Download or read book Theoretical and Simulations based Modeling of Micellization in Linear and Branched Surfactant Systems written by Jonathan David Mendenhall and published by . This book was released on 2012 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surfactants are chemically-heterogeneous molecules possessing hydrophilic (head) and hydrophobic (tail) moieties. This dual nature of surfactants leads to interesting phase behavior in aqueous solution as a function of surfactant concentration, including: (i) formation of surfactant monolayers at surfaces and interfaces, and (ii) self-assembly into finite aggregates (micelles) in the bulk solution beyond the critical micelle concentration (cmc). This concentration-dependent phase behavior induces changes in solution properties. For example, the surface activity of surfactants can decrease the surface tension, and self-assembly in bulk solution can lead to changes in viscosity, equivalent conductivity, solubilization capacity, and other bulk properties. These effects make surfactants quite attractive and unique for use in product formulations, where they are utilized as detergents, dispersants, emulsifiers, solubilizers, surface and interfacial tension modifiers, and in other contexts. The specific chemical structure of the surfactant head and tail is essential in determining the overall performance properties of a surfactant in aqueous media. The surfactant tail drives the self-assembly process through the hydrophobic effect, while the surfactant head imparts a certain extent of solubility to the surfactant in aqueous solution through preferential interactions with the hydrogen-bonding network of water. The interplay between these two effects gives rise to the particular phase diagram of a surfactant, including the specific cmc at which micelles begin to form. In addition to serving as a quantitative indicator of micelle formation, the cmc represents a limit to surface monolayer formation, and hence to surface and interfacial tension reduction, because surfactant adsorption at interfaces remains approximately constant beyond the cmc. In addition, the cmc represents the onset of changes in bulk solution properties. This Thesis is concerned with the prediction of cmc's and other micellization properties for a variety of linear and branched surfactant chemical architectures which are commonly encountered in practice. Single-component surfactant solutions are investigated, in order to clarify the specific contributions of the surfactant head and tail to the free energy of micellization, a quantity which determines the cmc and all other aspects of micellization. First, a molecular-thermodynamic (MT) theory is presented which makes use of bulk-phase thermodynamics and a phenomenological thought process to describe the energetics related to the formation of a micelle from its constituent surfactant monomers. Second, a combined computer-simulation/molecular-thermodynamic (CSMT) framework is discussed which provides a more detailed quantification of the hydrophobic effect using molecular dynamics simulations. A novel computational strategy to identify surfactant head and tail using an iterative dividing surface approach, along with simulated micelle results, is proposed. Force-field development for novel surfactant structures is also discussed. Third, a statistical-thermodynamic, single-chain, mean-field theory for linear and branched tail packing is formulated, which enables quantification of the specific energetic penalties related to confinement and constraint of surfactant tails within micelles. Finally, these theoretical and simulations-based strategies are used to predict the micellization behavior of 55 linear surfactants and 28 branched surfactants. Critical micelle concentration and optimal micelle properties are reported and compared with experiment, demonstrating good agreement across a range of surfactant head and tail types. In particular, the CSMT framework is found to provide improved agreement with experimental cmc's for the branched surfactants considered.
Download or read book Theoretical Modeling of Micellization and Solubilization in Ionic Surfactant Systems written by Vibha Srinivasan and published by . This book was released on 2003 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) The micellization theory was applied to surfactant solutions containing monovalent counterions (specifically, alkali metal ions), multivalent counterions (specifically, A13+ and Ca2+), and organic counterions having pendant hydrophobic groups that penetrate into the micelle core (specifically, the salicylate ion). For all the surfactant systems considered, the quantitative predictions made compared well with the relevant experimental results available in the literature. The second objective of this thesis was to study the effect of the surfactant tail (chain) molecular structure on the surfactant micellar solution properties, for surfactants having more complex tail structures than linear alkyl tails, including: (i) branched akyl tails, (ii) alkylbenzene tails, and (iii) fluorocarbon tails. For surfactants with branched alkyl tails and alkylbenzene tails, a single-chain mean-field theory of chain packing was combined with suitable Rotational Isomeric State (RIS) models describing the chain torsional conformations, and the chain conformational characteristics as well as the packing free energy were predicted. Although the micellar solution properties of these surfactants were not investigated, the predicted packing characteristics can be viewed as a valuable "first-step" in the development of a comprehensive, predictive, molecularly-based micellization theory for these surfactants. In the case of fluorocarbon surfactants, in addition to modeling chain packing within the micelle core using suitable RIS models for the fluorocarbon chains, the remaining free-energy changes associated with micelle formation were modeled as well ...
Download or read book A Computer Simulation and Molecular thermodynamic Framework to Model the Micellization of Ionic Branched Surfactants in Aqueous Solution written by Shangchao Lin and published by . This book was released on 2008 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) Another key input required in the CS-MT modeling approach is the fractional degree of hydration of each atomic group in the ionic branched surfactants considered in this thesis, which can be used to accurately quantify the hydrophobic driving force for micelle formation in aqueous media. Fractional hydration profiles were obtained by conducting two MD simulations, one in a bulk water environment and the other in a micellar environment. By investigating the radial distribution function (RDF) between each surfactant group and hydrating atoms which are capable of forming hydrogen-bonds and coordinate-bonds, an updated cutoff distance for counting hydrating contacts was selected. These simulated fractional hydration profiles were then utilized as inputs in the MT model, which enables calculation of the minimum free energy associated with micelle formation, from which the CMC and the optimal micelle shape and size can be predicted at the molecular level. The MD simulations were shown to extend the applicability of the traditional MT modeling approach to more complex surfactant systems than had been possible to date. A rich variety of ionic branched surfactants were modeled using the new CS-MT modeling approach, including two homologous series of simple secondary alkyl sulfonates and three classes of more complex ionic branched surfactants possessing aromatic moieties. For each of the ionic branched surfactants modeled, the predictions of the CS-MT modeling approach were found to be in reasonable agreement with the experimental data, including accounting for the chemical and structural complexities of the branched surfactants more accurately. The CS-MT modeling approach developed in this thesis not only extends our ability to make accurate molecular-level predictions of the micellization behavior of complex surfactants, but it also contributes to our overall fundamental understanding of the solution behavior of surfactants.
Download or read book Modeling the Micellization Behavior of Fluorosurfactants Using Molecular thermodynamic Theory written by Jaisree Kannan Iyer and published by . This book was released on 2013 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluorinated surfactants are an important class of surfactants because they possess properties that are far superior than those of their hydrocarbon analogs. As a result, they are used in a wide variety of applications including in paints, polishes, fire-fighting foams, and emulsion polymerization processes. However, concerns regarding the non-biodegradability and toxicity of fluorinated surfactants have prompted the search for new, benign alternative surfactant formulations that possess micellization properties comparable to those of traditional fluorinated surfactants. With this need in mind, this thesis focuses on gaining a molecular-level understanding of the micellization behavior of traditional fluorinated surfactants, and then using the acquired knowledge to design novel surfactant formulations that can reduce the use of fluorinated surfactants. Molecular-thermodynamic (MT) models were developed to calculate the various contributions to the free energy of micellization for discoidal and biaxial ellipsoidal micelles; two important micelle shapes in the context of fluorocarbon-based surfactants. These models explicitly incorporate the effect of the position-dependent curvature associated with discs and biaxial ellipsoids. Comparison between the models developed here with those that do not explicitly account for the varying curvature shows that accounting for the position-dependent curvature is extremely important in modeling these two micelle shapes. The new MT model for the free energy of micellization is also used to demonstrate the feasibility of realizing biaxial ellipsoidal micelles, a result refuted in the past in many theoretical studies on the basis of average geometrical properties of the micelle. A new computer-simulation-molecular-thermodynamic (CSMT) framework was developed to predict the micellization behavior of mixtures of fluorocarbon-based surfactants. To facilitate the practical implementation of the mixture CSMT framework, which involves the computationally intensive task of simulating several mixed micelles, an approximation to the mixture CSMT model was developed. In this approximation, relevant properties for a mixed micelle are estimated using a micelle-composition based weighted average of the analogous properties obtained from simulations of the single-component surfactant micelles for each of the surfactants comprising the mixture. Therefore, in this approximation, the need for simulating mixed micelles is eliminated. The approximation was found to compare well with the mixture CSMT model for various binary surfactant mixtures considered, except for those containing alkyl ethoxylate surfactants. A rationalization of this finding is presented. CMC predictions made using the mixture CSMT model were found to compare very well with the experimental CMCs for several binary mixtures of linear surfactants, thereby laying the foundation for using the CSMT model to predict micellization properties of mixtures of surfactants that have a more complex chemical architecture. Finally, an MT framework was also developed to predict the micellization properties of mixtures of fluorocarbon-based and hydrocarbon-based surfactants. This mixing reduces the use of fluorinated surfactants in the surfactant formulation, thereby addressing the non-biodegradability and toxicity concerns associated with fluorinated surfactants. An enthalpy of mixing contribution resulting from the interactions between the fluorocarbon tails and the hydrocarbon tails, estimated using the Regular Solution Theory, was included in the MT framework. The ability of the MT framework to predict the coexistence of two types of mixed micelles in solution was demonstrated. The MT framework predictions of micelle population distributions, CMCs, and optimal micelle compositions were compared with the experimental values for various mixtures of fluorocarbon-based and hydrocarbon-based surfactants. The models developed in this thesis provide a molecular level understanding of the micellization behavior of fluorocarbon-based surfactants and their mixtures. The models are able to predict several important micellization properties of surfactants and their mixtures that can guide surfactant formulators in the synthesis, characterization, design, and optimization of surfactant formulations that exhibit desirable properties.
Download or read book Lattice Monte Carlo Simulations of Mixed Surfactant Systems and Polymer Surfactant Systems written by Michael J. Zaldivar and published by . This book was released on 2003 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Dynamics Simulations of Micellization in Model Surfactant CO2 Systems written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mixed Surfactant Systems written by Keizo Ogino and published by CRC Press. This book was released on 1992-12-22 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work describes the solubility, solution properties, thermodynamics, miscibility, solubilization, mesomorphic character and other physical properties of mixed surfactant systems - presenting both theoretical analysis and a wide range of practical applications. Equations clarify complex and abstract constructs.;The book also: treats mixed critical micelle concentrations, surface tension, flotation and absorption in terms of thermodynamic models; explores the miscibility of fluorocarbon and hydrocarbon surfactants in the micelles, covering micelle formation, liquid-liquid solubility and thermodynamics of mixed micellization; determines the mean aggregation number by steady-state quenching methods, and analyzes the composition of mixed micelles; discusses the mechanisms and experimental studies of adsorption from mixed surfactant systems; examines surface activity of surfactant mixtures, mixing phenomena and liquid crystal phase behaviour; and reviews means of investigation that use ion-specific electrodes, light scattering, and NMR and flourescence probing.
Download or read book Molecular Dynamics Simulations of Micellization in Model Surfactant written by Zhengmin Li and published by . This book was released on 2003 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: micelle, supercritcal carbon dioxide, surfactant.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2003 with total page 778 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Giant Micelles written by Raoul Zana and published by CRC Press. This book was released on 2007-05-30 with total page 577 pages. Available in PDF, EPUB and Kindle. Book excerpt: The co-evolution of a strong theoretical framework alongside application of a range of sophisticated experimental tools engendered rapid advancement in the study ofgiant micelles. Beginning with Anacker and Debye's 1951 experimental study of elongated micelles by light scattering and their subsequent theoretical inference that the thermodynamic
Download or read book Petroleum Abstracts written by and published by . This book was released on 1992 with total page 1716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Wormlike Micelles written by Cecile A Dreiss and published by Royal Society of Chemistry. This book was released on 2017-03-21 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wormlike Micelles describes the latest developments in the field including new systems, characterization and applications.
Download or read book Phenomena in Mixed Surfactant Systems written by John F. Scamehorn and published by . This book was released on 1986 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Micellar Catalysis written by Mohammad Niyaz Khan and published by CRC Press. This book was released on 2006-08-24 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micelles are prevalent in naturally occurring and biological catalytic reactions. However, it is only in recent decades that scientists have developed kinetic models clarifying how micelle-mediated catalysis works at a molecular level. Written by a leading expert in the field, Micellar Catalysis is an in-depth examination of how micelles affect rea
Download or read book Mixed Surfactant Systems written by Paul M. Holland and published by . This book was released on 1992 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a broad survey of the properties, behavior, and modeling of mixed surfactant systems, including mixed micellar solutions, phenomena at interfaces, phase behavior, and mixtures with unusual surfactant types. Covers chemical reactions in mixed micelles, approaches to molecular modeling of mixed surfactant aggregates, and new experimental techniques for studying mixed micelles and adsorption on surfaces. Features contributions from leading specialists in colloid and surface science, including Robert S. Schechter, John F. Scamehorn, Milton J. Rosen, Keizo Ogino, and Denver G. Hall.
Download or read book Self Assembly written by Ramanathan Nagarajan and published by John Wiley & Sons. This book was released on 2019-01-07 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: An introduction to the state-of-the-art of the diverse self-assembly systems Self-Assembly: From Surfactants to Nanoparticles provides an effective entry for new researchers into this exciting field while also giving the state of the art assessment of the diverse self-assembling systems for those already engaged in this research. Over the last twenty years, self-assembly has emerged as a distinct science/technology field, going well beyond the classical surfactant and block copolymer molecules, and encompassing much larger and complex molecular, biomolecular and nanoparticle systems. Within its ten chapters, each contributed by pioneers of the respective research topics, the book: Discusses the fundamental physical chemical principles that govern the formation and properties of self-assembled systems Describes important experimental techniques to characterize the properties of self-assembled systems, particularly the nature of molecular organization and structure at the nano, meso or micro scales. Provides the first exhaustive accounting of self-assembly derived from various kinds of biomolecules including peptides, DNA and proteins. Outlines methods of synthesis and functionalization of self-assembled nanoparticles and the further self-assembly of the nanoparticles into one, two or three dimensional materials. Explores numerous potential applications of self-assembled structures including nanomedicine applications of drug delivery, imaging, molecular diagnostics and theranostics, and design of materials to specification such as smart responsive materials and self-healing materials. Highlights the unifying as well as contrasting features of self-assembly, as we move from surfactant molecules to nanoparticles. Written for students and academic and industrial scientists and engineers, by pioneers of the research field, Self-Assembly: From Surfactants to Nanoparticles is a comprehensive resource on diverse self-assembly systems, that is simultaneously introductory as well as the state of the art.
Download or read book Surfactants and Polymers in Aqueous Solution written by Krister Holmberg and published by Wiley. This book was released on 2002-11-22 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many industrial formulations such as detergents, paints, foodstuff and cosmetics contain both surfactants and polymers and their interaction govern many of the properties. This book is unique in that it discusses the solution chemistry of both surfactants and polymers and also the interactions between the two. The book, which is based on successful courses given by the authors since 1992, is a revised and extended version of the first edition that became a market success with six reprints since 1998. Surfactants and Polymers in Aqueous Solution is broad in scope, providing both theoretical insights and practical help for those active in the area. This book contains a thorough discussion of surfactant types and gives information of main routes of preparation. A chapter on novel surfactants has been included in the new edition. Physicochemical phenomena such as self-assembly in solution, adsorption, gel formation and foaming are discussed in detail. Particular attention is paid to the solution behaviour of surfactants and polymers containing polyoxyethylene chains. Surface active polymers are presented and their interaction with surfactants is a core topic of the book. Protein-surfactant interaction is also important and a new chapter deals with this issue. Microemulsions are treated in depth and several important application such as detergency and their use as media for chemical reactions are presented. Emulsions and the choice of emulsifier is discussed in some detail. The new edition also contains chapters on rheology and wetting. Surfactants and Polymers in Aqueous Solution is aimed at those dealing with surface chemistry research at universities and with surfactant formulation in industry.
