Microscopy, SAXD, and NMR studies of phase behavior of the monoolein-diolein-water system
Microscopy, SAXD, and NMR studies of phase behavior of the monoolein-diolein-water system
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DOI：
10.1021/la000619e
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发表时间：
2000-12-26
期刊：
影响因子：
3.9
通讯作者：
Khan, A
中科院分区：
文献类型：
--
作者：
Borné, J;Nylander, T;Khan, A
研究了单油精（MO）-二油精（DO）-水（（H2O）-H2）三元体系的相行为。通过偏光显微镜、小角X射线衍射和核磁共振方法研究了实验相行为和微观结构。单油酸甘油酯形成广泛的反向双连续立方液晶相（C），其在贫水侧与层状液晶相（L-α）平衡，在另一侧与过量水平衡。MO-水体系中少量DO的存在足以使C和L-α液晶相不稳定。从立方相的反六方（HII）相的形成发生在一个较低的转变温度比报告的MO-水系统。在立方区域内，金刚石立方相CD比螺旋型C-G更不稳定。当MO含量增加时，DO在该相中的溶解度增加，并且该相在4wt%DO时达到其最大稳定性。在三元体系中形成的大的HII相与水平衡，并且其在其稳定范围内溶解约30重量%的DO。在甚至更高的DO浓度下形成稳定的分散体。随着极性体积分数的增加，观察到的HII相的理想溶胀，而烃链的长度沿着六方面是恒定的。我们测量的平均面积每分子在H-II相与DO浓度的轻微变化。液晶相的形成和稳定性可以从自聚集模型中定性地理解，使用脂质的几何堆积参数。
The phase behavior of the ternary monoolein (MO)-diolein (DO)-water ((H2O)-H-2) system is presented. The experimental phase behavior and microstructure are studied by a combination of polarizing microscopy, small-angle X-ray diffraction, and NMR methods. Monoolein forms extensive reversed bicontinuous cubic liquid crystalline phases (C) that are in equilibrium with a lamellar liquid crystalline phase (L-alpha) on the water-poor side and with excess water on the other side. The presence of small amounts of DO in the MO-water system is sufficient to destabilize the C and L-alpha liquid crystalline phases. Formation of a reversed hexagonal (HII) phase from the cubic phase occurs at a lower transition temperature than that reported for the MO-water system. Within the cubic region, the diamond cubic phase, CD, is less stable than the gyroid type, C-G. The solubility of DO increases within this phase when the MO content increases, and the phase reaches its maximum stability at 4 wt % DO. The large HII-phase formed in the ternary system is in equilibrium with water, and it solubilizes about 30 wt % DO within its stability range. A stable dispersion is formed at even higher DO concentrations. An ideal swelling of the HII-phase with increasing polar volume fraction is observed, whereas the length of the hydrocarbon chains along the hexagonal faces is constant. We measure a slight change of the average area per molecule in the H-II-phase with DO concentration. The formation and stability of the liquid crystalline phases can be qualitatively understood from the self-aggregation model, using the geometrical packing parameter of the lipids.