“Breathing” Vesicles with Jellyfish‐like On–Off Switchable Fluorescence Behavior

Controlled, deep breathing: Polymeric vesicles that exhibit reversible pH-induced “breathing” behavior accompanied by switchable fluorescence (see picture) were prepared through the aqueous self-assembly of an amphiphilic block copolymer. Mechanistic studies showed that this jellyfish-like breathing and light-emitting behavior originates from protonation- or deprotonation-induced changes in the conformation of the azobenzene chromophores.