Electrostatic Interaction-Induced Clusteroluminescence of Polyelectrolyte with UCST Behavior.

Polymers composed of zwitterionic monomer units generally exhibit upper critical solution temperature (UCST)-type thermoresponsive behavior. However, these monomers possess specialized structures, involve complex synthesis, and have limited varieties available. Herein, we report a novel polyelectrolyte that exhibits UCST behavior in aqueous solutions, achieved by regulating the content and sequence distribution of anionic and cationic monomers. The effects of ionic group content and counterion incorporation on the molecular chain conformation and UCST behavior are investigated. Meanwhile, the polymer solution demonstrates clusteroluminescence with aggregation-enhanced and temperature-dependent emission. As the temperature decreases, intermolecular electrostatic interactions are enhanced, which rigidifies the chain conformation and increases the clusteroluminescence. This work provides a facile approach for preparing polymers with UCST behavior by copolymerizing two ionic monomers with opposite charges. This broadens the selection of monomers, which promises the development of these thermoresponsive luminescent polymers exhibit potential for applications in fields such as visualization sensing.