Mechanically Robust Ultrahigh Molecular Weight Supramolecular Hydrogels Reinforced by Synergistic Chain Entanglement, Hydrogen Bonding, and Nanoparticle Incorporation

Tuning the mechanical properties of ultrahigh molecular weight (UHMW) physically crosslinked hydrogels remains a significant challenge. We address this by utilizing Fenton‐initiated reversible addition‐fragmentation chain transfer (RAFT) polymerization to synthesize poly(methacrylic acid) (PMAA) with molecular weights of up to 1700 kg mol −1 under mild aqueous conditions. These UHMW polymers leverage extensive chain entanglement and hydrogen bonding to form strong and tough supramolecular hydrogels, exhibiting a tensile strength of up to 0.16 MPa, a fracture strain of 2000%, and a toughness of 2.93 MJ m −3 . Furthermore, the incorporation of PMAA‐stabilized nanoparticles (spheres or worms) as secondary physical crosslinks significantly enhances energy dissipation and overall mechanical properties, resulting in a 2.5‐fold increase in toughness relative to the neat UHMW PMAA hydrogel. This approach offers a versatile framework for designing high‐performance soft materials through hierarchical molecular and nanoscale engineering.