Phase behavior of diglycerol fatty acid esters-nonpolar oil systems.
Phase behavior of diglycerol fatty acid esters-nonpolar oil systems.
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DOI：
10.1021/la052622
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发表时间：
2006-01
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通讯作者：
L. Shrestha;M. Kaneko;Takaaki Sato;Durga P. Acharya;T. Iwanaga;H. Kunieda
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文献类型：
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作者：
L. Shrestha;M. Kaneko;Takaaki Sato;Durga P. Acharya;T. Iwanaga;H. Kunieda
研究了双甘油脂肪酸酯（Qn-D，n = 10-16）在不同非极性油、液体石蜡（LP 70）、角鲨烷和角鲨烯中的相行为。在较低温度下存在表面活性剂固体，并且表面活性剂固体在油中不溶胀，并且在很宽的组成范围内熔融温度几乎恒定。在所有的系统中，在固体熔化温度和各向同性两相或单相区域之间的温度下，在集中区域中形成层状液晶（L（α））。在稀相区，L（α）+ O区形成反向囊泡。在L（alpha）存在区上方存在两个液相区。该两相边界对应于非离子表面活性剂水溶液的浊点曲线。然而，表面活性剂在高温下变得更易溶于有机溶剂，而不是在高温下由于浊点而更难溶于水。即温度对溶解度的影响与混浊现象相反。当双甘油表面活性剂的烃链减少时，两相区变宽。在固定表面活性剂的情况下，表面活性剂与角鲨烯最易混溶（最西两相区），溶解倾向的顺序为角鲨烯> LP 70>角鲨烷。这些结果表明，亲水部分（双甘油基团）是更不溶于油相比，传统的聚（环氧乙烷）型非离子表面活性剂。SAXS散射曲线证实了反棒状胶束的形成。当表面活性剂的烃链较短时，胶束尺寸变大。在固定的表面活性剂体系中，通过将油从角鲨烯改变为LP 70，反胶束尺寸增加。少量的水诱导反胶束的急剧延长。
Phase behavior of diglycerol fatty acid esters (Qn-D, where n represents the carbon number in the alkyl chain length of amphiphile, n = 10-16) were investigated in different nonpolar oils, liquid paraffin (LP70), squalane, and squalene. There is surfactant solid at lower temperature, and the surfactant solid does not swell in oil, and the melting temperature is almost constant in a wide range of compositions. In all of the systems, a lamellar liquid crystal (L(alpha)) is formed in a concentrated region at a temperature between the solid melting temperature and the isotropic two- or single-phase regions. In the dilute regions, reverse vesicles are formed in L(alpha) + O regions. There are two liquid-phase regions above the L(alpha) present region. This two-phase boundary corresponds to the cloud-point curve of nonionic surfactant aqueous solutions. However, instead of being less soluble in water at high temperature for the cloud point, the surfactant becomes more soluble in the organic solvents at high temperature. Namely, the effect of temperature on the solubility is opposite to the clouding phenomenon. When the hydrocarbon chain of the diglycerol surfactant decreases, the two-phase region becomes wider. In the case of a fixed surfactant, the surfactant is most miscible with squalene (narrowest two-phase regions) and the order of dissolutions tendency is squalene > LP70 > squalane. These results show that the hydrophilic moiety (diglycerol group) is more insoluble in oil compared with that of a conventional poly(oxyethylene)-type nonionic surfactant. Formation of reversed rodlike micelles was confirmed by SAXS scattering curve. When the hydrocarbon chain of surfactant is short, the micellar size becomes larger. In a fixed surfactant system, the reverse micellar size increases by changing oil from squalene to LP70. A small amount of water induces a dramatic elongation of reverse micelles.