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  • 101.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Meurk, A
    YKI – Ytkemiska institutet.
    Measuring granule friction and adhesion with an atomic force microscope2002Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 206-213, s. 63-66Artikkel i tidsskrift (Fagfellevurdert)
  • 102.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Meurk, A
    YKI – Ytkemiska institutet.
    Arwin, H
    YKI – Ytkemiska institutet.
    Rowcliffe, DJ
    YKI – Ytkemiska institutet.
    Estimation of Hamaker constants of ceramic materials from optical data using Lifshitz theory1996Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 79, s. 339-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Hamaker constants of 8 different ceramic materials, 6H-SiC, tetragonal, partially stabilized-ZrO2 (3% Y2O3), b-Si3N4, a-Al2O3, Y2O3, sapphire (single crystal a-Al2O3), MgO, MgAl2O4, and fused silica, across air, water, and n-dodecane at room temperature and across silica at 2000 K have been calculated from optical data using Lifshitz theory. Spectroscopic ellipsometry was used to measure the photon energy dependence of the refractive index, n, and the extinction coefficient, k, in the visible and near-UV range on several important ceramic materials. This relatively simple, nondestructive technique has proved to yield reliable optical data on sintered, polycrystalline materials like Si3N4, SiC, ZrO2 and Al2O3. For the other materials, Y2O3, sapphire, MgO, MgAl2O4 and fused silica, optical data from the literature were used to calculate the Hamaker constants. The calculated Hamaker constants were estimated to be accurate within ± 10%.

  • 103.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Interfacial characterization of silicon nitride powders1989Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 72, s. 103-109Artikkel i tidsskrift (Fagfellevurdert)
  • 104.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Schilling, CH
    Aksay, IA
    Consolidation behavior of flocculated alumina suspensions1992Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 75, s. 3305-3314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The consolidation behavior of flocculated alumina suspensions was analyzed as a function of the interparticle energy. Consolidation was performed by a centrifugal force field or by gravity and both the time dependent and equilibrium density profiles were measured by a gamma ray absorption technique. The interparticle energy at contact was controlled by adsorbing fatty acids of varying molecular weight at the alumina/decalin interface. We found that strongly attractive interactions result in a particle network which resists consolidation and shows compressible behavior over a large stress range. The most weakly flocculated suspension showed an essentially incompressible, homogeneous density profile after consolidation at different centrifugal speeds. We also found a significant variation in the maximum volume fraction, m, obtained, with m 0.54 for the most strongly flocculated suspension to m 0.63 for the most weakly flocculated suspension. The compressive yield stresses show a behavior which can be fitted to a modified power law. In this paper, we discuss possible correlations between the fitting parameters and physical properties of the flocculated suspensions.

  • 105.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Shinozaki, K
    Tomiyama, H
    Mizutani, N
    Colloidal processing of a very fine BaTiO3 powder-effect of particle interactions on the suspension properties, consolidation and sintering behavior1997Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 80, s. 291-300Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relation between the suspension state and the rheological properties, the consolidation, and packing of a very fine (nanosized) BaTiO3 powder has been investigated. The BaTiO3 powder was suspended in a non-aqueous medium by adsorbing fatty acids and a polymeric dispersant, poly(12-hydroxy stearic acid), (PHS), at the BaTiO3/decane interface. Calculated interparticle energies implies that the suspension with PHS adsorbed is colloidally stable while the suspensions with oleic and octanoic acid can be characterised as weakly and strongly flocculated, respectively. Analysis of settling experiments and rheological measurements at high concentrations confirmed this characteristics. Pressure filtration resulted in nearly identical green body densities in spite of the differences in colloidal properties, but the preliminary sintering experiments and microstructural characterisation showed that the strongly flocculated suspension displays a significantly retarded sinterability compared to the colloidally stable and the weakly flocculated suspensions. The absence of a correlation between green density and sintering behavior was explained by considering both the volume taken by the adsorbed fatty acids and the PHS polymer-which can be substantial for nanosized powders- and the state of the suspension. While a decrease in the thickness of adsorbed surfactant or polymer layer will enable a higher particle packing density, such a thin adsorbed layer result in a more strongly flocculated suspension which will resist dense packing. Hence, it is suggested that the green bodies of the colloidally stable and the weakly flocculated suspensions correspond to a relatively homogeneous, but loosely packed, green body microstructure. The strongly flocculated suspension results in a green body with a more inhomogeneous microstructure.

  • 106.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Sjöström, E
    YKI – Ytkemiska institutet.
    Temperature induced flocculation of concentrated ceramic suspensions: rheological properties1999Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 19, s. 2117-2123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Concentrated, sterically stabilised ceramic suspensions have been reversibly flocculated by changing the temperature. Using an amphiphilic polymer, Hypermer KD3, as dispersant for alumina and alumina-silicon carbide whisker composite mixtures in pentanol resulted in a transition from dispersed to flocculated state close to room temperature. The collapse of the adsorbed polymer layer with decreasing solvency (temperature) in the marginal solvent pentanol induces flocculation when the long-range van der Waals force overcomes the remaining steric repulsion. Temperature induced flocculation (TIF) has a drastic effect on the rheological properties. At high temperatures, T>30 °C, the suspensions have a low viscosity and neglible elasticity. When the temperature is lowered below 20 °C, the viscosity increases significantly and the viscoelastic behaviour becomes predominatly elastic. The elasticity and the associated particle network strength are sufficiently high for a highly concentrated gelled suspension to support its own weight. The potential use of TIF as a novel forming method was discussed with relation to other new shaping techniques.

  • 107.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Stemme, S
    Dahlfors, T
    Arwin, H
    Ödberg, L
    Spectroscopic ellipsometry characterisation and estimation of the Hamaker constant of cellulose1999Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 6, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Calculations of Hamaker constants using Lifshitz theory require the availability of accurate dielectric data, especially in the visible-ultraviolet region. We present spectroscopic ellipsometry data on well defined cellulose films of a limited thickness range (100–140 layers) deposited on an oxidised and hydrophobised silicon substrate. The spectral data, representing measurements from a perpendicular orientation to the fibre deposition direction, was used for estimates of the necessary spectral parameters, i.e. the oscillator strengths and characteristic frequencies in the UV-range. Our calculations show that cellulose has a relatively low Hamaker constant in air (58 zJ) and water (8.0 zJ). The implications for the surface energy estimates of cellulose and colloidal interactions between cellulose and various types of fillers and coating colours were discussed.

  • 108.
    Bergström, Lennart
    YKI – Ytkemiska institutet.
    Colloidal processing of ceramics2002Inngår i: Handbook of Applied Colloid and Surface Chemistry / [ed] Krister Holmberg, Chichester; Weinheim: Wiley , 2002, s. 201-218Kapittel i bok, del av antologi (Fagfellevurdert)
  • 109.
    Bergström, Lennart
    YKI – Ytkemiska institutet.
    Från beck till pulverfärg2001Inngår i: Med färg i blicken, Uppsala: Ord & Vetande AB , 2001, s. 89-98Kapittel i bok, del av antologi (Fagfellevurdert)
  • 110.
    Bergström, LM
    YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Bending elasticity of nonionic surfactant layers2009Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 4, s. 1949-1960Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel approach to evaluate the bending elasticity of monolayers formed by nonionic surfactants with a rigid head group is introduced by means of considering head group repulsion as derived from the free energy of mixing rigid hydrophilic head groups with surrounding solvent molecules as well as contributions related to the hydrophobic tails. Explicit expressions for the spontaneous curvature (H0), bending rigidity (kc) and saddle-splay constant (k̄c) have been derived for the constraint of constant chemical potential of free surfactant (thermodynamically open layers) as well as the constraint of constant aggregation number (thermodynamically closed layers). Most interestingly, it is demonstrated that kc for thermodynamically open layers formed by a nonionic surfactant with rigid tail and head group always must be zero. However, kc for surfactants with a flexible tail as a function of the head group-to-tail volume ratio is found to go through a maximum at some large, positive value of k c and H0 ≈ 0. Eventually, kc falls below zero as the head group volume increases above a certain value. Hence, we may conclude that nonionic surfactants with a rigid head group may form thermodynamically stable fluid layers or aggregates only insofar the hydrophobic part is flexible with respect to chain conformational degrees of freedom and the head group is not too voluminous. It is found that the head group repulsion contribution to kcH0 is always positive whereas the corresponding contribution to k̄c may be positive or negative depending on whether the hydrophobic layer of the film is thicker or thinner than the hydrophilic layer.

  • 111. Bergström, LM
    et al.
    Bastardo, LA
    YKI – Ytkemiska institutet.
    Garamus, VM
    A small-angle neutron and static light scattering study of micelles formed in aqueous mixtures of a nonionic alkylglucoside and an anionic surfactant2005Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, s. 12387-12393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The size and shape of micelles formed in aqueous mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic sugar-based surfactant n-decyl â-D-glucopyranoside (C10G) at different concentrations of added salt have been investigated with small-angle neutron and static light scattering. Rather small prolate ellipsoidal micelles form in the absence of added salt and at [NaCl] ) 10 mM in D2O. The micelles grow considerably in length to large rods as the electrolyte concentration is raised to [NaCl] ) 0.1 M. In excess of nonionic surfactant ([SDS]/[C10G] ) 1:3) at [NaCl] ) 0.1 M in D2O, several thousands of Ångstroms long wormlike micelles are observed. Most interestingly, a conspicuously large isotope solvent effect was observed from static light scattering data according to which micelles formed at [SDS]/[C10G] ) 1:3 and [NaCl] ) 0.1 M in H2O are at least five times smaller than micelles formed in the corresponding samples in D2O.

  • 112.
    Bergström, M
    YKI – Ytkemiska institutet.
    Derivation of expressions for the spontaneous curvature, mean and Gaussian bending constants of thermodynamically open surfactant monolayers and bilayers2003Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, s. 1440-1452Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have derived expressions for the spontaneous curvature H0, the mean and Gaussian bending constants, kc and c, respectively, for a surfactant film of finite thickness that is open in a thermodynamic sense. Geometrical packing constraints are taken into account and give rise to explicit large and important contributions to kc c, and kcH0. From its contribution to the latter quantity we may deduce that surfactant aggregates (micelles, vesicles, microemulsion droplets) are expected to dramatically increase their size with increasing surfactant tail length. Moreover, the coupling between free energy contributions related to surfactant head group and tail with geometrical packing constraints give rise to dominant terms on the form 2 pH0, where p is the thickness of a planar film, in the expressions for kc In the case of repulsive head group effects that favor a large spontaneous curvature, such as electrostatics, these terms raise kc and thus increase the rigidity of the film. Due to the constraint of constant free monomer chemical potentials, the composition of the film becomes a function of curvature. As a result, the ability of a surfactant film to have different surfactant compositions in differently curved parts (e.g., inner and outer layer of a vesicle, central parts and end caps of rod or threadlike micelles, etc.) may considerably reduce kc, whereas c and kcH0 are mainly unaffected by mixing. The magnitude of the reduction of kc of a binary surfactant film increases with increasing asymmetry between the two surfactants with respect to charge number, head group size, and tail volume

  • 113.
    Bergström, M
    YKI – Ytkemiska institutet.
    Molecular interpretation of the mean bending constant for a thermodynamically open vesicle bilayer2001Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, s. 7675-7686Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Expressions for the various molecular contributions to the mean bending constant kc of a thermodynamically open vesicle bilayer have been derived, from which kc may be calculated from an appropriate molecular-thermodynamic model as a function of the structure of the surfactants making up the aggregates as well as the solution state. It is demonstrated that kc determines the shape of a vesicle bilayer insofar as spherical vesicles form when kc is large and positive whereas nonspherical vesicles predominate at values of kc close to or below zero. It is found that contributions due to electrostatics and residual headgroup effects, which are present for one-component as well as mixed aggregates, mainly give rise to a positive value of kc whereas geometrical packing constraints are less important. However, the mixing of two or more surfactants can significantly reduce kc to values where nonspherical vesicles may begin to form. The magnitude of the reduction of kc due to mixing increases with increasing asymmetry with respect to headgroup cross-section area, charge number, and hydrocarbon tail volume between two surfactants in a binary surfactant mixture. The asymmetry is most pronounced for a binary mixture where the surfactant that carries the charge has the larger headgroup and the smaller tail. The reduction of kc due to mixing is, however, expected to be less than the corresponding effect for the bilayer bending constant of a spherical vesicle as a result of an additional positive contribution in the expression for the compositional contribution to kc

  • 114.
    Bergström, M
    YKI – Ytkemiska institutet.
    Synergistic effects in mixtures of an anionic and a cationic surfactant2000Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, s. 993-998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synergistic effects in mixtures of an anionic and a cationic surfactant have been theoretically investigated. We derive an explicit expression for the critical micelle concentration (cmc) as a function of the aggregate composition from the Poisson-Boltzmann mean field theory and, thus, demonstrate that the conspicuously large synergistic effects that have been experimentally observed can be rationalized without the need of invoking any specific interactions between the surfactant headgroups. The simple relation = -4el/kT is derived, i.e., the "interaction parameter" is directly related to the electrostatic free energy contribution el for the pure surfactant, implying, among other things, that the magnitude of decreases with increasing cmc for the pure surfactant in agreement with experimental observations. We furthermore demonstrate that the aggregate composition is close to equimolar composition (x1 = 0.5) at cmc in almost the entire regime of overall surfactant compositions and that the free monomer concentration of the surfactant in excess is generally much larger than the corresponding quantity for the surfactant in deficit.

  • 115.
    Bergström, M
    YKI – Ytkemiska institutet.
    Thermodynamics of anisotropic surfactant micelles. I. The influence of the curvature free energy on the micellar size and shape2000Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, s. 5559-5568Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel theory for the structural behavior of surfactant micelles is expounded. The micelles are considered to be generally shaped as triaxial tablets with distinct thickness width and length, respectively, and may become spherical, spherocylindrical or disk-shaped in the special cases where two or more of the dimensions are equal. It is demonstrated that the average width and length of a tablet-shaped micelle with a fixed thickness is mainly determined by two constants, k1 and k2, related to the first and second order correction in curvature of the micellar end caps. The size of the micelles is found to be mainly determined by k1, whereas k2 influences the shape, i.e., the length-to-width ratio, of the micelles so that the micellar size increases with increasing k1 and the length-to-width ratio decreases with increasing k2. Hence, large positive values of k2 promote the formation of tablets rather than very long spherocylinders. An additional parameter related to the curvature of the straight cylindrical rims may influence the structure of the tablet-shaped micelles insofar k2 is close to or below zero.

  • 116.
    Bergström, M
    YKI – Ytkemiska institutet.
    Thermodynamics of anisotropic surfactant micelles. II. A molecular interpretation of the micellar curvature free energy2000Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, s. 5569-5579Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Explicit expressions have been derived for the two curvature constants k1 and k2 that mainly influence the size and shape, respectively, of generally shaped micelles (triaxial tablets with a thickness

  • 117.
    Bergström, M
    YKI – Ytkemiska institutet.
    Thermodynamics of surfactant micelles and vesicles2001Inngår i: Handbook of Surfaces and Interfaces of Materials: Biomolecules, Biointerfaces and Applications / [ed] Hari Singh Nalwa, Academic Press, 2001, s. 233-264Kapittel i bok, del av antologi (Fagfellevurdert)
  • 118.
    Bergström, M
    YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Thermodynamics of unilamellar vesicles: Influence of mixing on the curvature free energy of a vesicle bilayer2001Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 240, s. 294-306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Endothelial cell layers from umbilical cords were grown on methylated silica surfaces. Fluorescence microscopy showed this layer to be confluent and to consist of living cells. Initial ellipsometry measurements were performed to illustrate both the stability of the model surface in ellipsometry measurements and the Ca2+-dependent binding of lipoproteins at the cell-based substrate. The present substrate holds promise as a model substrate for in vitro investigations of lipoprotein deposition at the endothelium surface under close to in vivo conditions.

  • 119.
    Bergström, M
    et al.
    YKI – Ytkemiska institutet.
    Eriksson, JC
    YKI – Ytkemiska institutet.
    A theoretical analysis of synergistic effects in mixed surfactant systems2000Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, s. 7173-7181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synergistic effects in mixed binary surfactant systems have been investigated by analyzing the main contributions to the free energy of forming a mixed surfactant aggregate. We show that a nonlinear behavior of the critical micelle concentration (cmc) with respect to the surfactant composition of the aggregates is determined by a nonlinear behavior of the free energy per aggregated surfactant. It appears that synergistic effects are due mainly to entropic free energy contributions related with the surfactant headgroups. For a mixture of a monovalent ionic and a nonionic surfactant in the absence of added salt we obtain, entirely because of electrostatic reasons, a negative deviation from ideal behavior of the cmc vs the aggregate composition corresponding to an interaction parameter -1, whereas values on the order of -5 or even less can arise for mixtures of two ionic surfactants with the same charge number but with different hydrocarbon moieties. Moreover, we introduce a novel expression for the free energy of mixing aggregated surfactant headgroups with surrounding solvent molecules. Accordingly, synergistic effects arise as a result of different headgroup cross-section areas in mixtures of two nonionic surfactants with rigid headgroups. These effects are found to be rather small, with 0 > > -1, when the difference in headgroup size is modest but can become more significant when the size difference is larger. In mixtures of an ionic and a nonionic surfactant with different headgroup cross-section areas the two contributions to synergistic effects always enhance one another and, hence, values below -1 are obtained. Generally, the synergistic effects tend to increase with increasing asymmetry between the two surfactants.

  • 120.
    Bergström, M
    et al.
    YKI – Ytkemiska institutet.
    Eriksson, JC
    YKI – Ytkemiska institutet.
    Synergistic effects in binary surfactant mixtures2004Inngår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 123, s. 16-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By considering the main contributions to the micellar free energy we have analysed the synergistic effect often seen on the CMC of a binary surfactant mixture. The synergistic effects are due mainly to the entropic free energy contributions related with the surfactant head groups. Several cases have been treated: (i) For a mixture of a monovalent ionic and a non-ionic surfactant in the absence of added salt we obtain, entirely because of electrostatic reasons, a negative deviation from the ideal behaviour corresponding to an interaction parameter β≈-1. Upon adding an inert salt we found that the magnitude of the synergistic effect first increases, reaches a maximum and eventually decreases. (ii) For mixtures of two ionic surfactants with the same charge number but with different hydrocarbon moieties β-values as low as -10 may arise. (iii) For mixtures of an anionic and a cationic surfactant enormous effects are anticipated yielding β≤-20 depending on the CMCs of respective pure surfactant. (iv) Synergistic effects due to different cross-section areas of the head groups are found to be rather small, with 0 > β > -1, provided the difference in head group size is modest but can become more significant when the size difference is larger.

  • 121.
    Bergström, M
    et al.
    YKI – Ytkemiska institutet.
    Jonsson, P
    YKI – Ytkemiska institutet.
    Persson, M
    YKI – Ytkemiska institutet.
    Eriksson, JC
    YKI – Ytkemiska institutet.
    A model independent evaluation of experimental data, and comparison with theory, of synergistic effects in mixtures of an ionic and a nonionic surfactant2003Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, s. 10719-10725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Critical micelle concentrations for mixtures of an anionic (sodium dodecyl sulfate) and a nonionic (decyl β-glucoside) surfactant was obtained from surface tension measurements at different concentrations of added NaCl. The observed synergistic effects were analyzed by means of introducing a novel model-independent synergy parameter. The model-independent evaluation has enabled the comparison of experimental results with a theoretical model based on the Poisson-Boltzmann (PB) mean field theory for spherical, cylindrical, and planar geometries, respectively. We found that best agreement with experimental data was obtained for largely curved structures (spherical and cylindrical micelles) at all [NaCl], which is consistent with the fact that rather small micelles, as a rule, form at the critical micelle concentration. Moreover, the PB theory was found to better describe synergistic behavior of the experimental data than the more conventional regular mixture theory, in particular at low electrolyte concentrations. The magnitude of the observed synergistic effects was found to increase as a small amount of NaCl was added and reach a maximum at [NaCl] = 10 mM, in agreement with the PB theory. As expected, synergism was observed to decrease in magnitude upon further addition of NaCl.

  • 122. Bergström, M
    et al.
    Kjellin, URM
    Claesson, PM
    YKI – Ytkemiska institutet.
    Grillo, I
    Small-angle neutron scattering study of mixtures of cationic polyelectrolyte and anionic surfactant: Effect of polyelectrolyte charge density Polyelectrolyte and Anionic Surfactant: Effect of Polyelectrolyte Charge2004Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, s. 1874-1881Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied mixtures of an anionic surfactant (deuterated sodium dodecyl sulfate, SDS-d) and cationic polyelectrolytes with different charge densities (10%, 30%, 60%, and 100%) using small-angle neutron scattering (SANS). Near compositions corresponding to charge neutralization, the solutions phase separate into a complex phase (precipitate) consisting of, in the cases of 30%, 60%, and 100% charge density, a two-dimensional (2D) hexagonal lattice of close-packed cylindrical micelles and a clear liquid. When either polyelectrolyte with charge density less than 100% or SDS-d is present in sufficient excess, the solution becomes clear and isotropic, and from the scattering data we may conclude that prolate or rod-shaped micelles are present. The micelles are seen to grow in length with increasing SDS-d concentration and polyelectrolyte charge density from about 80 Å to 550 Å, whereas the cross-sectional radius is 15 Å and approximately constant. The number of micelles per polyelectrolyte chain is found to be slightly larger than unity (1-6). In some of the (turbid) samples rod-shaped micelles are found to coexist with larger polyelectrolyte-surfactant complexes. Solutions consisting of 10% charged polyelectrolyte and SDS-d are very viscous and gellike, and the complex phase is much less defined with a much larger distance between adjacent aggregates in the complex phase.

  • 123.
    Bergström, M
    et al.
    YKI – Ytkemiska institutet.
    Kjellin, URM
    Claesson, PM
    YKI – Ytkemiska institutet.
    Pedersen, JS
    Nielsen, MM
    A small-angle x-ray scattering study of complexes formed in mixtures of a cationic polyelectrolyte and an anionic surfactant2002Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 106, s. 11412-11419Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The internal structure of the solid phase formed in mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and a range of oppositely charged polyelectrolytes with different side chains and charge density has been investigated using small-angle X-ray scattering. Polyelectrolytes with short side chains [3-(2-methylpropionamido)propyl]trimethylammonium chloride, MAPTAC, and poly{[(2-propionyloxy)ethyl]trimethylammonium chloride}, PCMA) form a 2-dimensional hexagonal structure with SDS, whereas a polyelectrolyte without side chains (poly(vinlyamine), PVAm) forms a lamellar structure. The hexagonal structure of MAPTAC is retained either when a neutral monomer (acrylamide, AM) is included in the polymer backbone to reduce the charge density or when a nonionic surfactant is admixed to the SDS/polyelctrolyte complex. The unit cell length of AM-MAPTAC increases with decreasing charge density from a = 47.7 Å (MAPTAC, 100% charge density) to 58.5 Å (AM-MAPTAC, 30% charge density). The unit cell length in the lamellar SDS/PVAm complex (a = 36.1 Å) is significantly smaller than for the different hexagonal structures. It is conjectured that the cylinders in the hexagonal structure and the bilayers in the lamellar structure are based on self-assembled surfactant aggregates with the polyelectrolyte mainly located in the aqueous region adjacent to the charged surfactant headgroups

  • 124.
    Bergström, M
    et al.
    YKI – Ytkemiska institutet.
    Pedersen, JS
    A small-angle neutron scattering study of surfactant aggregates formed in aqueous mixtures of sodium dodecyl sulfate and didodecyldimethylammonium bromide2000Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 104, s. 4155-4163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of aggregates formed in aqueous mixtures of a single-chain anionic surfactant, sodium dodecyl sulfate (SDS), and a double-chain cationic surfactant, didodecyldimethylammonium bromide (DDAB), has been investigated at 38° C using small-angle neutron scattering (SANS). Several overall surfactant concentrations [SDS] + [DDAB] between 0.1 and 5 wt % were measured at the two SDS-rich compositions [SDS]:[DDAB] = 90:10 and 95:5. Samples with a concentration above about [SDS] + [DDAB] = 1 wt % at [SDS]:[DDAB] = 95:5 contained only somewhat elongated tablet-shaped micelles (triaxial ellipsoids) with typical values of the half-axes a (related to the thickness) = 14 Å, b (related to the width) = 23 Å, and c (related to the length) = 27 Å. When a sample at [SDS]:[DDAB] = 95:5 is diluted below about [SDS] + [DDAB] = 1 wt %, an increasing amount of small unilamellar vesicles forms, and in the samples below about 0.2 wt %, only vesicles are observed. The average radius of the vesicles increases from about 90 Å at 0.3 wt % to 110 Å at 0.1 wt %. The transition from micelles to vesicles with decreasing surfactant concentration was also observed in the samples at [SDS]:[DDAB] = 90:10 in which, however, an additional amount of bilayer sheets was seen to be always present. Compared with the micelles at [SDS]:[DDAB] = 95:5, the micelles formed at [SDS]:[DDAB] = 90:10 were considerably longer (c ≈40 Å), but with similar cross section dimensions, and the vesicles formed were seen to be somewhat larger than the corresponding aggregates at 95:5. The relative standard deviation σR/ of the (number-weighted) vesicle size distributions was in the range 0.2 < σR/ < 0.3.

  • 125.
    Bergström, Magnus
    YKI – Ytkemiska institutet.
    Size and shape analysis of micellar systems2002Inngår i: Encyclopedia of Surface and Colloid Science / [ed] Hubbard A and Somasundaran P, Marcel Dekker, 2002, s. 4684-4699Kapittel i bok, del av antologi (Fagfellevurdert)
  • 126. Biais, J
    et al.
    Ödberg, L
    Stenius, P
    YKI – Ytkemiska institutet.
    Thermodynamic properties of microemulsions : pseudophase equilibrium - vaporpressure measurements1982Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 86, s. 350-358Artikkel i tidsskrift (Fagfellevurdert)
  • 127. Bijelic, Goran
    et al.
    Shovsky, Alexander
    Varga, Imre
    Makuska, Ricardas
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Adsorption characteristics of brush polyelectrolytes on silicon oxynitride revealed by dual polarization interferometry2010Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, nr 1, s. 189-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorption properties of bottle-brush polyelectrolytes have been investigated using dual polarization interferometry (DPI), which provides real time monitoring of adsorbed layer thickness and refractive index. The adsorption on silicon oxynitride was carried out from aqueous solution with no added inorganic salt, and the adsorbed polyelectrolyte layer was subsequently rinsed with NaCl solutions of increasing concentration. The bottle-brush polyelectrolytes investigated in this study have different ratios of permanent cationic charged segments and uncharged PEO side chains. Both the cationic groups and the PEO side chains have affinity for silica-like surfaces, and thus contribute to the adsorption process that becomes rather complex. Adsorption properties in water, responses to changes in ionic strength of the surrounding medium, adsorption kinetics and the layer structure are all strongly dependent on the ratio between backbone charges and side chains. The results are interpreted in terms of competitive adsorption of segments with different chemical nature. The adsorption kinetics is relatively fast, taking only tens to hundreds of seconds when adsorbed from dilute 100 ppm solutions. The DPI technique was found to be suitable for studying such rapid adsorption processes, including determination of the initial adsorption kinetics. We expect that the effects observed in this study are of general importance for synthetic and biological polymers carrying segments of different nature.

  • 128.
    Biverstedt, A
    et al.
    YKI – Ytkemiska institutet.
    Jönsson, S
    ESCA-analys för industriell kontroll, analys och utveckling : del 21983Inngår i: Kemisk Tidskrift, ISSN 1650-0725, Vol. 7, s. 30-35Artikkel i tidsskrift (Fagfellevurdert)
  • 129.
    Björn, Camilla
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Håkansson, Joakim
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Myhrman, E
    Sjöstrand, V
    Haug, T
    Lindgren, K
    Anti-infectious and anti-inflammatory effects of peptide fragments sequentially derived from the antimicrobial peptide centrocin 1 isolated from the green sea urchin, Strongylocentrotus droebachiensis2012Inngår i: AMB Express, ISSN 2191-0855, E-ISSN 2191-0855, Vol. 2, nr 1, artikkel-id art.no 67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bacterial resistance against antibiotic treatment has become a major threat to public health. Antimicrobial peptides (AMPs) have emerged as promising alternative agents for treatment of infectious diseases. This study characterizes novel synthetic peptides sequentially derived from the AMP centrocin 1, isolated from the green sea urchin, for their applicability as anti-infective agents. The microbicidal effect of centrocin 1 heavy chain (CEN1 HC-Br), its debrominated analogue (CEN1 HC), the C-terminal truncated variants of both peptides, i.e. CEN1 HC-Br (1–20) and CEN1 HC (1–20), as well as the cysteine to serine substituted equivalent CEN1 HC (Ser) was evaluated using minimal microbicidal concentration assay. The anti-inflammatory properties were assessed by measuring the inhibition of secretion of pro-inflammatory cytokines. All the peptides tested exhibited marked microbicidal and anti-inflammatory properties. No difference in efficacy was seen comparing CEN1 HC-Br and CEN1 HC, while the brominated variant had higher cytotoxicity. C-terminal truncation of both peptides reduced salt-tolerability of the microbicidal effect as well as anti-inflammatory actions. Also, serine substitution of cysteine residue decreased the microbicidal effect. Thus, from the peptide variants tested, CEN1 HC showed the best efficacy and safety profile. Further, CEN1 HC significantly reduced bacterial counts in two different animal models of infected wounds, while Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance against this peptide under continued selection pressure. In summary, CEN1 HC appears a promising new antimicrobial agent, and clinical studies are warranted to evaluate the applicability of this AMP for local treatment of infections in man.

  • 130. Blom, C
    et al.
    Claesson, P
    YKI – Ytkemiska institutet.
    Eriksson, JC
    Herder, P
    Stenius, P
    YKI – Ytkemiska institutet.
    Krafter mellan ytor på molekylära avstånd1986Inngår i: Kemisk Tidskrift, ISSN 1650-0725, Vol. 98, nr 9, s. 47-50Artikkel i tidsskrift (Fagfellevurdert)
  • 131. Blomberg, E
    et al.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Proteins at surfaces studied with the surface force technique1995Inngår i: Proteins at Interfaces II: Fundamentals and Applications / [ed] Horbett, T.A. & Brash, J.L., American Chemical Society (ACS), 1995, s. 296-310Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Some results obtained by using the interferometric surface force technique for studying the interactions between adsorbed protein layers and between such layers and surfaces are presented. We have chosen to report results obtained for several types of proteins in order to emphasize differences and similarities in the behaviour. In this chapter we have also included sections describing the normal experimental procedure as well as some common difficulties which we have encountered during our studies of proteins with the surface force technique. It is hoped that these sections can be of use for readers that has no or a limited experience with this technique.

  • 132.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Interactions between poly(ethylene oxide) coated surfaces and between such surfaces and proteins1998Inngår i: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 19, s. 1107-1126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surfaces coated with poly(ethylene oxide) containing nonionic polymers are of interest in medical applications due to, among other things, the low adsorption of proteins on such surfaces. In this paper we have studied the interfacial properties of surfaces coated with PEO by measuring the forces acting between two such surfaces in water and across a protein solution as well as between one such surface and a surface carrying adsorbed proteins. One type of surface coating was a graft copolymer of poly(ethylene imine) and poly(ethylene oxide) where the cationic poly(ethylene imine) group anchored the polymer to negatively charged mica surfaces. Three different ways to prepare this coating was used and compared. It was found that this coating was not stable in the presence of lysozyme, a small positively charged protein, when the PEO graft density was low. The other type of coating was obtained by adsorbing ethyl(hydroxyethyl)-cellulose onto hydrophobised mica surfaces. The driving force for adsorption is in this case the hydrophobic interaction between nonpolar segments of the polymer and the surface. The EHEC coating was stable in the presence of lysozyme and the interactions between adsorbed layers of lysozyme and EHEC coated surfaces are purely repulsive due to long-range steric forces.

  • 133.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Christenson, HK
    Elastohydrodynamic effects with adsorbed layers in surface force measurements1990Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 138, s. 291-293Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When two elastic surfaces carrying adsorbed layers are forced together under high loads, as in measurement with the surface forces apparatus, a bell-shaped deformation develops in the flattened contact zone. This behavior is due to the elastohydrodynamic "lubrication" of the adsorbed layer. Compression of molecules thus trapped between the surfaces may under some cicumstances, e.g., in the cases of surfaces carrying weakly adsorbed proteins, lead to irreversible changes in the adsorbed layer and consequently in the surface interaction.

  • 134.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Fröberg, JC
    Tilton, RD
    Interaction between adsorbed layers of lysozyme studied with the surface force technique1994Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, s. 2325-2334Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The surface force technique was employed to investigate the adsorption of positively charged lysozyme onto negatively charged mica surfaces in 10-3 M NaCl at pH 5.6 at lysozyme concentrations ranging from 0.002 to 0.2 mg/ml. At equilibrium the adsorbed lysozyme nearly neutralizes the surface charge of the mica at all bulk lysozyme concentrations investigated. Prior to charge neutralization the decay length of the longrange force is consistent with the electrostatic double-layer force predicted by the DLVO theory. At low concentration, 0.002 mg/ml, a densely packed side-on oriented layer adsorbs on the mica surface. Above 0.02 mg lysozyme/ml, a rather thick layer is adsorbed onto the surface. It consists of an inner, strongly bound layer of both side-on and end-on adsorbed proteins and outer, weakly adsorbed proteins. An adhesion force is established upon contact of the adsorbed protein layers. The force measured between one lysozyme coated surface and one bare mica surface is attractive at short separations. It was demonstrated that at a concentration of 0.02 mg/ml, lysozyme adsorbs "irreversibly" with respect to dilution with 10-3 M NaCl.

  • 135.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Gölander, CG
    Adsorbed layers of human serum albumin investigated by the surface force technique1991Inngår i: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 12, s. 179-200Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interactions between human serum albumin (HSA) layers adsorbed from solution onto muscovite mica have been investigated by means of surface force measurements. The effects of varying the ionic strength and the serum albumin concentration have been studied at pH=5.5. The negatively charged protein cannot be desorbed from the negatively charged mica surface by dilution with water. The thickness of the (compressed) adsorbed layer is small compared to the dimension of HSA, except at the highest concentration used (1mg/ml). Hence, under a compressive load at low packing densities the protein conformation on the surface is different from that in bulk solution. No adhesion was observed when the amount adsorbed was large. However, an attractive

  • 136.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Konradsson, P
    Liedberg B,
    Globotriose- and Oligo(ethylene glycol)-Terminated Self-Assembled Monolayers: Surface forces, wetting, and surfactant adsorption2006Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, s. 10038-10046Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A set of oligo(ethylene glycol)-terminated and globotriose-terminated self-assembled monolayers (SAMs) has been prepared on gold substrates. Such model surfaces are well defined and have good stability due to the strong binding of thiols and disulfides to the gold substrate. They are thus very suitable for addressing questions related to effects of surface composition on wetting properties, surface interactions, and surfactant adsorption. These issues are addressed in this report. Accurate wetting tension measurements have been performed as a function of temperature using the Wilhelmy plate technique. The results show that the nonpolar character of oligo(ethylene glycol)-terminated SAMs increases slightly but significantly with temperature in the range 20-55 C. On the other hand, globotriose-terminated SAMs are fully wetted by water at room temperature. Surface forces measurements have been performed and demonstrated that the interactions between oligo(ethylene glycol)-terminated SAMs are purely repulsive and similar to those determined between adsorbed surfactant layers with the same terminal headgroup. On the other hand, the interactions between globotriose-terminated SAMs include a short-range attractive force component that is strongly affected by the packing density in the layer. In some cases it is found that the attractive force component increases with contact time. Both these observations are rationalized by an orientation- and conformation-dependent interaction between globotriose headgroups, and it is suggested that hydrogen-bond formation, directly or via bridging water molecules, is the molecular origin of these effects.

  • 137.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Tilton, RD
    Short-range interaction between adsorbed layers of human serum albumin1994Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 166, s. 427-436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption of human serum albumin (HSA) onto muscovite mica has been investigated by means of surface force and ESCA measurements. The range of protein concentration explored was 0.001-1.0 mg/ml in 10-3 M NaCl at pH 5.6. It was found that negatively charged albumin adsorbs onto negatively charged mica. Co-adsorption of small ions into the adsorbed protein layer was also inferred. Small structural changes are induced by the adsorption, and further structural changes can be induced by applying an external compressive force. The structure of the adsorbed layer depends on the surface density. As surfaces with a low adsorption density of HSA are brought together, the protein molecules are able to diffuse along the surface, facilitating the merging of the two HSA layers into one single HSA layer in the gap between the surfaces. At high surface density crowding effects impede the rearrangement of the HSA layers and two separate layers of HSA remain in the gap between the surfaces. An adhesion force is present at low packing but not at high packing densities. It was found that the short-range interaction between one HSA-coated surface and one bare mica surface was strongly attractive, demonstrating that the adhesion forces likely are induced by HSA molecules bridging between two surfaces and not by attractive interactions between the proteins themselves.

  • 138.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wärnheim, T
    Surface interactions in emulsion and liposome solutions1999Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 159, s. 149-157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used two surface force techniques to investigate the interactions between hydrophilic and negatively charged mica and glass surfaces across concentrated and dilute oil-in-water emulsions, as well as across aqueous liposome solutions. It was observed with both the interferometric surface force apparatus, using mica surfaces, and with the non-interferometric MASIF technique, employing glass surfaces, that emulsion droplets adsorbed onto the surfaces. Under a high compressive force the adsorbed emulsion droplets were disintegrated and this resulted in a phase separation in the gap between the surfaces. The forces measured in the presence of the capillary condensate compared favourably with theoretical expectations. In contrast, no adsorption of large aggregates could be detected in the liposome solution. Instead it appears that upon adsorption the liposomes disintegrate and the surfaces become covered by a disordered layer of phospholipids. Measurements with the interferometric surface force apparatus, that allows absolute distances to be determined, allow us to draw the conclusion that some bilayer aggregates are adsorbed and that the inner layer consists of an intercalated monolayer.

  • 139.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Gölander, C-G
    Adhesion of trimyristin fat to radio frequency plasma treated PVC and chromium1990Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 6, s. 1499-1504Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is an increasing belief in the use of surface modification techniques to reduce the adhesion of soil to surface so that only weak detergents or mechanical means is required for the soil removal. In this work, we have studied how the soil adhesion is affected by controlled and well-defined modification of thr surface. Various surfaces were prepared by radio frequency plasma treatment combined with surface derivatization techninques. Adsorption and displacement of trimyristin , a model soil, were investigated by ellipsometry. Two fundametally different and succesful approaches to realize a good soil-repellant surface werw found:(i) strongly polar surfaces of poly(ethylene oxide) that interact strongly with water or (ii) surfaces which contain cross-linked fluorocarbon moieties.

  • 140.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Kumpulainen, A
    David, C
    Amiel, C
    Polymer bilayer formation due to specific interactions between β-cyclodextrin and adamantane: A surface force study2004Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, s. 10449-10454Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purposes of this study are to utilize the interactions between an adamantane end-capped poly-(ethylene oxide) (PEO) and a cationic polymer of β-cyclodextrin to build polymer bilayers on negatively charged surfaces, and to investigate the interactions between such layers. The association of this system in solution has been studied by rheology, light scattering, and fluorescence measurements. It was found that the adamantane-terminated PEO (PEO-Ad) mixed with the β-cyclodextrin polymer gives complexes where the interpolymer links are formed by specific inclusion of the adamantane groups in the β-cyclodextrin cavities. This results in a higher viscosity of the solution and growth of intermolecular clusters. The interactions between surfaces coated with a cationized β-cyclodextrin polymer across a water solution containing PEO-Ad polymers were studied by employing the interferometric surface force apparatus (SFA). In the first step, the interaction between mica surfaces coated with the cationized β-cyclodextrin polymer in pure water was investigated. It was found that the β-cyclodextrin polymer adsorbs onto mica and almost neutralizes the surface charge. The adsorbed layers of the β-cyclodextrin polymer are rather compact, with a layer thickness of about 60Å(30Å per surface). Upon separation, a very weak attractive force is observed. The β-cyclodextrin solution was then diluted by pure water by a factor of 3000 and a PEO-Ad polymer was introduced into the solution. Two different architectures of the PEO-Ad polymer were investigated: a four-arm structure and a linear structure. After the adsorption of the PEO polymer onto the β-cyclodextrin layer reached equilibrium, the forces were measured again. It was found that the weak repulsive longrange force had disappeared and an attractive force caused the surfaces to jump into contact, and that the compressed layer thickness had increased. The attractive force is interpreted as being due to a specific recognition between the hydrophobic adamantane groups on the PEO-Ad polymer and the hydrophobic cavity in the β-cyclodextrin molecules. Furthermore, the attractive force observed on separation has increased significantly, which is a further indication of a specific interaction between the β-cyclodextrin polymer and the adamantane groups

  • 141.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Poptoshev, E
    YKI – Ytkemiska institutet.
    Caruso, F
    Surface interactions during polyelectrolyte multilayer build-up. 2. The effect of ionic strength on the structure of preformed multilayers2006Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 9, s. 4153-4157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interactions between surfaces bearing multilayer films of poly(allylamine hydrochloride) (PAH) and poly-(styrenesulfonate sodium salt) (PSS) were investigated across a range of aqueous KBr solutions. Three layer films (PAH/PSS/PAH) were preassembled on mica surfaces, and the resulting interactions were measured with the interferometric surface force apparatus (SFA). Increasing the ionic strength of the medium resulted in a progressive swelling of the multilayer films. Interactions in solutions containing more than 10-3 M KBr were dominated by a long-ranged steric repulsion originating from compression of polyelectrolyte segments extending into solution. In 10-1 M KBr, repeated measurements at the same contact position showed a considerable reduction of the range and the strength of the steric force, indicating a flattening of the film during initial approach. Furthermore, this flattening was irreversible on the time scale of the experiments, and measurements performed up to 72 h after the initial compression showed no signs of relaxation. These studies aid in understanding the dominant interactions between polyelectrolyte multilayers, including polyelectrolyte films deposited on colloidal particles, which is important for the preparation of colloidally stable nanoengineered particles.

  • 142.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Poptoshev, E
    Claesson, PM
    YKI – Ytkemiska institutet.
    Caruso, F
    Surface interactions during polyelectrolyte multilayer buildup. 1. Interactions and layer structure in dilute electrolyte solutions2004Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, s. 5432-5438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the investigation of surface forces between polyelectrolyte multilayers of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate sodium salt) (PSS) assembled on mica surfaces during film buildup using a surface force apparatus. Up to four polyelectrolyte layers were prepared on each surface ex situ, and the surface interactions were measured in 10-4 M KBr solutions. The film thickness under high compressive loads (above 2000 μN/m) increased linearly with the number of deposited layers. In all cases, the interaction between identical surfaces at large separations (>100 Å from contact) was dominated by electrostatic double-layer repulsion. By fitting DLVO theory to the experimental force curves, the apparent double-layer potential of the interacting surfaces was calculated. At shorter separations, an additional non-DLVO repulsion was present due to polyelectrolyte chains extending some distance from the surface into solution, thus generating an electrosteric type of repulsion. Forces between dissimilar multilayers (i.e., one of the multilayers terminated with PSS and the other with PAH) were attractive at large separations (30-400 Å) owing to a combination of electrostatic attraction and polyelectrolyte bridging.

  • 143.
    Blomberg, E
    et al.
    YKI – Ytkemiska institutet.
    Verrall, R
    Claesson, PM
    YKI – Ytkemiska institutet.
    Interactions between adsorbed layers of cationic gemini surfactants2008Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 4, s. 1133-1140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The forces acting between glass and between mica surfaces in the presence of two cationic gemini surfactants, 1,4 diDDAB (1,4-butyl-bis(dimethyldodecylammonium bromide)) and 1,12 diDTDAB (1,12-dodecyl-bis(dimethyldodecylammonium bromide)), have been investigated below the critical micelle concentration (cmc) of the surfactants using two different surface force techniques. In both cases, it was found that a recharging of the surfaces occurred at a surfactant concentration of about 0.1 x cmc, and at all surfactant concentrations investigated repulsive double-layer forces dominated the interaction at large separations. At smaller separations, attractive forces, or regions of separation with (close to) constant force, were observed. This was interpreted as being due to desorption and rearrangement in the adsorbed layer induced by the proximity of a second surface. Analysis of the decay length of the repulsive double-layer force showed that the majority of the gemini surfactants were fully dissociated. However, the degree of ion pair formation, between a gemini surfactant anda bromide counterion, increased with increasing surfactant concentration and was larger for the gemini surfactant with a shorter spacer length.

  • 144.
    Blomberg, Eva
    et al.
    YKI – Ytkemiska institutet.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Surface forces and emulsion stability: Chapter 72004Inngår i: Food emulsions: Revised and Expanded / [ed] Stig Friberg, Kare Larsson, Johan Sjöblom, CRC Press, 2004, 4th, s. 257-297Kapittel i bok, del av antologi (Fagfellevurdert)
  • 145.
    Blomberg, Eva
    et al.
    YKI – Ytkemiska institutet.
    Lundin, Maria
    YKI – Ytkemiska institutet.
    Layer-by-layer assembly of biomacromolecular multilayers2011Inngår i: Encyclopedia of Surface and Colloid Science / [ed] Ponisseril Somasundaran; Arthur Hubbard, CRC Press, 2011, 2ndKapittel i bok, del av antologi (Fagfellevurdert)
  • 146.
    Blute, I
    et al.
    YKI – Ytkemiska institutet.
    Jansson, M
    YKI – Ytkemiska institutet.
    Oh, SG
    Shah, DO
    The molecular mechanism for destabilization of foams by organic ions1994Inngår i: Journal of the American Oil Chemists Society, ISSN 0003-021X, E-ISSN 1558-9331, Vol. 71, s. 41-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The destabilization of foams by electrolytes with tetraalkylammonium ions has been investigated. The presence of large tetraalkylammonium ions at the oil/water interface perturbs the packing of surfactants, producing noncoherent films of low stability. A comparison between the foam destabilizing efficiency of tetraalkylammonium bromide salts with tributyl phosphate and 2-ethyl hexanol, which are used in many commercial antifoaming formulations, demonstrated that the organic salts have a potential for being useful in technical applications involving foam inhibition.

  • 147. Blute, I
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Svensson, M
    Unelius, R
    Phase behaviour of alkyl glycerol ether surfactants1998Inngår i: Tenside Surfactants Detergents, ISSN 0932-3414, E-ISSN 2195-8564, Vol. 35, s. 207-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper the phase behaviour and physical properties of a series of alkyl (C6, C8, C12 and iso-C8) monoglycerol ethers and 2-hydroxyalkyl (C6, C8, C12) monoglycerol ethers are presented. The binary phase diagram for the surfactants shows very little dependence on temperature. It is shown that as the alkyl chain length increases the tendency to form lamellar liquid crystalline phases increases. The branched alkyl chain shows no formation of lamellar phase even at high concentrations of surfactant. The differences in phase behaviour between the surfactants is attributed to the variation in the critical packing parameter (CPP) of the surfactants. The presence of an additional hydroxyl group in the alkyl chain causes a temperature independent solubility behaviour. Ternary phase diagrams were prepared using dodecane as the oil phase. Hexyl glycerol ether was the only of the alkyl glycerol ethers which was sufficiently water soluble to determine the surface tension and CMC. The CMC was determined to 15 mM (and surface tension to 26 mN m-1).

  • 148. Blute, I
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    van de Pas, J
    Callaghan, I
    Industrial manufactured silica nanoparticle sols. 2: Surface tension, particle concentration, foam generation and stability2009Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 337, nr 1-3, s. 127-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several earlier papers have revealed that several key parameters, such as hydrophobicity (contact angle), size, shape and degree of agglomeration, have an important influence on the behavior of particles at the air/water interface. However, the origin of foaming with particles is still not clear. In this article, we have tentatively related surface tension measurements and particle concentrations to the generation and stability of foam produced fromindustrial manufactured silica nanoparticle sols. Surprisingly, only slight reductions in surface tensionwere observed and the differences between the hydrophophilic and partially modified hydrophobic sols were small. However, in the case of the partially modified hydrophobic sol, the surface tension/concentration gradient was found to be pH and concentration responsive. Also, the greatest reduction in surface tension was found to occur at low pH (in the region of the pHpzc) and could be related to the highest foamability (foam generation) as determined in our earlier publication [I. Blute, R.J. Pugh, J. van de Pas, I. Callaghan, Silica nanoparticle sols. 1. Surface chemical characterization and evaluation of the foam generation (foamability), J. Colloid Interface Sci. 313 (2007) 645–655]. Also, after centrifugation of the moderately hydrophobic modified concentrated sols, foaming tests carried out on the supernatant indicated that the particle concentration had a dominant influence on foamability and foam stability. Since only transient foams, with relatively short lifetimes, could be produced with thesemodified silica nanoparticles then (a) further surface modification or the reduction of pH to increase the surface activity or (b) the addition of a cosurfactant would be needed to increase the foamability and achieve foams with extended lifetimes.

  • 149. Blute, I
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    van de Pas, J
    Callaghan, I
    Silica nanoparticle sols 1. Surface chemical characterization and evaluation of the foam generation (foamability)2007Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 313, s. 645-655Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5–40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pHpzc which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6–40 nm range) and (b) increased with particle concentration (within the range of 1–15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration.

  • 150. Blute, I
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    van de Pas, J
    Callaghan, I
    Silica nanoparticle sols. Part 3: Monitoring the state of agglomeration at the air/water interface using the Langmuir-Blodgett technique2009Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, nr 2, s. 584-591Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Langmuir–Blodgett films were prepared at the air/water interface from dispersions of hydrophilic and partially, hydrophobically modified industrially manufactured silica nanoparticles. The hydrophilic particles featured expanded, fairly easily compressible, surface pressure (p)–area (A) isotherms with well defined collapse pressures which appeared to be caused by the formation of loosely structured agglomerates which exhibited elastic behavior at low surface pressure and inelastic behavior at high surface pressure. Lateral electrostatic interparticle interactions seemingly played an important role in this hydrophilic system. This contrasted with the hydrophobically modified particles which were more difficult to disperse in the ethanol/chloroform spreading solvent and appeared to be in the semi-agglomerated state at low surface pressures and exhibited a more difficult to compress compacted film. Both types of particulate films were shown to be sensitive to the spreading environment and changes in pH were found to increase particle agglomeration which drastically reduced the particulate area for the hydrophilic sol but less so, in the case of the moderately hydrophobically modified sol. In general, the LB technique proved to be a useful method to monitor changes in the state of aggregation of nanosized silica particles at the air/water interface. These results also appear to give some support of our ideas, presented in earlier publications [1,2] in which it was suggested that the major role of the hydrophobically modified hydrophilic particles in foaming was to produce an aggregated particulate film surrounding the air/water interface which provides a physical barrier preventing coalescence of bubbles.

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