Light-Responsive Block Copolymer Nanosheets With Well-Ordered and Switchable Channels

Light-responsive shape-switching block copolymer (BCP) particles have garnered growing interest in recent years. Although significant efforts have been devoted to controlling the light-triggered morphological transformation of BCP particles, precisely modulating their morphologies using visible light remains a formidable challenge. Herein, we fabricated the light-responsive polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) nanosheets via emulsion-confined assembly in a spiropyran photoacid (SPPA) solution. Upon exposure to visible light, the non-porous nanosheets gradually transformed into porous nanosheets with hexagonally arrayed P4VP cylindrical pores, attributed to proton release from SPPA photoisomerization under irradiation and subsequent pH-dependent switching of P4VP cylindrical channels. Besides, owing to the reversibility of SPPA photoisomerization, the resulting porous nanosheets can revert to the non-porous nanosheets in the dark. Furthermore, nanosheets with a controlled pore structure can serve as templates for the in situ deposition of gold nanoparticles (AuNPs), yielding hybrid PS-b-P4VP/AuNPs nanosheets with tunable porosity. The hybrid nanosheets can be used as catalysts for the reduction of 4-nitrophenol, and the porous nanosheets exhibited greater catalytic efficiency than the non-porous nanosheets. Thus, the reversible morphological transition of BCP particles can be precisely modulated by visible-light stimulus and BCP particles can function as scaffolds for constructing hybrid BCP/NPs particles with adjustable catalytic efficiency, thereby broadening their application.