Poly(2-isopropyl-2-oxazoline) (POx) is well known thermoresponsive polymer, which exhibits a reversible and rapid hydrophilic-hydrophobic interconversions through the lower critical solution temperature (LCST). Narrow molecular weight distributions of POx can be achieved by cationic living polymerization of oxazoline monomer. More importantly, we can readily introduce various end functional groups to the imitation or termination ends owing to the living polymerization process. We can utilize functional initiators to introduce specific functional groups at initiation end. Alternatively, termination end can be easily modified by treating with functional nucleophile to the living cationic terminal.
Recently, we have designed multimodal stimuli-responsive dendritic-linear block copolymers and light sensitive telechelic polymers have been designed through the end functional modification of POxs. LCST of the dendritic-linear block copolymers was greatly dependent of the solution pH. Azobenzene-bearing telechelic POx exhibited multimodal stimuli responsiveness. POxs were conjugated with three representative blue, green, and red fluorescence dyes for the temperature-dependent control of fluorescence emission. The three POx-dye hybrids exhibited clear hydrophilic–hydrophobic transitions via heating and cooling processes, accompanied by emission changes. By blending of the POx-dye hybrids, fully reversible emission color controls from blue to green, green to red, and blue to red have been achieved. Furthermore, the emission color can be tuned by changing the mixing ratio of each POx-dye hybrids. These unique fluorescence-tunable systems have great potential for applications in various photonic devices and sensors. In this symposium, we are going to report details of our recent research on multimodal stimuli responsive POxs.