Bio-inspired transparent, hydrophobic, and mechanically stable wood coating by cellulose nanocrystals

Protection of wood against environmental degradation requires advanced surface protection strategies like imitating nature's lotus effect, characterized by the superhydrophobic surface of lotus leaves with hierarchical micro- and nanoscale structures. This study replicates said phenomenon by coating wood surfaces with cellulose nanocrystals (CNCs) derived from cotton linters. At first, microcrystalline cellulose was converted to CNCs by high-pressure homogenization and subsequent hydrophobization using esterification with lauroyl chloride. The resulting lauroyl-modified CNCs (LCNC) were dispersed in a non-polar solvent at 2 wt% and applied to beech wood specimens in a low quantity of 0.8–1.6 g/m 2 by spraying. ATR-FTIR and 13 C NMR measurements confirmed a successful modification. Water contact angle measurements (WCA) verified successful hydrophobization of LCNCs demonstrating WCAs up to 150° on pressed LCNC pellets. Wood surfaces coated with LCNCs showed enhanced hydrophobicity over a 10 min time period with initial WCAs up to 125°, surpassing those of commercial oil-based wood coatings. Additionally, the coating was highly transparent, preserving the natural color, gloss, and brightness of wood. The present study demonstrates that coating with hydrophobized CNCs enables transparent, and highly hydrophobic wood surfaces with enhanced abrasion resistance, thus offering an effective and visually unobtrusive strategy for green wood protection. • Esterified cellulose nanocrystals exhibit water contact angles up to 150° • Stable dispersion of LCNCs in non-polar solvent, applied to beech wood at low quantity < 2 g/m 2 on a solid basis • Transparent, mechanically stable wood coating retaining the natural aesthetics of untreated wood • Superior hydrophobicity and abrasion resistance outperforming traditional oil-treated surfaces