Computer Simulation–Molecular-Thermodynamic Framework to Predict the Micellization Behavior of Mixtures of Surfactants: Application to Binary Surfactant Mixtures

Abstract

We present a computer simulation-molecular-thermodynamic (CSMT) framework to model the micellization behavior of mixtures of surfactants in which hydration information from all-atomistic simulations of surfactant mixed micelles and monomers in aqueous solution is incorporated into a well-established molecular-thermodynamic framework for mixed surfactant micellization. In addition, we address the challenges associated with the practical implementation of the CSMT framework by formulating a simpler mixture CSMT model based on a composition-weighted average approach involving single-component micelle simulations of the mixture constituents. We show that the simpler mixture CSMT model works well for all of the binary surfactant mixtures considered, except for those containing alkyl ethoxylate surfactants, and rationalize this finding molecularly. The mixture CSMT model is then utilized to predict mixture CMCs, and we find that the predicted CMCs compare very well with the experimental CMCs for various binary mixtures of linear surfactants. This paper lays the foundation for the mixture CSMT framework, which can be used to predict the micellization properties of mixtures of surfactants that possess a complex chemical architecture, and are therefore not amenable to traditional molecular-thermodynamic modeling.

Molecular thermodynamics of soft self-assembling structures for engineering applications

“…This general theoretical problem still awaits solution. Currently there are only a few first steps towards solving this problem within molecular thermodynamic models.…”

“…The relation between this approach and the classical aggregation models has been established . Classical aggregation models have been extended to describe solubilization and microemulsions, and new methods are emerging as discussed below.…”

“…36,37,53 Impressively good prediction has been obtained from COSMOmic for a large number of organic solutes that partition between the solution and a mixed micelle 37 or a lipid membrane. 36 In the so-called computer simulation − molecular-thermodynamic (CSMT) framework 17,34,35 the hydrophobic and the interfacial terms of a classical micellization model are corrected from detailed knowledge of the hydration states of surfactant molecules gained from a full-atom MD simulation. Both individual surfactants and mixed perfluorocarbon-hydrocarbon surfactant's micelles have been described very well by this new method.…”

Communication: Truncated non-bonded potentials can yield unphysical behavior in molecular dynamics simulations of interfaces

“…If the resulting metastability of states remains undetected, the use of truncated interaction potentials could lead to wrong inferences about physical properties being made. While this conclusion has resulted from a simulation of wetting, similar implications could hold for other interfacial phenomena such as capillary flow 40,41 , evaporation/condensation 42,43 , mixtures [44][45][46] or heterogeneous nucleation [47][48][49][50][51] where it is commonplace to use truncated interactions.…”

A Surfactant Concentration Model for the Systematic Determination of the Critical Micellar Concentration and the Transition Width

“…The big variety of empiric procedures for the determination of the cmc from experimental data is probably also due to the complex physicochemical models and numeric simulations of the micellization process [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Although increasingly sophisticated and precise, these models and simulations are not aimed towards the analysis of experimental data and therefore do not offer fitting functions with the cmc as an adjustable parameter that could be fitted to experimental data.…”