COMPLEX COLLOIDAL MATERIALS VIA INTERFACIAL ENGINEERING

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Doctor of Philosophy (PhD)
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Chemical and Biomolecular Engineering
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Engineering
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2023
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Rosenfeld, Joseph, Azriel
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Abstract

A colloid most generally and most simply is a dispersion of one phase of physical matter within a second continuous phase, with the characteristic length scale of the dispersed phase ranging from a few nanometers to tens of micrometers, with the dispersed phase being generally referred to as colloidal particles. Colloidal particles tend to aggregate as their surface contact with the continuous phases produces an interfacial tension that is minimized upon coalescence or agglomeration of the particles. Numerous methods are employed to prevent aggregation ranging from steric short-range repulsion strategies to long-range electrostatic repulsion. Interfacial stabilizers have also been utilized to imbue colloids with added functionality creating novel composite materials. In this thesis, novel interfacial stabilizers are explored for colloidal stabilization and composite fabrication. Emulsions are stabilized by ion-pairing of polyelectrolytes of high naturality with oppositely charged surfactants enabling control over emulsion morphology and phase inversion. The onset of phase inversion is hypothesized to coincide with surfactant micellization based on oil-water partition coefficient measurements. Nanoemulsions are fabricated using a precipitation approach and their growing interfaces are stabilized by co-precipitating a polymer followed by interfacial crosslinking, creating a nanocapsule. Deeper understanding of nanocapsule size control is achieved via computational fluid dynamics in conjunction with ternary phase diagrams, the conclusion being that the degree of polymer supersaturation drives the final nanocapsule size. Addition of nanoparticles to the precipitation mixture enables arrangement of the nanoparticles within the nanocapsule according to the nanoparticle wetting properties, thereby creating a nanocomposite with a range of potential desirable bulk or interfacial properties. Finally, the thermal properties of a colloidal suspension are investigated using infrared thermometry of a microfluidic platform, potentially displaying unique interfacial behavior. This work thus aims to expand the palette of colloidal stabilizers and potential colloidal morphologies possible while providing fundamental insights into the phenomena that enable these techniques.

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Lee, Daeyeon
Date of degree
2023
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