Molecular thermodynamic theory

In an effort to go beyond regular solution theory and better understand the molecular basis of mixed surfactant system behavior, several molecular-thermodynamic theories for surfactant mixtures have been developed. The molecular-thermodynamic theory will be brieLy introduced and discussed below. Readers are referred to a recent summary (Shiloach and Blankschtein, 1998) o can obtain more detailed description and discussion in literature (Nagarajan, 1985, 1986 Puwada and Blankschtein, 1990,1992 Nargarajan and Ruckenstein, 1991 Bergstroem and Eriksson, 1992 Sarmoria et al., 1992 Zoeller and Blankschtein, 1995, 1998 Almgren et al., 1996 Barzykin and Almgren, 1996 Bergstroem, 1996 Zoeller et al., 1996 Blankschtein et al., 1997 Shiloach and Blankschtein, 1997,1998 Thomas et al., 1997 Shiloach et al., 1998). 

In the molecular-thermodynamic theory of mixed micellization, the size and shape of the mixed micelles can also be predicted by calculating the size and composition distribution. This distribution can be expressed as a function of two fundamental parameters that control the size of the mixed micelles. The Lrst parameter, is deLned as (Puwada and Blankschtein, 1992a,b) to be... 

Recently, Huibers et al. (1996) presented a predictive model using topological predictors, which is capable of predicting CMC values for a wide variety of nonionic surfactants. Zoeller and Blankschtein (1995) attempted to predict CMC based on molecular-thermodynamic theory. Others have tried to predict the influence of temperature (Muller, 1993 Di Toro et al., 1990), of ionic strength (Carale et al., 1994 Di Toro et al., 1990), and of mixing (Zoeller et al., 1995) on the CMC. Combinations of these techniques could make it possible to predict CMCs as a measure of hydrophobicity of surfactants under given environmental conditions. 

Ashbaugh HS, Truskett TM, Debenedetti PG. A simple molecular thermodynamic theory of hydrophobic hydration. J. Chem. Phys. 2002 116 2907-2921. 

UV-visible, fluorescence, and IR spectroscopy have been used to characterize the solvent strength of pure and mixed supercritical fluid solvents, and to study solute-solvent interactions. The use of spectroscopic probes for the determination of clustering of pure and binary supercritical fluids about solutes is discussed. Spectroscopic studies of solvent strength and solute-solvent interactions are valuable for the development of molecular thermodynamic theory, engineering models, and for the molecular design of separation and reaction processes. 

S. Puvvada and D. Blankschtein, Molecular thermodynamic Theory of mixed micellar solution, in Mixed surfactant systems ACS symposium Series Vol. 501, Eds. ... 

Blankschtein and co-workers [65] have done pioneer work through theoretical modeling, aided by the computer, to predict the properties of mixed surfactant systems. Also, based on the necklace model proposed by Shirahama et al. [67,68], they have proposed a molecular thermodynamic theory of the com-plexation of nonionic polymers and surfactants in diluted aqueous solutions [66], Application of this method can help predict the interaction parameters for several nonionic polymer-surfactant mixtures. 

The molecular thermodynamic theory for micelle formation has heen worked out with increasing sophistication following the pioneering work of Israelachvili, Mitchell, and Ninham.26 The most comprehensive reports on micelle formation are those of Nagarajan and Ruckenstein and of Shiloah and Blankschtein. Many other theoretical approaches have been used in recent years to account for the formation of micelles and their properties thermod3mamics of small systems, the self-consistent field lattice model, the scaled particle theory, and Monte-Carlo and molecular dynamics MD simulations. MC and DC simulations are presently much in favor due to the increased availability of fast computers. A prediction common to all these theories is that micelles represent a thermodynamically stable state and that micellar solutions are single-phase systems. Several recent results of MD and (MC) simulations are in agreement with experimental results. ... 

Murphy, A., Taggart, G. A comparison of predicted and experimental critical micelle concentration values of cationic and anionic ternary surfactant mixtures using molecular-thermodynamic theory and pseudophase-separation theory. Colloids Surf. A 2002, 205(3), 237-248. 

The kinetic theory attempts to describe the individual molecules energies and interactions statistical thermodynamics attempts to fundamentally develop the equation of state from considerations of groupings of molecules. These approaches are complementary in many ways (3,123,124). A weU-referenced text covering molecular thermodynamics is also available (125). 

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

The development of theoretical chemistry ceased at about 1930. The last significant contributions came from the first of the modern theoretical physicists, who have long since lost interest in the subject. It is not uncommon today, to hear prominent chemists explain how chemistry is an experimental science, adequately practiced without any need of quantum mechanics or the theories of relativity. Chemical thermodynamics is routinely rehashed in the terminology and concepts of the late nineteenth century. The formulation of chemical reaction and kinetic theories take scant account of statistical mechanics and non-equilibrium thermodynamics. Theories of molecular structure are entirely classical and molecular cohesion is commonly analyzed in terms of isolated bonds. Holistic effects and emergent properties that could... 

A synopsis of the topics treated in this monograph follows. Chapter 1 is a brief survey of historical developments in the field of isotope effects through the early 1930s. Chapters 2 and 3 give developments of the fundamental quantum mechanical, thermodynamic, and molecular vibration theory required to under-... 

Mauritz et al., motivated by these experimental results, developed a statistical mechanical, water content and cation-dependent model for the counterion dissociation equilibrium as pictured in Figure 12. This model was then utilized in a molecular based theory of thermodynamic water activity, aw, for the hydrated clusters, which were treated as microsolutions. determines osmotic pressure, which, in turn, controls membrane swelling subject to the counteractive forces posed by the deformed polymer chains. The reader is directed to the original paper for the concepts and theoretical ingredients. 

Instead of the classical approaches, a molecular-based statistical thermodynamic theory can be applied to allow a model of adsorption to be related to the microscopic properties of the system in terms of fluid-fluid and fluid-solid interactions, pore size, pore geometry and temperature. Using such theories the whole range of pore sizes measured can be calculated using a single approach. Two simulation... 

Formal thermodynamics does not rest on KMT or other molecular assumptions (hence, their relegation to sidebar status in this book). Nevertheless, thermodynamic studies are highly valued for their ability to provide fundamental insights into the intermolecular forces that underlie chemical phenomena. Indeed, the most successful advances in thermodynamic theory and practice are often inspired by molecular insights, and the productive interplay between microscopic and macroscopic domains should be emphasized in a pedagogically useful presentation of thermodynamic principles. Accordingly, we discuss equations of state in terms of their ability to suggest improvements over the KMT ideal gas picture of intermolecular interactions. 

Current thermodynamic theories for polymer systems are combinations of the Flory -Huggins, Guggenheim, and Equations-of-State approaches. All of these theories make use of empirical parameters and are based on assumptions about the underlying molecular model. 

An important step in developing the mean-field concept was done by Landau [8, 10]. Without discussing the relation between such fundamental quantities as disorder-order transitions and symmetry lowering, we just want to note here that his theory is based on thermodynamics and the derivation of the temperature dependence of the order parameter via the thermodynamic potential minimization (e.g., the free energy A(r),T)) which is a function of the order parameter. It is assumed that the function A(rj,T) is analytical in the parameter 77 and thus near the phase transition point could be expanded into the series in 77 usually it is a polynomial expansion with temperature-dependent coefficients. Despite the fact that such a thermodynamical approach differs from the original molecular field theory, they are quite similar conceptually. In particular, the r.h.s. of the equation of state for the pressure of gases or liquids and the external field in ferromagnetics, respectively, have the same polynomial form. 

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