Title: Exploring the experimental and theoretical foundations of polymer rheology: the tip of iceberg after six decades

Speaker: Prof. Shi-Qing Wang

Time:2008.12.3  9:30am

Address: Rm 410 Main Buidling

Biographical Sketch

Shi-Qing Wang was born in Beijing, raised in Harbin, and at 18 caught the first wave (after the Great Cultural Revolution) to enter college in spring 1978 (77 Gi).  He majored in Physics at Wuhan University.  In fall of 1981, he successfully participated in the China-US Examination and Application (CUSPEA) program and ranked among the top 50 among over 500 participants who were pre-selected throughout China to compete in CUSPEA.

He arrived in the US in the fall of 1982 and completed his Ph.D. degree in Physics at University of Chicago in 1987, working with Karl Freed on polymer solution theory.  After two years of postdoctoral research at University of California at Los Angeles, Shi-Qing Wang joined the faculty of Macromolecular Science and Engineering at Case Western Reserve University, and rose from Assistant to Full Professor in 1998.  He was elected to be a Fellow of the American Physical Society in 1997.  Since fall 2000, he has been in Department of Polymer Science at University of Akron.  His research interest is polymer physics and engineering.  His group currently focuses on re-establishing the experimental and theoretical foundations of (nonlinear) polymer rheology.

Abstract

Five years have passed since we first started to examine the conceptual foundation of polymer rheology concerning its nonlinear aspects.  Nearly 20 papers from Akron have provided enough evidence to indicate that understanding polymer flow should begin with the key question of how entangled polymers initially respond to suddenly imposed fast deformation.  In my presentation, I will describe the exciting developments in the field of polymer rheology and explain why polymer entanglement provides transient cohesion and how elastic yielding occurs during and after flow.  In other words, we show that entangled polymeric liquids yield during fast continual deformation, transitioning from elastic response to plastic flow.  Our newly developed particle-tracking velocimetric method [Macromol. Mater. Eng, 292, 15 (2007)] allows us to reveal that the plasticity often occurs in a localized way, resulting in shear banding in steady state.  The unifying theoretical understanding [J. Chem. Phys. 127, 06903-14 (2007)] allows us to depict both shear and extensional deformation on equal footing, leading to a fresh outlook on how polymer rheology may guide industrial processing.