Structural and interfacial properties of the CO2-in-water foams prepared with Sodium Dodecyl Sulfate (SDS): A Molecular Dynamics Simulation study

Abstract Structural characteristics, interfacial distribution and molecular interactions of the components of the CO 2 (gas)/SDS/water/SDS/CO 2 (gas) systems as a function of the CO 2 (gas)/water interface coverage by the SDS surfactant to different amounts of the CO 2 were studied with molecular dynamics simulations and the NVT ensemble. Initially, the repulsive nonbonding parameter between the water oxygen and CO 2 oxygen was adjusted to improve the prediction of the solvation free energy, solubility of the CO 2 gas in water and the behavior of the CO 2 (gas)/SDS/water/SDS/CO 2 (gas) systems at molecular level. Our results show that the stability of the studied foams can be improved incrementing of the vapor/water interface coverage with the SDS surfactant and the amount of CO 2 in the system. With the highest interface coverage, the sulfate group has a molecular array more compact at the interface. Furthermore, CO 2 gas have a reduction of the diffusion across of the hydrocarbon chains to the water layer with an increment of the number of CO 2 molecules in the system, indicating a behavior more hydrophobic of the CO 2 gas. The tendencies obtained of the simulations are consistent with the reported experimental results.