Super-tough and thermo-healable hydrogel - promising for shape-memory absorbent fiber

Recoverable hydrogels with high stretch and toughness have been synthesized by a one-step radical polymerization. They consist of covalently crosslinked polyacrylamide (PAAm) and ionically crosslinked carrageenan. Such double network (DN) hydrogels can be stretched beyond 20 times their initial length, and their fracture energy reached a high value of ∼9500 J m^-2. By comparing hydrogel tensile properties at different temperatures, the contribution of ionic network to the toughness was quantitatively determined in percentage for the first time. The stretched hydrogels were completely healed by short treatment at a mild temperature. Through drying at stretch, they were also transformed into stiff absorbent fibers that still preserved their shape memory of wet state.