Covalently Cross-Linked Colloidosomes

Abstract

Model poly(glycerol monomethacrylate)-based macromonomers have been used to prepare sterically stabilized polystyrene latexes by either aqueous emulsion or alcoholic dispersion polymerization, affording mean latex diameters of approximately 107 or 1188 nm respectively as judged by dynamic light scattering. Such PGMA50−PS latexes have appropriate surface wettability to stabilize 25−250 μm oil-in-water Pickering emulsions, depending on the latex concentration and oil type. Colloidosomes were formed by covalent cross-linking of the hydroxyl-functional stabilizer chains from within the oil droplets using a polymeric diisocyanate (tolylene 2,4-diisocyanate-terminated poly(propylene glycol) [PPG-TDI]. This oil-soluble cross-linker was confined within the oil droplets, allowing colloidosomes to be prepared at 50 vol % solids without any aggregation. The resulting microcapsules survive removal of the internal oil phase using excess alcohol, unlike the noncross-linked Pickering emulsion precursor. These observations confirm the robust nature of these covalently stabilized colloidosomes. A method for controlling the permeability of these colloidosomes by exploiting the solvent properties of binary oil mixtures has also been evaluated. Finally, microcapsule permeability has been explored via dye release experiments. Less permeable microcapsules can be obtained by deposition of polypyrrole onto the colloidosome exterior.