(410b) Relationship Between Self-Association Of Molecules In Supersaturated Solutions And Solid State Outcome

Understanding the link between solution and solid state is crucial in controlling the crystallization process in order to obtain products with desired properties, in particular the polymorphic form. In this work, small angle X-ray scattering was utilized to examine the early stages of crystallization in supersaturated solutions of glycine, in order to determine the role of initial molecular association in the polymorphic outcome. The majority of glycine molecules were found to exist as dimers in aqueous solutions, and monomers in acetic acid-water mixtures. Aqueous solutions rich in dimers crystallized into &alpha-glycine with a double layer structure composed of dimers, while the acidic solutions rich in monomers produced the &gamma-form with a polar chain structure built of monomeric units. These results suggest a direct correlation between the initial association of molecules in solution and the final crystal structure, which can be beneficial in selection of solvents favoring the nucleation of different polymorphic forms.