Synthesis of Water-Soluble Spiropyran-Modified Poly(acrylic acid) Micelles and Their Optical Behaviors

In this study, a spiropyran derivative (SPOH) is firstly grafted onto a polymer backbone of a poly(acrylic acid) (PAA) via an esterification process. The synthesized spiropyran-modified poly(acrylic acid) (PAA-SP) polymer is characterized by FTIR and 1H NMR. The synthesized PAA-SP is then dissolved into water to achieve water-soluble micelles. The optical behaviors of PAA-SP micelles are investigated by ultraviolet-visible (UV-Vis) absorption spectra and fluorescence emission spectra under acid/base and light stimuli in aqueous solution. Our experimental results reveal that the as-prepared PAA-SP micelles are water-soluble and show good photochromic and emissive behaviors. Meanwhile, the optical behaviors of the micelles are light-responsive and acid/base-responsive and hence can be tailored via the adjustments of both light and pH value of the solution sample. And our results may be meaningful for practical application of hydrophobic spiropyran derivatives in aquatic environments.