Molecular Dynamics Simulation of Self-Assembly and Tensile Deformation of Silk-Mimetic Polymers

J Kim and YM Zhang and S Burgula and RH Zha and YF Shi, BIOMACROMOLECULES, 26, 2852-2867 (2025).

DOI: 10.1021/acs.biomac.4c01623

Silk is a natural biopolymer with outstanding mechanical properties due to its nanocomposite microstructure of crystalline beta-sheets in an amorphous matrix. However, there remains a lack of understanding of the relationship between amino acid sequence, supramolecular structure formation, and mechanical properties. In this work, we developed a reactive coarse-grained molecular dynamics model to simulate the self- assembly, tensile deformation, and fracture of a segmented copolymer based on the repetitive core domain of spider dragline spidroins. We find that the beta-sheet nanocrystal content is determined by the length ratio of beta-sheet to non-beta-sheet segments. We reveal that the chain length affects the chain-to-chain network connectivity between the nanocrystals. High nanocrystal content and high connectivity improve the strength and stiffness at the cost of extensibility. Toughness does not continue to increase past a threshold beta-sheet-to-non-sheet segment ratio. Our findings provide important insights to guide the rational molecular design of silk-mimetic materials.

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