Complexation of charged polymers and nanoparticles at all aqueous interfaces for functional membrane formation

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CBET - 1705891PI: Lee, DaeyeonMicrocapsules are particles consisting of an interior core surrounded by a membrane. They are widely used in applications where the interior of the microcapsule contains an active ingredient that is released to the surroundings. Microcapsules are used in a variety of products, including food additives, drug carriers for timed release, healing agents, and pesticides. Microcapsules are especially effective when the permeability of the membrane is selective so that release rates of chemical components inside the microcapsule can be controlled and can be programmed to respond to changes in environmental conditions. This award will support experiments to synthesize and characterize microcapsules made with membranes composed of pairs of polyelectrolytes or a polyelectrolyte and nanoparticle. The membrane is formed by the spontaneous formation of a complex at the interface between two aqueous phases. The advantage of these microcapsules is that they are formulated completely in water-based systems, which makes them compatible with living cells and organisms. The details of the membrane formation process, the transport and mechanical properties of the membrane, and the encapsulation efficiency will be studied using a variety of techniques. The project will provide opportunities for graduate and undergraduate students to participate in the research. The team will also prepare a hands-on kit for students and teachers that demonstrates emulsion formation.This award will support an experimental program to understand the transport phenomena and thermodynamics that govern the formation and properties of functional membranes synthesized from polyelectrolytes and charged nanoparticles via interfacial complexation of polyelectrolyte-polyelectrolyte pairs or polyelectrolyte-nanoparticle pairs in aqueous two phase systems. The growth of the membranes and membrane dynamics will be investigated using (1) fluorescence microscopy of membranes formed with labeled components to identify their location as membranes form; (2) pendant drop-based observation and characterization of the elastic membranes, complemented by atomic force microscopy measurements;(3) fluorescence recovery after photobleaching-enabled measurements of polyelectrolyte mobility within the membranes; and (4) isothermal titration calorimetry to detect the thermal events during complexation. Membrane mechanical properties will be measured using micropipette aspiration and osmotic pressure-induced buckling methods. Results of the research will not only improve methods of forming microcapsules with functional membranes, but also will provide information that can be applied to the formation of functional membranes in other configurations.