| 1. |
- Amenitsch, H, et al.
(författare)
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Bile salts form lyotropic liquid crystals
- 2003
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 0927-7757 .- 1873-4359. ; 213:1, s. 79-92
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Tidskriftsartikel (refereegranskat)abstract
- A reinvestigation of the phase diagrams relative to some conjugated and non-conjugated bile salts in water has demonstrated the formation of lyotropic liquid crystalline phases, in contradiction with generally accepted statements. The phase behaviour is complex and the phase diagrams are unusual, compared to most surfactants and lipids. In particular, coexistence of liquid crystalline phases with crystals has been obser ed. The formation of liquid crystalline phases requires very long equilibration times and the thermal stability of the lyotropic phases is moderate. The observed structure is tentatively assumed to be of the reverse hexagonal type. Structural relations with currently accepted models for the organisation of bile salts into micelles and solid form have been found. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
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| 3. |
- Boija, Susanne, et al.
(författare)
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Determination of conditional stability constants for some divalent transition metal ion-EDTA complexes by electrospray ionization mass spectrometry
- 2014
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 49:7, s. 550-556
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Tidskriftsartikel (refereegranskat)abstract
- Conditional stability constants of coordination complexes comprising divalent transition metals, Cu2+, Ni2+, Zn2+, Co2+, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co2+ and Zn2+ competed for EDTA at pH 5. When Cu2+ and Ni2+ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
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| 4. |
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| 5. |
- Bydén Sjöbom, Malin, et al.
(författare)
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BinaBinary Phase Equilibria and Structure of the Two α-Methyl-Substituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate ry Phase Exuilibria and Structure of the Chiral α-Methylsubstituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate
- 1999
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 15:8, s. 2654-2660
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present the binary phase diagrams for the aqueous systems of the alkyldecanoic salts racemic sodium 2-methyldecanoate and sodium (R)-2-methyldecanoate, respectively. Both systems form a micellar solution phase, as well as a normal hexagonal, a cubic, and a lamellar liquid crystalline phase. They also form a very narrow intermediate phase, situated between the hexagonal and cubic liquid crystalline phases. The methods used for characterization were crossed polaroids, polarizing optical microscope and 2H NMR quadrupolar splittings combined with SAXS studies. The cubic phase gave a well-resolved SAXS diffraction pattern, with eight peaks present, which establishes the bicontinuous cubic structure as Ia3d. A significant difference in these two phase diagrams, compared to those of unsubstituted alkanoates with the same chain length, is the very low Krafft boundary.
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| 6. |
- Bydén Sjöbom, Malin, et al.
(författare)
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Binary Phase Equilibria of Three alfa-Methylsubstituted Sodium Alkanoate Surfactant Systems.
- 2003
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797. ; 257:2, s. 333-336
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we continue our study of methyl -substituted surfactants and present the aqueous binary phase diagrams of racemic sodium 2-methyloctanoate, -nonanoate, and -dodecanoate, respectively. All systems have very low Krafft temperatures within the solution phase, between 1 and 4 degreesC. The phase sequences of the two shorter surfactants are very similar to those of the unsubstituted sodium octanoate, although with somewhat different range of existence for the phases formed. The sodium 2-methyldodecanoate system is different from the unsubstituted sodium dodecanoate system, as the former seems to lack a hexagonal phase. The surfactant systems were delineated using H-2 NMR splittings and crossed polarizers, and combined with SAXS for determination of phase structure.
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| 7. |
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| 8. |
- Bydén Sjöbom, Malin, et al.
(författare)
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Phase Equilibria of the Mixed Didodecyldimethylammonium Bromide-Taurodeoxycholate-Water System with a Large Solution Region.
- 2005
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Ingår i: Colloids and Surfaces. - : Elsevier BV. - 0166-6622 .- 1873-4340. ; 269:1-3, s. 87-95
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior over the entire concentration range for the system didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate (STDC)-water, at 25 degrees C, has been investigated, with emphasis on the DDAB-rich part. Polarizing microscopy, SAXS, H-2 NMR and H-1 self-diffusion NMR have been used in combination as probing techniques for phase behavior and microstructure. The system forms four major phases, all deriving from the respective binary surfactant systems. The two lamellar phases originating from the binary DDAB-water axis (D-I and D-II, at 3-30 and 83-91 wt.% DDAB, respectively) are only able to incorporate small amounts of STDC. The D-II phase solubilizes a comparatively higher amount of bile salt (up to ca. 6 wt.%), while the D, phase takes up less than 0.25 wt.%. From the STDC-water axis, a solution phase and a "hexagonal-like" liquid crystalline phase are derived, at 0-26 and 37-60 wt.% of STDC, respectively. Heterogeneous regions are also indicated on the basis of NMR and SAXS data. The most striking feature is the large extension of the isotropic solution phase, which originates from the water corner and curves toward the DDAB-rich side of the phase diagram. Even though at the upper limit of the solution phase the amount of water is reduced to 10 wt.%, the measured water and DDAB self-diffusion coefficients exclude the possibility of reverse-type structures.
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| 9. |
- Carlsson, Håkan, et al.
(författare)
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Competition Between Monovalent and Divalent Counterions in a Surfactant / Water System
- 1996
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 180:2, s. 598-604
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Tidskriftsartikel (refereegranskat)abstract
- Competition between mono- and divalent ions in the association of counterions to the headgroups of amphiphiles was studied in one surfactant system with organic counterions (piperidine+/piperazine2+octanesulfonate) and one with inorganic counterions (Na+/Ca2+octyl sulfate). By conductivity and13C NMR chemical shift measurements the critical micelle concentration (CMC) was found to decrease drastically when small amounts of divalent counterions were present in the system. Self-diffusion coefficients of surfactant ions and organic counterions were measured in the micellar phase by the Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR method. The degree of counterion binding in the micellar system with piperidine+/piperazine2+counterions was obtained from FT-PGSE NMR measurements. It was observed that the divalent counterions were more strongly bound than the monovalent counterions. The experimental results were compared with theoretical Poisson–Boltzmann calculations. The cell model was used to study the electrostatic effects. Good agreement between electrostatic theory and experiment was observed; however, an attractive force exists between the monovalent piperidine counterions and the micelle, probably because of hydrophobic interactions.
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| 10. |
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