Phase Transition and Fluorescence Emission of Multiresponsive Poly(ethylene glycol-co-siloxane) and Its Application for Uric Acid Detection

In recent years, multiresponsive polymers with nonconjugated chromophores featuring cluster-triggered emission (CTE) have attracted significant attention due to their wide applications and interests in fundamental studies. There is a lack of studies correlating the fluorescent properties to their distinct stimuli-responsiveness although CTE materials have been well studied. Herein, we introduced a poly(ethylene glycol)-polysiloxane copolymer, PEG-Si, which exhibits responsiveness to temperature, pH, CO2, and salinity, with adjustable phase transition and reversible fluorescence. PEG-Si was synthesized by a catalyst-free aza-Michael addition of PEG diacrylate with bis(3-aminopropyl)-tetramethyldisiloxane in dichloromethane. The structure of PEG-Si was characterized using various spectroscopic methods such as NMR and Fourier transform infrared spectroscopy (FTIR). The light transmittance and fluorescence performance of PEG-Si were measured at different temperatures under varying conditions, including polymer composition, concentration, pH, and bubbled CO2, to observe their evolution. The relationship between fluorescence properties and the phase transition process was described. The results demonstrate that PEG-Si can be used as a temperature and pH fluorescence thermometer and biosensor for detection of uric acid with a detection limit of 1.02 μmol/L. This study proposes a practical strategy for designing multiresponsive polymers with CTE features and provides significant insights into the correlation between stimuli-responsiveness and fluorescent properties, which contributes to the development of advanced materials with diverse applications.