Rachel A. Stanhope (2017)
Reducing the Interfacial Tension of Magnetic Surfactants in Magnetic Fields
This thesis discusses the theory, experimental research methods, and findings of the effects that magnetic fields have on the interfacial tension of magnetic surfactant solutions. Analyzing how magnetic fields affect the properties of magnetic surfactants, including interfacial tension, is the first step to creating low energy, magnetic field induced separations to address the problem of growing energy demands for chemical and biological separations. Surfactants are organic structures that contain both a hydrophilic head group and a hydrophobic tail, which aggregate toward the interface of solutions and decrease the interfacial tension until the critical micelle concentration is reached. Magnetic surfactants are created by replacing the counterion of a non-magnetic surfactant with a metal-counterion. Theoretically, when magnetic surfactants are exposed to a magnetic field the monomers will tightly align, allowing for more monomers at the interface and resulting in a decrease in surface tension. To test this theory, magnetic surfactants were exposed to two different magnetic fields produced by a solenoid magnetic field and a set of two permanent magnets parallel to the surfactants. C38H84N2Br2CoCl2, C19H42NBrDyCl3, and C19H42NBrFeCl3 were the surfactants which at several concentrations were suspended into the magnetic fields as droplets from needles, and the pendant drop method was used to analyze the dimensions of the droplets and calculate the surface tension. The surface tension decreased as the surfactant concentrations increased with a slight dip and rise in surface tension. Considering the surfactants were not completely pure solutions, this was expected, as previous research has shown that the interfacial tension of surfactants can display a slight dip and rise near their critical micelle concentration (CMC) values. Some data points followed the hypothesis, while others showed trends opposing the hypothesis. Some data points showed a general trend between surface tension and magnetic field strength. Due to the large range in standard deviation values, the inconsistent trends, and the possible presence of impure surfactant solutions, the research would benefit from taking data on ten to fifteen droplets for each concentration, using more purified surfactants, and determining the surface tension at more concentrations past the CMC.
Ward B. Toler (2018)
Imidazolium Magnetic Ionic Liquid Solubilities in Water
Magnetic ionic liquids (MILs) are room temperature ionic liquids that exhibit paramagnetic behavior. These liquids have tunable physiochemical properties with proposed applications in separations and drug delivery. It is, therefore, useful to know the solubility and micellar behavior of MILs in aqueous environments. Our group synthesized MILs with a FeCl4 anion and 1-alkyl-3-methylimidazolium cations and investigated aqueous solubility vs alkyl size (C2 through C10). We measured water solubility (MIL content in water saturated with the MIL) using UV-Vis spectroscopy, total organic carbon (TOC) analysis, and Total Nitrogen (TN) analysis. After observing micellar behavior for C(n)mim[FeCl4], where n > 6, we investigated the critical micelle concentration (CMC) of these MILs. Finally, we used Linear Free Energy Relationship (LFER) semi-empirical models to correlate the MIL water solubility to the MIL’s molecular volume. In the future, this LFER can predict the solubility of a MIL in water before the MIL is synthesized.