Development of light-responsive, reversible shape-changing block copolymer particles using Au nanoparticles

Abstract

Dynamic particles with switchable shapes in response to light have attracted great interest to develop programmable smart materials with superior spatial and temporal resolution. Herein, a facile strategy for light-responsive, shape-changing block copolymer (BCP) particles is developed. The key strategy is to exploit azobenzene-grafted Au nanoparticles (Au@Azo NPs) as active surfactants, showing light-dependent wetting behavior on each block of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCP particles through photoisomerization of Azo ligands between trans- and cis-isomer under visible and UV light, respectively. Thus, visible light induces the formation of onion-like BCP particles with PS-outermost layer, while UV-driven shape-shifting from the spheres to ellipsoids with both PS and P2VP exposed on the surface. The reversible shape evolution mechanism between the spheres and ellipsoids is further clarified using a cryogenic electron microscope. Furthermore, light-dependent fluorescence and shape of the hybrid particles are successfully demonstrated, enabling the visualization of particle shape into an optical signal.