Mild Acidic Solvent Inducing Tobacco Stem Cellulose Nanocrystals for Fabrication of Film Materials With Enhanced Flexibility and Toughness

With rapid development of material science, application of lignocellulose and agricultural wastes to produce green and functional packaging materials has received much interest. Herein, tobacco stem cellulose nanocrystals (TC) were firstly prepared via facile and mild formic acid/choline chloride (FA/ChCl) deep eutectic solvent (DES) treatment. Systematic comparison of the TC nanomaterials with conventional cotton cellulose nanocrystals (CNCs) were performed from nanoscale to the applicable functions of the prepared films. Tobacco stem showed notable delignification after the FA/ChCl treatment with well-maintaining of xylan matrix, which induced more sphere (with average width of ~32 nm) and shorter nanocrystals after homogenization. The treatment also caused a series of crystalline structural variations, including reduced crystallinity and crystallite size, favorable for promoting molecular flexibility of TC. Vacuum-assisted drying induced the fabrication of the film materials. Even though TC films had less visible iridescence than CNCs films, they exhibited satisfying mechanical strength promotion, with breakage of ~30 MPa, and the elongation of ~14%, mainly due to the reduced rigidity, crystallinity and remaining xylan matrix. Therefore, the present study provided a novel approach to controllable fabricating high-quality cellulose nanocrystals for film materials fabrication, as well as a facile strategy for high-value added utilization of tobacco stem biomass.