In-situ observation of heterogeneous nucleation of organic crystals induced by templates with Synchrotron radiation X-ray techniques

该研究项目的主要目的是阐明模板诱导有机晶体异相成核的机制。所考察的生长体系分别是以物理气相沉积法制备的薄膜为模板的本体溶液和添加了高熔点疏水表面活性剂的水包油（O/W）乳液。利用同步辐射X射线束耦合技术和差示扫描量热仪对成核过程进行了原位观察，并对同一样品进行了同步辐射X射线束耦合和差示扫描量热仪分析。在本工作中使用的有机物质是具有不同碳数的正构烷烃，三酰甘油和植物脂肪。1）在正构烷烃O/W乳状液中，不添加模板剂时，三斜晶均成核。然而，伪六方-正交晶体在三斜多晶型物之前成核。这是由于添加剂的模板膜在正构烷烃成核之前优先结晶。2）在由三酰甘油制成的O/W乳液中，在没有添加剂的情况下，α晶体成核。然而，添加剂的加入诱导了β '晶体的成核。3）在本体溶液中，模板薄膜的存在改变了成核的取向、多晶型和成核速率，并从模板薄膜诱导的非均质成核理论出发对上述结果进行了讨论。乳液中的模板效应通过高熔点疏水链的冻结来揭示。体相溶液中的模板效应表明了模板与新生成晶体的外延关系

The principal aim of this research project was to clarify the mechanisms of heterogeneous nucleation of organic crystals that were induced by the presence of templates. The growth systems examined were bulk solution in which thin films prepared by physical vapor deposition were put as the template, and oil-in-water (0/W) emulsion in which hydrophobic surfactants with high-melting points were added. The in-situ observation of the nucleation processes were done by using Synchrotron radiation X-ray beam couples with DSC, both were analyzed at the same time for the same sample. The organic substances employed in the present work were n-alkanes with different carbon numbers, triacylglycerols and vegetable fats. The following results were obtained1) In the O/W emulsion made of n-alkanes, triclinic crystals were nucleated without the template additives. However, pseudo-hexagonal-orthorhombic crystal was nucleated prior to triclinic polymorph. This is ascribed to the template films of the additives that were preferentially crystallized before the nucleation of n-alkanes2) In the O/W emulsion made of triacylglycerols, alpha crystals were nucleated without the additives. The addition of the additives, however, induced the nucleation of beta-prime crystals. This result was also interpreted with the help of the template films formed at the oil-in-water interface3) In the bulk solution, orientation, polymorphism and rate of nucleation were modified by the presence of the template thin filmsThe above results were discussed in a theory of heterogeneous nucleation Induced by the template films. The template effect in the emulsion was revealed by the freezing of the hydrophobic chains with high-melting points. The template effects in the bulk solution showed epitaxial relationships of the template and newly-formed crystals