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

ABSTRACT 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.