Effect of Alkyl Spacer Length of Photoisomerizable Surfactant on Light-Responsive Shape Transition of Block Copolymer Particles

We introduce a novel class of block copolymer particles that exhibit dynamic and reversible morphological transitions in response to specific light wavelengths. The dynamic shape transition of those BCP particles is triggered by the incorporation of a spiropyran photoacid (SPPA) which induces the pH modulation upon photoisomerization. This pH modulation interacts with the pH-responsive block, P4VP, within the PS-b-P4VP particles, driving the morphological transitions. Under 420 nm light exposure, deprotonated SP formed SPPA affords the swelling of the P4VP domain, resulting in particle elongation. In contrast, when stop up the light irradiation, SPPA with MCH form yields the deswelling of the P4VP domains and contraction of the particle. Importantly, the switching of shape and fluorescence properties of the BCP particles is rapid and reversible over multiple cycles of light exposure. Furthermore, dynamic, shape-changeable BCP particles are integrated into hydrogel film to demonstrate reversible patterning and color changes upon activation by specific light wavelengths.