Supramolecular Entanglement Driven Emissive Aggregate Densification Enabling Room‐Temperature Phosphorescence Hydrogels with Ultrastretchability and Crack‐Tolerance

Polymeric room temperature phosphorescence (RTP) hydrogels are emerging candidates for many advanced photonic applications. Unfortunately, phosphorescence of the introduced RTP chromophores can easily be quenched in water‐swollen hydrogel networks, limiting their luminescence performance and application adaptability. Herein, we propose a supramolecular confinement‐entanglement synergy strategy to produce ultrastretchable RTP hydrogels by in‐situ polymerizing high‐concentration 2‐(acryloyloxy)ethyl trimethylammonium chloride (AETC) in the presence of preassembled 4‐biphenylboronic acid@β‐cyclodextrin (4‐BB@β‐CD) emissive aggregates. The hyper‐entangled poly(AETC) (PAETC) chains, formed under water‐limiting conditions, synergistically densify the 4‐BB@β‐CD aggregates through supramolecular confinement, effectively suppressing molecular vibrations and stabilizing triplet states. Impressively, the hydrogels exhibit intense afterglow and ultralong phosphorescence lifetime up to 1.1 s under room conditions. Crucially, the entanglement‐dominated physical network free of static chemical crosslinking enables continuing chain disentanglement during stretching for efficient energy dissipation. Segment length between physical entanglement points can thus be significantly enlarged to reduce network fracture and avoid crack propagation, achieving record‐breaking uniaxial/biaxial (21 000%/10 000%) stretchability. Even the notched hydrogels are capable of being unprecedentedly stretched to 20 500% and exhibit a fracture energy as high as 157 kJ m⁻ 2 , demonstrating intrinsic crack‐tolerance. This study opens new avenues of polymeric RTP hydrogels by bringing superior mechanical performance and should merit their application exploration.