Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics

Diamant, Haim; Andelman, David

doi:10.1016/j.cocis.2016.03.004

Cited by 18 publications

(13 citation statements)

References 43 publications

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“…Furthermore, the case is even more complex than that, since we have shown that complexation excess free energy is in competition with various quenching energy terms, such as the formation of curved extractant film, different headgroup repulsion, branching of the extractant chains, diluent penetration power, shrinkage of the accessible volume of the ions and water molecules confined in the polar core, energy penalties due to the breaking of stable HDEHP dimers, and dissociation of HDEHP. Only by considering all energy terms that contribute to the formation of the particular aggregate and all the independent system variables can the free energy of the system be properly minimized …”

Section: Resultsmentioning

confidence: 99%

Synergistic Solvent Extraction Is Driven by Entropy

et al. 2019

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In solvent extraction, the self-assembly of amphiphilic molecules into an organized structure is the phenomenon responsible for the transfer of the metal ion from the aqueous phase to the organic solvent. Despite their significance for chemical engineering and separation science, the forces driving the solute transfer are not fully understood. Instead of assuming the simple complexation reaction with predefined stoichiometry, we model synergistic extraction systems by a colloidal approach that explicitly takes into account the self-assembly resulting from the amphiphilic nature of the extractants. Contrary to the current paradigm of simple stoichiometry behind liquid–liquid extraction, there is a severe polydispersity of aggregates completely different in compositions, but similar in the free energy. This variety of structures on the nanoscale is responsible for the synergistic transfer of ions to the organic phase. Synergy can be understood as a reciprocal effect of chelation: it enhances extraction because it increases the configurational entropy of an extracted ion. The global overview of the complex nature of a synergistic mixture shows different regimes in self-assembly, and thus in the extraction efficiency, which can be tuned with respect to the green chemistry aspect.

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Section: Resultsmentioning

confidence: 99%

Synergistic Solvent Extraction Is Driven by Entropy

et al. 2019

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“…In this latter system and many others like it, there is an emerging consensus that solute aggregation can have a profound impact on the chemical behavior of the organic solution, notably on both the efficiency and selectivity of the process. − In fact, reverse micellar solvents with the macroscopic appearance of a homogeneous solution are routinely employed in organic- and biological-based separation, purification, and conversion processes with little understanding of the morphology and arrangement of the micelle domains. , These contemporary applications are revolutionizing fundamental separations concepts by shifting the focus away from the classical enthalpic drivers associated with local, molecular-scale interactions into multiscale-ordering, which is hypothesized to include large entropic contributions that may dominate the energy landscape of bulk behaviors that are hallmarks of coacervation and microemulsions . However, the relationships between the microscopic solute structures and phase behaviors remains largely unresolved.…”

Section: Introductionmentioning

confidence: 99%

A Telescoping View of Solute Architectures in a Complex Fluid System

et al. 2018

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Short- and long-range correlations between solutes in solvents can influence the macroscopic chemistry and physical properties of solutions in ways that are not fully understood. The class of liquids known as complex (structured) fluids—containing multiscale aggregates resulting from weak self-assembly—are especially important in energy-relevant systems employed for a variety of chemical- and biological-based purification, separation, and catalytic processes. In these, solute (mass) transfer across liquid–liquid (water, oil) phase boundaries is the core function. Oftentimes the operational success of phase transfer chemistry is dependent upon the bulk fluid structures for which a common functional motif and an archetype aggregate is the micelle. In particular, there is an emerging consensus that mass transfer and bulk organic phase behaviors—notably the critical phenomenon of phase splitting—are impacted by the effects of micellar-like aggregates in water-in-oil microemulsions. In this study, we elucidate the microscopic structures and mesoscopic architectures of metal-, water-, and acid-loaded organic phases using a combination of X-ray and neutron experimentation as well as density functional theory and molecular dynamics simulations. The key conclusion is that the transfer of metal ions between an aqueous phase and an organic one involves the formation of small mononuclear clusters typical of metal–ligand coordination chemistry, at one extreme, in the organic phase, and their aggregation to multinuclear primary clusters that self-assemble to form even larger superclusters typical of supramolecular chemistry, at the other. Our metrical results add an orthogonal perspective to the energetics-based view of phase splitting in chemical separations known as the micellar model—founded upon the interpretation of small-angle neutron scattering data—with respect to a more general phase-space (gas–liquid) model of soft matter self-assembly and particle growth. The structure hierarchy observed in the aggregation of our quinary (zirconium nitrate–nitric acid–water–tri-n-butyl phosphate–n-octane) system is relevant to understanding solution phase transitions, in general, and the function of engineered fluids with metalloamphiphiles, in particular, for mass transfer applications, such as demixing in separation and synthesis in catalysis science.

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“…A general method for the determination of the cmc from linear and nonlinear properties should be based on a common definition of the cmc directly related to the surfactant concentration itself and then derive the experimental properties from this concentration. The concentration model we propose is not the only possible and can still be refined and adapted, but it has so far proven to reproduce excellently several properties, to yield coherent cmc values and to contribute to a better understanding of how properties depend on the surfactant concentrations, the cmc and the transition width [ 23 , 24 , 64 ].…”

Section: Influence Of Nonlinear Property-concentration Relationships On the Cmc Valuementioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Al‐Soufi

Novo

2021

Molecules

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The critical micellar concentration (cmc) is a fundamental property of surfactant solutions. Many proposed methods for the definition and determination of the cmc from property-concentration plots yield values, which depend on the studied property, on the specific technique used for its analysis and in many cases on the subjective choice of the chosen type of plot and concentration interval. In this focus review, we revise the application of a surfactant concentration model we proposed earlier that defines the cmc directly based on the surfactant concentration. Known equations for the concentration-dependence of different surfactant properties can then be combined with this concentration model and fitted to experimental data. This modular concept makes it possible to determine the cmc and the transition width in a systematic and unambiguous way. We revise its use in the literature in different contexts: the determination of the cmc of surfactants and their mixtures from different properties (electrical conductivity, NMR chemical shift, self-diffusion, surface tension, UV-Vis absorption, fluorescence intensity and fluorescence correlation). We also revise the dependence of the width of the transition region on composition, detailed studies of the properties of fluorescent probes and the aggregation of non-surfactant systems, namely amyloid peptides.

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Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics

Cited by 18 publications

References 43 publications

Synergistic Solvent Extraction Is Driven by Entropy

Synergistic Solvent Extraction Is Driven by Entropy

A Telescoping View of Solute Architectures in a Complex Fluid System

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

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