Microemulsions: Structure and Dynamics


Book Description

This book describes the microemulsion phenomenon in a systematic manner and not only provides an up-to-date introduction to this topic but aslo serves as the basis for further development in the area.The progress of microemulsion research has taken place in well-defined stages. The introduction period was founded on Schulman‘s original discovery and was, as expected, focused on the interfacial free energy. Because Schulman obtained his microemulsions from a macroemulsion by the addition of a cosurfactant.The present stage is characterized by an extensively enhanced knowledge about structure and dynamics in these systems. This has led to the realization that the structure of the microemulsions is related both to solutions with critical behaviour and long range order structures, the lyotropic liquid crystals. These two aspects have been elucidated independently by the French groups and by the Lund Spectroscopy group.




Microemulsions: Structure and Dynamics


Book Description

This book describes the microemulsion phenomenon in a systematic manner and not only provides an up-to-date introduction to this topic but aslo serves as the basis for further development in the area.The progress of microemulsion research has taken place in well-defined stages. The introduction period was founded on Schulman‘s original discovery and was, as expected, focused on the interfacial free energy. Because Schulman obtained his microemulsions from a macroemulsion by the addition of a cosurfactant.The present stage is characterized by an extensively enhanced knowledge about structure and dynamics in these systems. This has led to the realization that the structure of the microemulsions is related both to solutions with critical behaviour and long range order structures, the lyotropic liquid crystals. These two aspects have been elucidated independently by the French groups and by the Lund Spectroscopy group.




Micellar Solutions and Microemulsions


Book Description

During the last decade there has been a renewed interest in research on supramolecular assemblies in solutions, such as micelles and microemulsions, not only because of their extensive applications in industries dealing with catalysts, detergency, biotechnology, and enhanced oil recovery, but also due to the development of new and more powerful experimental and theoretical tools for probing the microscopic behavior of these systems. Prominent among the array of the newly available experimental techniques are photon correlation spectroscopy, small-angle neutron and X-ray scattering, and neutron spin-echo and nuclear magnetic resonance spectroscopies. On the theoretical side, the traditionally emphasized thermodynamic approach to the study of the phase behavior of self-assembled systems in solutions is gradually being replaced by statistical mechanical studies of semi-micro scopic and microscopic models of the assemblies. Since the statistical mechanical approach demands as its starting point the microscopic struc tural information of the self-assembled system, the experimental determina tion of the structures of micelles and microemulsions becomes of paramount interest. In this regard the scattering techniques mentioned above have played an important role in recent years and will continue to do so in the future. In applying the scattering techniques to the supramolecular species in solution, one cannot often regard the solution to be ideal. This is because the inter-aggregate interaction is often long-ranged since it is coulombic in nature and the interparticle correlations are thus appreciable.










Microemulsions


Book Description




Structure and Dynamics of Microemulsions in Bulk, at Interfaces, and in Confined Geometries . Progress Report


Book Description

The authors have been constructing a special purpose small angle neutron scattering spectrometer (SAND) in collaboration with IPNS of Argonne National Laboratory and Texaco Research Laboratories in Beacon, New York. The spectrometer, having a moderate neutron flux, will be uniquely suited for detailed studies of complex fluids in their various phases. This spectrometer will be fully available to general users of the small angle scattering community after a year of testing and upon installation of the auxiliary equipment. The general research objective of the MIT group is to continue studies of the microstructural relationship to phase-behavior in three-component microemulsion systems. Specifically, they shall study the (1) variation of bulk structures when a microemulsion undergoes a non-wetting to wetting transition, (2) correlating interfacial reflectivity measurements of these wetting transitions to the SANS results, (3) use the contrast variation technique they recently developed for measuring the mean and Gaussian curvatures of the surfactant sheet to study the structural inversion of water-in-oil to oil-in-water microemulsions and the transition of disordered bicontinuous microemulsion to ordered lamellar phases, (4) investigation of the effects of spatial confinement on the phase behavior and structure of bicontinuous microemulsions, and finally (5) they shall continue the study of the recently discovered non-exponential relaxation of droplet density fluctuations near the critical and percolation points in water-in-oil droplet microemulsions.




Extremely Diluted Microemulsions


Book Description

@Les microémulsions sont des phases de films flexibles de tensioactifs à l'interface entre l'eau et l'huile. Leur stabilité est déterminée par une compétition entre l'entropie du système et l'énergie élastique du film interfacial. Dans les systèmes de microémulsions classiquement étudiés, la constante élastique K de courbure du film est de l'ordre de kBT. Nous nous intéressons à un système contenant des interfaces plus rigides. Toutefois, l'interface est choisie telle que K reste suffisamment faible (de l'ordre de 2-4 kBT) pour que les fluctuations thermiques du système jouent encore un rôle important. Dans le présent travail, nous étudions le diagramme de phases du système eau/NaCL/décane/SDS/octanol. Dans ce diagramme particulièrement riche on trouve, outre des phases microémulsion extrêmement diluées, des phases présentant un ordre à longue distance (hexagonal, tétragonal, cubique ou mésophases intermédiaires) dont la taille caractéristique atteint 2000-3000 Å. Nos études, essentiellement menées par diffusion de rayonnement (rayons X et lumière), nous apportent des informations sur la symétrie de ces phases, la nature des transitions et le rôle du cosurfactant et de la température. Par ailleurs, l'étude par diffusion dynamique de la lumière des phases microémulsion met en évidence un nouveau mode de relaxation diffusif, que nous interprétons comme un mode de relaxation topologique lié à des processus de fusion du film. Nous soulignons le rôle de la courbure spontanée dans (interprétation de nos résultats.







Dynamics of Surfactant Self-Assemblies


Book Description

Dynamics of Surfactant Self-Assemblies explains the dynamics of micellar equilibria, tracking surfactant exchange, and micelle formation/breakdown processes. Highlighting the structural similarities of amphiphilic block copolymers to surfactants, this volume elucidates the dynamics of more complex self-assemblies that surfactants and amphiphilic bl