The microbeam X-ray diffraction study for the crystallization process of oil phase in oil-in-water emulsion

在本研究课题中，得到了以下结果：(1)大光束（直径mm大小的同步加速器x射线束）的结果1-1。在油相为偶数正构烷烃的水包油（O/W）乳状液中，加入高熔点表面活性剂后，形成了伪六方晶和正交晶。相反，在不添加添加剂的液滴中，以及在添加和不添加添加剂的散装液体中，都形成了三斜晶。结果表明，添加剂分子的吸附膜在油水界面发生了非均相成核。这些结果表明，通过添加合适的添加剂来改变界面的非均相成核行为，乳液可以形成新的晶体多晶结构。在油相为正十六烷的大粒径油水乳状液中，观察到一种瞬态旋转相。因此，我们证实了在散装样品中观察到的正十六烷中旋转相的存在。表明油水界面处的旋转相对体结晶起先导作用。(2)微束（直径μm大小的同步加速器x射线束）2-1的结果。微束x射线在结晶温度下通过添加添加剂的油/水乳状液油滴边缘时，出现两种衍射峰；伪六方和三斜。而当微光束穿过同一样品的油滴中心时，只出现一个三斜晶型的衍射峰。这些结果表明，模板膜存在于油水界面，界面附近的正十六烷在模板膜的影响下结晶为伪六方晶型。在直径大于10 μm的油滴中存在大量的晶体。通过微束扫描，估计每个晶体尺寸小于3 μm。

In this research subject, the following results have been obtained ;(1)Results for macro-beam (synchrotron X-ray beam of mm-sized diameter)1-1.In the oil-in-water (O/W) emulsion whose oil phase consisted of even-numbered n-alkanes, when high-melting -point surfactants were added to the droplets, pseudohexagonal and orthorhombic crystals were nucleated. In contrast, triclinic crystals formed in the droplets without the additive, and in bulk liquid both with and without the additives. It is suggested that interfacial heterogeneous nucleation occurred at the oil-water interface by freezing of the adsorbed films of the additive molecules. These results indicate that emulsion can be used to form a new crystalline polymorphic structure by using suitable additives that modify interfacial heterogeneous nucleation behavior.1-2.On the large sized O/W emulsion, without additives, whose oil phase consisted of n-hexadecane, a transient rotator phase was observed. Thus we confirmed the existence of rotator phase in n-hexadecane that was observed in bulk samples. It is suggested that the rotator phase at the oil-water interface plays a precursor role for bulk crystallization.(2)Results for micro-beam (synchrotron X-ray beam of μm-sized diameter)2-1.When microbeam X-ray passed through the edge of an oil droplet which was the O/W emulsion with additives under crystallization temperature, two kinds of diffraction peak appeared; pseudohexagonal and triclinic. In contrast, only a diffraction peak from triclinic polymorph appeared when the microbeam passed through the center of an oil droplet of the same sample. These results suggest that the template film exists at the oil-water interface and n-hexadecane near the interface is crystallized as a pseudohexagonal polymorph in the influence of the teplate film.2-2.A lot of crystals exist in an oil droplet whose diameter is more than 10 μm. Each crystal size was estimated less than 3 μm by scanning the microbeam.