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Please use this identifier to cite or link to this item:
https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/93228
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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: | [Graduate Institute & Department of Chemical and Materials Engineering] Journal Article
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