Thermodynamic and Transport Properties Modeling of Deep Eutectic Solvents: A Review on g^E-Models, Equations of State, and Molecular Dynamics

Abstract

Deep eutectic solvents (DESs) have gained attention in recent years as attractive alternatives to traditional solvents. There is a growing number of publications dealing with the thermodynamic modeling of DESs highlighting the importance of modeling the solutions' properties. In this review, we summarize the state-of-the-art in DES modeling as well as its current challenges. We also summarize the various modeling approaches to phase equilibria and properties of DESs with g E -models, equations of state (EOS), and molecular dynamics (MD) simulations. Most of the current g E -model and EOS-based approaches handle DESs as pseudocomponents in order to simplify the parametrizations and calculation strategies. However, for the models to become more transferable and predictive, it would be preferable to model the individual DES constituents instead of modeling it as pseudocomponent. This implies that validation with more detailed experimental data that includes the distribution of the DES components is also required. MD simulations, in contrast to g E -models and EOS, are capable of providing information about the liquid structure and can predict dynamic properties, although the latter quantities still show some imprecisions. Therefore, insights into the liquid structure of DES systems from MD could also aid in improving present modeling strategies in addition to allowing a better understanding. Finally, the latest developments for DES force fields are discussed as the quality of the applied force fields determines the results of the MD simulations.

Physicochemical Characterization and Simulation of the Solid–Liquid Equilibrium Phase Diagram of Terpene-Based Eutectic Solvent Systems

“…For the real systems, the diagrams are computed using the COSMO-RS and UNIFAC models, as shown in Figure 4 along with results of DSC experiments. Assuming that the calculations are acceptably accurate [5,40], from these plots, the eutectic temperatures and molar ratios at the eutectic point can be estimated (Table 6). For the menthol-based solvent systems, a low extent in the negative deviation from ideality is observed in the SLE diagrams.…”

“…They are prepared by combining a hydrogen bond donor and hydrogen bond acceptor near the eutectic point (eutectic temperature and molar ratio) at a temperature above the melting temperature of the homogenous mixture formed. The resulting system should have a considerably lower melting point compared to its ideal eutectic and the melting point of its individual constituents [ 1 , 2 , 3 ] as they are characterized by the presence of hydrogen bonding and strong non-ideal attractive interactions [ 4 , 5 ].…”

Computer Simulations of Deep Eutectic Solvents. Challenges, Solutions, and Perspectives

“…Pelaquim et al [16], Liu et al [15], and Shama et al [33] have provided overviews of studies devoted to modeling gas solubility in DESs. De Castilla et al [34] discussed research on simulating thermodynamic and transport properties of DESs in their review. Ma et al [28] analyzed the effect of water on DESs and provided a review of related simulations.…”

“…The above shows the complexity of finding universal charge scaling and parameterization for different DES systems. For a more comprehensive discussion on simulations of DES transport properties, we refer the reader to the excellent review by the group of Smirnova [34].…”

Group contribution and atomic contribution models for the prediction of various physical properties of deep eutectic solvents

“…Despite this, up to now, there are no general thermodynamic models available which can directly estimate a desired physical property without requirement of other properties of the DES. One category of modeling studies in the literature involves equations of state 14 – 17 , which require knowledge of the critical properties and acentric factor. A number of correlations are also available, some being component specific only, so applicable to only the one specific DES that the constants of the model were optimized for 18 , 19 .…”