Casali Institute of Applied Chemistry, The Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Langmuir. 2009 Nov 17;25(22):13106-13. doi: 10.1021/la901195t.
We investigated the effect of ascorbic acid (AA) cosolubilized with vitamin E (VE) on reverse hexagonal (H(II)) mesophase. The H(II) phase comprises monoolein (GMO)/d-alpha-tocopherol (VE) in a ratio of 90/10 by weight and 12.5 wt % water. The macrostructural characteristics of this system were determined by polarized light microscopy and small-angle X-ray scattering measurements. We used differential scanning calorimetry and attenuated total reflectance Fourier transform infrared to characterize the microstructure, the vibration of the functional groups, and the location of the AA guest molecule. AA was incorporated to the system in two steps: 1-4 wt % AA and 5-6 wt % AA. We compared this system to one containing tricaprylin as the oil phase, as previously reported. These measurements revealed that AA is localized first in the water rich-core and in the interface, and acts as a chaotropic molecule that decreases the water melting point. When a larger quantity of AA (5-6 wt %) is added, the system is saturated, and the AA is located in the inner cylinder and manifested by more moderate distortion. The addition of AA also causes alteration in the behavior of the GMO hydrocarbon chains and makes them more flexible. Further addition of AA caused the GMO hydrocarbon chain to be more solvated by the VE hydrocarbon chain and enabled additional migration of VE; hence a decrease in the hydrophobic melting temperature occurred (similar to tricaprylin). Increasing the amount of AA weakened the bonding between the GMO and water and created new bonds between AA and GMO and AA with water.
我们研究了抗坏血酸（AA）与维生素 E（VE）共溶对反六方（H(II)）中间相的影响。H(II)相由重量比为 90/10 的单油酸甘油酯（GMO）/d-α-生育酚（VE）和 12.5wt%的水组成。该系统的宏观结构特征通过偏光显微镜和小角 X 射线散射测量来确定。我们使用差示扫描量热法和衰减全反射傅里叶变换红外光谱来表征微观结构、官能团的振动以及 AA 客体分子的位置。AA 分两步加入到系统中：1-4wt%AA 和 5-6wt%AA。我们将该系统与之前报道的含有三辛酸甘油酯作为油相的系统进行了比较。这些测量结果表明，AA 首先定位于富含水的核心和界面中，并且作为一种变混乱的分子，降低了水的熔点。当加入更多量的 AA（5-6wt%）时，系统达到饱和，AA 位于内筒中，表现出更温和的变形。AA 的加入还导致 GMO 烃链的行为发生变化，使它们更加灵活。进一步加入 AA 导致 GMO 烃链被 VE 烃链更多地溶剂化，并使 VE 发生额外迁移；因此，疏水性熔点降低（类似于三辛酸甘油酯）。增加 AA 的量削弱了 GMO 与水之间的结合，并在 AA 与 GMO 之间以及 AA 与水之间形成了新的键。
