Tough hydrogels enabled by transient entanglements

Achieving high toughness and strength simultaneously in single-covalent-network hydrogels remains a longstanding challenge. Herein, we report a simple yet effective strategy to resolve this strength-toughness conflict by constructing polyacrylamide (PAAm) networks with abundant dangling chains that form transient entanglements. Unlike permanently trapped entanglements, these transient entanglements can slip and fully disentangle upon loading, enabling highly efficient energy dissipation and stress redistribution over a broad range of strains. Besides, these networks exhibit superior homogeneity compared to other structures, effectively mitigating stress concentration. As a result, our single-covalent-network hydrogels exhibit good mechanical properties, including a fracture strain of 5071%, a fracture strength of 1.06 MPa, a fatigue threshold of 1968 J·m⁻², and a fracture energy of approximately 60,000 J·m⁻². Moreover, these hydrogels feature low friction and high wear-resistance. Such a simple yet robust design paradigm effectively overcomes the longstanding strength-toughness trade-off without the complexity of multi-network architectures, opening avenues for next-generation hydrogels in biomedicine, wearable electronics, and other demanding environments.