Do Deep Eutectic Solvents Form Uniform Mixtures Beyond Molecular Microheterogeneities?

• DOI: 10.1021/acs.jpcb.0c06317
• Publication Date: 2020-09-18T13:19:42Z
• Authors: Lucie Percevault; Aicha Jani; Thibaut Sohier; Laurence Noirez; Ludovic Paquin; Fabienne Gauffre; Denis Morineau
• Keywords: Deep eutectic solvent; Solvation shell

We have performed small-angle neutron scattering in a momentum transfer range (0.05 < Q 0.5 Å–1) to study long-range order and concentration fluctuations deep eutectic solvents (DESs) their aqueous solutions. Ethaline (choline chloride/ethylene glycol), glycerol/lactic acid, menthol/decanoic acid mixtures were selected illustrate individually the case of ionic, nonionic, hydrophobic mixtures. Carefully designed isotopic labeling was used emphasize selectively spatial correlations between different solvent components. For ethaline DESs solutions, weak low-Q peak observed only for certain compositions some partial structure factors revealed mesoscopic segregation ethylene glycol molecules that do not participate solvation ionic units, either because they are excess with respect stoichiometry (1:4 neat ethaline) or substituted by water (4w-ethaline higher dilutions). nonionic hydrophilic such observed. This indicates better balanced interactions three H-bonded components (water, lactic glycerol) favor homogeneous mixing. DESs, we an coherent intensity centered at = 0, which could be reproduced model noninteracting spherical domains. Local excluded either. However, unlike liquid tendency demix, found no evidence expansion domains large scale.