Molecular simulation of structure and thermodynamic properties of pure tri- and tetra-ethylene glycols and their aqueous mixtures

Structural properties, thermodynamic properties and phase equilibria of tri-ethylene glycol and tetra-ethylene glycol are calculated with Monte Carlo simulation. A united-atom (UA) force field developed previously for other organic compounds is used for such purposes. For the efficient molecular simulation of glycol chain molecules, various appropriate elementary Monte Carlo moves are used. For all pure component properties examined, with the exception of tetra-ethylene glycol vapor pressure, reasonably good agreement between literature experimental data and simulation results is obtained. Water–glycol mixtures, that are highly non-ideal mainly due to strong hydrogen bonding between like and unlike molecules, are also examined. Liquid structure and mixture densities are calculated. Significant deviations are observed between experimental data and simulation results which call for an improved force field for interactions between unlike molecules.