Solvent‐Induced Polyelectrolyte Conjugation for Fluorescence‐Dependence Solvent Detection

Abstract Solvated assembly and fluorescence are two distinct features of conjugated polyelectrolytes for remarkable optoelectronic properties. However, the essential correlation between solvated assembly and fluorescence properties is still undiscovered. Here, two homopolymers based on benzotriazole (BTz) backbones with pyridinium cation‐pendants (PBTz‐PyrBr) and quaternary amine cation‐pendants (PBTz‐TMABr) are designed to distinguish fluorescence response in polar solvents, which evokes a novel application in fluorescence‐dependence solvent detection. The conjugated backbones offer orderly aligned electron‐rich nitrogen atoms to chemically react with the quaternary amine cation‐pendants for creating a space conjugation, serving as a fluorescence sensing site in polar solvents. In low‐polarity solvents, conjugated chains tend to twist and aggregate, accompanied by the space‐conjugation enhancement. This behavior increases the fluorescence performance by suppressing both inter‐ and intra‐molecular charge transfer. Furthermore, a theoretical linear‐correlation is established between fluorescence and solvent polarity/concentration to elucidate the experimental rule, giving a robust opportunity for solvent detection.