(692d) Using Fluid Dynamics and Interface Engineering to Control Polymorphism and Morphology of Organic Molecules.

Crystallization of organic materials as thin films is an area of interest in multiple fields, such as in the pharmaceutical industry, organic electronics and for the multiple applications afforded by metal organic frameworks (MOFs). Over the past decade, significant work has been accomplished in terms of understanding how polymorphism of organic molecules can be enhanced through crystallization as a thin film, through innovative techniques such as confinement, polymer additives, and control of deposition conditions such as the use of electric fields. A deeper understanding of how these polymorphs are formed is critically missing from literature.

In this work, we use a mix of experimental and computational work to study the formation of thin film polymorphs of pharmaceutical compounds and organic semiconductors. The use of interface engineering can influence both the morphology and the polymorphism of acetaminophen, a pharmaceutical compound, and TIPS-pentacene, an organic semiconductor. We also show that changing the flow coating parameters can tune the nucleation and growth rates of organic semiconductors, which then impact the molecule polymorph, crystal size, and crystal orientation. In-situ X-ray diffraction data shows the changes in crystal growth conditions due to changing the fluid dynamics conditions and provides valuable insight in the mechanism of crystal nucleation. Controlling the interface precisely to obtain the desired polymorphs and crystal morphologies will be discussed as well.