Structure of a Binary Mixture of Ethylammonium Nitrate and Methanol

Abstract

We report a joint experimental (X-ray and neutron diffraction) and computational study on a binary mixture of ethylammonium nitrate (EAN), a protic ionic liquid, and methanol, the shortest alcohol. These two amphiphilic compounds are also characterized by the existence of an extended hydrogen bonding network in their neat states. We explore how these similar compounds structurally organize at the micro- and mesoscopic levels when mixed in a homogeneous state. The study demonstrates that the mixture is organized similarly to neat EAN, where the polar versus apolar dualism of the ionic liquid determines the segregation of alkyl tails into domains embedded into the ionic, percolating matrix. Methanol, due to the strong hydrogen bond with the nitrate anion, tends to intrude into this polar network, merging at EAN’s polar–apolar interface. Further studies are proposed to rationalize the emerging mesoscopic density fluctuations that develop when approaching methanol-rich conditions.