High-strength and recyclable hydroplastic films from hydrophobic cellulose nanofibers produced via deep eutectic solvents

To alleviate the dilemma of plastic recycling, the development of sustainable bioplastics that are compatible with the environment throughout the whole material life cycle has received widespread attention. We report a vacuum-assisted filtration method for preparation of high-strength bioplastic films made from hydrophobic cellulose nanofibers that were obtained by esterification of natural cellulose with dodecenylsuccinic anhydride in recyclable deep eutectic solvent (triethylmethylammonium chloride/imidazole). The tensile strengths of the resultant hydrophobic films were 150.8 MPa and 94.8 MPa under dry and humid conditions, respectively. Importantly, these films could be programmed into various shapes, such as "U" shaped bracket, helix, and ring via a hydrosetting method and the strong hydrogen bonding interactions between cellulose nanofibers contributed to shape fixation. Benefiting from their hydroplastic properties, various shapes of bioplastic films could be reversibly engineered by kirigami, origami, and embossing. Meanwhile, the disposal of waste films followed the recycling route to regain hydrophobic cellulose nanofibers. This work provided a facile approach for the preparation of high-strength and recyclable hydroplastic cellulose nanofiber films.