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Mulab 7 free download1/6/2024 ![]() Carboxyl groups were the predominant groups in binding with Na⁺, and ethoxy segment within NPEO4C and NPEO7C were the governing groups in being solvated with water. Results showed that NPEO7C exhibited the highest activity in lowering the interfacial tension of n-decane/water, and kept the interfacial activity in the presence of NaCl. Salt tolerance of NPEOnC were estimated by the bound pairs between surfactant and water as well as those between surfactant and Na⁺, especially the structural relaxation dynamics of those bound pairs. ![]() The interfacial activities of NPEOnC were demonstrated by the arrangement of surfactant monolayer, the structures of n-decane/water interface, and the interfacial tensions. ![]() The interfacial activity in reducing interfacial tension and salt tolerance of NPEOnC were investigated and the effect of numbers of ethoxy unit were quantified. In the present study, carboxylated nonylphenol ethoxylate surfactant (NPEOnC, n = 2, 4, and 7) at n-decane/water interface has been studied using molecular dynamics simulation in the absence and in the presence of NaCl with different concentrations. Ionic alkoxy-based surfactants recently attract more attentions because they possess advantages of both nonionic and anionic surfactants, and surfactant structure is the key factor affecting the interfacial property and salt tolerance of ionic alkoxy-based surfactant. The results implied that biosurfactant surfactin and alkylbenzene sulfonate mixed well at the n‐decane/water interface, though they were both anionic surfactants. The results suggested that the structure of the mixed monolayers was more compact than that of the individual system of alkylbenzene sulfonate and the interfacial tension was more efficiently reduced, and the translational activities of both surfactants within the mixed monolayers were much lower. The density distributions of the surfactants along the direction normal to the interface, radial distribution functions of the surfactant head groups, hydrophobic contacts between surfactants, translational activities of both surfactants and counterions, and the dynamics of the hydrogen bonds formed between surfactant and water were calculated. In the present work, mixed monolayers of surfactin and branched alkylbenzene sulfonate at the n‐decane/water interface were studied using atomistic molecular dynamics simulations, and the presence of surfactin affecting the microstructure and dynamic properties of the mixed monolayer was evaluated at molecular level. Morphology of monolayer and molecular orientation were independent of the change in structure of headgroup, but surfactant with less methylene on the hydrophilic group had the less steric hindrance, which induced more hydration water, more neighboring surfactants, and more stable of binding pairs between COO⁻ and water.īiosurfactants show synergic effects with synthesized surfactant in reducing hydrophobic/hydrophilic interfacial tension, while the understanding of the synergistic mechanism is limited. As for the surfactants with the phenyl group located at 16- of the hydrophobic tail of BZS, molecules were arranged more perpendicular at the interface and formed a flat monolayer and construct stable binding pairs with water and cations. The results showed that waved monolayers were formed when the phenyl group located at the 7- carbon atom of the hydrophobic tail of BZS, and there were more hydration water and cations surrounding the hydrophilic group of surfactants. The structure-property relationship was demonstrated by the structure of surfactant monolayer, the overall arrangement of surfactant molecules at the interface, and the dynamic properties of binding pairs between surfactant and water/cations. ![]() The other three were the homologues of 10B, and were different in the structures of hydrophilic groups. The four of them were isomers of BZS, in which the phenyl groups were located at the 7-, 10-, 13-, and 16- carbon atom of the octadecanoyl group. In this study, molecular dynamics simulation was employed to investigate the interfacial behaviors of bio-based zwitterionic surfactants (BZS) with seven structures at the air/water interface. Therefore, understanding the relationship between the structure of bio-based zwitterionic surfactants and interfacial behaviors has significance for its industrial applications. Bio-based zwitterionic surfactants have received increasing attention owing to their structural diversity and good interfacial activity.
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