Efficient Dissolution and Spinning of Chitosan Using Ionic Liquids for Green and Sustainable Fiber Production Guided by Conductor-Like Screening Model for Real Solvents

Chitosan (CS) has gained widespread attention for its excellent biocompatibility and antibacterial activity, but its poor solubility significantly limits its applications. In this work, based on the Conductor-like Screening Model for Real Solvents (COSMO-RS), the solution capacity of CS was evaluated in 441 ionic liquids (ILs) using CS trisaccharide as a model. According to the results of ln γ and total excess enthalpy, the dissolving behavior of CS in ILs is dominated by anions, with cations having a moderate effect. Experiments on six ILs confirmed the predicted trends. Additionally, the hydrogen bond basicity and polarity of these ILs were tested, revealing that higher values of both parameters correspond to increased CS solubility in ILs. Among the selected ILs, 1-methyl-1,5-diazabicyclo[4.3.0]-non-5-enium dimethylphosphate ([DBNM]DMP) was able to completely dissolve 3 wt % CS within 48 min, with a degradation degree of only 17%, providing a solid foundation for subsequent spinning applications. The rheological behavior of CS spinning solutions and their phase separation process in the coagulation bath were studied to optimize spinning process parameters. Finally, regenerated chitosan fibers (RCFs) were successfully fabricated by the dry-jet wet spinning process, exhibiting outstanding mechanical properties, with a tensile strength of 1.30 cN/dtex and an elongation of 1.67%. Furthermore, [DBNM]DMP demonstrated excellent recycling performance, laying a foundation for future industrial production.