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  • 1
    Digitale Medien
    Digitale Medien
    From vesicles to the L3 (sponge) phase in alkyldimethylamine oxide/heptanol systems (1992)
    s.l. : American Chemical Society
    Langmuir 8 (1992), S. 2629-2638 
    Details
    ISSN: 1520-5827
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/la00047a011
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  • 2
    Digitale Medien
    Digitale Medien
    Surfactant Systems with Charged Multilamellar Vesicles and Their Rheological Properties (1994)
    s.l. : American Chemical Society
    Langmuir 10 (1994), S. 3972-3981 
    Details
    ISSN: 1520-5827
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/la00023a013
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  • 3
    Digitale Medien
    Digitale Medien
    Complex fluids with a yield value; their microstructures and rheological properties (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1373-1390 
    Details
    ISSN: 0392-6737
    Schlagwort(e): Mechanical properties of liquids ; Conference proceedings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary A general method is presented for the preparation of viscoelastic surfactant phases that consist of densely packed multilamellar vesicles in water. The phases form spontaneously when ionic surfactants are added to Lα-or L3-phases from uncharged surfactants and cosurfactants. The dimensions and the structure of the vesicles were studied from FF-TEM micrographs for 100 mM surfactant solutions. The average diameter of the vesicles is in the range of 1 μm, the interlamellar spacing is around 800 Å. Under these conditions the vesicles are densely packed and cannot pass each other. The systems are highly viscoelastic and have a yield value. The storage and the loss moduli were determined by oscillating rheological measurements. The storage modulus was about one order of magnitude larger than the loss modulus and independent of frequency. Both parameters were determined as a function of the concentration and the chain length of the surfactant and cosurfactant, the charge density and ionic strength, the solubilization of hydrocarbon and temperature. The yield values and shear moduli increase linearly with the surfactant concentration. For constant surfactant concentration the moduli increase in a S-shaped form with the charge density and reach saturation for a mole fraction of about 7% of ionic surfactant. The storage moduli and yield values decrease with the addition of excess salt. The storage moduli depend strongly on the chain length of the surfactant. The values of the moduli are explained on the basis of a hard-sphere model in which the multilamellar vesicles are considered as hard-sphere particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02462022
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  • 4
    Digitale Medien
    Digitale Medien
    Experimental results for the L3 phase in a zwitterionic surfactant system and their implications regarding structures (1990)
    Springer
    Colloid & polymer science 268 (1990), S. 1066-1072 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Alkyldimethylamine oxide ; surfactantsphasediagrams ; L 3 -phase ; plate likemicelles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Conditions for existence of the L3 phase have been determined for a system containing water, n-hexanol, and the zwitterionic surfactant n-tetradecyldimethylamineoxide. Electric birefringence, light-scattering, rheology, and electrical-conductivity experiments were performed on this phase. Results are consistent with the existence of platelike micelles, whose diameter changes with surfactant concentration in such a way that it remains comparable to mean plate spacing. This behavior can be understood in terms of a previous L3 phase theory containing randomly oriented plates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01410596
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  • 5
    Digitale Medien
    Digitale Medien
    Electron microscopic and light scattering observation on a system with two iridescent phases (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 604-611 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Electron microscopy ; light scattering ; dodecyldimethylaminoxide/hexanol/water ; iridescent phase ; bicontinuous sponge phase ; vesicle phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Electron microscopic observations and classical light-scattering measurements have been carried out for dodecyldimethylaminoxide/hexanol/water mixtures in the concentration range where iridescent colors occur. This system has two different iridescent phases. The iridescent phase with more hexanol forms quickly, and the phase with less hexanol forms very slowly. Three different isotropic phases which show strong flow birefringence are found near both iridescent phases. The electron microscopic pictures show clearly that only one of these isotropic phases with strong flow birefringence is a bicontinuous sponge phase (L3h -phase). This is the phase which comes out by adding some alkanol to the upper lamellar phase. The flow birefringent phase below the lower lamellar phase forms unilamellar vesicles. The flow birefringent phase which occurs between both iridescent phases contains multilamellar vesicles and is shown to be a precursor of a lamellar phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00653228
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  • 6
    Digitale Medien
    Digitale Medien
    Phase behavior and dynamic properties in mixed systems of anionic and cationic surfactants: lithium perfluorooctanesulfonate/diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) and lithium dodecyl sulfate/DEFUMAC aqueous mixtures (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 885-893 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Fluorocarbonsurfactant ; mixedsystem ; ion-pairedsurfactant ; P β phase ; lamellarphase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Two ternary phase diagrams of the cationic perfluorosurfactant diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) with an anionic perfluorosurfactant lithium perfluorooctanesulfonate (LiFOS) and an anionic hydrocarbon surfactant lithium dodecyl sulfate (LiDS) have been established at 25°C. The total surfactant concentration was less than 20wt%. In a wide mixing region of the LiFOS/DEFUMAC system, a lamellar-type phase,P β, was identified by its texture under a polarization microscope and by its x-ray diffraction pattern. Dispersed fragments ofP β-phase are present in the dilute solutions in which one surfactant was in excess. The anisotropy of electrical conductivity, flow birefringence, dynamic light scattering, and electric briefringence demonstrate that theP β fragments are disk-like with a radius of 0.7 μm. The disk-likeP β particles are transformed by shear into a spherical aggregate ofL α above a critical shear gradient. LiDS/DEFUMAC mixed solution forms dispersed and precipitatedL α in the dominant region. Radius and micropolarity of the dispersedL α aggregates are decreased as the ratio of LiDS:DEFUMAC approaches 1:1. On the basis of x-ray diffraction measurement the structure of precipitatedL α-phase seems to consist of monolayers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657733
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  • 7
    Digitale Medien
    Digitale Medien
    Phase and aggregation behaviour of double-chain cationic surfactants from the class of N-alkyl-N-alkyl′-N, N-dimethylammonium bromide surfactants (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 856-867 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Double chain surfactants ; Aggregates ; Phase diagrams ; Lamellar phases ; Electron microscopy ; SANS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We present the phase diagrams and the properties of newly synthesised double-chain cationic N-alkyl-N-alkyl′-N,N-dimethylammonium bromide surfactants [C x C y DMABr (x = 12, 14 and 16; y = 10, 11, 12, 14 and 16)]. All the systems studied form liquid-crystalline lamellar phases but with different morphologies: unilamellar vesicles at low surfactant concentrations, multilamellar vesicles and tubular aggregates for surfactant concentrations between 2 and 10 wt% and at even higher concentrations planar bilayers of surfactant molecules in the classical Lα phase. The phase diagrams were determined with macroscopic and microscopic methods (polarisation microscopy, freeze-fracture transmission electron microscopy, scanning electron microscopy and differential interference contrast microscopy). The properties of the surfactant solutions were determined with differential scanning calorimetry measurements for Krafft point determination and small-angle neutron scattering measurements for interlamellar spacing and bilayer thickness. Finally, conductivity and viscosity measurements for phase characterisation were carried out.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050462
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