Engineering Defects in Molecular Hydrates

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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.