Biography
Prof. Eamor M. Woo
Prof. Eamor M. Woo
Chemical Engineering Dept., National Cheng Kung University, Chinese Taipei
Title: Fractal-Branching Growth Mechanisms for Periodicity in Crystal Packing of Polymers
Abstract: 
The hierarchical self-assembly array of lamellae in ring-banded spherulite (RBS) is the very fundamental arrangement in polymer morphology and crystallization. It has been a long-term challenge to understand the hierarchical lamellar self-assembly mechanism in semi-crystalline polymers since the 1950s [1-3]. A comprehensive review on the plausibility and novelty of the mechanisms of crystal packing in several widely studied polymers are analyzed in details: high-density polyethylene (HDPE), poly(ethylene adipate) (PEA), and poly(-caprolactone) (PCL). Discussions are mainly illustrated by using PCL as an example with supporting data demonstrating the other polymer systems (PEA and PE). To perceive 3D ring-banded spherulites (RBS) self-assembly, poly(ɛ-caprolactone) (PCL) are characterized using a polarized optical microscope (POM), atomic-force microscopy (AFM), scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS), etc. The specimens of RBS were fractured in delicate ways to study correaltion of the top-surface vs. interior lamellae, and how these crystal species self-assemble to display morphological fractals and optical-banding periodicity. The results indicate that the PCL-RBS (r ≈70μm) at 35oC can form slightly different banding patterns depending on the nucleus-center locations (top, the middle and bottom surface) of the PCL films (typpically 5-20 um). The self-assembly patterns in these interior-fractured RBS reveal a universal packing into periodicity via fratal-repetitive growth of branches coupled with lamellar widening and occassional twisting and bending. Horizontally oriented branching lamellae are assembled in valleys, where the length of these horizontal lamellae crystal increases with respect to Tc. From each end of this horizontal lamellar crystal, vertically oriented lamellae are packed underneath the ridges periodically. The length of the horizontal lamellar crystals is correlted with increase of the band spacing of RBS. Fractals exhibit similar patterns with expanding symmetry, where branching replication is highly similar or the same at next-cycle scale. Similarity of interior lamellae assemblies are proven to present in the other polyerms: PE and PEA or others [4-7]. Novel proposals of 3D-interior lamellae self-assembly arrangement of the alternate ridge and valley bands with periodic growth mechanisms leadign to varieties of polymer RBS are surveyed and analzyed in these three polymers for proofs of universality of the proposed mechanisms that differ significantly from the classical models of continuous helix-twisting. 

References:
(1) Poudel, P.; Majumder, S.; Chandran, S.; Zhang, H.; Reiter, G. Formation of Periodically Modulated Polymer Crystals. Macromolecules 2018, 51 (15), 6119–6126.
(2) Keller, A. The Spherulitic Structure of Crystalline Polymers. Part I. Investigations with the Polarizing Microscope. Journal of Polymer Science 1955, 17, 291–308.
(3) Keith, H. D.; Padden, F. J. Banding in Polyethylene and Other Spherulites. Macromolecules 1996, 29 (24), 7776–7786.
(4)   G. Lugito, E.M. Woo, Multishell Oblate Spheroid Growth in Poly(trimethylene terephthalate) Banded Spherulites, Macromolecules. 50 (2017) 5898–5904. doi:10.1021/acs.macromol.7b00838.
(5)  E.M. Woo, L.-Y. Wang, S. Nurkhamidah, Crystal Lamellae of Mutually Perpendicular Orientations by Dissecting onto Interiors of Poly(ethylene adipate) Spherulites Crystallized in Bulk Form, Macromolecules. 45 (2012) 1375–1383.
(6)K. Tashiro, T. Yoshioka, H. Yamamoto, H. Wang, E.M. Woo, K. Funaki, H. Murase, Relationship between twisting phenomenon and structural discontinuity of stacked lamellae in the spherulite of poly(ethylene adipate) as studied by the synchrotron X-ray microbeam technique, Polym. J. 51 (2019) 131–141. doi:10.1038/s41428-018-0122-y.
(7)E.M. Woo, K.C. Yen, Y.T. Yeh, L.Y. Wang, Biomimetically Structured Lamellae Assembly in Periodic Banding of Poly(ethylene adipate) Crystals, Macromolecules. 51 (2018) 3845–3854. doi:10.1021/acs.macromol.8b00549.
Biography: 
Dr. Eamor M. Woo is currently Professor with Endowed Chair in Chemical Engineering Dept. of National Cheng Kung University (NCKU), Tainan, Taiwan.  He received Ph.D. degree from University of Texas at Austin (Austin, Texas, USA). 
After several years of academic and industry experiences in USA, he joined faculty in Dept. of Chemical Engineering of NCKU, Tainan, Taiwan since 1992 to present, with research fields focusing on polymer morphology, crystallization, and structures characterization of biodegradable, bio-based plastics and green materials; phase behavior and phase separation; self-assembly of lamellae in spherulites, etc.
He has published over 265 refereed and highly cited original papers, with H-index=36, including several review articles (Prog. Polym. Sci., Crystals, Euro. Polym. J., Polymers, Polym. Crystal, etc.), and three book chapters or edited books (Handbook of Adhesives, Encyclopedia of Polymer Science and Technology, Handbooks of Epoxy Blends (Springer-Nature), etc.), and made over 260 conference presentations internationally, with many keynotes and plenary speeches in major conferences. 
He has received numerous distinguished academic honors/awards including Research Excellence, Outstanding Researcher Award, etc. from Ministry of Science and Technology, Ministry of Education, and professional Societies, Taiwan.
In professional services, he is Senior Editor for Journal of Polymer Research (Springer-Nature). He also served as Guest Editor for a special issue-2017 in “Crystals”, and another in 2018 for “Polymers”, and Editorials board members in several journals. He now is elected Fellows in Taiwan’s Polymer Society and Chem. Eng. Society.