Sustainable Design of Superhydrophobic Cellulose Nanocrystal-Films by Combined Surface Engineering and Catalysis

Superhydrophobic surfaces are very interesting for applications in industry due to their water repellency, self-cleaning, friction reduction, and antifouling properties. The combination of both surface chemistry and morphology can create a high water-repellant and self-cleaning surface if designed properly. Herein, we combined surface engineering and organocatalytic surface-functionalization as a sustainable approach for creating superhydrophobic cellulose nanocrystal (CNC) films. The self-assembly of the rod-like CNCs into a chiral nematic phase resulted in a film with a rough surface at the microscale. Next, we performed organocatalytic modification using a variety of non-fluorinated alkoxysilanes and non-toxic organic acids as catalysts. The resulting CNC films exhibited a high-water contact angle (>150°) and excellent water-resistant properties. Thus, without the use of carcinogenic fluorocarbon compounds, we were able to create superhydrophobic CNC films with a lotus-leaf inspired surface. In addition, the methodology allowed for the introduction of several functional groups and significantly improved the oxygen barrier property in high relative humidity.