Prof. Eamor M. Woo
National Cheng Kung University
Title: Probing the Assembly Mechanisms in Polymer Periodic Crystal Aggregates
Abstract:
Periodic self-assembly of lamellae in ring-banded polymer spherulites
(RBS) has been a long-term challenge to understand the fundamental mechanisms
since 1950s. This speech covers a comprehensive review on the plausibility and
novelty of the mechanisms of crystal packing in several widely studied
polymers, as well as small-molecule compounds for comparative reinforcement,
are analyzed in details. Biodegradable poly(L-lactic acid) (PLLA), poly(b-hydroxybutyrate)
(PHB) and poly(p-dioxanone) (PPDO), etc. To
perceive 3D ring-banded spherulites (RBS), the assemblies are characterized
using a polarized optical microscope (POM), atomic-force microscopy (AFM),
scanning electron microscopy (SEM), synchrotron-radiation microbeam wide-angle
X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), etc. The interior assemblies 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. Novel proposals
of 3D-interior lamellae self-assembly arrangement of crystal-by-crystal
assembly with periodically fractals leading to varieties of polymeric
architectures potentially acting similarly to photonic crystals. Furthermore, the polymer
crystals with orderly banding periodicity in grating architectures can act as
structural crystals for iridescence colourful spectra.
Biography:
Eamor M. Woo received Ph.D. degree from University of Texas at
Austin (Austin, Texas, USA) and is Chair Professor in National Cheng Kung University (NCKU),
Taiwan. He has published over 275 highly cited original papers and major review
articles, three book chapters and edited books. He has received numerous
distinguished academic honors/awards, and is elected Fellow in Taiwan’s Polymer
Society and Fellow in Chem. Eng. Society. He is Senior Editor for
Journal of Polymer Research (Springer-Nature), also served as Guest Editors
“Crystals”, and “Polymers”, and Editorials board members in several journals.