Alany R G, Tucker I G, Davies N M, Rades T
School of Pharmacy, University of Otago, P.O. Box 913, Dunedin 9001, New Zealand.
Drug Dev Ind Pharm. 2001 Jan;27(1):31-8. doi: 10.1081/ddc-100000125.
Two pseudoternary phase diagrams were constructed using ethyl oleate, water, and a surfactant blend containing poly (oxyethylene 20) sorbitan monooleate and sorbitan monolaurate with or without the cosurfactant 1-butanol. Two colloidal regions were identified in the cosurfactant-free phase diagram; a microemulsion (ME) and a region containing lamellar liquid crystals (LC). The addition of 1-butanol increased the area in which systems formed microemulsions and eliminated the formation of any liquid crystalline phases. Samples that form the colloidal regions of both systems were investigated by freeze-fracture transmission electron microscopy and by viscosity and conductivity measurements. The three techniques were compared and evaluated as characterisation tools for such colloidal systems and also to identify transitions between the colloidal systems formed. A droplet ME was present at a low water volume fraction (phi w) in both systems (phi w < 0.15) as revealed by electron microscopy. At higher phi w values, LC structures were observed in micrographs of samples taken from the cosurfactant-free system while the structure of samples from the cosurfactant-containing system was that of a bicontinuous ME. The viscosity of both systems increased with increasing phi w to 0.15 and flow was Newtonian. However, formation of LC in the cosurfactant-free system resulted in a dramatic increase in viscosity that was dependent on phi w and a change to pseudoplastic flow. In contrast, the viscosity of the bicontinuous ME was independent of phi w. Three different methods were used to estimate the percolation threshold from the conductivity data for the cosurfactant-containing system. The use of nonlinear curve fitting was found to be most useful yielding a value close to 0.15 for the phi w.
使用油酸乙酯、水以及一种含有聚氧乙烯20山梨醇单油酸酯和山梨醇单月桂酸酯的表面活性剂混合物（有或没有助表面活性剂1-丁醇）构建了两个拟三元相图。在无助表面活性剂的相图中确定了两个胶体区域；一个微乳液（ME）区域和一个含有层状液晶（LC）的区域。添加1-丁醇增加了形成微乳液的体系的面积，并消除了任何液晶相的形成。通过冷冻断裂透射电子显微镜以及粘度和电导率测量对形成两个体系胶体区域的样品进行了研究。对这三种技术进行了比较和评估，将其作为此类胶体体系的表征工具，同时也用于识别所形成的胶体体系之间的转变。电子显微镜显示，在两个体系中，当水体积分数较低（φw）时（φw < 0.15）存在液滴微乳液。在较高的φw值下，从无助表面活性剂体系中取出的样品的显微照片中观察到了液晶结构，而含助表面活性剂体系的样品结构为双连续微乳液。两个体系的粘度均随着φw增加至0.15而增大，且流动呈牛顿流体特性。然而，在无助表面活性剂体系中液晶的形成导致粘度急剧增加，这取决于φw，并转变为假塑性流动。相比之下，双连续微乳液的粘度与φw无关。使用三种不同方法从含助表面活性剂体系的电导率数据估算渗滤阈值。发现使用非线性曲线拟合最为有用，得出的φw值接近0.15。
