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Modifiers are commonly used in natural, biological, and synthetic crystallization to tailor the growth of diverse materials. Here, we identify tautomers as a new class of modifiers where the dynamic interconversion between solute and its corresponding tautomer(s) produces native crystal growth inhibitors. The macroscopic and microscopic effects imposed by inhibitor-crystal interactions reveal dual mechanisms of inhibition where tautomer occlusion within crystals that leads to natural bending, tunes elastic modulus, and selectively alters the rate of crystal dissolution. Our study focuses on ammonium urate crystallization and shows that the keto-enol form of urate, which exists as a minor tautomer, is a potent inhibitor that nearly suppresses crystal growth at select solution alkalinity and supersaturation. The generalizability of this phenomenon is demonstrated for two additional tautomers with relevance to biological systems and pharmaceuticals. These findings offer potential routes in crystal engineering to strategically control the mechanical or physicochemical properties of tautomeric materials.

In recent years, nonconjugated, fluorophore‐free organic polymers have emerged as potentially useful light‐emitting materials. The fluorescence properties of a novel class of nonconjugated,tert‐butyl carboxylate functionalized stilbene‐containing alternating copolymers are investigated in this work. These sterically crowded, semi‐rigid copolymers exhibit very strong blue fluorescence in organic solvents upon irradiation. The origin of the fluorescent band with high quantum yield is attributed to the “through space” π–π interactions between the phenyl rings from the stilbene and CO groups from the anhydride groups. To the best of our knowledge, the di‐tert‐butyl group‐containing stilbene and maleic anhydride alternating copolymer showed one of the highest fluorescent intensities among all fluorophore‐free polymers. The excellent linearity of the luminescence property of this copolymer is an important attribute for future potential quantitative applications. The fluorescence is maintained when thetert‐butyl groups are removed and the resulting carboxylic acid‐functionalized copolymer is dissolved in water at neutral pH, which can render these copolymers as attractive candidates for diagnostic and therapeutic applications.