For many applications, amorphous solids (glasses) are preferred over crystalline solids. Amorphous drugs, for example, are more soluble than crystalline drugs, a property useful for delivering the increasing number of highly potent but poorly soluble drugs. Any amorphous material must be stable against crystallization for crystallization negates its advantages. We are interested in how organic glasses crystallize. It is remarkable that despite the freezing of liquid-like molecular mobility, a glass can still crystallize, even at rates faster than permitted by diffusion. We are studying two mechanisms leading to fast crystal growth: transition from diffusion-controlled to “diffusionless” crystal growth and surface-enhanced crystal growth. To our knowledge, these phenomena have been observed only for organic glass formers.
Some questions being investigated include:
- Is crystal growth from glasses controlled by crystal/liquid structural similarity?
- How does crystal growth from glasses differ from diffusion-controlled growth in low-viscosity liquids?
- Is surface-enhanced crystal growth caused by high surface molecular mobility?
- Can surface crystallization be suppressed with a coating?
- How does surface-enhanced crystallization differ from bulk crystallization?