Surfactant chain length and concentration influence on the interfacial tension of two immiscible model liquids a coarse grained approach

TL;DR

This study uses coarse grained simulations to analyze how surfactant chain length and concentration affect the interfacial tension between two immiscible liquids, aligning with theoretical models and predicting critical micelle concentrations.

Contribution

It provides a computational approach to understanding surfactant effects on interfacial tension, validating models like Langmuir and Szyszkowski, and predicting critical micelle concentrations.

Findings

Interfacial tension decreases with surfactant concentration across chain lengths.

Adsorption isotherms match Langmuir model predictions.

Critical micelle concentration decreases exponentially with chain length.

Abstract

The interfacial tension between immiscible liquids is studied as a function of a model linear surfactant length and concentration using coarse grained, dissipative particle dynamics numerical simulations. The adsorption isotherms obtained from the simulations are found to be in agreement with Langmuir model. The reduction of the interfacial tension with increasing surfactant concentration is found to display some common characteristics for all the values of chain length modeled, with our predictions being in agreement with Szyszkowski equation. Lastly, the critical micelle concentration is predicted for all surfactant lengths, finding exponentially decaying behavior, in agreement with Kleven model. It is argued that these findings can be helpful guiding tools in the interpretation of available experiments and in the design of new ones with new surfactants and polymers.