Crystallization and Fracture of Pure and Polymer Doped Molecular Glasses

Small-molecule organic glasses are useful materials in the fields of pharmaceutics, electronics and bio-preservation. In the case of pharmaceutics, the amorphous phase is advantageous due to its higher solubility, facilitating drug delivery. For any application of a molecular glass, it must resist crystallization and maintain its mechanical integrity in order to achieve the desired outcome.;The crystallization of molecular glasses is remarkable and is the primary focus of this work. Standard models of crystal growth fail to anticipate the rapid crystallization seen in these materials. New insights into the conditions under which this fast crystallization begins are gained by considering the liquid dynamics and growth behavior of a variety of systems, including some newly characterized. A standard technique to inhibit crystallization is to add polymers into these glasses. In order to understand what properties of a polymer make for a successful crystal growth inhibitor, a variety of polymers were doped into the amorphous phase. From the alteration of the crystal growth behavior, it was discovered that the dynamics of the polymers added are the key to predicting crystal growth inhibition with slower polymer more effective at slowing crystal growth. A new framework to understand the fast crystal growth is developed in this thesis. The connection between material fracture and high surface mobility may explain the rapid crystal growth behavior.;Finally, these glasses ability to resist fracture is measured. This measurement is the first of its kind for this class of materials and it is further demonstrated that adding high-molecular weight polymers substantially increase the resistance to fracture.