A molecular strategy for creating functional vesicles with balancing structural stability and stimuli-responsiveness

Vesicles, closed bilayer structures composed of amphiphiles, draw much attention as functional materials for water remediation and biomedical applications. Toward next-generation functional vesicles, both structural stability and stimuli-responsiveness are required. However, there is a dilemma between these properties because the desired membrane structure differs for structural stability and stimuli sensitivity. Here, we have provided a new approach for developing giant vesicles (GVs) through the molecular design and synthesis of amphiphiles having/not having amide linkages in the hydrophobic moiety. From the 1H NMR analysis and fluorescence spectrum of environmental-responsive probes, intermolecular hydrogen bonding between amide linkages in the membrane contributed to enhance structural stability of GVs. Moreover, by adding amphiphiles having photoresponsive azobenzene moiety to GVs composed of amphiphiles having/not having amide linkages, a different manner in photoresponsive deformation was observed: the former exhibited irreversible deformation, but the latter reversible manner due to photoisomerisation of azobenzene under ultraviolet and the subsequent visible light illumination. This was also owing to the stable membrane structure caused by intermolecular hydrogen bonding.