Secondary Structure-Governed Polypeptide Cross-Linked Polymeric Hydrogels

Modulation of the secondary structures of peptides gives rise to a range of natural peptide-based soft materials with outstanding mechanical properties. Here, we discuss detailed insights on how the secondary structure of tailor-made polypeptides governs the mechanical properties of polymeric hydrogels. To this end, we developed a series of polymeric hydrogels cross-linked by poly(3-propyl-acrylate-glutamine) with tailorable secondary structures—α-helices and random coils. Interestingly, the hydrogels cross-linked by the α-helical cross-linker exhibit a high tensile strength and toughness because of the cooperative intramolecular hydrogen bonding along the polypeptide backbone. Furthermore, the α-helices endow the hydrogels with high resilience and rapid recovery because of their reversible cooperative hydrogen bonding. In contrast, the hydrogels cross-linked by the random coil cross-linker show inferior tensile strength and toughness. Our study establishes quantitative nanoscale/macroscale structure–property relationships in polymeric hydrogels and has important implications for the rational design of soft materials using polypeptides with a specific secondary structure.