Biomimetic Ultratough, Strong, and Ductile Artificial Polymer Fiber Based on Immovable and Slidable Cross-links.

It remains a challenge to artificially fabricate fibers with the macroscopic mechanical properties and characteristics of spider silk. Herein, a covalently cross-linked double-network strategy was proposed to disrupt the inverse relation of strength and toughness in the fabrication of ultratough and superstrong artificial polymer fibers. Our design utilized a strong fishnet-like structure based on immovable cellulose nanocrystal cross-links to mimic the function of the β-sheet nanocrystallites and a slidable mechanically interlocked network based on polyrotaxane to imitate the dissipative stick-slip motion of the β-strands in spider silk. The resultant fiber exhibited superior mechanical properties, including gigapascal tensile strength, a ductility of over 60%, and a toughness exceeding 420 MJ/m 3 . The fibers also showed robust biological functions similar to those of spider silks, demonstrating mechanical enhancement, energy absorption ability, and shape memory. A composite with our artificial fibers as reinforcing fibers exhibited remarkable tear and fatigue resistance.