Effect of Bond Rigidity and Molecular Structure on the Self-Assembly of Amphiphilic Molecules Using Second-Order Classical Density Functional Theory

Abstract

Second-order classical density functional theory is applied to assess the effect of surfactant properties on the interfacial structure and interfacial tension of a planar oil/water interface. Specifically the affect of the relative locations of the hydrophobic and hydrophilic portions, rigidity vs flexibility, and bond angle of the surfactant are investigated. It is found that bond angle and branching significantly affect the tendency of a surfactant to adsorb on the interface and the degree to which the interfacial tension is lowered.

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

“…Additionally, since the iSAFT used in this work is based on Wertheim's first order thermodynamic perturbation theory(TPT1), the surfactant molecule is flexible and no bond rigidity is considered which can be included by a TPT2 approach. 44 Free energy contributions due to partial charges on surfactant molecules 12 may also be developed and included in the iSAFT framework for a more realistic description of the systems containing ionic surfactants. In the future, investigations on the effects of external conditions such as temperature and pressure on the formation of the micelle and the formation of microemulsions will be made.…”

“…Surfactants, being amphiphilic, are modeled as a chain built of oil-like segments and water-like segments. 27,33,44 The comparison of vapor pressures and saturated liquid densities between results from iSAFT and experiments is shown in Figure 3. For the segments in the head of surfactants, the water diameter and Lennard-Jones energy are used.…”

Janus dumbbells near surfaces modified with tethered chains

“…The considered model of the dumbbell can be viewed as a coarse-grained model of real amphiphilic molecules or small colloidal particles (Marshall et al 2012;Mondal and Yethiraj 2011;Thompson et al 2012). The amphiphiles contain both solvophobic and solvophilic parts.…”

Extensions of the SAFT model for complex association in the bulk and interface

“…In this section, we will focus on inhomogeneous systems with the presence of surfactants and the application of interfacial Statistical Associating Fluid Theory or iSAFT [25,68] for such systems. iSAFT has been applied to block copolymers [69,70], polymer brushes [71][72][73], associating molecules [74][75][76][77][78], and surfactants [79,80]. Here we consider micelle formation.…”

“…The theoretical tool we use to study the structure and properties of these systems is the interfacial Statistical Associating Fluid Theory or iSAFT [25,68]. iSAFT was previously used to explore the parameter space of structure-property relationships of surfactants at liquid-liquid interfaces by Emborsky et al [79] and study the behavior of amphiphilic molecules with associating sites at water/oil interface by Marshall et al [78,80]. The theory has been shown to be able to produce Traube's rule [83] and reveal the structure and properties of interfaces in good agreement with molecular simulations [77].…”