Effects of oxidized cellulose nanocrystals on the structure and mechanical properties of regenerated collagen fibers

The mechanical properties of regenerated collagen composite materials are of use in diverse applications. However, there are few efficient strategies to enhance the mechanical properties of regenerated collagen fibers. Herein, oxidized cellulose nanocrystals (oCNCs) were successfully prepared in aqueous media via oxidation of the hydroxyl groups on the surface of cellulose nanocrystals (CNCs) using ammonium persulfate (APS) as an oxidant. Collagen composite fibers were then prepared by introducing oCNCs into the collagen matrix via a dry-jet wet-spinning technique. The morphology, structures, and properties of prepared collagen composite fibers were carefully investigated. The results indicate that oCNCs and CNCs can induce collagen microfibril orientation during the formation process of fibers and protect the possibility of their interactions with collagen molecules. The oCNCs offered better enhancement efficiency than CNCs, and the as-prepared collagen/oCNC composite fibers exhibited extraordinary improvements in both tensile strength and toughness with only a 0.05 wt% oCNCs loading. The reason for this improvement is that the hydroxyl groups and carboxyl groups of oCNCs can form stronger hydrogen bonds and electrostatic interactions with collagen molecules, thus resulting in a synergistic enhancement of the tensile strength, toughness, and thermal stability of collagen composite fibers. This work provides an efficient and facile method to achieve collagen composite fibers with high mechanical properties for broad applications.