Light-responsive ionic azo-homopolymer assemblies driven by the synergy of electrostatic force and aromatic–aromatic interaction

The precisely adjusting the morphology and size of self-assembled structures has attracted considerable interest but still challenging. Herein, we develop to fabricate the assemblies with controllable sizes based on the synergistic effect of electrostatic force and aromatic–aromatic interaction. Two kinds of homopolymers with pyridinium cation moiety and alkyl azobenzene pendant were systematically designed and synthesized via acyclic diene metathesis polymerization, and can further self-assemble into the spherical micelles and hollow vesicles by varying the alkyl chain length between two functional pendants. Upon alternating irradiation of UV-light and Vis-light, the micelle with reversible shape transition and the vesicle with recoverable size variation were ultimately formed through the different trans → cis isomerization efficiency of azobenzene chromophore to control π–π interaction within an appropriate range. The formation of uniform assemblies and the morphological evolution process confirmed that the relatively strong non-covalent interaction was essential for the self-assembly of homopolymer system. More importantly, the size of these spherical morphologies can be optionally adjusted by changing the self-assembly concentration. We expect that the importance of synergy and regulation multiple non-covalent interactions in reinforcing each other will offer a new avenue to induce self-assembly of homopolymer to produce the controlled morphology.