A Facile Eutectic Strategy for Scalable, Leakage‐Free Thermochromic Phase‐Change Composites Enabling Smart Temperature Labels and Secure Data Encryption

Solid–liquid phase change materials (PCMs), when used as solvents in organic thermochromic composite systems, often suffer from leakage issues, which degrade their reversible color‐changing capability. Although encapsulation and porous composite shape‐stabilization techniques can enhance the structural integrity of PCMs, these methods are often complex, limited to lab‐scale production, and costly. Hereby, a facile eutectic strategy is presented to develop leakage‐free PCMs for stabilizing organic thermochromic composites by integrating organic lauric acid (LA) and inorganic sodium acetate trihydrate (SAT). Molecular dynamics simulations reveal significantly enhanced intermolecular interactions between SAT and LA compared to those between LA molecules. These strengthened intermolecular interactions endow the SAT/LA eutectic with excellent shape stability, preventing leakage and phase separation. Benefiting from the superior properties of the SAT/LA eutectic, the resulting thermochromic composites exhibit outstanding shape stability, cyclically reversible thermochromic performance, and considerable latent heat capacity. Leveraging these advantages, applications in temperature indicators, thermally regulated quick response codes, information encryption, and data storage/disguise are successfully demonstrated. This work, guided by molecular dynamics simulations, offers a promising approach to designing industrial‐scale, cost‐effective, shape‐stabilized thermochromic materials for temperature indication and information encryption.