A multi-technique approach for probing the evolution of structural properties during crystallization of organic materials from solution.

We are engaged in a multidisciplinary study of fundamental aspects of the crystallization of organic molecular materials from solution, focusing on polymorphic systems under the recognition that such systems represent an ideal opportunity for obtaining a systematic understanding of competing pathways in crystallization processes. The range of techniques employed in this work are sensitive to structural properties on different length scales and are thus appropriate for mapping the changes that occur at different stages of the crystallization process, starting from the early aggregation events in solution (probed by solution-state NMR and molecular dynamics simulations, including studies of diffusion properties), leading to the growth of molecular aggregates (probed by small-angle neutron scattering), then the emergence of solid microcrystals dispersed in the crystallization solution (probed by small-angle neutron scattering and solid-state NMR) and finally the formation of the bulk solid crystalline phase (probed by powder X-ray diffraction). This paper reports preliminary results on the application of this multi-technique approach to study the crystallization of glycine (which has three known polymorphic forms under ambient conditions) from aqueous solution.