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Naphthalenediimide derivative-absorbed papers, which were prepared by dropping chloroform solution, showed fluorescence under photoirradiation after exposure to vapors of small aromatic guests. The fluorescence intensity and maximum wavelength depended on the type of guest aromatic molecules, similar to the crystal. The naphthalenediimide derivative-absorbed papers showed vapochromic and mechanochromic properties. [ABSTRACT FROM AUTHOR]

Information coding, recording, encryption, and decryption are of great importance in the field of anti‐counterfeiting, especially in the current AI information era. Herein, a paper‐like hydrogel composed of solely H‐bonded poly(vinyl alcohol) (PVA) and poly(n‐vinylcaprolactam) (PNVCL), namely VAPN, is developed for multiple ways of encryption and decryption based on chemical‐induced phase separation. It not only exhibits excellent ability of ink absorption and retention by the noncovalent H‐bonds and n−π* interactions and good mechanical strength but also maintains a negligible volume change during the phase separation that is crucial for the information fidelity. Given that the noncovalent interactions are the driving force to trigger the phase separation in the hydrogel, available chemical inks are numerous ranging from small molecules to polymers. Furthermore, together with thermally induced phase separation, the different dynamic processes of the association and dissociation between ink molecules and the hydrogel endow the latter with reversible information recording and self‐erasing, temporary or permanent, and customized encryption and decryption. [ABSTRACT FROM AUTHOR]