Thermosensitivity and luminescent properties of new tetraphenylethylene derivatives bearing peripheral oligo(ethylene glycol) chains

A class of new compounds consisting of a tetraphenylethene (TPE) core and hydrophilic peripheral oligo(ethylene glycol) chains was synthesized. These newly synthesized compounds showed aggregation-induced emission (AIE) nature which originated from the TPE core, and their peripheral oligo(ethylene glycol) chains impart water-solubility for the whole molecules. These compounds exhibit a lower critical solution temperature behavior in water. The phase transition temperature of TPE derivatives increases with the increase in the length of oligo(ethylene glycol) chains. By taking advantage of the AIE properties and thermosensitivity, these compounds are able to sense temperature by showing different emission intensities. When being heated above its phase-transition temperature, these compounds start to aggregate, which results in the restricted intramolecular rotation of the TPE moiety. Consequently, the aqueous solutions of these compounds show a stronger fluorescence. The temperature-induced fluorescence change is highly reversible.