Ultrathin Polymersomes with Controllable Light‐Responsivity via Adjusting the Electronic Effect from Para‐Substituents of Azobenzene

Abstract Achieving ultrathin polymersomes (UTPSs) with controllable light‐responsive kinetics poses a prospective strategy to address the growing demands of intelligent and miniature systems, but it remains challenging. Herein, we reported the self‐assembly of numerous side‐chain‐type amphiphilic alternating azocopolymers (AAACs) into a series of UTPSs with diameters spanning 210–270 nm and ultrathin vesicular thickness spanning 1.91–2.14 nm. The light‐triggered reversible size transitions for these UTPSs are rendered by the photo‐isomerization of azobenzene moiety upon alternating irradiation with UV and visible light. The systematical isomerization kinetic study proved that the light‐responsive rate of distinct UTPSs was highly dependent on the electronic effect of para ‐substituents of azobenzenes within AAACs. Notably, the rate constant of electron‐withdrawing nitro‐modified UTPSs was 6.7 times greater than that of electron‐donating hydroxyl‐modified UTPSs. The proof‐of‐concept cargo release activity for different UTPSs was evaluated using a hydrophilic model drug of methylene blue (MB), with a light‐controllable releasing performance that highly depended on the para ‐substituent‐induced light‐responsive kinetics. Our work offers an innovative strategy to fabricate stimuli‐responsive UTPSs with a controllable responsive performance for the targeted applications in bionanotechnology.