The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform

Stephen Garoff - One of the best experts on this subject based on the ideXlab platform.

  • Surfactant Self-Assemblies Controlling Spontaneous Dewetting
    Langmuir, 2002
    Co-Authors: And Robert Suter, Stephen Garoff
    Abstract:

    We have examined the structures of Surfactant Self-Assemblies left on substrates as a contact line spontaneously retreats across the surface during an autophobing event. A continuous structural gradient is formed during the spontaneous retreat:  from molecules lying down on the surface with low packing densities in a region never touched by the solution, to molecules standing up with higher packing densities in a region where the contact line has moved slowly. Despite significant free volumes within the Self-Assemblies, there is no evidence of clustering of molecules. We have observed a clear correlation between retreating contact line speeds and deposited Surfactant structures. The dynamics during at least a later period of the autophobing event is dominated by the time evolution of Young's force dictated by the self-assembly near the contact line.

  • Interfacial Structure and Rearrangement of Nonionic Surfactants near a Moving Contact Line
    Langmuir, 2001
    Co-Authors: Barry B. Luokkala, Stephen Garoff, ‡ Robert D. Tilton, Robert M. Suter
    Abstract:

    Surfactant solutions exhibit a wide variety of wetting and dewetting behaviors on high energy surfaces. These behaviors are driven by Surfactant Self-Assemblies at the moving contact line. To probe...

  • Temporal and spatial development of Surfactant Self-Assemblies controlling spreading of Surfactant solutions
    Langmuir, 1995
    Co-Authors: B. Frank, Stephen Garoff
    Abstract:

    When a substrate is immersed into a solution of strongly adsorbing Surfactant, the contact line advances by jumping forward along the surface. At low concentrations the contact line then retracts, exhibiting autophobic behavior. We have directly observed the development of the Surfactant assemblies at the contact line which cause these behaviors. Different macroscopic spreading behavior and microscopic development of the self-assembly occur above and below a bulk solution concentration of ∼0.45cmc. These Surfactant barriers ahead of the contact line exhibit two regions with distinctive structures and time evolutions. This structure ahead of the contact line combines with the Surfactant on the solid-liquid interface to form a self-assembled Surfactant structure which pins the advance of the contact line and causes stick-jump behavior. We put an upper limit on the size of the region on the solid surface relevant in determining the contact angles.

Bjorn Lindman - One of the best experts on this subject based on the ideXlab platform.

  • Per Ekwall and Physical Chemistry 1 in Lund: Ion Binding and Microstructure in Relation to Phase Behavior
    Journal of Dispersion Science and Technology, 2007
    Co-Authors: Bjorn Lindman
    Abstract:

    The research in the Department of Physical Chemistry 1 at Lund University includes topics such as Surfactant self-assembly; polymers, solutions, gels and phase behavior, polymer-Surfactant systems; protein and protein-amphiphile systems; adsorption and surface forces; experimental methodology in colloid science; and theory and modeling. (Annual Report (2004) Physical Chemistry 1; Lund University; Sweden.) How different research topics emerge is, of course, in many cases a complicated story and there are often long traces back. In this treatise, looking back on connections, we will demonstrate that early contacts with Per Ekwall have to a considerable extent influenced our research directions. As we will describe, the early contacts concerned experimental studies of ion binding in concentrated Surfactant systems. These inspired further studies of ion binding in a range of colloid systems and these, in turn, theoretical work on electrostatic interactions. Per Ekwall and his coworker Krister Fontell also introduced us into the fascinating subject of cubic liquid crystals, which inspired us into the problem of connectivity versus discreteness of Surfactant Self-Assemblies. Another significant aspect of the contacts with Per Ekwall and his group was that we learned the important role of phase diagrams in understanding Surfactant systems. After analyzing briefly the early contacts we will exemplify some of our work on ion binding and on microstructure; aspects on phase diagrams are discussed by Hakan Wennerstrom in another article in this volume.

  • Surfactant-polymer interactions
    Current Opinion in Colloid & Interface Science, 1996
    Co-Authors: Per Hansson, Bjorn Lindman
    Abstract:

    Whereas mixed solutions of a homopolymer and a Surfactant show interesting analogies with mixed polymer solutions, it has been demonstrated recently that mixtures of hydrophobically modified water-soluble polymers and Surfactants show analogies with mixed Surfactant systems. Other recent progress has concerned the micellization of an ionic Surfactant on a polyelectrolyte chain, the behavior of polymers in the presence of connected Surfactant Self-Assemblies, and Surfactant micellization in covalent polymer gels.

  • Self-assembly in concentrated polymer-Surfactant systems - a self-diffusion study of a non-ionic random copolymer-non-ionic Surfactant-water system
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1994
    Co-Authors: Kewei Zhang, Mikael Jonströmer, Bjorn Lindman
    Abstract:

    The Fourier transform-NMR-pulsed gradient spin-echo technique has been used to obtain self-diffusion coefficients in the ternary system non-ionic random copolymer-non-ionic Surfactant-water. The Surfactant used is tetraethylene glycol mono-n-dodecyl ether (C12E4), and the copolymer is a linear random copolymer of ethylene oxide and propylene oxide (UCON) with a molecular weight of 1700. From the self-diffusion coefficients of the different components, information has been deduced on interactions and self-assembly processes. In contrast to block copolymers, UCON does not readily take part in self-assembly. However UCON strongly affects Surfactant self-assembly and has the effect of breaking down Surfactant Self-Assemblies. The ethylene oxide and propylene oxide groups behave similarly with respect to their interaction with water, and the interaction is independent of the particular solute or its state of aggregation. © 1994.

Hans Jörg Limbach - One of the best experts on this subject based on the ideXlab platform.

  • Foams stabilized by multilamellar polyglycerol ester Self-Assemblies.
    Langmuir : the ACS journal of surfaces and colloids, 2012
    Co-Authors: Corina Curschellas, Peter Fischer, Erich J. Windhab, Joachim Kohlbrecher, Thomas Geue, Bertrand Schmitt, Martine Rouvet, Hans Jörg Limbach
    Abstract:

    The importance of Surfactant Self-Assemblies in foam stabilization is well-known. The aim of the current study was to investigate the Self-Assemblies of the nonionic Surfactant polyglycerol ester (PGE) in bulk solutions, at the interface and within foams, using a combined approach of small-angle neutron scattering, neutron reflectivity, and electron microscopy. PGE bulk solutions contain vesicles as well as open lamellar structures. Upon heating of the solutions the lamellar spacing increases, with significant differences in the presence of NaCl or CaCl2 as compared to the standard solution. The adsorption of the multilamellar structures present in the bulk solutions lead to a multilayered film at the air–water interface. The ordering within this film was increased as a result of a 20% area compression mimicking a coalescence event. Finally, PGE foams were shown to be stabilized not only by strong interfacial films but also by agglomerated Self-Assemblies within the interstitial areas of the foams.

  • Characteristics of polyglycerol ester and its different fractions
    Journal of colloid and interface science, 2012
    Co-Authors: Corina Curschellas, Erich J. Windhab, Kornél Nagy, Hans Jörg Limbach
    Abstract:

    Abstract Polyglycerol esters obtained from edible oils are commonly used Surfactants in the food industry. Despite their widespread application, the composition and properties of these Surfactants are still not well characterized. This study reveals the presence of so far unknown tetra-, penta-antennary constituents in polyglycerol esters, which exhibit very strong sodium affinity. The implications of these new insights on Surfactant activity were investigated. Liquid–liquid extraction was used to fractionate a polyglycerol ester ingredient in order to link physicochemical behavior to the polarity of the fractions. The most polar fraction showed faster adsorption kinetics and higher elastic moduli than the full mixture, whereas the least polar fraction showed slower adsorption kinetics and lower elastic moduli as compared to the complex mixture. The addition of Na + was shown to accelerate the agglomeration of Surfactant Self-Assemblies in bulk solutions and also to increase the elastic modulus at the air–water interface. These observations suggest that the composition of natural polyglycerol esters is more diverse than so far assumed and the overall behavior of these mixtures is determined not only by the amphyphilic interactions between mono- and penta-antennary forms, but also by the endogenous salt content of the ingredient.

B.d. Kulkarni - One of the best experts on this subject based on the ideXlab platform.

  • Rheological study of the L2 and L2/D phases in a ternary system
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1996
    Co-Authors: B.k. Jha, A. Manna, S.n. Shintre, B.d. Kulkarni
    Abstract:

    Abstract The rheology of sodium dodecyl sulfate (SDS)/alkanol/water solutions under different shear conditions has been investigated using a Ferranti-Shirley rheometer. The shear viscosity varies depending on whether the system belongs to the L2 or the L2/D region. The flow behavior of samples within the L2 or L2/D regions also varies significantly with composition and exhibits interesting phase transitions under shearing. The temperature and the [alkanol]/[SDS] molar ratio have considerable influences on the rheology of Surfactant Self-Assemblies.

Raoul Zana - One of the best experts on this subject based on the ideXlab platform.