Poly(2‐isopropyl‐2‐oxazoline) Bearing a Spiropyran Side‐Chain: Synthesis and Evaluation of Photo and Temperature‐Responsive Properties

Poly(2-isopropyl-2-oxazoline)s with varied loading of the spiropyran side-chain are synthesized, and their photochemical and thermosensitive properties are characterized in aqueous solution. The absorption spectrum of the sample aqueous solution (0.1 wt%) indicates that 7.8 mol% of the pendant groups are in the zwitterionic merocyanine form. The introduction of spiropyran groups causes a marked decrease in the cloud point of the aqueous solution even when the pendant groups contain the zwitterionic merocyanine form. The cloud point of the aqueous solution of the samples in the spiropyran form is slightly (less than 1 degrees C) lower than that bearing the merocyanine group. Moreover, the photoinduced phase transition is demonstrated at an optimum temperature for the spiropyran-bearing poly(2-isopropyl-2-oxazoline). This material can be made applicable to a light-driven drug releasing system by introducing a hydrophobic group to form micelles and increasing the photoinduced change of the cloud point.