Event

The dramatic slow-down of the dynamics and viscosity of a liquid upon super-cooling without a significant structural signature, has been the topic of intense theoretical debate. Growing local correlations in the dynamics of the equilibrium liquid or the existence of a dynamical phase transition below the glass transition temperature have been hypothesized as potential origins for this phenomenon. However, it is extremely difficult to experimentally distinguish between such theoretical models.

Free surfaces and interfaces can affect properties of glassy systems over length scales that can be much longer than the intermolecular interaction potential. For example, we have recently demonstrated that the dynamics of the glass surface can be as much as 8 decades faster than the bulk dynamics, resulting in an apparent glass to liquid transition in molecular glass films as thick as 30 nm. This strong perturbation allows us to experimentally explore the manifestations of these theoretical models and explore the existence of dynamical transitions in the bulk glass. In this talk I will discuss the properties of thin films of polymeric and molecular glasses and discuss how these properties fit in the broader theoretical picture.