Cyclodextrin-bearing telechelic poly(2-isopropyl-2-oxazoline): Extremely large shifts of phase transition temperature by photo-responsive guest inclusion.

As a dual-stimuli-responsive polymer, α-cyclodextrin-bearing telechelic poly(2-isopropyl-2-oxazoline) (CD-PiPrOx-CD) was prepared by living cationic ring opening polymerization followed by click reaction (copper-catalyzed alkyne-azide cycloaddition). The phase transition temperature (T) of CD-PiPrOx-CD (0.33 mM) in 10 mM PBS solution (150 mM NaCl, pH 7.4) was 42.9 °C, and dramatically changed to 8.5 °C upon addition of the azobenzene-bearing penta(ethylene glycol) (Az-5EG) (3.3 mM). A change in the T was again observed for the mixture solution of CD-PiPrOx-CD and Az-5EG upon ultra-violet (UV) irradiation at 365 nm. Under 365-nm UV irradiation for 30 min, the T of CD-PiPrOx-CD changed to 41.3 °C, indicating the release of Az-5EG from the host-guest complex. During alternate irradiation at 365 and 254 nm, the T changed in a fully reversible manner.