Doctor of Philosophy (PhD)
The theme of this work is time-lapse polymerizations triggered by pH clock reactions. The first chapter is the introduction and gives a long overview of the different chemistries studied here. The second chapter focuses on the bromate-sulfite clock reaction. Based on some simplified and accepted reaction equations for the bromate-sulfite clock. We presumed it may be possible to increase the pH of the solution via ammonia addition and hinder or significantly reduce the reactivity of the clock reagents, thus creating a storage stable reaction. Adding a polymer system that would not crosslink until the solution became acidic would have created a storable, cure-on-demand, adhesive or coating system that could be triggered by the drop in pH of the bromate-sulfite clock reaction. However, the clock time was only tunable on a 2 hour time scale and the polymer crosslinking system was not triggered by the change in pH of the clock reaction. Chapter 3 discusses the research performed on the urea-urease clock reaction as a trigger for the Michael-addition type polymerization of Thiocure® 1300 (ETTMP) and poly(ethylene glycol) diacrylate 700 (PEGDA). We had great success creating this time-lapse polymerization system and were even able to create the first isothermal frontal polymerization system that does not require the gel effect to propagate the polymer fronts. This work focuses on the effect changing reagent concentrations has on the clock time, gel time, storage modulus, and subsequent degradation time in the batch-cured trials. The swelling capabilities and mass loss over time of the lyophilized hydrogel were also studied. In the IFP trials front velocity and front occurrence as they were affected by the reagent concentration were investigated. It was found that the clock reaction displayed the same trends with and without monomers present. The hydrogel formed showed similar properties to the previously studied hydrogel formed without a clock reaction. Finally, the polymer fronts were determined to propagate with the pH fronts.
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Jee, Elizabeth, "Time-Lapse Polymerizations Triggered by pH clock Reactions" (2016). LSU Doctoral Dissertations. 576.
John A. Pojman