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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Shape control through molecular segregation in giant surfactant aggregates
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Shape control through molecular segregation in giant surfactant aggregates

机译：通过巨大的表面活性剂聚集体中的分子分离来控制形状

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摘要

Mixtures of cationic and anionic surfactants crystallized at various ratios in the absence of added salt form micrometer-sized colloids. Here, we propose and test a general mechanism explaining how this ratio controls the shape of the resulting colloidal structure, which can vary from nanodiscs to punctured planes; during cocrystallization, excess (nonstoichiometric) surfactant accumulates on edges or pores rather than being incorporated into crystalline bilayers. Molecular segregation then produces a sequence of shapes controlled by the initial mole ratio only. Using freeze-fracture electron microscopy, we identified three of these states and their corresponding coexistence regimes. Fluorescence confocal microscopy directly showed the segregation of anionic and cationic components within the aggregate. The observed shapes are consistently reproduced upon thermal cycling, demonstrating that the icosahedral shape corresponds to the existence of a local minimum of bending energy for facetted icosahedra when the optimal amount of excess segregated material is present.
机译：在不添加盐的情况下，阳离子和阴离子表面活性剂的混合物以各种比例结晶，形成微米级胶体。在这里，我们提出并测试了一种通用机制，解释了该比率如何控制所形成的胶体结构的形状，该胶体结构可以从纳米圆片到刺穿的平面变化。在共结晶过程中，过量的（非化学计量的）表面活性剂积聚在边缘或孔上，而不是掺入结晶双层中。然后分子分离产生仅受初始摩尔比控制的形状序列。使用冷冻断裂电子显微镜，我们确定了这些状态中的三个及其对应的共存机制。荧光共聚焦显微镜直接显示了聚集物中阴离子和阳离子成分的分离。观察到的形状在热循环中始终如一地再现，表明当存在最佳量的过量隔离材料时，二十面体形状对应于刻面二十面体的弯曲能量局部最小值。

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