Solvent-Exchange Assisted Wet-Annealing: a New Strategy for Super-Strong, Tough, Stretchable and Anti-Fatigue Hydrogels.

Hydrogels are widely used in tissue engineering, soft robots, wearable electronics, etc. However, it remains a great challenge to develop hydrogels possessing simultaneously high strength, large stretchability, great fracture energy and good fatigue threshold to suit different applications. Herein, we propose a novel solvent-exchange assisted wet-annealing strategy to prepare high performance poly(vinyl alcohol) (PVA) hydrogels by extensively tuning the macromolecular chain movement and optimizing the polymer network. The reinforcing and toughening mechanisms are found to be "macromolecule crystallization and entanglement". These hydrogels have large tensile strengths up to 11.19 ± 0.27 MPa and extremely high fracture strains of 1879 ± 10%. In addition, the fracture energy and fatigue threshold can reach as high as 25.39 ± 6.64 kJ m -2 and ∼1233 J m -2 , respectively. These superb mechanical properties compare favorably to those of other tough hydrogels, organogels and even natural tendons and synthetic rubbers. This work provides a new and effective method to fabricate super-strong, tough, stretchable and anti-fatigue hydrogels with potential applications in artificial tendons and ligaments. This article is protected by copyright. All rights reserved.