Tough, ultrastretchable and tear-resistant hydrogels enabled by linear macro-cross-linker

Strong, tough and tear-resistant hydrogels hold great promise for applications as load-bearing structural biomaterials such as cartilages, tendons and ligaments. Here, we design a macromolecule-cross-linked (MC) hydrogel by in situ polymerization of acrylamide (AM) with the presence of allyl functionalized chitosan (CS). The resulting MC hydrogel bears abundant dangling chains, which can form a large amount of instantaneous physical entanglements. The physical entanglements can easily disentangle upon deformation, leading to energy dissipation. Meanwhile, the macromolecular cross-linking points can adjust their conformation, generating a topologically reconfigurable network, which can distribute stress evenly throughout the material. As a result, the hydrogel shows outstanding stretchability, mechanical strength, toughness and tear-resistance. Such a facile strategy to prepare hydrogels with both physical entanglements and a topologically reconfigurable network is quite general and should enable the development of strong and tough hydrogels of practical usage.