Micelles‐Assisted Strengthening of Tough Photoswitchable Fluorescent Hydrogels for Recyclable Information Encryption and Anti‐Counterfeiting

ABSTRACT Photoswitchable fluorescent hydrogels for information encryption and anti‐counterfeiting hold great potential. Nevertheless, developing an effective and universal approach to integrate both the desired mechanical properties (i.e., high toughness and strength) and photoswitchable performance remains challenging. Herein, we described a strategy to achieve this purpose via using photoswitchable fluorescent micelles to strengthen tough hydrogels and endow them with photoswitchable fluorescence property. In our strategy, fluorescence resonance energy transfer (FRET)‐based photoswitchable fluorescent micelles are prepared by combining fluorogen (BTPEBT, donor) and spiropyran‐contained amphiphilic copolymers (Gal‐PEGMA ₆₁ ‐ b ‐P(St ₂₄₄ ‐ co ‐SPMA ₆ ), acceptor). Tough photoswitchable fluorescent hydrogels ( PFHs ) are fabricated by integrating micelles into poly(vinyl alcohol) (PVA) hydrogels via the synergy of freeze‐casting and salting out. The PFHs not only exhibited reversibly photoswitchable fluorescence, high contrast and brightness, and photo‐reversibility, but presented excellent mechanical performance (high toughness: 65.68 MJ/m ³ , tensile strength: 15.42 MPa), workability, and recyclability. Several examples indicated that the application potential of this strategy in integrating nanomaterials containing different fluorescent molecules into tough hydrogels. Thanks to their outstanding features, PFHs are also successfully applied to recyclable information encryption and anti‐counterfeiting. We thus envision that this reliable and universal strategy would promote the development of advanced multilevel information encryption, anti‐counterfeiting, and high‐density data storage.