10:30 - 11:00 a.m. Coffee with speaker | 11:00 a.m. - 12:00 p.m. Seminar
“Deciphering the “Dark Matter” in Semicrystalline Polymers: Effects of Oriented Amorphous Fraction on Physical Properties of Polymers"
Lei Zhu, Professor, Department of Macromolecular Science and Engineering, Case Western Reserve University
Abstract: It is well-known that X-ray scattering cannot unravel the structure of amorphous polymers because of the lack of ordered microdomains and thus well-defined diffractions. On the contrary, it is generally considered that structures of semicrystalline polymers have been well-understood if a simple two-phase model is used, i.e., folded-chain crystalline lamellae and the isotropic amorphous phase or fraction (IAF). However, the real world is not this simple. Often, a three-phase model needs to be used to describe the complicated structures of semicrystalline polymers. For semicrystalline polymers crystallized from the melt and/or after melt/solid-state processing, chain-folding may not be the major crystallization mechanism. Instead, a significant portion of polymer chains emanate from the crystalline lamellar basal planes to form a liquid crystal-like interphase with a certain degree of molecular orientation, which are called the oriented amorphous fraction (OAF). Unfortunately, due to the absence of crystalline registry, no diffractions can be observed for the OAF in semicrystalline polymers. In this presentation, we will explore experimental methods to “see” the OAF and reveal its impact on many physical properties, such as piezoelectric and mechanical properties of polymers.
Bio: Professor Lei Zhu received his B.S. degree in Materials Chemistry in 1993 and M.S. degree in Polymer Chemistry and Physics in 1996 from Fudan University. He received his Ph.D. degree in Polymer Science from University of Akron in 2000. After two-year post-doctoral experience at the Maurice Morton Institute, University of Akron, he joint Institute of Materials Science and Department of Chemical, Materials and Biomolecular Engineering at University of Connecticut, as an Assistant Professor. In 2009, he moved to Department of Macromolecular Science and Engineering at Case Western Reserve University as an Associate Professor. In 2013, he was promoted to full Professor. His research interests include high-κ polymers for capacitive energy storage and electroactive polymers for piezoelectric/electrostriction applications. He is recipient of NSF Career Award, 3M Non-tenured Faculty Award, DuPont Young Professor Award, Rogers Teaching Excellence Award, NSF Creativity Award, and University of Akron Department of Polymer Science Distinguished Alumni Award. He currently is the APS Fellow of DPOLY. He is author and co-author of 271 refereed journal publications and 10 book chapters, and he has delivered over 200 invited presentations.