Project Description
For nearly two decades, there has been growing interest in the identification of “green” alternatives to conventional organic solvents, whose volatility and toxicity frequently render them environmentally problematic. One such alternative, “deep-melting eutectics” (DMEs; also known as “deep-eutectic solvents”), form upon mixing certain organic solids capable of hydrogen-bonding interactions. The result of these interactions is a significant decrease in the melting point of the mixture relative to the initial organic solids, the extent of which varies with the mixture constituents and their proportions. By proper choice of components, ambient-temperature liquids that are biodegradable or environmentally benign can be obtained.
Unfortunately, to date, the practical utility of these novel liquids has been limited, a result of their significant water solubility. Recently, however, evidence has emerged to indicate that hydrophobic (i.e., water-immiscible) eutectics (dubbed HDMEs) can also be prepared, thus making possible the use of these solvents as the basis of two-phase systems for catalysis and separations. Under support provided previously by the SURF program, we have determined that HDMEs are unexpectedly common, and we have prepared a series of these materials comprising mixtures of various quaternary ammonium salts or menthol and any of a number of long-chain carboxylic acids. In addition, physicochemical characterization of these materials has begun. In the course of these investigations, it has become apparent that the utility of HDMEs would be greatly enhanced if it were possible to predict certain of their physical and chemical properties, most notably water content, which has been shown to control the partitioning of metal ions in conventional organic-aqueous biphasic systems.
Tasks and Responsibilites
The student will prepare and characterize (water solubility, viscosity, density, water content, thermal properties) a series of HDMEs comprising various combinations of hydrogen bond acceptors (e.g., quaternary ammonium halides) and donors (e.g., carboxylic and phosphoric acids). For donor-acceptor combinations found to yield an HDME, an attempt will be made to correlate the properties of the eutectics with that of its constituents. Efforts will also be undertaken to determine if various HDME properties follow regular trends. Of particular interest in these investigations will be HDME water content and the identification of the factors controlling it. Lastly, work will be undertaken to determine if the efficiency with which a solute is extracted into a HDME can be correlated with the water content of the solvent.
Desired Qualifications
None Listed