Doping Molecular Crystals

Georgetown University, Washington DC

Investigators

Abstract

Technical Abstract In this project supported by the Solid State and Materials Chemistry Program of the Division of Materials Research, the formation of solid solutions is explored as a means to tune the physical properties (e.g. thermal stability, solubility, hardness) of metastable molecular crystal phases. Solid solutions of uric acid dihydrate (UAD) and assorted inorganic, molecular and polymeric components are prepared. The physical properties of pure materials and solid solutions are analyzed using a battery of complementary techniques with the overall goal to establish structure-properties correlations. In situ AFM provides molecular-level insight into the growth mechanisms of solid solutions. Nanoindentation studies enable comparison of the mechanical properties of pure UAD, doped UAD and the more stable anhydrous uric acid phase. The application of solid solution strategies to a broader class of molecular components known to crystallize in both anhydrous and hydrated phases enables a fuller understanding of the true scope of property changes that can be achieved in organic systems through solid solution formation. X-ray diffraction, thermal analysis, and microscopy methods are used to compare the physical properties of pure and doped crystalline materials. Vapor sorption experiments are used to compare the deliquescence behavior of pure and doped metastable anhydrous phases. Non-technical Abstract Many industries such as pharmaceuticals, foods, agrochemicals and energetics rely on organic molecular crystals. This research aims to increase our understanding of the relationship between physical properties (e.g. stability, solubility, water uptake or release, mechanical strength) and the 3D structure of the crystal. Prof. Swift additionally establishes a collaboration with researchers at a National Lab facility. This collaborative research provides valuable interdisciplinary training opportunities for graduate, undergraduate and high school students.