Coarse-grained Molecular Dynamic Simulations of Interactions of Poly(amidoamine) with Sodium Octadecyl Sulfate at the Water/octane Interface

This study investigated the interactions of poly(amidoamine) (PAMAM) and sodium octadecyl sulfate (SOS) molecules at the water/octane interface by analyzing spatial structures and interfacial properties of water/PAMAM/SOS/octane (oil) systems. Coarse-grained molecular dynamic simulations were performed to examine the dependence of the systems on interfacial coverage (IC, corresponding to the concentration of SOS molecules) and PAMAM concentration (C-PAMAM) in terms of density profiles, interaction energy, interfacial thickness, order parameters (S-CD), interfacial tension (gamma), and area compressibility modulus (K-A). Simulation results showed that the presence of PAMAM molecules had a stronger effect on SOS head groups and pushed the head groups toward the oil phase. The interaction energy between PAMAM and SOS molecules increased with increments of C-PAMAM in a fixed IC. Interfacial thickness and S-CD increased with increased C-PAMAM. The gamma value in the presence of PAMAM was lower compared with pure SOS solutions and decreased with increased C-PAMAM. The area compressibility modulus (K-A) of SOS monolayer increased with increased C-PAMAM.