Deep eutectic solvents (DES) are characterized by the mixture of at least two components, whose resulting melting point is lower than of its precursors. Such compounds represent a promising alternative for utilization as solvents in several processes, since they are of ease preparation, low cost and most of them are biodegradable. The composition of these mixtures generally involves a hydrogen bond acceptor (HBA) and a donor (HBD). Commonly, quaternary ammonium or phosphonium salts are used as HBA, and as HBD amides, alcohols or carboxylic acids. Therefore, the properties of these solvents can be modulated accordingly to the nature of the species as well as their proportions, that will define the hydrogen bonding network within the liquid phase. In order to obtain a DES with desirable properties, as low melting point and low viscosity, is crucial the understanding of how the different intermolecular interactions, especially the hydrogen bonds, define such properties. In this project our goal is to systematically investigate a series of DES composed by ammonium and phosphonium salts with various hydrogen bond donors, using vibrational spectroscopy as the main tool. Our approach is to correlate physical and thermodynamic properties of the mixtures in different proportions with Raman and infrared (IR) data. In particular, the characterization of the low frequency vibrational modes should provide direct information about the hydrogen bonding in DES, what will contribute to a better choice of the components depending on the required application.
News published in Agência FAPESP Newsletter about the scholarship: