Date of Award

Summer 8-18-2017

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Advisor

William Gramlich

Second Committee Member

Barbara Cole

Third Committee Member

Matthew Brichacek

Abstract

Cellulose-based hydrogels - three dimensional "solid" structures composed primarily of liquid water and held together by an interconnected polymer network - were created by first functionalizing carboxymethyl cellulose (CMC), a cellulose derivative, with carbic anhydride in a basic aqueous reaction with the intent of developing novel hydrogels from renewable materials. The product of this reaction, carbic CMC (cCMC), had a new norbornene group as a subsection of the carbic group. Norbornene is a reactive alkene structure that allows for further chemistry with cCMC, such as crosslinking. cCMC was crosslinked with 2,2'-(ethylenedioxy)diethathiol to create hydrogels using a water-soluble, UV-sensitive radical initiator and UV light.

Hydrogels created with this method had advantageous, predictable, and controllable mechanical properties to be employed in biomedical science, agriculture, and consumer products. These materials were also durable enough that the degradation was measurable on a daily basis, but the structures were able to persist for one month and would be capable of lasting longer.

It was also found that cCMC and DEG reacted without the presumed necessary UV light and radical initiator that was used in forming hydrogels. These spontaneously reacting systems were named "autogels." The autogel mechanism was investigated for cause and benefit by determining the system's response to various conditions. Autogelation rate, which was tracked by rheology, was accelerated by increased reactant concentration, increased temperature, and decreased pH. Autogellation was also slowed by decreased dissolved oxygen content and high concentrations of hydroquinone radical inhibitor. These conditions suggest to some degree that a thiol-olefin cooxidation (TOCO) reaction is being observed, but does not explain all the reaction conditions such as the hydroquinone concentration effects.

Regardless of cause, there are potential applications for spontaneously-gelling hydrogel solutions under mild conditions.

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