A Simple Nanocellulose Coating for Self-Cleaning upon Water Action: Molecular Design of Stable Surface Hydrophilicity

Coating solid surfaces with cellulose nanofibril (CNF) monolayers via physical deposition was found to keep the surfaces free of a variety of oils, ranging from viscous engine oil to polar n-butanol, upon water action. The self-cleaning function was well correlated with the unique molecular structure of the CNF, in which abundant surface carboxyl and hydroxy groups are uniformly, densely, and symmetrically arranged to form a polar corona on a crystalline nanocellulose strand. This isotropic core-corona configuration offers new and easily adoptable guidance to design self-cleaning surfaces at the molecular level. Thanks to its excellent self-cleaning behavior, the CNF coating converted conventional meshes into highly effective membranes for oil-water separation with no prior surface treatment required.