HYDROGEL STABILIZED RESPONSIVE COMPLEX EMULSIONS

Restricted (Penn State Only)
Author:
Cho, Seung Wook
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
January 10, 2018
Committee Members:
  • Lauren Dell Zarzar, Thesis Advisor
  • James Hansell Adair, Committee Member
  • Robert John Hickey III, Committee Member
  • Michael Anthony Hickner, Committee Member
Keywords:
  • encapsulation
  • emulsions
  • complex emulsions
  • calcium alginate
Abstract:
Emulsions, which are mixtures of immiscible fluids, have found widespread interest and use in fields and applications ranging from medicine, food, and cosmetics to optics. Complex emulsions, in which the droplets contain multiple fluids, are especially exciting due to the correlation between droplet structure and properties. Recently, a method to reconfigure the morphology of complex droplets containing hydrocarbon and fluorocarbon oils in water was demonstrated.1 Such droplets display unique physical and chemical properties rendering them applicable in areas such as sensors and tunable optics. However, emulsions are inherently not stable for extended time periods resulting in a critical obstacle for various applications. Traditional encapsulation approaches that are useful for droplet stabilization would render these hydrocarbon and fluorocarbon droplets non-responsive, thereby negating their most advantageous properties. In this project we aim to address this stability issue by fabricating a thin spherical hydrogel shell around droplets as a barrier to prevent coalescence while simultaneously retaining the droplets’ responsive behavior. Hydrogels are interesting materials to explore as emulsion stabilizers because they can be both interfacially active and chemically and mechanically tunable. Herein, we will create hydrogel shells composed of both ionically and covalently crosslinked alginate. In this work, we will explore the effects of a spherical hydrogel shell encapsulating the complex emulsion droplet on the droplet’s responsive behavior. We delve into the hydrogel interfacial behavior, how the droplets respond to the hydrogel and small molecule surfactants in combination, and characterize the hydrogel shell using confocal microscopy and optical microscopy.