Multifunctional Entropy-Driven Supramolecular Glasses From Thermopolymerization of Metal-Urea Deep Eutectic Solvents

Glasses are central to modern science and technology, yet conventional silicate, organic polymer, and metallic glasses share persistent limitations: energy-intensive processing and poor recyclability. To address these challenges, we report the large-scale synthesis of supramolecular glasses (SGs) from urea (UR) and ZnCl₂ via a facile grinding-heating-cooling process conducted within a deep eutectic solvent (DES) framework. During heating, the DES facilitates in situ UR polymerization, generating biuret (BU) and cyanuric acid (CA) intermediates that partially coordinate with Zn²⁺ ions to yield entropy-stabilized amorphous glass networks. The resulting SGs exhibit excitation-wavelength-dependent ultralong phosphorescence with emission tunable across blue, green, and yellow. In addition to this photonic functionality, the SGs adhere strongly to diverse substrates (e.g., silicate glass, wood, and ceramics) and display exceptional flame retardancy. This combination of tunable luminescence, substrate adhesion, and flame retardancy positions the SGs as promising candidates for intelligent anti-counterfeiting labels, decorative coatings, and flame retardancy applications. This work thereby establishes a sustainable, scalable, and low-cost platform for producing multifunctional glass materials from commercially available precursors, with broad implications for photonics, smart materials, and surface protection.