Programmable Budding and Fission of Janus Polymersomes for Tunable Cargo Release

ABSTRACT Internally phase‐separated Janus polymersomes are attractive biomimetic compartments, yet their formation remains fundamentally limited by membrane fission arising from strong copolymer incompatibility. Here, we show that a solvent‐assisted double‐emulsion strategy overcomes this limitation by enabling the formation of kinetically stable Janus giant unilamellar vesicles (JGUVs) across a substantially broader thermodynamic window than solvent‐free methods. Using a Flory‐Huggins‐based phase diagram, we establish a thermodynamic framework that correlates the Gibbs free energy of mixing with membrane morphology, and is fully consistent with the experimentally observed structures. This framework reveals how transient solvent plasticization during self‐assembly promotes copolymer compatibilization and suppresses premature membrane fission, while fluorescence recovery after photobleaching (FRAP) confirms that enhanced membrane fluidity occurs only during assembly and that no significant residual solvent remains after evaporation. Building on these stable Janus architectures, we demonstrate programmable membrane remodeling through osmotic stress, enabling reversible budding, controlled fission via long‐lived intermediate states, and operation down to 5 µm vesicle sizes. Finally, we show that these membrane transformations provide staged and tunable release of encapsulated cargo. Together, these findings establish a general strategy for programming the formation, remodeling, and function of Janus polymersomes, opening new opportunities for controlled delivery, artificial cell engineering, and adaptive biomimetic materials.