A World of Information From the Picosecond Dynamics

Predicting the macroscopic properties of a material from its microscopic features is the Holy Grail of Material Science. It is nevertheless a daunting task, due to the complexity of molecular interactions and emergent phenomena happening at multiple length and time scales, often inaccessible to either simulations or experiments. The hunt is then open for simple microscopic markers of macroscopic behavior, which would shed light on the fundamental physics of these phenomena and provide tools to guide new materials design.

I will show that the mean square displacement of particles at the picosecond time scale, accessible to both simulations and experiments, is a powerful predictor of the glassy dynamics and viscoelastic properties of many glass-forming materials (atomic, polymeric and beyond). The theoretical advancements started more than a decade ago provide insight into the nature of the glass transition, linking the picosecond displacement to the dynamical heterogeneity, relaxation time and elastic modulus of glass-formers. Recent advancements built on these ideas gave rise to predictive relations for the shear-thinning of polymer melts, state-of-the-art modeling techniques for dynamically informed Coarse-Grained models of polymers, and guidelines for the development of new elastoplastic materials.

Bio

Andrea Giuntoli is a postdoctoral researcher in the Civil and Environmental Engineering department at Northwestern University in Prof. Sinan Keten's Lab. He obtained a Ph.D. in computational polymer physics at the University of Pisa (Italy) and spent one year at the National Institute of Standards and Technology (NIST, Maryland), studying polymer dynamics and mechanical properties and linking the picosecond dynamics of glass-forming liquids to their rheological behavior. At Northwestern he is developing new models for polymer nanocomposites within the CHiMaD collaboration, applying his fundamental studies to the design of next-generation materials.