Luminescent amphiphilic dendrimers with oligo(p-phenylene vinylene) core branches and oligo(ethylene oxide) terminal chains:: syntheses and stimuli-responsive properties

A class of new dendrimers consisting of hydrophobic oligo(p-phenylene vinylene) core branches and hydrophilic oligo( ethylene oxide) terminal chains was synthesized. These amphiphilic dendritic molecules are highly luminescent and exhibit critical micellization behaviors. They also show a lower critical solution temperature (LCST) in an aqueous medium. Both the critical micelle concentration (CMC) and LCST increased with increasing branch number and the ratio of the hydrophilic oligo( ethylene oxide) to hydrophobic oligo(p-phenylene vinylene) moieties. Besides, a temperature-dependent phase transition from a clear to cloudy aqueous solution was observed. The temperature-induced phase transition was also reflected by fluorescence quenching, H-1 NMR resonance peak broadening, and UV - vis absorption shift arising from the hydrophobic conjugated core. These changes in the phase structure and photophysical properties were demonstrated to be highly reversible, indicating some interesting stimuli-responsive behaviors.