Date of Award

7-11-2017

Document Type

Thesis

Degree Name

Master of Chemical Engineering (MChE)

Department

Chemical Engineering

First Advisor

Adam Nolte

Second Advisor

David Henthorn

Third Advisor

Mark Brandt

Abstract

Hydrogels are soft materials used in several important biomedical applications such as drug delivery, wound dressing, tissue phantoms, and tissue engineering. Gelatin hydrogels, in particular, have several properties which would make them ideal materials, however, their poor mechanical and thermal properties often require enhancement to be viable. This report focuses on the addition of sodium alginate, another common biomacromolecule, to gelatin hydrogels and the resulting viscoelastic properties of these hybrid materials. Initial data collected using a parallel plate compression-to-failure testing setup suggested the hybrid samples had a larger toughness while showing a negligible change in the elastic modulus, an important parameter for biomimickry. Stress relaxation tests were performed in an attempt to characterize the linear viscoelastic properties of these materials along with thermogravimetric analysis (TGA) to elucidate the underlying mechanism responsible. Additional failure tests were conducted while varying pH to determine what effect, if any, electrostatic interactions between neighboring macromolecules, a common source of viscoelasticity, had on the overall mechanical properties. An additional set of failure tests was performed using a spherical indenter and confined sample geometry in order to confirm the previously observed toughening effect while mitigating several sources of error inherent to the parallel plate test. These two experiments gave conflicting results regarding the bulk toughness of these samples. However, qualitative differences observed during these experiments, in conjunction with sessile drop contact angle measurements, may point towards a change in the surface characteristics, the hydrophilicity in particular, of these materials as a potential cause for the previously observed toughness enhancement.

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