Dynamic Microcapsules with Rapid and Reversible Permeability Switching

Dynamic microcapsules are reported that exhibit shell membranes with fast and reversible changes in permeability in response to external stimuli. A hydrophobic anhydride monomer is employed in the thiol-ene polymerization as a disguised precursor for the acid-containing shells; this enables the direct encapsulation of aqueous cargo in the liquid core using microfluidic fabrication of water-in-oil-in-water double emulsion drops. The poly(anhydride) shells hydrolyze in their aqueous environment without further chemical treatment, yielding cross-linked poly(acid) microcapsules that exhibit trigger-responsive and reversible property changes. The microcapsule shell can actively be switched numerous times between impermeable and permeable due to the exceptional mechanical properties of the thiol-ene network that prevent rupture or failure of the membrane, allowing it to withstand the mechanical stresses imposed on the capsule during the dynamic property changes. The permeability and molecular weight cutoff of the microcapsules can dynamically be controlled with triggers such as pH and ionic environment. The reversibly triggered changes in permeability of the shell exhibit a response time of seconds, enabling actively adjustable release profiles, as well as on-demand capture, trapping, and release of cargo molecules with molecular selectivity and fast on-off rates.