Deciphering the role of water in ethanol uptake within PIM-1 membranes

M Mahmud and B Van der Bruggen and F Artzner and A Ghoufi and A Szymczyk, JOURNAL OF MEMBRANE SCIENCE, 733, 124314 (2025).

DOI: 10.1016/j.memsci.2025.124314

Molecular interactions between solvents and membranes are a key factor for understanding the performance of organic solvent nanofiltration membranes. In this study, the behavior of pure water and ethanol as well as their mixtures confined in a PIM-1 membrane was investigated by means of molecular dynamics simulations. The nitrogen atom of PIM-1 was found to be the preferential interaction site for the various systems. The uptake of pure water and ethanol by the PIM-1 membrane was found similar. However, the ethanol uptake greatly increased in the presence of water, whatever the composition of the mixture. This intriguing behavior was further explained by molecular simulations, which revealed that water molecules create molecular bridges between the PIM-1 nitrogen atoms and ethanol molecules via hydrogen bonds, thus providing additional adsorption sites for ethanol. Simulations also highlighted that the translational dynamics of ethanol in the PIM-1 membrane was slowed down more than that of water due to the larger molecular size of ethanol (greater degree of confinement) and that it was more strongly impacted by the membrane confinement than by water-ethanol interactions. The same conclusion was drawn for rotational dynamics. However, for confined mixtures, the rotational dynamics of confined water were found to be imposed by ethanol, with similar relaxation times for both kinds of dipoles.

Return to Publications page