Date of Award

Spring 4-2014

Embargo Period

11-6-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor(s)

Shelley Anna

Abstract

Complex interfaces stabilized with materials including surfactants, polymers, and particles have dilatational properties that are important in processing emulsions and foams. Dilatational rheology is difficult to measure on interfaces due to the coupling of dilatation and shear inherent in common measurement apparatuses. Compounding the problem is the lack of control over complex interface formation in emulsification, which can obscure relationships between interfacial rheology and bulk emulsion properties. This thesis provides tools to measure dilatational properties of interfaces and generate interfaces with controlled surface coverage. A small amplitude analysis of dilatational rheology on capillary pressure tensiometers is used to develop a method for separating intrinsic rheology from surface tension effects. This analysis is applied in dilatational measurements of insoluble interfaces at the microscale, and good agreement is observed between the microscale measurements and Langmuir trough measurements. The second half of the thesis focuses on the controlled generation of particle-stabilized interfaces. A two-lobed shape transition is observed for confined bubbles traveling in a surface active particle suspension, and a model is developed to predict the particle surface coverage on the bubble interface. This model is then applied to generate monodisperse bubbles with uniform nonspherical bubbles due to particle jamming at the interface. The tools developed in this thesis are crucial to future development of relationships between the dilatational rheology of interfaces and the bulk properties of emulsions and foams.

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