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Exploring Glassy Dynamics in Soft Matter Systems via Nonlinear Langevin Equation Theoretical Approach

Speaker

Rui Zhang, South China University of Technology

Time

2019.05.21 14:00-15:00

Venue

Room 306,No. 5, Science Building

Abstract

Glass-forming soft matter systems (e.g., supercooled liquids, polymer plastics, dense colloidal gels) are of diverse scientific interest and technological relevance. At the heart of understanding their unique relaxation, diffusion, viscoelastic and rheological properties is a microscopic-level elucidation of the elementary activated hopping process. The nonlinear Langevin equation (NLE) theoretical approach is built on a dynamic mean field theory framework, and has successfully addressed activated dynamics in a broad range of glassy soft materials. In this talk I will first review key physical ideas and formulations of the NLE approach, then present our recent work in exploring two general types of cooperative activated motion. First, I will discuss how coupled translational-rotational dynamics in concentrated nonspherical colloids leads to new types of nonequilibrium kinetic arrest phases. Unusual glass-fluid-gel re-entrancy and multi-step relaxation behaviors will be described, and quantitative comparisons to experiments presented. Second, I will discuss the dynamical cooperation between different components in glass-forming mixtures. I will take penetrant hopping transport as a focused topic to demonstrate the basic theoretical ideas and rich dynamical properties as a consequence of the inter-component cooperation. Examples from both colloidal and molecular/polymeric systems will be given.

Bio

Dr. Rui Zhang is a special researcher in Advanced Institute for Soft Matter Science and Technology (AISMST) at South China University of Technology. He received the B.S. from Fundamental Science Class of Tsinghua University in 2003, M.S. in physics from McMaster University in 2006, and Ph. D. in materials science from the University of Illinois at Urbana-Champaign (UIUC) in 2011. Prior to Joining AISMST in 2018, he was a postdoctoral fellow at Northwestern University and UIUC. Dr. Zhang’s research interest broadly lies in developing and applying statistical mechanical theories and computer simulation methods to study soft material structure and dynamics. His lab currently focuses on three specific research areas, all in close collaboration with leading experimental groups in AISMST: 1) hierarchical structure and dynamics in giant molecule and supramolecular systems; 2) transport process in polymer composite materials; 3) glass transition phenomena in soft matter systems.