Ultralong Room‐Temperature Phosphorescence Achieved by Microcapsule Rupture‐Triggered In‐Situ Polymerization for High‐Contrast Damage Visualization and Advanced Anti‐counterfeiting

Abstract Polymer materials with mechano‐responsive ultralong room‐temperature phosphorescence (RTP) are highly desired but challenging to achieve. Herein, a microcapsule (MC) rupture‐triggered in‐situ polymerization strategy is proposed to achieve such RTP with full‐color tunable emissions. It involves co‐encapsulating organic phosphors and moisture‐reactive hexamethylene diisocyanate (HDI) in MCs, which are dispersed into a polymer matrix. Mechanical damage ruptures MCs, releasing HDI that undergoes moisture‐initiated polymerization to form a rigid cross‐linked network at the damaged site. This network effectively suppresses non‐radiative decay pathways of triplet excitons, thereby activating “turn‐on” ultralong RTP signals specifically and exclusively at the damaged sites. The system achieves ultralong RTP lifetimes exceeding 1.5 s and a phosphorescence quantum yield of 11.2%. Notably, these RTP systems demonstrate exceptional stability under harsh conditions, including immersing in neutral, acidic, alkaline aqueous environments and various organic solvents, as well as exposure to high temperatures. Full‐color tunable afterglow emissions, ranging from blue to red, are readily achieved by employing different organic phosphors. This approach facilitates the development of self‐repairing smart coatings with high‐contrast damage visualization and advanced anti‐counterfeiting systems featuring mechanically activated dynamic RTP responses. Furthermore, the compatibility of MCs with diverse polymer matrices expands the practical applicability of such stimuli‐responsive ultralong RTP materials.