Hydrogen Bond‐Associated Photofluorochromism for Time‐Resolved Information Encryption and Anti‐counterfeiting

Time‐resolved photofluorochromism constitutes a powerful approach to enhance information encryption security but remains challenging. Herein, we report a strategy of using hydrogen bonds to regulate the time for initiating photofluorochromism. In our strategy, copolymers containing negative photochromic spiropyran (NSP), naphthalimide, and multiple hydrogen‐bonding (UPy) units are designed, which display photo‐switchable fluorescence resonance energy transfer (FRET) process from naphthalimide donor to the NSP acceptor. Interestingly, the FRET is locked via the dynamic hydrogen‐bonding interaction between ring‐opened NSP and UPy moieties, resulting in time‐dependent fluorescence. The change in fluorescence can be finely regulated via UPy fraction in the polymers. Besides the novel time‐dependent fluorescence, the polymers also take advantage of visible‐light triggerable, excellent photostability, photoreversibility, and processability. We demonstrate that these properties enable them many application opportunities such as fluorescent security labels and multilevel information encryption patterns.