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  1. This study revisits the material properties of solid “liquid crystalline” films made from synthetic helical polypeptides and explores their structure–property relationships. Poly(γ-benzyl-l-glutamate) (PBLG) with various molecular weights and architectures (linear, comb-, and brush-like) were transformed into films through mechanical hot pressing. The resulting materials are composed of helical PBLGs arranged in a near-hexagonal lattice, similar to those formed by casting from a concentrated solution in 1,2-dichloroethane (EDC). Despite exhibiting lower apparent crystallinity, these films showed superior mechanical strength, potentially due to the promotion of more interrupted helices and their entanglements under high temperature and pressure. A pronounced chain length effect on the tensile modulus and mechanical strength was observed, aligning with the “interrupted helices” model proposed by us and others. Macromolecules with a polynorbornene (PN) backbone and PBLG side chains mirrored the mechanical and viscoelastic properties of linear PBLGs. Our findings suggest that the folding structures of polypeptide chains and the discontinuity of the folding in longer chains are more influential in determining the macroscopic mechanical properties of the resultant materials than crystallinity, packing ordering, or macromolecular architecture, emphasizing the critical role of cohesive chain network formation in achieving enhanced mechanical strength. This research also presents a versatile approach to fabricating solid-state polypeptide materials, circumventing solubility challenges associated with traditional solution-based processing methods. 
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    Free, publicly-accessible full text available March 12, 2025
  2. The biological significance of self-assembled protein filament networks and their unique mechanical properties have sparked interest in the development of synthetic filament networks that mimic these attributes. Building on the recent advancement of autoaccelerated ring-opening polymerization of amino acid N-carboxyanhydrides (NCAs), this study strategically explores a series of random copolymers comprising multiple amino acids, aiming to elucidate the core principles governing gelation pathways of these purpose-designed copolypeptides. Utilizing glutamate (Glu) as the primary component of copolypeptides, two targeted pathways were pursued: first, achieving a fast fibrillation rate with lower interaction potential using serine (Ser) as a comonomer, facilitating the creation of homogeneous fibril networks; and second, creating more rigid networks of fibril clusters by incorporating alanine (Ala) and valine (Val) as comonomers. The selection of amino acids played a pivotal role in steering both the morphology of fibril superstructures and their assembly kinetics, subsequently determining their potential to form sample-spanning networks. Importantly, the viscoelastic properties of the resulting supramolecular hydrogels can be tailored according to the specific copolypeptide composition through modulations in filament densities and lengths. The findings enhance our understanding of directed self-assembly in high molecular weight synthetic copolypeptides, offering valuable insights for the development of synthetic fibrous networks and biomimetic supramolecular materials with custom-designed properties. 
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    Free, publicly-accessible full text available March 6, 2025