报告题目：Precise Synthesis of Brush Block Copolymers of Norbornenyl Polystyrene and POSS Moieties via Combination of Living Anionic Polymerization and Ring Opening Metathesis Polymerization
报告人：Prof. Jae-Suk Lee
Gwangju Institute of Science and Technology (GIST)
Abstract:Precise synthetic methods to prepare bottlebrush copolymers with dense and regular side chains toward ultrahigh molecular weight have received much attention for application as optical materials due to large domain size exceeding 100 nm.1-3 To make brush polymers, grafting through is a powerful tool. In spite of outstanding advances toward controlled brush polymers, there are a few reports for synthesis of brush copolymers with ultrahigh molecular weight through combination of living anionic polymerization and ring opening metathesis polymerization,4 because synthetic challenges disrupt a facile synthesis.
In this study, we focused on novel preparation of well-defined brush copolymers based on acrylate substitutes, styrene moieties and norbornenyl POSS. New macromonomers were synthesized by living anionic polymerization using end-functionalized polymers as end-capping of carbanion to make ω-norbornenyl polystyrene moieties. These monomers were narrowly dipersed (< 1.1) and had the predicted molecular weight (< 6.0 kDa). Ring opening metatheis polymerization of all macromonomers was sequencially performed with 3rd Ru catalyst in THF at ambient conditions to synthesize well-defined brush block copolymeres. Block coolymers with ultrahigh molecular weight (> 2500 kDa) and narrow dipersity (< 1.15) were successfully prepared by combination of living polymerizations. Furthermore, new macromonomers during polymerization followed linear first-order kinetic and showed living characteristics.
Such high-quality macromonomers were converted to be well-defined brush polymers by ROMP. The brush block copolymers obtained by sequential ROMP were utilized for the fabrication of highly ordered photonic crystals.
Miyake, G. M.; Weitekamp, R. A.; Piunova, V. A.; Grubbs, R. H. J. Am. Chem. Soc. 2012, 134, 14249.
Sveinbjornsson, B. R.; Weitekamp, R. A.; Miyake, G. M.; Xia, Y.; Atwater, H. A.; Grubbs. R. H. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 14332.
Song, D.-P.; Li, C.; Colella, N. S.; Lu, X.; Lee, J.-H. Adv. Opt. Mater. 2015, 3, 1169.
Dalsin, S. J.; Rions-Maehren, T. G.; Beam, M. D.; Bates, F. S.; Hillmyer, M. A.; Matsen, M. W. ACSNano2015, 9, 12233.
Yu, Y.-G., Lee, J.-S. et al. Macromolecules,2018, 51, 447.
Chae, C.-G., Lee, J.-S. et al.Macromolecules,2018, in revision.
报告题目：Crystalline PEDOT:PSS-Based Electrochemical Transistors and Bio-Electronic Interfaces
报告人：A/Prof. Myung-Han Yoon
Gwangju Institute of Science and Technology (GIST)
CV: Associate Professor Myung-Han Yoon graduated from Seoul National University (B. S. 1999, M. S. 2001). He obtained PhD degree at Northwestern University (Advisor: Professor Tobin J. Marks & Professor Antonio Facchetti) in 2006. He has been a Postdoctor at Harvard University (2006-2009, with Prof. Hongkun Park), a Visiting Scholar at University of Illinois at Chicago (2010), and a Visiting Scholar at Northwestern University (2010). He has worked at GIST since 2010 and become an Associate Professor since 2015. He has published 3 book chapters and more than 70 articles in some journals such as NPG Asia Mater., Adv. Mater., Adv. Funct. Mater., Nano Lett., J. Am. Chem. Soc., Nanoscale, J. Mater. Chem. (A, B, C), Small, and ACS Applied Materials & Interfaces and been authorized 11 patents.
Research interests: High-performance organic & metal oxide thin-film transistors for flexible printed electronics, neuronal interfaces based on organic & hybrid electronics and vertical silicon nanostructure platforms, biophysics on neuro-nanostructure interaction and 3D neuronal network culture via nanofiber hydrogel, and environmental purification & renewable energy (e.g., hydrogen, triboelectric, thermoelectric) materials.
Abstract:We investigated the correlation among film microstructure/composition, electrochemical transistor (OECT) performance, and underwater stability in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films. Various film characterizations confirmed that crystallized PEDOT:PSS (Crys-P) films have the highly-crystallized anisotropic microstructure with vertically edge-on and horizontally π-π orderings, while unbound styrene sulfonate residues were minimized. Compared with the conventional PEDOT:PSS film, the highly-organized film microstructure in Crys-P lead to remarkable OECT characteristics such as large transconductance (> 20 mS), low contact resistance (< 1 /cm), and extraordinary volumetric capacitance (113 F cm-2). Simultaneously, minimal styrene sulfonate residues in the Crys-P film substantially attenuated the film swelling and afforded the robust OECT stability even after > 20-day water immersion, > 2000-time repeated on-off switching, or high-temperature/pressure sterilization. We expect that the present study will contribute to the in-depth understanding of the material microstructure/composition effect on channel-electrolyte interfaces and mixed ion-hole/electron transport, and the future development of implantable bioelectronics targeting at prolonged neural recording/stimulation.
 Seong-Min Kim, Nara Kim, Youngseok Kim, Min-Seo Baik, Minsu Yoo, Dongyoon Kim, Won-June Lee, Dong-Hee Kang, Sohee Kim, Kwanghee Lee,* Myung-Han Yoon,* “Solution-Processed Conductive Polymer Cellular Interfaces for Direct Electrical Stimulation and Recording”,NPG Asia Mater. 2018, in press.