Synthesis and In Situ\nThermal Induction of β‑Sheet\nNanocrystals in Spider Silk-Inspired Copolypeptides

Spider\nsilk, known for its exceptional tensile strength,\nextensibility,\nand toughness, continues to inspire advancements in polymer and materials\nscience. Despite extensive research, synthesizing materials that encompass\nall these properties remains a significant challenge. This study addresses\nthis challenge by developing high molecular-weight multiblock synthetic\ncopolypeptides that mimic the hierarchical structure and mechanical\nproperties of spider silk. Using autoaccelerated ring-opening polymerization\nof <i>N</i>-carboxyanhydrides, we synthesized copolypeptides\nfeaturing transformable β-sheet blocks. These blocks retain\na helical structure during synthesis but transition into β-sheet\nnanocrystals in situ during solvent-free thermal mechanical processing.\nCompression molding was employed to induce hierarchical ordering within\nthe copolypeptide films, resulting in a solid “liquid crystalline”\nstructure that undergoes a temperature-induced α-to-β\nstructural transformation. This transformation integrates β-sheet\nnanocrystals throughout the helical block matrix, significantly enhancing\nthe material’s mechanical performance. Our innovative synthesis\nand processing strategy, which involves alternating sequences of α-helical\nand β-sheet blocks with various β-sheet-forming NCAs,\nenables the customization of diverse mechanical characteristics. These\nadvancements not only deepen our understanding of the fundamental\ndesign principles of spider silk but also pave the way for a new generation\nof high-performance, silk-inspired synthetic copolypeptides with broad\napplication potential.