Facile synthesis of regenerated chitosan nanowhiskers with concentration-dependent self-assembly behavior

The conversion of chitosan into nanowhiskers significantly enhances its application potential and value. However, current methods for producing chitosan nanowhiskers (CNWs) typically involve harsh acid/base treatments, chemical modifications, or toxic solvents, resulting in demanding processing conditions, high costs, structural alterations, and environmental concerns. Here, we present a mild, cost-effective, and eco-friendly approach that eliminates the need for chemical modification. Raw chitosan was dissolved in dilute acetic acid, regenerated via pH adjustment, and mechanically processed to obtain CNWs. The resulting CNWs, with a 95 % degree of deacetylation, exhibited diameters of ∼7.4 nm and lengths of ∼93.6 nm. The CNWs displayed concentration-dependent self-assembly in water, forming interconnected nanofibrous networks at high concentrations while remaining well-dispersed as individual nanowhiskers at low concentrations. Leveraging this behavior, CNWs served as effective suspending agents and Pickering emulsifiers, stabilizing particles for over 72 h and emulsions for over 30 d at additive concentrations of 5-10 mg/mL. Additionally, CNW films and aerogels prepared through self-assembly demonstrated excellent water stability and mechanical strength, with Young's modulus and compressive modulus reaching ∼3.5 GPa and ∼110.2 KPa, respectively. This study establishes a foundation for the facile and large-scale production of CNWs and their high-value applications.