Spectroscopic investigations of fluorescent solutes in alternative solvent systems: Labeled polymers in supercritical carbon dioxide and biological species in aerosol-OT reverse micelles

The development of chemical processes depends on many factors (e.g., industry, economics, government regulations). Demands such as high product purity and yield, lower production costs, and reduced environmental impact require active research into the area of reaction “optimization”. Significant effort has centered on the development of alternatives to volatile organic compounds (VOCs) as solvents. Room temperature ionic liquids, macro/micro emulsions, reverse micelles, and supercritical fluids are amongst the most investigated systems. Optimization of reaction conditions in these systems necessitates a fundamental understanding of the solvation dynamics that occur on the molecular level.; Supercritical CO₂ has found appeal as an alternative to VOCs because of its physicochemical properties and “tunability.” Its physicochemical properties (i.e., density, dielectric constant, viscosity, diffusivity, and refractive index) lie intermediate between that of a liquid and a gas, and may be adjusted continuously by changes in system temperature and pressure. Supercritical CO₂ has found wide-spread use as a polymerization solvent, as mobile phases in supercritical fluid chromatography, and as a solvent for extractions.; Reverse micelles are thermodynamically stable assembles of surfactants and water in an apolar phase. These nanoscopic water pools exhibit physicochemical properties different from those of pure water, providing a unique environment for the solubilization of species and for carrying out reactions. In addition, these properties depend on the amount of water within the core and the system temperature. Reverse micelles have found application in areas such as oil recovery, separations, phase transfer catalysis, the synthesis of nanomaterials, and chemical reactions.; This dissertation focuses on determining the dynamics of several solutes in two of these alternative solvents. In the first half of this dissertation, a polymer junction is studied in pure organic liquids and supercritical CO ₂ as a function of solvent polarity, added CO₂ density and/or temperature. In the second half the effect of added water and temperature on the dynamic behavior of fluorescent solutes and biolomolecules in reverse micelles is studied. The results of this dissertation provide molecular-level insights into how the physicochemical properties of these solvent systems can be tuned and why they are tunable.