Deep eutectic solvent assisted oil - water interfacial behavior on polystyrene surfaces: a computational study

Oil-water separation on hydrophobic polymer surfaces, such as polystyrene (PS), faces significant challenges due to poor interfacial control and low wettability. This study computationally explores the efficacy of Deep Eutectic Solvents (DES) as environmentally friendly additives to modify interfacial behavior and enhance compatibility between oil, water, and the polymer surface. Utilizing classical all-atom molecular dynamics (MD) simulations, we investigated the molecular-level interactions and structural organization at the oil-water-DES-PS interface. Our molecular structural analysis reveals that DES preferentially adsorbs onto the PS surface, displacing water and facilitating enhanced contact between octane and PS. Radial Distribution Function (RDF) analysis quantifies this effect, showing a reduction in direct PS-water interactions and a strong, specific affinity between PS carbon atoms and DES choline. Furthermore, interaction energy analysis confirms that DES significantly strengthens the van der Waals attraction between PS and octane, primarily driven by the strong interaction of choline with PS. These molecular insights are crucial for the rational design of advanced, DES-assisted membrane systems, offering a promising avenue for efficient and sustainable oil-water separation.