Melt Densification Enables Fracture-Resistant Blend Hydrogels

Hydrogels and elastomers are integral components in biomedical and electronics devices, but their toughness and crack resistance are often unsatisfactory for load-bearing applications. Synthetic polymer networks predominantly rely on solution fabrication, which compromises the ultimate mechanical properties. This work presents a universal melt crosslinking strategy, which densifies entanglements well beyond solvated conditions. When deformed, mutually entangled dissimilar chains stiffen the gels, while sparse crosslinks amplify fracture resistance. At water contents up to 83%, the resultant hydrogels demonstrate over 2 orders increase in mechanical properties, including moduli (1.3-35 MPa), toughness (0.7-24.5 kJ/m²), and fatigue thresholds (1.2-3.3 kJ/m²), tunable in a wide range beyond existing hydrogels. Furthermore, the hydrogels show high optical clarity (>96%), oxygen permeability (Dk/t > 40), and anti-fouling properties (<0.6 µg cm^-2). This generalizable strategy could guide the design of tough functional soft materials in fields such as healthcare and smart electronics.