High strength chitin nanocrystal/alginate filament prepared by wet-spinning in “green” coagulating bath

Chitin nanocrystals (ChNCs) are an alternative biomaterial of exceptional mechanical stiffness, biocompatibility and sustainability. Wet-spinning is a convenient pathway to control alignment direction and give full play to the advantages of the high strength of ChNCs. Herein, sodium alginate (SA) was added as thickener and cross-linking molecules to improve the gelation rate and orientation degree of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized carboxylated ChNCs in CaCl₂ coagulating bath. The effects of an additive amount of SA on the morphology and microstructure of wet-spun filaments were systematically studied. The optimized concentration of SA was 0.8%, and the tensile strength and orientation degree of the corresponding filament were 261 MPa and 0.209, respectively. The optical properties and surface morphology changes during the drying process were monitored via a polarizing microscope. The addition of glycerol and glucose negatively influenced the formation of hydrogen bonds between ChNCs, decreasing mechanical strength and suppressing the appearance of wrinkles on the filament surface. The stretching process could improve the mechanical strength but cause a reduction in strain ratio. This bio-based composite filament with good biocompatibility had potential application in the field of biomedical.