Tuning Hydrate Properties

有机分子可以以多种形式结晶，其中一些包括水（水合物，H），另一些不包括水（无水物，a）。H和A的形态在物理性质和相对稳定性上有所不同。温度和相对湿度等外部参数的变化可以诱导H向A转化。脱水可能是无意的，也可能是有意的，尽管反应的机制和最终产物的结构很难预测。在该项目中，由材料研究部固态和材料化学项目支持，通过数据挖掘工作和实验研究的结合，对H到a转换有了更深入的了解。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理解结晶固体的吸水/失水，可以显著提高我们预测这类广泛材料性质的能力，并将固态脱水作为创造新晶体形式的合理手段。通过这些研究获得的见解对触及社会各个方面的材料有直接的影响，包括制药，食品，电子和高能材料。此外，本研究为不同教育水平的学生提供了跨学科的训练机会，并使研究生能够在国家实验室获得宝贵的经验。摘要水合物是一类重要的分子晶体，但我们对脱水机理和反应产物的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，本研究建立了水合物堆积基序与特定脱水机制和无水产物拓扑结构之间的相关性。数据挖掘工作用于识别有利于特定脱水机制和无水产物的包装基序。采用时间分辨同步加速器PXRD（在先进光子源）和准弹性中子散射（在NIST）监测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体系的脱水研究进行严格测试。掺杂研究旨在限制水合物内的分子运动，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理解。这项研究为不同教育水平的学生提供了跨学科的训练机会，并使研究生能够在国家实验室获得宝贵的经验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.