Synthesis, properties, and applications of poly(ethylene glycol)-decorated tetraphenylethenes

Non-charged, water soluble poly(ethytene glycol) (PEG)-decorated teraphenylethenes (TPEs) with different polymer chain numbers are synthesized in high yields by azide-alkyne cycloaddition. Their aggregation and thermosensitive behaviours are investigated by means of fluorescence spectroscopy, transmission electron microscopy (TEM), zeta potential and dynamic mechanical analyses. All the luminogens are non-emissive in solutions, but emit intensely when aggregated in aqueous solutions, or forming micelles, demonstrating a phenomenon of aggregation-induced emission. The TPE derivative (1) carrying one PEG chain forms hydrogels in the THF-water mixture depending on the concentration, water fraction and temperature. All the luminogens are thermosensitive, with their cloud point being tunable by varying the solvent composition and their hydrophilicity. Luminogen 1 is biocompatible and can function as a fluorescent visualizer for intracellular imaging.