Revisiting aqueous-acetone mixtures through the concept of molecular emulsions

Abstract

Aqueous acetone mixtures represent a good example of perfectly miscible liquids in reality, and that hard to mix in silico. This is related to a key problem in molecular simulations, which is to distinguish between strongly micro-segregated mixtures from phase-separated ones. The Kirkwood-Buff integrals of in silico aqueous mixtures are often found to be dramatically higher than the experimental ones, hinting at a possible underlying phase separation. This is the case for many combinations of the force field models chosen for water or for acetone. Herein, we demonstrate, through a proper handling of the tail of the correlation functions, that these high values of the Kirkwood-Buff integrals represent in fact a transient regime within the segregated spatial domains, and that they asymptotically settle down to values in much better agreement with the experimental ones. The concept central to this new approach is that of molecular emulsions, where the long range part of the correlations is modulated by the micro-segregated domains, and that it is necessary to take into this modulation in order to recover the correct thermodynamical properties.

A comparative study of aqueous DMSO mixtures by computer simulations and integral equation theories

“…Following this line of reasoning, water is more likely to bind with itself, and preserve pockets of tetrahedrally bound water molecules. This is what happens with monools [42] and acetone [43]. We would then expect something similar with DMSO as well, and at even greater scale, since the valence is smaller.…”

Simple and complex forms of disorder in ionic liquids

“…It is interesting that this micro-heterogeneity is equally witnessed in associated liquids (water and alcohols for example) and mixtures involving them [13,14,29]. The common feature between the microheterogeneity in both types of systems is the fact that it is due to Coulomb charge pairing.…”

“…Following our previous research in aqueous and non-aqueous mixtures [12][13][14][15][16][17], one of the points that we have put forward is that the micro-heterogeneous nature of these mixtures is associated with a pre-peak in the oxygen-oxygen partial structure factor. The existence of a pre-peak in the scattered intensity or the total structure factor of aqueous mixtures of small solute molecules is yet elusive from experimental point of view [18,19].…”

Simple and complex disorder in binary mixtures with benzene as a common solvent

“…Nevertheless, we do observe well defined water pockets in water poor aqueous mixtures. 38,[41][42][43][44] It would seem that the ability of a mixture to exhibit pre-peak is related to the presence of inert methyl sites in the molecules, which steers the formation of specific clusters. Since water lacks such sites, it is more difficult to characterize the existence of a pre-peak within simulations.…”