| 1. |
- Backlund, S, et al.
(författare)
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Partial phase behavior of ionic microemulsions stabilized by sodium dodecylsulfate and alcohol cosurfactants
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- Ionic microemulsions, stabilized by sodium dodecylsulfate and alcohol cosurfactants, have been characterized with respect to phase behavior, particularly the composition of the different phases in Winsor type I, II and III systems. The system containing brine, octane, sodium dodecylsulfate and 1-butanol shows a regular phase behavior, in conformity with the anticipated behavior, i.e., 2-3-2 phases. The phase transitions with increasing 1-butanol concentration are analogous to those occurring with increasing salinity, when compared with previous investigations. For the system containing brine, cyclohexane, sodium dodecylsulfate and benzyl alcohol, the behavior becomes more complex, even at low surfactant contents. The transitions are 2-3-2-3-2 phases over a wide composition range. The compositions of the phases at equilibrium are discussed in relation to structural considerations, as determined by conductivity and NMR self-diffusion measurements.
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| 2. |
- Backlund, S, et al.
(författare)
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Partical phase equilibria and partition of alcohol cosurfactants in ionic microemulsions
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 290-295
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Tidskriftsartikel (refereegranskat)abstract
- The partial phase behaviour of quintinary microemulsions containing water (0.5 m NaCl), sodium dodecylfate, octane and alcohol, where the alcohol is a butanol or pentanol isomer, has been determined. In addition, the partition of the cosurfactant between the phases has been investigated, as well as in detail for the 1-butanol system. The efficiency of the cosurfactant for forming microemulsions is found to exhibit no simple relationship to its solubility properties. In addition, while branched alcohol cosurfactants promote the formation of solution phases at high surfactant contents.
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| 3. |
- Claesson, PM, et al.
(författare)
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Amine functionalized surfactants - pH effects on adsorption and interaction
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 64-73
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between layers of two hydrolyzable surfactants, dodecylamine (DA) and tetraoxyethylene dodecylamine (TEDA), adsorbed on negatively charged muscovite mica have been investigated. It was found that the variation of the interaction and adsorption as a function of pH was similar, but not identical, for the two kinds of surfactants. At a concentration of 10-4 M at low pH (below 8) both types of surfactants adsorb electrostatically to form a monolayer. The resulting surfaces have a hydrophobic character, particularly in the case of dodecylamine. A series of events takes place as the pH is increased. For DA the first event is that uncharged molecules adsorb within the monolayer. This does not occur to any significant degree for TEDA due to steric hindrance within the adsorbed layer. In the next step a bilayer builds up on the surface. The binding of the outer layer is stronger for DA than for TEDA. The DA bilayer becomes uncharged at pH 10.3, and liquid dodecylamine droplets, which phase separate from the bulk solution at this pH-value, precipitate on the surface. At pH-values above 11-12 the affinity between both types of surfactants and the surface decreases significantly, resulting in a less ordered first layer. In addition a strong surface charge develops that prevents multilayer build-up.
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| 4. |
- Claesson, PM, et al.
(författare)
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Functionalized mica surfaces obtained by a cold plasma process
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 330-336
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Tidskriftsartikel (refereegranskat)abstract
- A surface modification procedure based on the cold plasma technique has been utilized in order to introduce new functional groups onto muscovite mica surfaces. In the first reaction step mica surfaces are exposed to a water vapor plasma. The interaction between mica surfaces and reactive species in the plasma results in information of surface hydroxyl groups. These groups are reactive toward chlorosilanes in the gas phase, which provides a versatile way to obtain mica surfaces with a variety of different surface chemical groups. For instance, poly(ethylene oxide) chains have been covalently attached to mica surfaces.-In a different surface modification route, mica surfaces have been coated with thin plasma polymer layers. Mechanical and surface properties of plasma polymer films depend, of course, on the type of monomer, but also on the condition used during polymerization (e.g., flow rate, pressure and discharge power). The surface force technique has, together with spectroscopic analyses, provided information about how the adhesion force and mechanical strength of different plasma polymers of acrylic acid depend on the polymer structure.
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| 5. |
- Dahlgren, MAG, et al.
(författare)
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Surface forces between adsorbed polyelectrolytes in salt solution
- 1993
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 93, s. 206-208
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Tidskriftsartikel (refereegranskat)abstract
- Highly charged cationic polyelectrolyte was adsorbed onto mica from 10-4 M KBr and 10-4 M K2SO4 solutions. The results show that the structure of the adsorbed layer and the total amount adsorbed is dependent on the anion valency. Both the layer thickness and the adsorbed amount increase when the salt anion is of higher valency. Desorption over several days into 10-4 M K2SO4 solution was followed. This indicates the adsorbed layer initially overcompensates the mica lattice charge. After some time, the sign of the charge is re-reversed, due to desorption. Adhesion between the adsorbed layers increase during the desorption process. This adhesion is attributed to bridging of entropic origin.
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| 6. |
- Erlandsson, Ragnar, et al.
(författare)
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Scanning force microscopy - examples of applications to surface chemistry
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 154-161
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Tidskriftsartikel (refereegranskat)abstract
- Some recent results from the scanning force microscopy activity at our laboratory are presented. A brief description of attractive mode force microscopy is followed by a discussion of the following examples: O2/H2-induced morphology changes in thin palladium films, structure of spin cast polysulfone films, fibrinogen adsorption on hydrophobic SiO2, and force measurements on hydrophobic/hydrophilic substrates.
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| 7. |
- Huldén, M, et al.
(författare)
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Adsorption of some common surfactants and polymers on TiO2 pigments
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 28-37
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of nonylphenol deca (oxyethyleneglycol) monoether (NPE10), sodium dodecyl sulphate (SDS), polyacrylic acid sodium salt (PAA) and ethyl hydroxyethyl cellulose (EHEC) on TiO2-pigment coated with different mineral oxides is reported. The adsorption isotherms are compared with data obtained by electrophoretic mobility measurements. Despite the limitationsinherent in the mobility measurements, we show that this technique can be used to gain adequate information on the adsorption.-Coating of the TiO2-pigment with different mineral oxides has a strong influence on the adsorption. This can be understood from the different acid/base characteristics of the coatings, e.g., TiO2 coated with Al2 O3 or (Al2 O 3 + SiO2) results in a basic and an acidic surface, respectively. SDS, PAA, and EHEC adsorb on the basic pigment, but not on the acidic one. NPE10 does not adsorb on either pigment, nor does it adsorb on pigment stabilized with pre-adsorbed PAA. The competitive adsorption of PAA and EHEC was studied by the consecutive addition of the polymers to the pigment dispersion. The total amount of adsorbed polymer was always larger with two polymers present compared to one single polymer. EHEC does not significantly influence the adsorption of PAA, irrespectively of whether it is adsorbed before or after the PAA. Conversely, 45% of the preadsorbed EHEC desorbs upon the addition of PAA. When EHEC is added to a pigment with pre-adsorbed PAA, the final amount of EHEC on the surface is significantly lower than the amount adsorbed on the bare pigment.
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| 8. |
- Kronberg, B, et al.
(författare)
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On the nature and role of water structuring in the adsorption of nonionic surfactants on hydrophobic surfaces
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 83, s. 75-83
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Tidskriftsartikel (refereegranskat)abstract
- High pressure liquid chromatography (HPLC) results were used to calculate the temperature dependence of the hydrocarbon-water interaction parameter. The temperaturte dependence has been interpreted in terms of water structuring around the hydrocarbon. The role of water structuring is to enhance the solubility of hydrocarbons in water, which is equivalent to a decrease of the hydrocarbon-water interaction parameter. The poor solubility of hydrocarbons in water is not due to the water structuring, but to other factors such as the large energy required to form a cavity in the water for the hydrocarbon. This is a reflection of the very large cohesive forces in liquid water. These results, together with the temperature dependence of the polyethylene oxide-water interaction parameter, have been used to calculate the temperature dependence of the adsorption of a nonionic surfactant, viz. an ethoxylated nonyl phenol with 20 ethylene oxide units (NP-EO20). It is shown, that water structuring causes, an increased adsorption with temperature. Without water structuring a decreased adsorption is predicted.
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| 9. |
- Wärnheim, T, et al.
(författare)
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Phase behaviour of alkanolammonium carboxylates
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 18-22
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Tidskriftsartikel (refereegranskat)abstract
- Partial binary phase diagrams for thirteen different alkanolammonium carboxylates with water have been determined. The alkanolamines employed were monoethanolamine, triethanolamine and triisopropanol--amine, while the fatty acid has been varied with respect to chain length (C8 - C22) and saturation. The phase diagrams show the features that distinguish them from ordinary soap-water phase diagrams. First, multi-phase regions and miscibility gaps occur at low concentrations of surfactant, in particular for triethanolammonium carboxylates. Secondly, the stability regions of the liquid crystalline phases are different, and in general smaller com--pared to those formed by the corresponding alkali carboxylates. It is suggested that the first feature is due to that alkanolamines are weak bases and thus, that any surfactant aggregate comprises a few percent of unhydrolyzed acid, while the second feature is attributed to the larger size of the counterion compared to alkali ions, which tends to destabilize ordered structures.
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| 10. |
- Wärnheim, T, et al.
(författare)
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Phase diagrams for cationic surfactants in polar solvent systems
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- Phase diagrams are presented for cationic surfactants, and alkyltrimethyl ammonium bromide in polar solvent systems, such as ethylene glycol, formamide, glycerol, and their mixtures with water. Provided that the solvent is sufficiently lipophobic, and that the hydrocarbon moiety of the surfactant is sufficiently large, liquid crystalline phases form according to the normal association pattern for ionic surfactants. In, for example, ethylene glycol, liquid crystals are only formed with surfactants with a longer alkyl chain length than dodecyl.-The formation of didodecyldimethylammonium bromide microemulsions containing polar solvents- mainly formamide, water and their mixtures-and hydrocarbon has been studied. The extension of the solution phase region may decrease, although the mutual miscibility of polar solvent and the hydrocarbon increases. NMR self-diffusion measurements reveal that this is accompanied by a corresponding loss of structure, i.e., a smaller distinction between polar and apolar regions.
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