Shape-Switchable Block Copolymer Particles Exhibiting Light-Responsive Surfactants

Particles capable of changing their shape in response to external light irradiation may serve as promising bio-inspired, smart materials for clinical and biomedical applications due to their remarkable spatial/temporal resolution. Herein, we report polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer (BCP) particles exhibiting shape and morphological transition induced by light irradiation. Key of forming light-dependent BCP particles is to design surfactants containing light-active groups (i.e., nitrobenzyl ester and coumarin ester), which can light-dependently modulate interfacial activity. With irradiating light, a sphere with onion-like inner morphology changes to prolate or oblate ellipsoids with axially stacked nanostructures. In addition, wavelength-selective shape transformation of BCP particles is achieved by a mixture of two light-active surfactants, which respond to the light with different wavelengths (i.e., 254 and 420 nm). Moreover, we demonstrate the color- and shape-changing particles in response to the light, which can be achieved by the use of light-emitting, photo-responsive surfactants. Finally, we integrate shape-switchable BCP particles into a hydrogel film to demonstrate the modulation of the particle shape in sub-micrometer resolution.