Specific interactions of carbon dioxide in supercritical fluid processes and nanoparticle processing

Specific interactions of molecules with supercritical carbon dioxide (CO2) are of fundamental importance to the understanding of current processes and to the development of new processes. While relatively weak interactions are important for solubility and dissolution concerns, strong interactions play a major role in reaction chemistry. Chapter 1 provides background information on the solvent characteristics of CO2, FTIR and NMR spectroscopy methods to examine high-pressure solutions and specific solvent-solute interactions. It also gives motivation to further examine solute-solvent interactions in CO2 and to apply knowledge of these interactions to various processes.; Chapter 2 discusses the utilization of Fourier transform infrared (FTIR) spectroscopy to study the effect of CO2 density on the dimerization of various carboxylic acids. The interaction of CO2 with the carboxylic acid functional group is shown to be relatively strong. These strong interactions can be used to manipulate reactions involving carboxylic acids.; Chapter 3 discusses the use of high pressure nuclear magnetic resonance (NMR) spectroscopy to probe the nature of the interactions between CO 2 and carboxylic acids. The change of the chemical shift of the acidic proton of a carboxylic acid with CO2 density is shown to be nonlinear, suggesting a specific interaction with CO2. Unfortunately, the acid peak is the composite of the monomer and the dimer peaks, so the changing equilibrium constant with CO2 density also results in a nonlinear change with CO2 density. These effects on the peak shift are therefore indistinguishable.; Chapter 4 discusses the visualization of the supercritical fluid antisolvent (SAS) precipitation process. This process takes advantage of the interactions of CO2 with an injected solvent to cause mutual diffusion leading to the precipitation of an insoluble solute. This process can show drastically different behavior by simple adjustments of the processing parameters. (Abstract shortened by UMI.)...