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Träfflista för sökning "WFRF:(Orädd Greger) ;pers:(Almgren Mats)"

Sökning: WFRF:(Orädd Greger) > Almgren Mats

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1.
  • Orädd, Greger, et al. (författare)
  • Intermediate phases in the system egg lecithin/CTAC/brine. SAXS and NMR studies
  • 2001
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:11, s. 3227-34
  • Tidskriftsartikel (refereegranskat)abstract
    • The phase behavior and phase structures in the pseudo ternary system egg lecithin (EPC)/ cetyltrimethylammonium chloride/brine (100 mM NaCl) have been investigated by H-2 and P-31 NMR spectroscopy and small-angle X-ray diffraction (SAXS). At solvent contents higher than 55 wt %, micellar, hexagonal, and lamellar phases are formed. At lower solvent content, an intermediate phase occurs consisting of rods with noncircular cross-sections farming a centered rectangular phase of space symmetry c2mm. This phase is connected to both the lamellar phase and the hexagonal phase by two-phase regions. There is a large region of the lamellar phase where the bilayers contain water-filled defects in the form of pores and/or slits. SAXS diffractograms from the defect lamellar phase exhibit interlamellar Bragg reflections as well as a broad reflection originating from the water-filled defects. The variation of the distances obtained as a function of water content and CTAC/EPC ratio is consistent with theoretical predictions on water-filled defects in lamellae. The rectangular phase is characterized by several sharp SAXS reflections which have been indexed to the space group c2mm. The NMR line shapes are of biaxial symmetry with an asymmetry parameter ranging from 0.6 to 1.0. From an analysis of the SAXS and NMR data, we have found evidence of molecular segregation in that lecithin is enriched in the flat regions of the noncircular cylinders.
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2.
  • Wang, Ke, et al. (författare)
  • Phase Behavior and Phase Structure of a Cationic Fluorosurfactant in Water
  • 2000
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:3, s. 1042-9
  • Tidskriftsartikel (refereegranskat)abstract
    • The phase behavior of the cationic fluorocarbon surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride in water has been studied using small-angle X-ray and 2H NMR spectroscopy as the main techniques. The following phase sequence was found: micellar (L1), hexagonal (HI), centered rectangular (R; spacegroup c2mm) and centered trigonal (T, spacegroup Rm) with increasing surfactant concentration. At higher concentrations evidence for random mesh phase and a lamellar phase was found, at high temperatures a bicontinuous cubic phase was found. Compared to a cationic hydrocarbon surfactant of similar hydrophobicity, the occurrence of the intermediate phases is more extensive in the phase diagram, and the fluorocarbon surfactant prefers to form intermediate phases instead of a cubic phase. The surface curvature of the aggregates changes from highly curved cylindrical structures of the hexagonal phase to the planar bilayer structure of the lamellar phase over a sequence of geometries that allow the average of the mean curvature to change gradually as water content is decreased.
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  • Resultat 1-2 av 2
Typ av publikation
tidskriftsartikel (2)
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refereegranskat (2)
Författare/redaktör
Orädd, Greger (2)
Bergenståhl, Björn (1)
Asakawa, Tsuyoshi (1)
Gustafsson, Jonas (1)
Wang, Ke (1)
Lärosäte
Umeå universitet (2)
Språk
Engelska (2)

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