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.