Highly stretchable, tough, and self-recoverable and self-healable dual physically crosslinked hydrogels with synergistic "soft and hard" networks

Strength, toughness and self-recoverability are among the most important properties of hydrogels for tissue-engineering applications. Yet, it remains a challenge to achieve these desired properties from the synthesis of a single-polymer hydrogel. Here, we report our one-pot, a monomer-polymerization approach to addressing the challenge by creating dual physically crosslinked hybrid networks, in particular, synergistic "soft and hard" polyacrylic acid-Fe3+ hydrogels (SHPAAc-Fe3+). Favorable mechanical properties achieved from such SHPAAc-Fe3+ hydrogels included high tensile strength (about 1.08 MPa), large elongation at break (about 38 times), excellent work of extension (about 19 MJ m(-3)), and full self-recoverability (100% recovery of initial properties within 15 min at 50 degrees C and within 60 min in ambient conditions, respectively). In addition, the hydrogels exhibited good self-healing capabilities at ambient conditions (about 40% tensile strength recovery without any external stimuli). This work demonstrates that dual physical crosslinking combining hydrophobic interaction and ionic association can be achieved in single-polymer hydrogels with significantly improved mechanical performance but without sacrificing favorable properties. POLYM. ENG. SCI., 59:145-154, 2019. (c) 2018 Society of Plastics Engineers