Formation of 10-100 nm size-controlled emulsions through a sub-PIT cycle.
Formation of 10-100 nm size-controlled emulsions through a sub-PIT cycle.
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DOI：
10.1021/la903401g
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发表时间：
2010-03
期刊：
影响因子：
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通讯作者：
K. Roger;B. Cabane;U. Olsson
中科院分区：
文献类型：
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作者：
K. Roger;B. Cabane;U. Olsson
我们重新研究了相转化温度（PIT）乳化过程。这是一种低能耗方法，使用物理化学驱动器在没有高剪切流的情况下产生非常细的油/水乳液。我们使用聚氧乙烯8十六烷基醚（C（16）E（8））/十六烷/水体系，其具有76.2 ℃的PIT。我们发现，成功的乳化取决于两个条件。首先，混合物必须在整个过程中以低速搅拌：这使得在表面活性剂浓度太低而不能形成平衡微乳液的情况下产生乳液成为可能。第二，搅拌的混合物必须加热到称为清除边界（CB）的阈值以上，然后淬火到较低的温度。澄清边界由搅拌混合物的浊度的最小值通过实验确定，所述最小值由所有油溶解成溶胀胶束而产生。这与乳化失败边界相匹配，并且其在数学上由条件R*C（0）= 1表示，其中R* 是由单分散球体的油/表面活性剂组合物产生的半径，并且C（0）是表面活性剂的自发球面曲率。因此，我们表明，这样的周期不需要跨越PIT。事实上，子PIT周期和跨PIT周期给出了完全相同的结果。这些条件导致具有窄尺寸分布和由油/表面活性剂比率控制的平均直径的乳液。这些直径的典型范围为20-100 nm。此外，与用较短的油和表面活性剂分子制成的乳液相比，这些乳液具有优异的亚稳定性。
We have re-examined the phase inversion temperature (PIT) emulsification process. This is a low-energy method that uses a physicochemical drive to produce very fine oil/water emulsions in the absence of high shear flows. We used the polyoxyethylene 8 cetyl ether (C(16)E(8))/hexadecane/water system, which has a PIT of 76.2 degrees C. We find that successful emulsification depends on two conditions. First, the mixture must be stirred at low speed throughout the whole process: this makes it possible to produce emulsions at surfactant concentrations that are too low to form an equilibrium microemulsion. Second, the stirred mixtures must be heated above a threshold called the clearing boundary (CB) and then quenched to lower temperatures. The clearing boundary is determined experimentally by a minimum in the turbidity of the stirred mixture, which results from solubilization of all the oil into swollen micelles. This matches the emulsification failure boundary, and it is expressed mathematically by the condition R*C(0) = 1, where R* is the radius that results from the oil/surfactant composition for monodisperse spheres and C(0) is the spontaneous spherical curvature of the surfactant. Thus, we show that such cycles do not need to cross the PIT. In fact, sub-PIT cycles and cross-PIT cycles give exactly the same result. These conditions lead to emulsions that have a narrow size distribution and a mean diameter controlled by the oil/surfactant ratio. The typical range of those diameters is 20-100 nm. Moreover, these emulsions have an excellent metastability, in contrast with emulsions made with shorter oil and surfactant molecules.