Systematic Parameterization of Ion-Surfactant Interactions in Dissipative Particle Dynamics Using Setschenow...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Soft Matter Physics

Background:

• Nonionic surfactants form micelles, and their critical micelle concentration (CMC) is influenced by additives like salts.
• The Setschenow relationship describes the salting-out effect on solute solubility, often applied to CMC changes.
• Understanding ion-specific effects on surfactant behavior is crucial for various applications.

Purpose of the Study:

• To investigate the effect of added salt on nonionic surfactant micelle formation using Dissipative Particle Dynamics (DPD) simulations.
• To validate the Setschenow relationship in a simulated system and determine the Setschenow coefficients.
• To develop a systematic method for parameterizing ion-surfactant interactions based on experimental data.

Main Methods:

• Performing DPD simulations of nonionic surfactants in the presence of varying salt concentrations.
• Analyzing simulation data to determine the critical micelle concentration (CMC) at each salt concentration.
• Calculating Setschenow coefficients from the simulated CMC data.
• Optimizing DPD parameters for ion-surfactant interactions by matching simulated Setschenow coefficients to experimental values.

Main Results:

• The DPD simulations successfully reproduced the Setschenow relationship, showing a log-linear dependence of CMC on salt concentration.
• Simulated Setschenow coefficients were found to depend on DPD bead-bead repulsion amplitudes.
• Matching simulated coefficients to experimental values provided a systematic way to parameterize ion-surfactant interactions.
• The optimized ion-specific interaction parameters were transferable and aligned with the trends observed in the empirical Hofmeister series.

Conclusions:

• DPD simulations are a viable tool for studying the effects of salt on surfactant aggregation behavior.
• The study provides a robust method for parameterizing ion-specific interactions in DPD simulations.
• The findings support the applicability of the Hofmeister series trends to ion-surfactant interactions at a molecular simulation level.