Tuning Hydrate Properties

非技术摘要有机分子可以以各种形式结晶，其中一些包括水(水合物，H)和其他不包括水(水合物，A)。H型和A型的物理性质和相对稳定性不同。外部参数的变化，如温度和相对湿度，会导致H到A的转换。脱水可能是无意的，也可能是故意的，尽管反应的机理(S)和最终产物的结构(S)很难预测。在这个项目中，在材料研究部固态和材料化学计划的支持下，通过数据挖掘和实验研究的结合，对H到A的转换有了更深的理解。实验研究利用了现场提供的一系列补充技术，并通过与美国国家实验室的研究人员合作进行。开发一个更好的概念框架来了解结晶固体的吸水/失水，可以显著提高我们预测这一大类材料的性质的能力，并将固态脱水作为一种合理的手段来创造新的结晶形式。通过这些研究获得的洞察力对接触社会方方面面的材料具有直接影响，包括药品、食品、电子和高能材料。此外，这项研究为许多教育水平的学生提供了强有力的跨学科培训机会，并允许研究生在国家实验室获得宝贵的经验。技术摘要水合物是一类重要的分子晶体，然而我们对脱水机理和反应产物的集体理解和预测能力相当有限。在材料研究部固态和材料化学项目的支持下，这项研究建立了水合物堆积基元与特定脱水机理和无水产品拓扑结构之间的关联。数据挖掘工作被用来识别有利于特定脱水机制和无水产品的包装主题。用时间分辨同步加速器X射线衍射仪(在先进光子源处)和准弹性中子散射(在NIST)来监测整个脱水反应过程中的结构变化和相关的水动力学。通过这些结构-机制研究确定的相关性的预测能力，然后通过对新水合物系统的脱水研究进行严格测试。旨在限制水合物中分子运动的掺杂研究也有助于完善我们对晶体材料中脱水反应如何发生的机理的理解。这项研究为许多教育水平的学生提供了强有力的跨学科培训机会，并允许研究生在国家实验室获得宝贵的经验。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical AbstractOrganic molecules can crystallize in a variety of forms, some of which include water (hydrates, H) and others that do not (anhydrates, A). H and A forms differ in their physical properties and their relative stabilities. Changes in external parameters such as temperature and relative humidity can induce H to A transformations. Dehydration may be unintentional or intentional, though the mechanism(s) of the reaction and the structure(s) of the final products are difficult to predict. In this project, supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, a deeper understanding of H to A transformations is developed through a combination of data mining efforts and experimental studies. The experimental studies make use of a range of complementary techniques available on site and through collaborations with researchers at United States National Laboratories. Developing a better conceptual framework for understanding water uptake/loss from crystalline solids can significantly improve our ability to predict the properties of this broad class of materials and to employ solid state dehydration as a rational means to create new crystalline forms. The insight gained through these studies has direct implications for materials that touch all aspects of society including pharmaceuticals, foods, electronic and energetic materials. Additionally, this research provides strong interdisciplinary training opportunities for students at many education levels and allows graduate students to gain valuable experience at national laboratories. Technical AbstractHydrates are an important class of molecular crystals, yet our collective understanding and ability to predict dehydration mechanisms and reaction products is quite limited. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this research establishes correlations between hydrate packing motifs and specific dehydration mechanisms and anhydrous product topologies. Data mining efforts are used to identify packing motifs which favor particular dehydration mechanisms and anhydrous products. Time resolved synchrotron PXRD (at the Advanced Photon Source) and quasi-elastic neutron scattering (at NIST) are employed to monitor structural changes throughout the dehydration reaction and the associated water dynamics. The predictive power of the correlations identified through these structure-mechanism studies are then rigorously tested through dehydration studies on new hydrate systems. Doping studies which aim to restrict the molecular motions within the hydrate also help to refine our mechanistic understanding of how dehydration reactions occur in crystalline materials. This research provides strong interdisciplinary training opportunities for students at many education levels and allows graduate students to gain valuable experience at national laboratories.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.