A multistimuli-responsive fluorescent hydrogel based on a fluorescence response to macromolecular segmental motion

Abstract

Fluorescent hydrogels with fast and reversible responses have attracted extensive attention, and it remains a challenge to design multistimuli-responsive fluorescent hydrogel through a facile and versatile method. Meanwhile, the segmental motion in hydrogels is of significance for the various functions of hydrogels such as chemical reactivity, self-healing, and mechanical strength, etc., however, it is difficult and complicated to in situ investigate the segmental motion under different conditions. In this work, a multistimuli-responsive fluorescent hydrogel was designed and fabricated by introducing a tetraphenylethylene (TPE) derivative as a nonaggregated crosslinker in the gel network. Since the intermolecular rotation of TPE at the crosslinking point was directly integrated with the dynamic conformational transition of the macromolecular network, the mobility of macromolecular segments can be monitored by the fluorescence intensity of the hydrogel. The prepared hydrogel has promising fluorescence responses to temperature, pH, metal ions, and hydrogen bonding agents, and characterization of the fluorescence and the chain segmental motion showed that the weaker the mobility of the network macromolecular chain is, the stronger the fluorescence intensity is. Furthermore, due to the multistimuli-responsive fluorescence of the hydrogel, such fluorescent hydrogels can be designed as reversible patterning displays and biomimetic color/shape adjustable actuators, with various potential applications.