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  • 1. Bain, CD
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Langevin, D
    Meszaros, R
    Nylander, T
    Stubenrauch, C
    Complexes of surfactants with oppositely charged polymers at surfaces and in bulk2010In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, no 1-2, p. 32-49Article in journal (Refereed)
    Abstract [en]

    Addition of surfactants to aqueous solutions of polyelectrolytes carrying an opposite charge causes the spontaneous formation of complexes in the bulk phase in certain concentration ranges. Under some conditions, compact monodispersemultichain complexes are obtained in the bulk. The size of these complexes depends on the mixing procedure and it can be varied in a controlled way from nanometers up to micrometers. The complexes exhibit microstructures analoguous to those of the precipitates formed at higher concentrations. In other cases, however, the bulk complexes are large, soft and polydisperse. In most cases, the dispersions are only kinetically stable and exhibit pronounced non-equilibrium features. Association at air-water interfaces readily occurs, even at very small concentrations. When the surfactant concentration is small, the surface complexes are usually made of a surfactantmonolayer to which the polymer binds and adsorbs in a flat-like configuration. However, under some conditions, thicker layers can be found,with bulk complexes sticking to the surface. The association at solid-water interfaces ismore complex and depends on the specific interactions between surfactants, polymers and the surface. However, the behaviour can be understood if distinctions between hydrophilic surfaces and hydrophobic surfaces are made. Note that the behaviour at air-water interfaces is closer to that of hydrophobic than that of hydrophilic solid surfaces. The relation between bulk and surface complexation will be discussed in this review. The emphasiswill be given to the results obtained by the teams of the EC-funded Marie Curie RTN “SOCON”.

  • 2. Bergeron, V
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Structural forces reflecting polyelectrolyte organization from bulk solutions and within surface complexes2002In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 96, p. 1-20Article in journal (Refereed)
    Abstract [en]

    The interactions between two macroscopic surfaces approaching one another underlies many of the phenomena observed in Colloid and Interface science. In Russia this gave rise to the branch of colloid science now referred to as Surface Forces. Important discoveries, such as the molecular organization of solvent molecules at an interface, have been unveiled by surface force measurements. More recently, forces and structures at macromolecular length scales have been uncovered. In particular, oscillatory force profiles have been detected from aqueous solutions containing polyelectrolytes. The force¯structure relationship can reflect organization in the bulk solution or the internal structure of the adsorbed layer. Using a range of surface force techniques, combined with X-ray and neutron scattering results, we review the main features of these fascinating systems and provide an overview of how they relate to other systems such as micellar solutions, polymer¯surfactant complexes and simple solvents.

  • 3.
    Bergström, L
    YKI – Ytkemiska institutet.
    Hamaker constants of inorganic materials1997In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 70, p. 125-169Article in journal (Refereed)
    Abstract [en]

    Calculations of Hamaker constants using Lifshitz theory require the availability of accurate dielectric data, especially in the ultraviolet spectral region, and the use of a convenient and appropriate mathematical representation. In this review, a multiple oscillator model– the so called Ninham-Parsegian (N-P) representation– has been used and spectral parameters for 31 different inorganic materials (including diamond) have been generated from critically evaluated optical data or collected from the literature. For most materials, a two-oscillator model (one UV and one IR term) was used but more detailed representations were included when available. The spectral parameters presented here can be combined with previous data, mainly focused on hydrocarbon and organic systems, to yield an extensive spectral data base for both solids and liquids enabling Lifshitz calculations of Hamaker constants for many materials combinations. Non-retarded Hamaker constants for symmetric material combinations across vacuum (A1v1) and water (A1w1) have been calculated for the different materials; these calculations were performed using the full Lifshitz theory. Asymmetric combinations, A1v3 and A1w3, against four commonly used materials in atomic force microscopy studies: silica, amorphous silicon nitride, sapphire, and muscovite mica, have also been covered. The use of a new dielectric representation for water resulted in significantly lower values of A1w1 compared to previous calculations. Analytical approximations to the full Lifshitz theory were evaluated and found to give surprisingly accurate results (the Tabor-Winterton approximation) for A1v1 when the IR contribution is of minor importance. An attempt to make the TW approximation more general by establishing some scaling relationship between between n0 and wUV was met with little success; only the UV spectral parameters of the covalent oxides, sulphides and nitrides may be fitted to a simple power law relation. The Lifshitz calculations in this study was compared with an alternative method where a more detailed dielectric representation in the visible-ultraviolet spectral range was obtained through Kramers-Kronig (K-K) transformation of reflectivity data over a broad frequency range. Despite the difference in dielectric information, the two methods generally yield non-retarded Hamaker constants which do not differ significantly. This is not true for all materials, e.g. water, where a more detailed representation using either a N-P representations with several oscillators or the K-K representation must be used. It was shown that the omission of the static and low frequency contribution in the latter method may result in a significant underestimation of the value for A1w1 when the dispersive contribution becomes very small.

  • 4. Christenson, HK
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Direct measurements of the force between hydrophobic surfaces in water2001In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 91, p. 391-436Article in journal (Refereed)
    Abstract [en]

    Direct measurements of the force between hydrophobic surfaces across aqueous solutions are reviewed. The results are presented according to the method of preparation of the hydrophobic surfaces. No single model appears to fit all published results, and an attempt is made to classify the measured interactions in three different categories. The large variation of the measured interaction, often within each class, depending on the type of hydrophobic surface is emphasized. (I) Stable hydrophobic surfaces show only a comparatively short-range interaction, although little quantitative data on this attraction have been published. (II) Many results showing very long-range attractive forces are most likely due to the presence of sub-microscopic bubbles on the hydrophobic surfaces. Such an interaction is typically measured between silica surfaces made hydrophobic by silylation. Between self-assembled thiol layers on gold surfaces very short-range attractive forces are possibly due to the presence or nucleation of bubbles. The reason for the apparent stability of these bubbles is not clear and warrants further investigation. (III) Results obtained with LB films of surfactants or lipids on mica appear to give rise to a different type of force that fits neither of these two categories. This force is an exponentially decaying attraction, often of considerable range. The force turns more attractive at smaller separations, and may at short range be similar to the interaction measured between stable hydrophobic surfaces. An apparently similar, exponential attraction is also found between mica surfaces bearing surfactants adsorbed from cyclohexane, between silylated, plasma-treated mica surfaces and between both mica and silica surfaces with surfactants adsorbed in situ. This type of force also occurs between some surfaces of relatively low hydrophobicity as well as between one such hydrophobic surface and a hydrophilic surface. No convincing model can explain this third type of interaction for all systems in which it has been observed. This review of work to date points to the importance of the morphology and structure of the hydrophobic surface, and how it may change during the interaction of two surfaces

  • 5.
    Claesson, PM
    et al.
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Fröberg, JC
    Nylander, T
    Arnebrant, T
    Protein interactions at solid surfaces1995In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 57, p. 161-227Article in journal (Refereed)
    Abstract [en]

    In this review article we discuss a large number of the studies of interactions between protein-coated surfaces that has been presented in the literature. We also demonstrate how to relate surface force data to results from other techniques in order to provide a more full picture of protein behaviour at interfaces. One aim of the article is to discuss the experimental procedure and the difficulties with surface force measurements in protein systems. It is particularly important to point out how the sensitivity of this technique differs from that of other techniques, e.g. in determining structural changes in adsorbed proteins and in detecting proteins adsorbed on top of an inner firmly bound layer. It is also important to realize which surface force data that cannot be easily compared with findings from other techniques (one example is the kinetics of adsorption and desorption). We have tried to group proteins into different classes depending on their size and structure, and to try to find results that are common within these classes. It was found that some observations for unordered proteins with amphiphilic character, and for the small compact proteins, appear consistently within the respective class. Hence, for these types of protein common features/principles of the interfacial behaviour are identified. The very large and flexible glycoproteins behave in a similar way to synthetic polymers, but we found it hard to draw any firm conclusions based on the surface force studies presented so far. Perhaps, the most complicated surface behaviour is observed for soft globular proteins that undergo large scale conformational changes upon adsorption and when the layers are held under a high compressive force.

  • 6.
    Claesson, PM
    et al.
    YKI – Ytkemiska institutet.
    Dedinaite, A
    YKI – Ytkemiska institutet.
    Rojas, OJ
    Polyelectrolytes as adhesion modifiers2003In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 104, p. 53-74Article in journal (Refereed)
    Abstract [en]

    Adsorbed layers of polyelectrolytes have been studied with atomic force microscopy (AFM) and the interferometric surface force apparatus (SFA). Particular emphasis was put on determining the effect of the polyelectrolyte charge density on surface topography, and the effect of the polyelectrolyte coating on the adhesive properties. The AFM was employed to image individual polymer chains at low adsorption densities and to characterize the layer topography and coverage at higher adsorption densities. The adhesive properties between two polyelectrolyte-coated surfaces in air were determined as a function of the number of contacts made at any given spot. The data provide evidence for formation of electrostatic bridges, particularly when highly charged polyelectrolytes are used. Further, material transport between the surfaces is observed when the polyelectrolyte is either highly charged or have a very low charge density. For intermediate charge densities we could not observe any indication of material transfer. The adhesion between one polyelectrolyte-coated surface and one bare surface was initially higher than that between two polyelectrolyte-coated surfaces. However, due to material transfer between the two surfaces the adhesion decreased significantly with the number of times that the surfaces were driven into contact. For the polyelectrolytes of the lowest charge density the results suggest that entanglement effects contribute to the adhesive interaction. The modification of the adhesion by polyelectrolytes in practical systems such as in the case of dry-strength additives to improve paper resistance is also considered

  • 7.
    Claesson, PM
    et al.
    YKI – Ytkemiska institutet.
    Ederth, T
    Bergeron, V
    Rutland, MW
    YKI – Ytkemiska institutet.
    Techniques for measuring surface forces1996In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 67, p. 119-183Article in journal (Refereed)
    Abstract [en]

    The forces acting between colloidal particles and between surfaces are of utmost importance for determining the behaviour of dispersed systems and adhesion phenomena. Several techniques are now available for direct measurement of these surface forces. In this review we focus on some of these methods. Two techniques for measuring forces between macroscopic solid surfaces; the interferometric surface force apparatus, known as the SFA, and a novel instrument which is based on a bimorph force sensor, the so called MASIF, are described in some detail. Forces between a macroscopic surface and a particle can be measured with the atomic force microscope (AFM) using a colloidal probe, or by employing total internal reflection microscopy (TIRM) to monitor the position of a colloidal particle trapped by a laser beam. We also describe two different techniques that can be used for measuring forces between "soft" interfaces, the thin film balance (TFB) for single foam, emulsion and solid/fluid/fluid films, and osmotic stress methods, commonly used for studying interactions in liquid crystalline surfactant phases or in concentrated dispersions. The advantages and limitations of each of these techniques are discussed and typical results are presented.

  • 8.
    Claesson, PM
    et al.
    YKI – Ytkemiska institutet.
    Makuska, R
    Varga, I
    Meszaros, R
    Titmuss, S
    Linse, P
    Bottle-brush polymers: Adsorption at surfaces and interactions with surfactants2010In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, no 1-2, p. 50-57Article in journal (Refereed)
    Abstract [en]

    Solution and adsorption properties of both charged and uncharged bottle-brush polymers have been investigated. The solution conformation and interactions in solution have been investigated by small-angle scattering techniques. The association of the bottle-brush polymers with anionic surfactants has also been studied. Surfactant binding isothermmeasurements,NMR, surface tensionmeasurements, aswell as SAXS, SANS and light scattering techniques were utilized for understanding the association behaviour in bulk solutions. The adsorption of the bottle-brush polymers onto oppositely charged surfaces has been explored using a battery of techniques, including reflectometry, ellipsometry, quartz crystal microbalance, and neutron reflectivity. The combination of these techniques allowed determination of adsorbedmass, layer thickness,water content, and structural changes occurring during layer formation. The adsorption ontomicawas found to be very different to that on silica, and an explanation for this was sought by employing a lattice mean-field theory. The model was able to reproduce a number of salient experimental features characterizing the adsorption of the bottle-brush polymers over a wide range of compositions, spanning fromuncharged bottle-brushes to linear polyelectrolytes. This allowed us to shed light on the importance of electrostatic surface properties and non-electrostatic surface-polymer affinity for the adsorption. The interactions between bottle-brush polymers and anionic surfactants in adsorbed layers have alsobeen elucidated using ellipsometry, neutron reflectivity and surface force measurements.

  • 9.
    Claesson, PM
    et al.
    YKI – Ytkemiska institutet.
    Poptoshev, E
    Blomberg, E
    YKI – Ytkemiska institutet.
    Dédinaité, A
    YKI – Ytkemiska institutet.
    Polyelectrolyte-mediated surface interactions2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114-115, p. 173-187Article in journal (Refereed)
    Abstract [en]

    The current understanding of interactions between surfaces coated with polyelectrolytes is reviewed. Experimental data obtained with various surface force techniques are reported and compared with theoretical predictions. The majority of the studies concerned with interactions between polyelectrolyte-coated surfaces deal with polyelectrolytes adsorbed to oppositely charged surfaces, and this is also the main focus of this review. However, we also consider polyelectrolytes adsorbed to uncharged surfaces and to similarly charged surfaces, areas where theoretical predictions are available, but relevant experimental data are mostly lacking. We also devote sections to interactions between polyelectrolyte brush-layers and to interactions due to non-adsorbing polyelectrolytes. Here, a sufficient amount of both theoretical and experimental studies are reported to allow us to comment on the agreement between theory and experiments. A topic of particular interest is the presence of trapped non-equilibrium states that often is encountered in experiments, but difficult to treat theoretically.

  • 10. Dickinson, E
    et al.
    Eriksson, L
    YKI – Ytkemiska institutet.
    Particle flocculation by adsorbing polymers1991In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 34, p. 1-29Article in journal (Refereed)
    Abstract [en]

    The flocculation of colloidal particles by adsorbing polymers is a phenomenon of considerable scientific and industrial importance. This article describes recent developments in the field with particular reference to flocculation of negatively charged particles by high-molecular-weight cationic polyelectrolytes by polymer bridging or charge neutralization. Experimental and theoretical studies of interactions between adsorbed polymer layers give insight into the favourable conditions for bridging flocculation. Neutron scattering and computer simulation give insight into the relationship between floc structure and the mechanism of flocculation.

  • 11. Elwing, H
    et al.
    Gölander, C-G
    YKI – Ytkemiska institutet.
    Protein and detergent interaction phenomena on solid surfaces with gradients in chemical composition1990In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 32, p. 317-339Article in journal (Refereed)
    Abstract [en]

    We have recently described a new method for analysis of protein interaction on solid surfaces. The basic idea of the method is to make a gradient of chemical groups on the surface and to quantify protein adsorption along the gradient with the use of optical methods such as fluorescence measurements or ellipsometry. We have used the technique for experiments on protein adsorption and exchange, and detergent interaction on wettability gradients made on, e.g., silicon oxide surfaces. Several new observations were made which can not be observed without the use of the gradient method. This contribution is a short review of these obtaineer results and related research problems.

  • 12.
    Folmer, BM
    YKI – Ytkemiska institutet.
    Sterol surfactants: from synthesis to applications2003In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 103, p. 99-119Article in journal (Refereed)
    Abstract [en]

    An overview is given of sterol surfactants, including raw material aspects, classification and synthesis routes, physico-chemical behaviour and applications in pharmaceuticals and cosmetics.

  • 13.
    Holmberg, K
    YKI – Ytkemiska institutet.
    Organic and bioorganic reactions in microemulsions1994In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 51, p. 137-174Article in journal (Refereed)
    Abstract [en]

    During the last two decades reactions in microemulsions have developed into an emerging technology . In most instances oilcontinuous micro emulsions (w/o systems ) have been used and the water dropl ets have proven useful as «minireactors » for various types of syntheses. This review discusses recent advances in the fields of organic and bioorganic reactions in microemulsions. In preparative organic synthesis microemulsions are of interest to overcome incompatibility problems between nonpolar organic compounds and inorganic salts. For this purpose, microemulsions can be regarded as an alternative to two phase systems with added phase transfer reagents. Properly formulated microemulsions may also accelerate organic reactions, various mechanisms of such rate enhancements are discussed. Transition from a homogeneous solvent system to a microemulsion may also affect the regioselectivity of organic reactions due to orientation of reactants at the oilwater interface. In bioorganic synthesis, microemulsions are of interest as a reaction medium for several reasons: (i) nonpolar substrates can be dissolved in high concentrations, (ii) thermodynamic equilibria of condensation/hydrolysis reactions can be shifted by adjusting water content, (iii) enzymes are sometimes found to be more stable and more active than in aqueous buffer. Lipases are the most widely used enzymes and reactions have been performed in different types of microemulsion systems. This review presents general aspects of enzymatic catalysis in microemulsions followed by a discussion of recent advances in preparative work focusing on lipase catalyzed processes.

  • 14.
    Holmberg, K
    et al.
    YKI – Ytkemiska institutet.
    Nyden, M
    Lee, LT
    Malmsten, M
    YKI – Ytkemiska institutet.
    Jha, BK
    Interactions between a lipase and charged surfactants – a comparison between bulk and interfaces2000In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 88, p. 223-241Article in journal (Refereed)
  • 15. Hunter, TN
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Frank, GV
    Jameson, GJ
    The role of particles in stabilising foams and emulsions2008In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 137, p. 57-81Article in journal (Refereed)
    Abstract [en]

    The use of particles as foam and emulsion stabilising species, with or without surfactants, has received great interest in recent years. The majority of work has studied the effects of particles as stabilisers in emulsion systems, but recent successes has widened consideration into foams, where industries such as flotation and food processing have encountered the effects of particle stabilisation for many years. This review seeks to clarify studies into emulsions, highlighting new research in this area, and relate similarities and differences to foam systems. Past research has focused on defining the interaction mechanisms of stability, such as principles of attachment energies, particleparticle forces at the interface and changes to the interfilm, with a view to ascertain conditions giving optimum stability. Studied conditions include effects of particle contact angle, aggregation formations, concentration, size and interactions of other species (i.e. surfactant). Mechanisms can be complex, but overall the principle of particles creating a steric barrier to coalescence, is a strait forward basis of interaction. Much research in emulsions can be applied to foam systems, however evidence would suggest foam systems are under a number of additional constraints, and the stability ‘window’ for particles is smaller, in terms of size and contact angle ranges. Also, because of increased density differences and interfilm perturbations in foam systems, retardation of drainage is often as important to stability as inhibiting coalescence.

  • 16.
    Kizling, J
    et al.
    YKI – Ytkemiska institutet.
    Kronberg, B
    YKI – Ytkemiska institutet.
    On the formation of concentrated stable w/o emulsions2001In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 89-90, p. 395-399Article in journal (Refereed)
    Abstract [en]

    The conditions for the formation of concentrated w/o emulsions based on Aerosol OT and aliphatic hydrocarbons were studied. It was found that high stability is obtained if the attraction between the emulsion droplets is kept to a minimum. This is achieved by matching the refractive index of the dispersed phase and the organic phase. Furthermore, it is shown that the mere presence of salt does not render any stability. Hence, the speculated mechanism that salt stabilises against Ostwald ripening does not hold for these emulsions.

  • 17.
    Kizling, J
    et al.
    YKI – Ytkemiska institutet.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Eriksson, JC
    On the formation and stability of high internal phase O/W emulsions2006In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 123-126, p. 295–302-Article in journal (Refereed)
    Abstract [en]

    High internal phase o/w emulsions have been investigated with respect to stability. A series of aliphatic hydrocarbons were used as the oil component. By matching the refractive index of both phases, transparent, concentrated emulsions were produced and these emulsions were found to have the highest long-term stability. The long-term stability of transparent emulsions is attributed to a minimum in free energy at the equilibrium thickness, which, in turn, is related to a reduced attraction over the thin aqueous lamellae. Another factor that contributes to the stability is the absence of the destabilizing mechanisms commonly encountered for ordinary emulsions and foams.

  • 18. Liljekvist, P
    et al.
    Kjellin, M
    YKI – Ytkemiska institutet.
    Eriksson, JC
    The surface pressure effect of pentaoxyethylene and maltoside surfactant head groups2001In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 89-90, p. 293-302Article in journal (Refereed)
    Abstract [en]

    From experimental surface tension data for water solutions of dodecyl-b-maltoside, C12M, and dodecyl penta (ethylene oxide), C12EO5, in the range below the CMC, the corresponding head group surface pressure functions vs. packing density have been derived. These functions are compared with theoretical expressions based on some different models of the mixed head group/water layer. Tentatively, we conclude that the two-dimensional hard fluid approach furnishes a convenient starting-point in order to account for the observed surface pressures of both the maltoside and EO head groups.

  • 19.
    Lorén, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Determination of local diffusion properties in heterogeneous biomaterials2009In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 150, no 1, p. 42139-Article in journal (Refereed)
    Abstract [en]

    The coupling between structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. Structural heterogeneity is defined and its implications for time-dependent diffusion are discussed in detail. The effect of structural heterogeneity in biomaterials on diffusion and the relevance of length scales are exemplified with regard to different biomaterials such as gels, emulsions, phase separated biopolymer mixtures and chocolate. Different diffusion measurement techniques for determination of diffusion properties at different length and time scales are presented. The interplay between local and global diffusion is discussed. New measurement techniques have emerged that enable simultaneous determination of both structure and local diffusion properties. Special emphasis is given to fluorescence recovery after photobleaching (FRAP). The possibilities of FRAP at a conceptual level is presented. The method of FRAP is briefly reviewed and its use in heterogeneous biomaterials, at barriers and during dynamic changes of the structure is discussed. © 2009 Elsevier B.V. All rights reserved.

  • 20. McNamee, Cathy E
    et al.
    Yamamoto, Shinpei
    Kappl, Michael
    Butt, Hans-Juergen
    Higashitani, Ko
    Dedinaite, Andra
    YKI – Ytkemiska institutet.
    Surface and friction forces between grafted polysaccharide layers in the absence and presence of surfactant2011In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 364, no 2, p. 351-358Article in journal (Refereed)
    Abstract [en]

    We analyzed the interaction between chemically grafted polysaccharide layers in aqueous solutions. To fabricate such layers, an end-terminated dextran silane coupling agent was synthesized and the polydextran was grafted to oxidized silicon wafers and to silica particles. This resulted in the formation of a 28 nm thick layer (in air) and a grafted amount of 40 mg/m(2) as determined by ellipsometry. The physical properties of the grafted layer were investigated in aqueous solutions by atomic force microscope imaging and colloidal probe force measurements. Surface and friction forces were measured between one bare and one polydextran coated silica surface. A notable feature was a bridging attraction due to affinity between dextran and the silica surface. Surface interactions and friction forces were also investigated between two surfaces coated with grafted polydextran. Repulsive forces were predominant, but nevertheless a high friction force was observed. The repulsive forces were enhanced by addition of sodium dodecyl sulfate (SDS) that associates with the tethered polydextran layers. SDS also decreased the friction force. Our data suggests that energy dissipation due to shear-induced structural changes within the grafted layer is of prime importance for the high friction forces observed, in particular deformation of protrusions in the surface layer.

  • 21.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Experimental techniques for studying the structure of foams and froths2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114-115, p. 239-251Article in journal (Refereed)
    Abstract [en]

    Several techniques are described in this review to study the structure and the stability of froths and foams. Image analysis has proved to be useful for detecting structure changes in 2-D foams and has enabled the drainage process and the gradients in bubble size distribution to be determined. However, studies on 3-D foams require more complex techniques such as Mutiple-Light Scattering Methods, Microphones and Optical Tomography. Under dynamic foaming conditions, the Foam Scan Column enables the water content of foams to be determined by conductivity analysis. It is clear that the same factors, which play a role in foam stability (film thickness, elasticity, etc.) have also have a decisive influence on the stability of isolated froth or foam films. Therefore, the experimental thin film balance (developed by the Bulgarian Researchers) to study thinning of microfilms formed by a concave liquid drop suspended in a short vertical capillary tube has proved useful. Direct measurement of the thickness of the aqueous microfilm is determined by a micro-reflectance method and can give fundamental information on drainage and thin film stability. It is also important to consider the influence of the mineral particles on the stability of the froth and it have been shown that particles of well defined size and hydrophobicity can be introduced into the thin film enabling stabilization/destabilization mechanisms to be proposed. It has also been shown that the dynamic and static stability can be increased by a reduction in particle size and an increase in particle concentration

  • 22.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Foaming, foam films, antifoaming and defoaming1996In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 64, p. 67-142Article in journal (Refereed)
    Abstract [en]

    A general introduction to foams, the initial stages in the production of foams in aqueous solution, foam structures and the classification of bulk foams according to their lifetimes and stability are presented. Fundamental studies on horizontal and vertical isolated foam lamellae with emphasis on drainage and stability are reviewed. For freshly prepared foams containing fairly thick lamellae, the mechanical-dynamical properties of.the surface adsorbed layers (surface tension gradients) are decisive for retaining stability. Important parameters to be taken into consideration are the surface elasticity, viscosity (bulk and surface), gravity drainage and capillary suction. Also the film should exhibit low permeability to gases. Providing the stability of a foam film (containing dilute surfactant) is retained during the initial dynamic drain age pr cess, then eventually a static (equilibrium) situation will be reached at film thicknesses < 100 nm. In this region, interfacial interactions dominate and the stability of the film must be discussed in terms of the intermolecular forces (electrostatic double layer repulsion, dispersion force attraction and steric forces). This may lead to the formation of common black and Newton black films and these structures have been shown to be resilient to rupture and have low gas transfer characteristics. At high surfactant concentrations (>c.m.c.) stabilization of films and foams can occur by a micellar laying mechanism (stratification). Antifoaming and defoaming theories are presented, together with the mechanisms of heterogeneous antifoaming agents (non-polar oil, hydrophobic solid particles or mixtures of both) including recent theories describing the role of the emulsion and pseudo-emulsion film in the stability of foams containing oil droplets. Finally, defoaming by ultrasonic waves is briefly reviewed.

  • 23. Shinoda, K
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Microemulsions : colloidal aspects1975In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 4, p. 281-300Article in journal (Refereed)
  • 24. Stubenrauch, C
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Rutland, M
    YKI – Ytkemiska institutet.
    Manev, E
    Johansson, I
    Pedersen, JS
    Mixtures of n-dodecyl-beta-D-maltoside and hexaoxyethylene dodecyl ether - Surface properties, bulk properties, foam films, and foams2010In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, no 1-2, p. 5-18Article in journal (Refereed)
    Abstract [en]

    Mixtures of the two non-ionic surfactants hexaoxyethylene dodecyl ether (C12E6) and n-dodecyl-β-D-maltoside (β-C12G2) were studied with regard to surface properties, bulk properties, foamfilms, and foams. The reason for studying amixture of an ethylene oxide (CiEj) andasugar (CnGm) based surfactant is that despite being non-ionic, these two surfactants behave quite differently. Firstly, the physico-chemical properties of aqueous solutions of CnGm surfactants are less temperature-sensitive than those of CiEj solutions. Secondly, the surface charge density q0 of foamfilms stabilized by CnGm surfactants is pH insensitive down to the so-called isoelectric point,while that of foam films stabilized by CiEj surfactants changes linearly with the pH. The third difference is related to interaction forces between solid surfaces. Under equilibrium conditions very high forces are needed to expel β-C12G2 from between thiolated gold surfaces, while for C12E6 low loads are sufficient. Fourthly, the adsorption of C12E6 and β-C12G2 on hydrophilic silica and titania, respectively, is inverted. While the surface excess of C12E6 is large on silica and negligible on titania, β-C12G2 adsorbs very little on silica but has a large surface excess on titania.What is the reason for this different behaviour? Under similar conditions and for comparable head group sizes, it was found that the hydration of CiEj surfactants is one order of magnitude higher but on average much weaker than that of CnGm surfactants. Moreover, CnGm surfactants possess a rigid maltoside unit, while CiEj surfactants have a very flexible hydrophilic part. Indeed,most of the different propertiesmentioned above can be explained by the different hydration and the head group flexibilities. The intriguing question of howmixtures of CiEj and CnGm surfactantswould behave arises organically. Thus various properties of C12E6+β-C12G2 mixtures in aqueous solution have been studied with a focus on the 1:1 mixture. The results are compared with those of the single surfactants and are discussed accordingly.

  • 25. Stålgren, J
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wärnheim, T
    Adsorption of liposomes and emulsions studied with a quartz crystal microbalance2001In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 89, p. 383-394Article in journal (Refereed)
    Abstract [en]

    The QCM (Quartz Crystal Microbalance) is an ultra sensitive weighing device based on the piezoelectric, electromechanical oscillator principle. It consists of a thin single-crystal quartz disk, with one metal electrode deposited on each side. When the electrodes are connected to an electric oscillator, the crystal can be made to oscillate in a very stable manner at its resonance frequency, f. When a mass is adsorbed on one or both of the electrodes, then this leads to a change in the resonance frequency of the quartz crystal. If the adsorbed mass is small compared to the mass of the quartz crystal and there is no slip or deformation due to the oscillatory motion, then the resonance frequency decreases proportionally to the mass of the adsorbed film. It is possible to determine very small changes of the resonance frequency and hence very small mass changes, since the QCM generally has very stable oscillations. However, there are situations where the change in resonance frequency is not linearly related to the change in deposited mass, for example, when the mass is not rigid, slipping on the surface, or not deposited evenly over the electrode(s). There are also other things besides an applied mass that can influence the resonant frequency of a QCM including electrical effects, pressure, and temperature. In this diploma work the interaction between hydrophilic potassium mica surface and hydrogen mica surface and airs of different humidities have been investigated. The resulting adsorption isotherms show how much water that is adsorbed on the two surfaces.

  • 26. von Klitzing, R
    et al.
    Thormann, E
    YKI – Ytkemiska institutet.
    Nylander, T
    Langevin, D
    Stubenrauch, C
    Confinement of linear polymers, surfactants, and particles between interfaces2010In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, p. 19-31Article in journal (Refereed)
    Abstract [en]

    The review addresses the effect of geometrical confinement on the structure formation of colloidal dispersions like particle suspensions, (non)micellar surfactant solutions, polyelectrolyte solutions and mixed dispersions. The dispersions are entrapped either between two fluid interfaces (foam film) in a Thin Film Pressure Balance (TFPB) or between two solid interfaces in a Colloidal Probe Atomic Force Microscope (Colloidal Probe AFM) or a Surface Force Apparatus (SFA). The oscillating concentration profile in front of the surface leads to an oscillating force during film thinning. It is shown that the characteristic lengths like the distance between particles, the distance between micelles, or the mesh size of the polymer network remain the same during the confining process. The influence of different parameters like ionic strength, molecular structure, and the properties of the outer surfaces on the structure formation are reported. The confinement of mixed dispersions might lead to phase separation and capillary condensation, which in turn causes a pronounced attraction between the two opposing film surfaces..

  • 27.
    Zhmud, B
    et al.
    YKI – Ytkemiska institutet.
    Tiberg, F
    Interfacial dynamics and structure of surfactant layers2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 113, p. 21-42Article in journal (Refereed)
    Abstract [en]

    The present article covers both the theoretical aspects of surfactant adsorption and the modern experimental methods for studying the properties of adsorbed surfactant layers. The principles of ellipsometry, photon correlation spectroscopy, small angle neutron scattering, and neutron reflectivity are explained in detail. A special attention is paid to the surface tension relaxation in micellar solutions, the properties of mixed surfactants, the wetting enhancement, and the damping effect of surfactant films on capillary waves

1 - 27 of 27
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