Peptide-Crosslinked, Highly Entangled Hydrogels with Excellent Mechanical Properties but Ultra-Low Solid Content

Low solid content is the ultimate reason for the brittleness and weakness of ordinary hydrogels. Here, hydrogels with ultra-low solid content but good mechanical properties are successfully synthesized using high monomer concentrations and low cross-linker/monomer ratios to obtain highly entangled structure and poly(l-lysine)-based cross-linker to introduce peptide chains. Compared with hydrogel cross-linked with N,N'-methylenebisacrylamide (BIS), the peptide-crosslinked one has a larger swelling degree in water, leading to fully swollen gel with ultra-low solid content (5.8%). However, it still exhibits excellent mechanical properties, including high stretchability (440%), high tensile strength (220 KPa), superb resilience (99%), high fracture toughness (2100 J m(-2)), excellent fatigue resistance (720 J m(-2)), low friction (0.0059), and high wear resistance. These properties are comparable to or even better than the BIS-crosslinked hydrogel, although the former has much lower solid content. The excellent mechanical properties of the peptide-crosslinked gel are attributed to its highly entangled structure and also to the introduction of a novel mechanism for energy dissipation, that is, energy dissipation via breakage of intramolecular hydrogen bonds stabilizing the helical structure of the peptide.

Automated summary

Hydrogels with ultra-low solid content but good mechanical properties are successfully synthesized using high monomer concentrations and low cross-linker/monomer ratios. The introduction of peptide chains through a poly(l-lysine)-based cross-linker contributes to the gel's excellent mechanical properties, including high stretchability, high tensile strength, superb resilience, high fracture toughness, excellent fatigue resistance, low friction, and high wear resistance. These properties, attributed to the highly entangled structure and a novel energy dissipation mechanism, allow the peptide-crosslinked gel to perform comparably to or better than traditional hydrogels with higher solid content.