Stimuli‐Responsive Recyclable Polymers with Room‐Temperature Ultralong Phosphorescence for Anti‐Counterfeiting

Abstract Developing stimulus‐responsive ultralong room‐temperature phosphorescent (RTP) organic materials, particularly in eco‐friendly, recyclable systems, remains a critical challenge in materials science. Here, a sustainable strategy is presented to achieve water‐ and heat‐responsive RTP with color‐tunable emissions using exclusively aqueous processing. By hydrogen‐bond linking (1,1′‐biphenyl)‐4,4′‐disulfonic acid (BP‐2TsOH) into a polyvinyl alcohol (PVA) matrix, polymer films that exhibit outstanding RTP performance, featuring a long‐lived afterglow (2.489 ms) and high quantum yield (66.42%), are fabricated. Tunable multicolor emission is realized through dopant integration: yellow afterglow with Rhodamine 6G and blue with Methyl Blue. Hydrogen bonding within the matrix enhances mechanical robustness, while its water‐mediated reversibility enables stimulus responsiveness and self‐repair. Specifically, water disrupts the hydrogen‐bonded rigid structure, dynamically switching RTP off/on in response to humidity or heat. This reversibility also permits mechanical damage repair via aqueous treatment, ensuring material longevity with minimal environmental impact. Finally, these films are successfully applied in digital encryption, decryption, anti‐counterfeiting, and rewritable devices, suggesting great potential for practical use in secure information storage and transmission.