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    Title: New Phases Found in Reverse Micelle Systems with High Concentrations of AOT
    Authors: Lai, Wei-Chi;Lai, Po-Hsiang
    Contributors: 淡江大學化學工程與材料工程學系
    Date: 2013-08-01
    Issue Date: 2013-12-10 13:11:44 (UTC+8)
    Publisher: Washington: American Chemical Society
    Abstract: This paper discusses the phase behavior, rheology, and structure of self-assembled sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle systems at high AOT concentrations. When the amount of AOT and wo (the molar ratio of water to AOT) were changed, many different phases were found, a fact which is not discussed in the literature. Opaque gel-like phase (phase separation) occurred with high concentrations of AOT in organic solvents without water. When the AOT concentration and wo were increased to 18–72 m and 2, respectively, the samples were gel-like and translucent. Dynamic rheological results indicate that the viscoelastic transition agreed with a multirelaxation time model. Small-angle X-ray scattering (SAXS) results imply that these samples showed a hexagonally close-packed cylindrical structure in which the diameter of a cylinder was 2.5–3.0 nm, depending on the water contents. Moreover, these AOT cylinders self-assembled into fiber bundles with a diameter of 1–10 μm, as determined using a polarized optical microscope. As wo was increased to 2–6 in 72 m AOT samples, similar rheological and SAXS results were obtained. However, a different type of viscoelastic transition occurred, from multirelaxation to single-relaxation, when wo was increased to 7–11. The samples were in the transparent gel-like phase, and the structures determined by SAXS were a combination of hexagonally packed cylindrical and lamellar structure. The close-packed cylindrical structures had larger radii and shorter lengths with increasing wo. Furthermore, when wo was increased to 12, the gel-like phase disappeared and a highly viscous solution was observed. This is because all the cylindrical structures collapsed and transformed into lamellar structures when the amount of water was further increased.
    Relation: The Journal of Physical Chemistry B 117(32), pp.9568-9575
    DOI: 10.1021/jp4062913
    Appears in Collections:[化學工程與材料工程學系暨研究所] 期刊論文

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