ABSTRACT
HYPOTHESIS: Colloidosomes made of stimuli-responsive microgels offer the opportunity to design polymeric capsules with a hierarchical and tunable pore distribution. Coacervates stabilized by a microgel monolayer represent a unique strategy to build colloidosomes from all-aqueous emulsion drops, while exploiting the sequestration and dissolution properties of the coacervates. EXPERIMENTS: Methacrylated poly(N-isopropylacrylamide) (pNIPAM) microgels are used to stabilize coacervates made of an ampholyte polymer at a pH close to its isoelectric point. They are further cross-linked under UV-irradiation. The resulting assemblies are studied by means of confocal microscopy. Their permeability towards dextrans and nanoparticles is studied before and after dissolution of the coacervate. FINDINGS: PNIPAM microgels are found to stabilize the coacervates by adsorbing at their surface. Inter cross-linking the microgels results in the formation of an elastic colloidosome that persists after the coacervate dissolution and withstands surface deformations up to about 200%. The coacervate is exploited as a sequestrating core to entrap a water-soluble payload, which can be further released upon coacervate dissolution, while the membrane exhibits a size-selecting permeability. The membrane properties can also be switched by the volume phase transition of the microgels. Coacervate-embedded colloidosomes open new perspectives in the area of encapsulation/extraction and controlled transport of water-soluble/dispersed species.
