Engineering Defects in Molecular Hydrates

有机分子可以以各种固态形式结晶，每种形式都表现出不同的物理性质。 虽然在任何给定的环境条件下只有一种形式是最稳定的，但由于环境条件（例如温度、相对湿度等）的变化，经常观察到水合（H）和无水（A）形式之间的转化。在该项目中，由材料研究部的固态和材料化学计划支持，研究了水合和无水形式的核酸晶体之间的固态转化。 这些晶体材料的结构，热和机械性能的分析使用电池的互补实验技术可在现场，并通过与美国国家实验室的研究人员合作。通过这项工作，晶体缺陷和表面结构对H和A相的材料性能的具体影响进行了探索。 通过这些基础研究获得的见解对依赖有机分子晶体的几个行业产生了直接影响，如制药，食品，农用化学品和能源。 技术摘要本研究的目的是系统地制备和表征具有明确定义的缺陷/掺杂剂浓度的嘌呤和嘧啶水合相的物理性质，并表征其结构、热和机械性质。将应用广泛的实验方法，包括衍射，显微镜，光谱，热分析，吸湿和纳米压痕。这项工作将推进我们的理解固态脱水和潮解过程中的一般，特别是在水合物和无水相之间的转换中的作用缺陷。这项合作研究为研究生、本科生和高中生提供了宝贵的跨学科培训机会。

Non-Technical AbstractOrganic molecules can crystallize in a variety of solid state forms, each of which exhibits different physical properties. While only one form can be the most stable under any given set of environmental conditions, transformations between hydrated (H) and anhydrous (A) forms are frequently observed as a consequence of changes in environmental conditions (e.g. temperature, relative humidity, etc). In this project supported by the Solid State and Materials Chemistry Program of the Division of Materials Research, the solid state transformations between hydrated and anhydrous forms of nucleic acid crystals are investigated. The structural, thermal, and mechanical properties of these crystalline materials are analyzed using a battery of complementary experimental techniques available on site and through collaborations with researchers at United States National Laboratories. Through this work, the specific effects of crystal defects and surface structures on the material properties of H and A phases are explored. Insight gained through these fundamental studies has direct impact on several industries that rely on organic molecular crystals such as pharmaceuticals, foods, agrochemicals and energetics. Technical AbstractThe objective of this research is to systematically prepare and characterize the physical properties of purine and pyrimidine hydrated phases with well-defined defect/dopant concentrations, and to characterize their structural, thermal and mechanical properties. A broad range of experimental methods will be applied including diffraction, microscopy, spectroscopy, thermal analysis, moisture sorption and nanoindentation. This work will advance our understanding of solid state dehydration and deliquescence processes in general, and specifically the role defects play in the transformations between hydrate and anhydrous phases. This collaborative research provides valuable interdisciplinary training opportunities for graduate, undergraduate and high school students.