| 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. |
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| 4. |
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| 5. |
- Bergström, Lars Magnus, et al.
(författare)
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Synergistic effects in binary surfactant mixtures
- 2004
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Ingår i: Progress in Colloid and Polymer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0340-255X .- 1437-8027. ; 123, s. 16-22
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
- Burns, NL, et al.
(författare)
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Surface charge characterization and protein adsorption at biomaterials surfaces
- 1996
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 100, s. 271-275
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to more fully understand the nature of protein adsorption, and the role adsorbed proteins have in mediating interfacial processes in biomaterial application, effect of surface charge is being explored. For this purpose, a novel electrokinetic technique whereby electroososmosis is measured at flat plates is being used to characterize surfaces with respect to effective surface charge and origin of charge. Protein adsorption is monitored by in situ ellipsometry or by an enzyme linked immunosorbent assay (ELISA). Correlations can then be made between the observed surface properties and biological response to the surface, including bacterial adherence and complement activation of blood proteins. Surfaces studied include a wide variety of radio frequency plasma polymers, and polysiloxane modified surfaces; all of interest as biomaterials. The plasma polymer surfaces are being used as model surfaces to study protein mediated bacterial adherence. Siloxane polymer coatings are being used to interfere with salivary pellicle and plaque formation on teeth, with different patterns in the adherence of oral bacteria observed with different polysiloxanes. In the above systems, patterns in protein adsorption related to surface charge and functionality, as well as other surface properties, can be identified. It appears that surface charge and charging properties are important factors in formation of biofilms.
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| 8. |
- Bydén, M., et al.
(författare)
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Phase equilibria in two aqueous chiral surfactant systems
- 1997
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 105, s. 360-364
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present the binary phase diagrams of the pure (R)- and the racemic aqueous sodium-2-methyldecanoate surfactant systems. The latter is a 1:1 mixture of the pure (S)- and pure (R)-form. The systems were investigated using crossed polaroids, polarizing optical microscope and 2HNMR splittings. Both systems form a micellar phase, followed by a hexagonal, some intermediate phase and a large cubic phase. At even higher concentrations, the 2HNMR studies showed larger quadrupolar splittings up to 1200 Hz, due to a lamellar phase. The intermediate phase was in both cases very narrow, and extended up to > 23°C in the racemic system and up to 30°C in the pure (R)-system. The similarity between these two binary phase diagrams indicates that the change in molecular packing is so small that it does not drastically affect the phase behavior. The Krafft temperature in the micellar phase in both systems is 1°C, which is very low compared to that of unsubstituted alkanoates with the same chain length.
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| 9. |
- 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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| 10. |
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