Molecular Thermodynamic Modeling of Droplet-Type Microemulsions

Moreira, Livia A.; Firoozabadi, Abbas

doi:10.1021/la203909b

Cited by 13 publications

(20 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Molecular-thermodynamic theory (MTT) provides yet another framework for the calculation of adsorption isotherms. MTT models are predictive in capturing nonideal free-energy contributions and have also been extended beyond pure adsorption predictions, e.g., for capturing micellization and microemulsion formation. − However, as with the adsorption isotherms discussed above, the utilization of MTT models requires the determination of numerous parameters, if not by experiment, then via empirical models. For example, one of the fundamental parameters in MTT is the driving force for surfactant adsorption, a parameter that, at the air–water interface, is mainly governed by the transfer free energy of the hydrophobic surfactant segment.…”

Section: Introductionmentioning

confidence: 99%

Combined Molecular Dynamics Simulation–Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions

et al. 2017

View full text Add to dashboard Cite

A molecular modeling approach is presented with a focus on quantitative predictions of the surface tension of aqueous surfactant solutions. The approach combines classical Molecular Dynamics (MD) simulations with a molecular-thermodynamic theory (MTT) [ Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992 , 8 , 2680 ]. The MD component is used to calculate thermodynamic and molecular parameters that are needed in the MTT model to determine the surface tension isotherm. The MD/MTT approach provides the important link between the surfactant bulk concentration, the experimental control parameter, and the surfactant surface concentration, the MD control parameter. We demonstrate the capability of the MD/MTT modeling approach on nonionic alkyl polyethylene glycol surfactants at the air-water interface and observe reasonable agreement of the predicted surface tensions and the experimental surface tension data over a wide range of surfactant concentrations below the critical micelle concentration. Our modeling approach can be extended to ionic surfactants and their mixtures with both ionic and nonionic surfactants at liquid-liquid interfaces.

show abstract

Section: Introductionmentioning

confidence: 99%

Combined Molecular Dynamics Simulation–Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions

et al. 2017

View full text Add to dashboard Cite

show abstract

“…They also assumed that only small micelles could be formed, with either a spherical or globular shape. In their subsequent works (Moreira and Firoozabadi, 2010;Moreira and Firoozabadi, 2012;Lukanov and Firoozabadi, 2014) those aspects were kept the same. Therefore, to the best of our knowledge, the present work is the only one that considers the minimum Gibbs free energy as the most stable state together with the micelles' size distributions and also analyzes the transition between small (spherical) and rod-like (spherocylindrical) micelles as a function of temperature and salt concentration.…”

Section: Introductionmentioning

confidence: 99%

Molecular Thermodynamics of Micellization: Micelle Size Distributions and Geometry Transitions

Santos

Tavares

Biscaia

2016

Braz. J. Chem. Eng.

View full text Add to dashboard Cite

-Surfactants are amphiphilic molecules that can spontaneously self-assemble in solution, forming structures known as micelles. Variations in temperature, pH, and electrolyte concentration imply changes in the interactions between surfactants and micelle stability conditions, including micelle size distribution and micelle shape. Here, molecular thermodynamics is used to describe and predict conditions of micelle formation in surfactant solutions by directly calculating the minimum Gibbs free energy of the system, corresponding to the most stable condition of the surfactant solution. In order to find it, the proposed methodology takes into account the micelle size distribution and two possible geometries (spherical and spherocylindrical). We propose a numerical optimization methodology where the minimum free energy can be reached faster and in a more reliable way. The proposed models predict the critical micelle concentration well when compared to experimental data, and also predict the effect of salt on micelle geometry transitions.

show abstract

“…To determine the effect and importance of polydispersity, we first investigate the ternary mixture of didodecyl dimethylammonium bromide (DDABr), water, and n-hexane. This system was studied in detail by Moreira and Firoozabadi, 23 allowing us to directly compare the two approaches. Figure 2a shows a surface plot of the Gibbs free energy function versus two independent variables (a and g O I /g S I ) as presented by Moreira and Firoozabadi.…”

Section: Resultsmentioning

confidence: 99%

“…The only other molecular thermodynamic model that we are aware of is by Moreira and Firoozabadi. 23 They adopted parts of Nagarajan and Ruckenstein's theory to develop a theoretical framework for droplet-type microemulsions based on global minimization of the Gibbs free energy. One of the main conclusions in their paper was that the assumption of monodispersity (also known as the maximum term approximation) exploited by both models is not a good approximation and that polydispersity needs to be accounted for, in contrast to micelle formation in aqueous systems.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Thermodynamic Modeling of Reverse Micelles and Water-in-Oil Microemulsions

Lukanov

Firoozabadi

2016

Langmuir

Self Cite

View full text Add to dashboard Cite

Surfactant aggregation plays an important role in a variety of chemical and biological nanoscale processes. On a larger scale, using small amounts of amphiphiles compared to large volumes of bulk-phase modifiers can improve the efficiency and reduce the environmental impact of many chemical and industrial processes. To model ternary mixtures of polar, nonpolar, and amphiphilic molecules, we develop a molecular thermodynamic theory for polydisperse water-in-oil (W/O) droplet-type microemulsions and reverse micelles based on global minimization of the Gibbs free energy of the system. The incorporation of size polydispersity into the theoretical formulation has a significant effect on the Gibbs free energy landscape and allows us to accurately predict micelle size distributions and micelle size variation with composition. Results are presented for two sample ionic surfactant/water/oil systems and compared with experimental data. By predicting the structural and compositional characteristics of w/o microemulsions, the molecular thermodynamic approach provides an important bridge between the modeling of ternary systems at the molecular and the macroscopic level.

show abstract

Molecular Thermodynamic Modeling of Droplet-Type Microemulsions

Cited by 13 publications

References 47 publications

Combined Molecular Dynamics Simulation–Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions

Combined Molecular Dynamics Simulation–Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions

Molecular Thermodynamics of Micellization: Micelle Size Distributions and Geometry Transitions

Molecular Thermodynamic Modeling of Reverse Micelles and Water-in-Oil Microemulsions

Contact Info

Product

Resources

About