Date of Graduation

Spring 2018

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Chemical Engineering - Cooperative Education

Research Sponsor

Dr. Bi-min Zhang Newby

First Reader

Dr. Lingyun Liu

Second Reader

Dr. Jie Zheng

Abstract

The purpose of the project was to observe the effects of the Hofmeister series of ions on the gelation of gelatin and Pluronic-127 hydrogels. Hydrogels are semi-solid materials that contain a network of joined molecules through intermolecular interactions which are capable of holding water. Gelatin and Pluronic-127 (PF-127) are thermoreversible, physical crosslinked gels. Gelation occurs when temperature, or other driving forces, reduce the polymer chain solubility until a distinct 2-phase system forms. When aqueous ions are present in solution, they exhibit specific ion effects that have either a stabilizing or destabilizing effect on the solubility of proteins and other polymers. The qualitative ordering of ions based on their ability to precipitate proteins is what is known as the Hofmeister series. The goal of the experiment was to show the specific ion effects on the time and rate of hydrogel gelation relative to their position in the Hofmeister series. The viscosity as a function of time was measured to show gelation progression. Both Hofmeister anions and cations were tested and compared to show the change in gelation properties due to a change in the relative destabilizing effects of these ions. The learnings from this paper will help to better understand the effects of salts present in time-critical gelation applications such as drug delivery.

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