Document Type

Thesis

Date of Degree Completion

Spring 2018

Degree Name

Master of Science (MS)

Department

Chemistry

Committee Chair

Dion Rivera

Second Committee Member

Yingbin Ge

Third Committee Member

JoAnn Peters

Abstract

Coacervates are systems that spontaneously form when two oppositely charged polyelectrolytes are mixed in a concentrated salt solution. When coacervates form, a biphasic equilibrium occurs in the sample with two phases present in the solution. The two phases are described as the dense phase and the lean phase, named after the amount of polyelectrolyte material in each phase. Coacervates have been topics of interest to researchers in a variety of fields including biomedical applications, drug delivery devices, and more. This thesis worked towards the characterization of coacervate systems on the molecular level by investigating the interaction of the polyelectrolytes and redox sensitive dyes that are doped into the matrix. This research sought to understand how a coacervate can stabilize the reactive species indigotetrasulfonate (ITS) and methylene blue and the reducing agent sodium bisulfite. The coacervate matrix is shown as a system that can engulf, aid in the reduction of redox dyes, and permanently stabilize the reduced dye. To study these systems a variety of analytical instrumentation was used. Fluorescence spectroscopy was used to investigate the partitioning of the engulfed materials in the coacervate. Reduced ITS is the only fluorescent material presented and it was determined that reduced ITS forms an aggregated system while engulfed in the coacervate matrix. Using fluorescence spectroscopy, it was also shown that the introduction of other dopants significantly influences the way that ITS molecules aggregate in the system. Infra-red spectroscopy was utilized to determine the thermodynamic cost of adding a redox dye or reducing agent to the coacervate system. It was shown that each charged particle added to the system significantly influences the ΔG values obtained for the biphasic equilibrium. Scanning electron microscopy was utilized to investigate the structural changes in reformed polyelectrolyte complexes (PEC) from doped coacervate samples. Each dopant molecule changed the structure of the PEC, inferring that the structure of the coacervate is also changed significantly post doping. Finally, cyclic voltammetry was utilized to investigate the catalytic and stabilizing ability of the coacervate matrix when engulfing ITS. It was shown that ITS is significantly easier to reduce when engulfed in the coacervate matrix and is significantly more difficult to oxidize once reduced in the system.

Available for download on Monday, June 05, 2023

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