Interface-tailored iridescent nanocellulose films with retentive antifouling and recyclable multi-environmental responsive properties

Cellulose nanocrystals (CNCs) with distinctive chiral nematic structures and attractive iridescent structural color after evaporation-induced-assembly have induced much interest. However, the hydrophilic nature and rigidity of CNCs materials greatly hindered their application in various environmental conditions. Herein, nature-derived xylose (Xyl) was introduced to regulate the chiral nematic structure of CNCs so as to improve their mechanical strength and flexibility. Facile solvent immersion strategy of materials in hydrophobic 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (C₁₆H₁₉F₁₇O₃Si, PFDTS) solution with various concentration was performed to endow hydrophobicity, as well as remaining their original cholesteric arrangements of the nanoparticles. Chemical and morphological characterizations proved the well distribution and intercalation of Xyl and PFDTS molecules into the chiral structures. The films after tailored interfacial modification exhibited satisfying hydrophobicity with highest water contact angle of ∼ 103°, and retentive anti-fouling capabilities were achieved for the films. Moreover, repeatable and highly sensitive humidity and acid response via iridescent change was fulfilled, well maintaining high mechanical strength (∼70 MPa) after recycling. Besides, excellent biocompatibility was confirmed for the modified materials via cell viability (>90 %) determination. Therefore, the proposed chiral CNCs-based hydrophobic films may greatly widen the application of cellulosic nanomaterials in areas of electrical devices, environmental protection and biomedical treatments, etc.