Abstract: Chitosan-based materials have attracted considerable attention owing to their inherent biodegradability, biocompatibility, and antimicrobial properties. However, the establishment of a scalable technology for the fabrication of high-strength and high-toughness chitosan films remains a major challenge. Herein, a new route for the fabrication of high-strength and high-toughness chitosan films mediated by a unique hydrated chitosan crystal structure is reported, using an aqueous KOH/urea solution as a solvent and an aqueous KCl solution as a neutralization bath. The KCl concentration, neutralization temperature, and neutralization time significantly affect the self-assembly and lateral aggregation of chitosan chains and the microstructure and morphology of the chitosan hydrogels and films. Furthermore, stretching orientation endows the chitosan films with a high tensile strength, Young’s modulus, and work of fracture of 579 ± 52 MPa, 18.8 ± 1.5 GPa, and 26.7 ± 6.9 MJ m−3, respectively. To the best of our knowledge, the chitosan films developed in this study are the first example of extremely high-strength and high-toughness chitosan films. We believe that our findings will be useful for the fabrication of polysaccharide-based films with excellent mechanical properties and in broader applications in the fields of biomedicine, flexible bioelectronics, water treatment, and food packaging.

Extremely strong and tough chitosan films mediated by unique hydrated chitosan crystal structures
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DOI: 10.1016/j.mattod.2021.10.030