Structural organization in a methanol:ethylammonium nitrate (1:4) mixture: A joint X-ray/Neutron diffraction and computational study

Abstract

The molecular organization and dynamics of a binary mixture of a Protic Ionic Liquid (PIL), Ethylammonium Nitrate (EAN), and methanol (χEAN=0.8) have been investigated by means of X-ray/Neutron Scattering with the support of classical Molecular Dynamics simulations. While at low EAN concentration, as some of us previously have reported (Russina, O. et al., 2014) [1], mesoscopic segregation occurs, in the present study the two components are fully miscible at mesoscopic level and no clustering is observed. The low alcohol's concentration does not lead to strong effects on the PIL's structure; on the other hand methanol's environment is substantially different than in the neat state. Enhanced interactions of EAN with alcohol lead to a loss of methanol–methanol correlations. Structural, dynamical and thermodynamical analysis on the computational model shows that the strongest and most probable hydrogen bond interactions of methanol occur with the nitrate anion, while its methyl group has an aliphatic interaction with EAN's terminal carbon and behaves like a pseudo hydrogen bond donor.