Peptide-crosslinked, highly entangled hydrogels with excellent mechanical properties but ultra-low solid content.

Ordinary hydrogels are brittle and weak for many reasons, but their low solid content is the ultimate one. Their mechanical properties usually worsen sharply with decreasing solid content. Here by combining two recently developed approaches, hydrogels with ultra-low solid content but good mechanical properties were successfully synthesized. The gels were synthesized using high monomer concentrations and low crosslinker/monomer ratios to obtain highly entangled structure. Peptide chains were introduced by using a poly(L-lysine)-based peptide crosslinker. Compared with hydrogel crosslinked with common crosslinker 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, despite that 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 the introduction of a novel mechanism for energy dissipation, i.e, energy dissipation via breakage of intramolecular hydrogen bonds stabilizing the helical structure of peptide. This article is protected by copyright. All rights reserved.