Epoxide straight to radical polythioether by cascade reaction and its AIE performance for chemical sensors

Functional polythioether was readily synthesized by cascade oxygen-sulfur exchange reaction (O–S ER) of 2,2,6,6,6-tetramethypiperidin-1-yl)oxy (TEMPO)-contained epoxide with thiocyanate and anionic ring-opening polymerization (AROP) of the in-situ generated episulfide in the protonic solvent and air atmosphere under mild conditions. Polythioether containing TEMPO pendants exhibited red fluorescence by the aggregation-induced emission and the concentration-enhanced emission characteristics, and the red shifts of 10 nm and 70 nm were observed in the UV–vis absorption and fluorescence emission spectra of radical polythioether, respectively, compared to the corresponding radical polyether. Such radical polythioether could also act as the chemical sensor to efficiently detect metal ions and antioxidants based on the strong binding affinity of metal ions and antioxidants to the TEMPO moiety, resulting in reduced fluorescence emission intensity or even complete quenching. Therefore, cascade O–S ER/AROP was proved to be an effective approach for the synthesis of functional polythioether with tunable photophysical properties.