Methanol-water solutions: a bi-percolating liquid mixture

TL;DR

This study combines neutron diffraction and molecular dynamics to reveal that methanol-water mixtures form separate, percolating networks within a specific concentration range, influencing their physical properties.

Contribution

It provides the first detailed evidence of bi-percolating networks in methanol-water solutions and links structural features to extremal thermodynamic and transport properties.

Findings

Methanol-water mixtures form extended, separate networks at certain concentrations.

Both components percolate simultaneously within the 0.27 to 0.54 mole fraction range.

Structural changes correlate with extremal thermodynamic and transport behaviors.

Abstract

An extensive series of neutron diffraction experiments and molecular dynamics simulations has shown that mixtures of methanol and water exhibit extended structures in solution despite the components being fully miscible in all proportions. Of particular interest is a concentration region(methanol mole fraction between 0.27 and 0.54) where {\em both} methanol and water appear to form separate, percolating networks. This is the concentration range where many transport properties and thermodynamic excess functions reach extremal values. The observed concentration dependence of several of these material properties of the solution may therefore have a structural origin.