, those surface structures collapse very easily, resulting in poor mechanical strength of the coating. To overcome this problem, cellulose nanocrystals (CNCs) are used as a framework material to prepare a necklace-like CNC/SiO₂ nanostructure (referred to as CNC/SiO₂ rod) via in-situ growth of SiO₂ as building blocks of superhydrophobic coatings. The CNC/SiO₂ superhydrophobic coatings could be prepared by spraying or smearing the CNC/SiO₂ rods onto substrates treated with a commercial spray adhesive. The reason for selecting CNC is its high strength and appropriate size, which results in the formation of a firm grass-like surface microstructure when it is partially installed within the adhesive. The resulting coatings have ultra-high mechanical robustness under very harsh conditions and can resist abrasion by 240 grit sandpaper for 50 cycles (1000 cm) under a load of 100 g. They also perform well under finger-wipe, knife-scratch, water-drip, ultraviolet radiation, and acidic and alkaline conditions as well as have self-cleaning and oil-water separation ability. Given the simplicity of the proposed method and the excellent performance, these coatings should find wide use in a range of applications.