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The microscopic structure of aqueous and ethanol mixtures of 1, n-diols

It’s known that binary mixtures of water and alcohols display the local immiscibility of components, so called micro-heterogeneity [1, 2]. However, the alcohols in question possess only one hydroxyl group. What happens in aqueous mixtures when alcohols with one hydroxyl group are replaced by those with two?In this work, we study binary mixtures of 1, 2-ethanediol and 1, 3-propandiol with water or ethanol using computer simulations. The insight into their structures is provided by radial distribution functions, site-site structure factors and cluster size distribution probabilities, while Kirkwood-Buff integrals evaluate the concentration fluctuations. We find that these mixtures are surprisingly homogeneous, despite their constituents’ strong hydrogen bonding tendencies.The aqueous diol mixtures are found to be close to ideal mixtures, while ethanol/diol mixtures show a weak non-ideality. All of these findings contrast strongly with the features found in aqueous mono-ol mixtures, implying that random disorder can arise in the presence of strong interactions. They also suggest how important molecular topology is in regards to concentration fluctuations in complex liquids. We propose the name of Lifshitz phases to designate such types of disordered systems [3]. [1] Dixit et al., Nature 416, 829-832 (2002) [2] R. Chitra and P. Smith, J. Chem. Phys. 114, 426-435 (2001) [3] M. Pozar and A. Perera, Phys. Chem. Chem. Phys. (2017), DOI:10.1039/C7CP01949A

computer-simulations, aqueous-diols, ethanol-diols, lifshitz-phase

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