Light-induced reversible self-assembly of multi-compartment patchy micelles

Abstract

Block copolymers represent an important class of nanomaterials that self-assemble into various hierarchical nanostructures with well-defined shapes and intriguing properties. However, effective and non-invasive routes to render reversible hierarchical self-assembly (RHSA) of block copolymers are relatively rare and limited, particularly in multicompartment patchy micelles. Moreover, there remains a great challenge to achieve multiple assembly structures from the same polymeric building block. Herein, we report a convenient strategy for light-induced RHSA of a light-responsive azobenzene-moiety-containing diblock copolymer, into an exciting variety of hierarchical self-assemblies. Programming the reversible assembly of patchy micelles into hierarchically complex structures is delicately constructed via a two-step, selective solvent-mediated self-assembly, that is, reversing micelles and swelling into subunits, followed by forming multi-compartment patchy micelles in mixed organic solvent/H₂O. More intriguingly, an array of multi-compartment patchy micelles of different shapes could be disassembled into subunits upon UV irradiation and then reversibly reassembled upon exposure to 450 nm visible light as a result of the trans–cis isomerization of azobenzene moieties. This work not only offers an effective approach to creating various multicompartment patchy micelles with the same diblock polymer, but also provides new insights into reversible self-assembly driven by specific wavelength light.