C12E6 and SDS surfactants simulated at the vacuum-water interface

Area of Science:

• Physical Chemistry
• Surface Science
• Computational Chemistry

Background:

• Surfactants self-assemble at interfaces, influencing material properties.
• Understanding aggregate structure is crucial for applications like emulsification and drug delivery.
• Molecular dynamics simulations offer atomic-level insights into interfacial phenomena.

Purpose of the Study:

• To investigate the impact of surface coverage on the aggregate structure of nonionic C(12)E(6) and anionic SDS surfactants.
• To compare the interfacial behavior and aggregate morphologies of C(12)E(6) and SDS.
• To elucidate the role of surfactant head group properties in determining interfacial organization.

Main Methods:

• Molecular dynamics simulations were employed to study surfactant behavior at the vacuum-water interface.
• Simulations were conducted across various surface coverages to observe structural transitions.
• Analysis focused on aggregate morphology, tail group orientation, and planar mobility.

Main Results:

• C(12)E(6) tail groups orient less perpendicularly to the interface than SDS.
• Interfacial C(12)E(6) transitions from a gaslike to a liquidlike phase with increasing surface density.
• C(12)E(6) aggregates remain more disordered than SDS aggregates, even at high coverage.
• Both surfactants show non-monotonic changes in planar mobility with varying surface area per molecule.

Conclusions:

• Surfactant head group characteristics (nonionic/flexible vs. ionic/rigid) significantly influence interfacial aggregate structure and dynamics.
• C(12)E(6)'s flexible, nonionic head groups lead to less ordered interfacial assemblies compared to SDS.
• The findings provide fundamental insights into surfactant self-assembly driven by molecular structure and surface coverage.