Molecular Dynamics Simulations and Free Energy Perturbation Calculations of Alkyl Aryl Sulfonate

To investigate the influence of surfactant molecular structure on micellization in solution, we used molecular dynamics to simulate the molecular structure and interaction of three alkyl aryl sulfonates in vacuum and in solution. The solvation free energy was calculated from the free energy perturbation (FEP) method and the obtained result was consistent with that obtained using the Surface tension method. Research has shown that the micellization of alkyl aryl sulfonates in an aqueous solution is a spontaneous process as the aromatic ring shifts from the edge to the center of long carbonic chains, which results in a decrease in the ability of micelles to form and a decrease in their stability. Changes in the "iceberg structure" around the hydrophobic groups and the water molecules may affect the stability of the micelles and we studied the "iceberg structure" by considering the lifetime of the hydrogen bonds. Additionally, we find that the number of hydrogen bonds between the hydrophilic groups of the alkyl aryl sulfonates and the water molecules can affect the decomposition and stability of the micelles.