Abstract
Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. Here, we utilize mesoscopic modelling, integrated with genetic block copolymer synthesis and bioinspired spinning process, to demonstrate de novo materials design that incorporates chemistry, processing and material characterization. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation. This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. The original homogeneous network structure becomes heterogeneous after spinning, enhancing the anisotropic network connectivity along the shear flow direction. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young's modulus. This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified.
Highlights
Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions
Despite the simple amino acid building blocks for silk proteins, spiders and silkworms produce silks with remarkable mechanical and adhesive properties by engineering nanoscale protein aggregate morphologies via multiple stages of spinning, relying at its foundation on selfassembly and shear flow-induced focusing along their microchannel-like spinning ducts
For the ‘A’ domain, the hydrophobic alanine (A) amino acids are responsible for the self-assembly of proteins into aggregates via b-sheet stacking, whereas the glycine (G) amino acids facilitate the hydrogen bonding between b-sheets
Summary
Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young’s modulus This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified. We reveal the structural evolution of the silk protein solution under shear flow and study how the ‘A’–‘B’ domain ratio and the protein molecular weight (polymer chain length) affect the fibre formation process. This molecular-level design principle for mechanically robust silk fibres is realized in our spinning and nanoindentation experiments
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