Color-Shifting Fluorescent System Based on an AIE Polymer with an Upper Critical Solution Temperature

The design of thermoresponsive luminescent polymers with both a tunable upper critical solution temperature (UCST) and a tunable color is of great challenge. Herein, a series of thermoresponsive copolymers with UCST and aggregation-induced emission (AIE) behaviors are prepared, and a color-shifting fluorescent system based on the energy conversion between the AIE polymers and fluorescent dyes is constructed. The copolymers are prepared from acrylamide and 6-(4-vinylphenyl)-2,4-diamino-1,3,5-triazine (VPhDT). Benefitting from VPhDT, an AIE-active monomer that can provide multiple hydrogen bonds and enhance association of the polymer chains, the obtained copolymers exhibit both UCST and AIE behaviors in aqueous solutions. Utilizing the AIE copolymers as the donor and fluorescent dyes as the acceptors, color-shifting fluorescent systems that can emit blue, green, and red lights are established. The color-shifting fluorescent systems also exhibit tunable luminescent intensities and colors with the stimuli of temperature and pH. Such a color-shifting fluorescent system may have promising applications in the fields of temperature sensors and information displays.