Jeffrey Pyun

Interests

Research

Organic Polymer Chemistry, nanomaterials, energy, photocatalysis, batteries, next generation optics & photonics

Teaching

Organic Chemistry, Polymer Chemistry, Materials Chemistry

Courses

Scholarly Contributions

Journals/Publications

• Anderson, L. E., Kleine, T. S., Zhang, Y., Phan, D. D., Namnabat, S., LaVilla, E. A., Konopka, K. M., Ruiz, D. L., Manchester, M. S., Schwiegerling, J., Glass, R. S., Mackay, M. E., Char, K., Norwood, R. A., & Pyun, J. (2017). Chalcogenide Hybrid Inorganic/Organic Polymers: Ultrahigh Refractive Index Polymers for Infrared Imaging.. ACS Macro Lett., 6(5), 500-504.
• Deese, S. M., Englade-Franklin, L. E., Hill, L. J., Pyun, J., Chan, J. Y., & Garno, J. C. (2017). Subsurface Imaging of the Cores of Polymer-Encapsulated Cobalt Nanoparticles Using Force Modulation Microscopy.. J. Phys. Chem. C, 121(42), 23499-23505.
• Dirlam, P. T., Glass, R. S., Char, K., & Pyun, J. (2017). The use of polymers in Li-S batteries: A review.. J. Polym. Sci., Part A: Polym. Chem., Ahead of Print.
• Glass, R. S., Char, K., & Pyun, J. (2017). From waste to valuable plastics-Discovery of new paradigms from well-studied systems with elemental sulfur.. Phosphorus, Sulfur Silicon Relat. Elem., 192(2), 157-161.
• Oleshko, V. P., Herzing, A. A., Twedt, K. A., Griebel, J. J., McClelland, J. J., Pyun, J., & Soles, C. L. (2017). Multimodal Characterization of the Morphology and Functional Interfaces in Composite Electrodes for Li-S Batteries by Li Ion and Electron Beams.. Langmuir, 33(37), 9361-9377.
• Park, J., Kim, E. T., Kim, C., Pyun, J., Jang, H., Shin, J., Choi, J. W., Char, K., & Sung, Y. (2017). The Importance of Confined Sulfur Nanodomains and Adjoining Electron Conductive Pathways in Subreaction Regimes of Li-S Batteries.. Adv. Energy Mater., 7(19), n/a.
• Pavlopoulos, N. G., Dubose, J. T., Liu, Y., Huang, X., Pinna, N., Willinger, M., Lian, T., Char, K., & Pyun, J. (2017). Type I vs. quasi-type II modulation in CdSe@CdS tetrapods: ramifications for noble metal tipping.. CrystEngComm, 19(43), 6443-6453.
• Yuan, H., Zvonkina, I. J., Al-Enizi, A. M., Elzatahry, A. A., Pyun, J., & Karim, A. (2017). Facile Assembly of Aligned Magnetic Nanoparticle Chains in Polymer Nanocomposite Films by Magnetic Flow Coating.. ACS Appl. Mater. Interfaces, 9(12), 11290-11298.
• Zhang, Y., Griebel, J. J., Dirlam, P. T., Nguyen, N. A., Glass, R. S., MacKay, M. E., Char, K., & Pyun, J. (2017). Inverse vulcanization of elemental sulfur and styrene for polymeric cathodes in Li-S batteries.. J. Polym. Sci., Part A: Polym. Chem., 55(1), 107-116.
• Zhang, Y., Konopka, K. M., Glass, R. S., Char, K., & Pyun, J. (2017). Chalcogenide hybrid inorganic/organic polymers (CHIPs) via inverse vulcanization and dynamic covalent polymerizations.. Polym. Chem., 8(34), 5167-5173.
• Dirlam, P. T., Park, J., Simmonds, A. G., Domanik, K., Arrington, C. B., Schaefer, J. L., Oleshko, V. P., Kleine, T. S., Char, K., Glass, R. S., Soles, C. L., Kim, C., Pinna, N., Sung, Y., & Pyun, J. (2016). Elemental Sulfur and Molybdenum Disulfide Composites for Li-S Batteries with Long Cycle Life and High-Rate Capability.. ACS Appl. Mater. Interfaces, 8(21), 13437-13448.
• Griebel, J. J., Glass, R. S., Char, K., & Pyun, J. (2016). Polymerizations with elemental sulfur: A novel route to high sulfur content polymers for sustainability, energy and defense.. Prog. Polym. Sci., 58, 90-125.
• Kim, E. T., Park, J., Kim, C., Simmonds, A. G., Sung, Y., Pyun, J., & Char, K. (2016). Conformal Polymeric Multilayer Coatings on Sulfur Cathodes via the Layer-by-Layer Deposition for High Capacity Retention in Li-S Batteries.. ACS Macro Lett., 5(4), 471-475.
• Kim, E. T., Park, J., Kim, C., Simmonds, A. G., Sung, Y., Pyun, J., & Char, K. (2016). Conformal Polymeric Multilayer Coatings on Sulfur Cathodes via the Layer-by-Layer Deposition for High Capacity Retention in Li-S Batteries.. ACS Macro Letters, Ahead of Print.
• Kleine, T. S., Nguyen, N. A., Anderson, L. E., Namnabat, S., LaVilla, E. A., Showghi, S. A., Dirlam, P. T., Arrington, C. B., Manchester, M. S., Schwiegerling, J., Glass, R. S., Char, K., Norwood, R. A., Mackay, M. E., & Pyun, J. (2016). High Refractive Index Copolymers with Improved Thermomechanical Properties via the Inverse Vulcanization of Sulfur and 1,3,5-Triisopropenylbenzene.. ACS Macro Lett., 5(10), 1152-1156.
• Lee, Y., Pyun, J., Lim, J., & Char, K. (2016). Modular synthesis of functional polymer nanoparticles from a versatile platform based on poly(pentafluorophenylmethacrylate).. J. Polym. Sci., Part A: Polym. Chem., 54(13), 1895-1901.
• Lee, Y., Pyun, J., Lim, J., & Char, K. (2016). Modular synthesis of functional polymer nanoparticles from a versatile platform based on poly(pentafluorophenylmethacrylate).. Journal of Polymer Science, Part A: Polymer Chemistry, Ahead of Print.
• Lim, J., Cho, Y., Kang, E., Yang, S., Pyun, J., Choi, T., & Char, K. (2016). A one-pot synthesis of polysulfane-bearing block copolymer nanoparticles with tunable size and refractive index.. Chem. Commun. (Cambridge, U. K.), 52(12), 2485-2488.
• Lim, J., Cho, Y., Kang, E., Yang, S., Pyun, J., Choi, T., & Char, K. (2016). A one-pot synthesis of polysulfane-bearing block copolymer nanoparticles with tunable size and refractive index.. Chemical Communications (Cambridge, United Kingdom), 52, 2485-2488.
• Oleshko, V. P., Herzing, A. A., Soles, C. L., Griebel, J. J., Chung, W. J., Simmonds, A. G., & Pyun, J. (2016). Analytical Multimode Scanning and Transmission Electron Imaging and Tomography of Multiscale Structural Architectures of Sulfur Copolymer-Based Composite Cathodes for Next-Generation High-Energy Density Li-S Batteries.. Microsc. Microanal., 22(6), 1198-1221.
• Park, J., Moon, J., Kim, C., Kang, J. H., Lim, E., Park, J., Lee, K. J., Yu, S., Seo, J., Lee, J., Heo, J., Tanaka, N., Cho, S., Pyun, J., Cabana, J., Hong, B. H., & Sung, Y. (2016). Graphene quantum dots: structural integrity and oxygen functional groups for high sulfur/sulfide utilization in lithium sulfur batteries.. NPG Asia Mater., 8(5), e272.
• Pavlopoulos, N. G., Dubose, J. T., Hartnett, E. D., Char, K., & Pyun, J. (2016). Colloidal Random Terpolymers: Controlling Reactivity Ratios of Colloidal Comonomers via Metal Tipping.. ACS Macro Lett., 5(8), 950-954.
• Pavlopoulos, N. G., Dubose, J. T., Pinna, N., Willinger, M., Char, K., & Pyun, J. (2016). Synthesis and Assembly of Dipolar Heterostructured Tetrapods: Colloidal Polymers with "Giant tert-butyl" Groups.. Angew. Chem., Int. Ed., 55(5), 1787-1791.
• Pavlopoulos, N. G., Dubose, J. T., Pinna, N., Willinger, M., Char, K., & Pyun, J. (2016). Synthesis and Assembly of Dipolar Heterostructured Tetrapods: Colloidal Polymers with "Giant tert-butyl" Groups.. Angewandte Chemie, International Edition, 55, 1787-1791.
• Sung, Y., Lim, J., Koh, J. H., Min, B. K., Pyun, J., & Char, K. (2016). Arm length dependency of Pt-decorated CdSe tetrapods on the performance of photocatalytic hydrogen generation.. Korean J. Chem. Eng., 33(8), 2287-2290.
• Dirlam, P. T., Simmonds, A. G., Kleine, T. S., Nguyen, N. A., Anderson, L. E., Klever, A. O., Florian, A., Costanzo, P. J., Theato, P., Mackay, M. E., Glass, R. S., Char, K., & Pyun, J. (2015). Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li-S batteries.. RSC Adv., 5(31), 24718-24722.
• Dirlam, P. T., Simmonds, A. G., Kleine, T. S., Nguyen, N. A., Anderson, L. E., Klever, A. O., Florian, A., Costanzo, P. J., Theato, P., Mackay, M. E., Glass, R. S., Char, K., & Pyun, J. (2015). Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li-S batteries.. RSC Advances, 5, 24718-24722.
• Dirlam, P. T., Simmonds, A. G., Shallcross, R. C., Arrington, K. J., Chung, W. J., Griebel, J. J., Hill, L. J., Glass, R. S., Char, K., & Pyun, J. (2015). Improving the Charge Conductance of Elemental Sulfur via Tandem Inverse Vulcanization and Electropolymerization.. ACS Macro Lett., 4(1), 111-114.
• Dirlam, P. T., Simmonds, A. G., Shallcross, R. C., Arrington, K. J., Chung, W. J., Griebel, J. J., Hill, L. J., Glass, R. S., Char, K., & Pyun, J. (2015). Improving the Charge Conductance of Elemental Sulfur via Tandem Inverse Vulcanization and Electropolymerization.. ACS Macro Letters, 4, 111-114.
• Ehamparam, R., Pavlopoulos, N. G., Liao, M. W., Hill, L. J., Armstrong, N. R., Pyun, J., & Saavedra, S. S. (2015). Band Edge Energetics of Heterostructured Nanorods: Photoemission Spectroscopy and Waveguide Spectroelectrochemistry of Au-Tipped CdSe Nanorod Monolayers.. ACS Nano, 9(9), 8786-8800.
• Ehamparam, R., Pavlopoulos, N. G., Liao, M. W., Hill, L. J., Armstrong, N. R., Pyun, J., & Saavedra, S. S. (2015). Band Edge Energetics of Heterostructured Nanorods: Photoemission Spectroscopy and Waveguide Spectroelectrochemistry of Au-Tipped CdSe Nanorod Monolayers.. ACS Nano, 9, 8786-8800.
• Griebel, J. J., Li, G., Glass, R. S., Char, K., & Pyun, J. (2015). Kilogram scale inverse vulcanization of elemental sulfur to prepare high capacity polymer electrodes for Li-S batteries.. J. Polym. Sci., Part A: Polym. Chem., 53(2), 173-177.
• Griebel, J. J., Li, G., Glass, R. S., Char, K., & Pyun, J. (2015). Kilogram scale inverse vulcanization of elemental sulfur to prepare high capacity polymer electrodes for Li-S batteries.. Journal of Polymer Science, Part A: Polymer Chemistry, 53, 173-177.
• Griebel, J. J., Nguyen, N. A., Namnabat, S., Anderson, L. E., Glass, R. S., Norwood, R. A., MacKay, M. E., Char, K., & Pyun, J. (2015). Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur for Healable Infrared Optical Materials.. ACS Macro Lett., 4(9), 862-866.
• Griebel, J. J., Nguyen, N. A., Namnabat, S., Anderson, L. E., Glass, R. S., Norwood, R. A., MacKay, M. E., Char, K., & Pyun, J. (2015). Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur for Healable Infrared Optical Materials.. ACS Macro Letters, 4, 862-866.
• Hill, L. J., Pinna, N., Char, K., & Pyun, J. (2015). Colloidal polymers from inorganic nanoparticle monomers.. Prog. Polym. Sci., 40, 85-120.
• Hill, L. J., Pinna, N., Char, K., & Pyun, J. (2015). Colloidal polymers from inorganic nanoparticle monomers.. Progress in Polymer Science, 40, 85-120.
• Lim, J., Jung, U., Joe, W. T., Kim, E. T., Pyun, J., & Char, K. (2015). High Sulfur Content Polymer Nanoparticles Obtained from Interfacial Polymerization of Sodium Polysulfide and 1,2,3-Trichloropropane in Water.. Macromol. Rapid Commun., 36(11), 1103-1107.
• Lim, J., Jung, U., Joe, W. T., Kim, E. T., Pyun, J., & Char, K. (2015). High Sulfur Content Polymer Nanoparticles Obtained from Interfacial Polymerization of Sodium Polysulfide and 1,2,3-Trichloropropane in Water.. Macromolecular Rapid Communications, 36, 1103-1107.
• Lim, J., Pyun, J., & Char, K. (2015). Recent Approaches for the Direct Use of Elemental Sulfur in the Synthesis and Processing of Advanced Materials.. Angew. Chem., Int. Ed., 54(11), 3249-3258.
• Lim, J., Pyun, J., & Char, K. (2015). Recent Approaches for the Direct Use of Elemental Sulfur in the Synthesis and Processing of Advanced Materials.. Angewandte Chemie, International Edition, 54, 3249-3258.
• Oleshko, V. P., Kim, J., Schaefer, J. L., Hudson, S. D., Soles, C. L., Simmonds, A. G., Griebel, J. J., Glass, R. S., Char, K., & Pyun, J. (2015). Structural origins of enhanced capacity retention in novel copolymerized sulfur-based composite cathodes for high-energy density Li-S batteries.. MRS Commun., 5(3), 353-364.
• Oleshko, V. P., Kim, J., Schaefer, J. L., Hudson, S. D., Soles, C. L., Simmonds, A. G., Griebel, J. J., Glass, R. S., Char, K., & Pyun, J. (2015). Structural origins of enhanced capacity retention in novel copolymerized sulfur-based composite cathodes for high-energy density Li-S batteries.. MRS Communications, 5, 353-364.
• Sung, Y., Lim, J., Koh, J. H., Hill, L. J., Min, B. K., Pyun, J., & Char, K. (2015). Uniform decoration of Pt nanoparticles on well-defined CdSe tetrapods and the effect of their Pt cluster size on photocatalytic H2 generation.. CrystEngComm, 17(44), 8423-8427.
• Sung, Y., Lim, J., Koh, J. H., Hill, L. J., Min, B. K., Pyun, J., & Char, K. (2015). Uniform decoration of Pt nanoparticles on well-defined CdSe tetrapods and the effect of their Pt cluster size on photocatalytic H2 generation.. CrystEngComm, 17, 8423-8427.
• Wu, K., Hill, L. J., Chen, J., McBride, J. R., Pavlopolous, N. G., Richey, N. E., Pyun, J., & Lian, T. (2015). Universal Length Dependence of Rod-to-Seed Exciton Localization Efficiency in Type I and Quasi-Type II CdSe@CdS Nanorods.. ACS Nano, 9(4), 4591-4599.
• Wu, K., Hill, L. J., Chen, J., McBride, J. R., Pavlopolous, N. G., Richey, N. E., Pyun, J., & Lian, T. (2015). Universal Length Dependence of Rod-to-Seed Exciton Localization Efficiency in Type I and Quasi-Type II CdSe@CdS Nanorods.. ACS Nano, 9, 4591-4599.
• Griebel, J. J., Namnabat, S., Kim, E. T., Himmelhuber, R., Moronta, D. H., Chung, W. J., Simmonds, A. G., Kim, K., van, J., Nguyen, N. A., Dereniak, E. L., Mackay, M. E., Char, K., Glass, R. S., Norwood, R. A., & Pyun, J. (2014). New infrared transmitting material via inverse vulcanization of elemental sulfur to prepare high refractive index polymers. Advanced Materials.
• Griebel, J. J., Nguyen, N. A., Astashkin, A. V., Glass, R. S., MacKay, M. E., Char, K., & Pyun, J. (2014). Preparation of Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur.. ACS Macro Lett., 3(12), 1258-1261.
• Griebel, J. J., Nguyen, N. A., Astashkin, A. V., Glass, R. S., MacKay, M. E., Char, K., & Pyun, J. (2014). Preparation of Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur.. ACS Macro Letters, 3, 1258-1261.
• Hill, L. J., & Pyun, J. (2014). Colloidal Polymers via Dipolar Assembly of Magnetic Nanoparticle Monomers.. ACS Applied Materials & Interfaces, 6, 6022-6032.
• Hill, L. J., Richey, N. E., Sung, Y., Dirlam, P. T., Griebel, J. J., Lavoie-Higgins, E., Shim, I., Pinna, N., Willinger, M., Vogel, W., Benkoski, J. J., Char, K., & Pyun, J. (2014). Colloidal Polymers from Dipolar Assembly of Cobalt-Tipped CdSe@CdS Nanorods.. ACS Nano, 8(4), 3272-3284.
• Hill, L. J., Richey, N. E., Sung, Y., Dirlam, P. T., Griebel, J. J., Lavoie-Higgins, E., Shim, I., Pinna, N., Willinger, M., Vogel, W., Benkoski, J. J., Char, K., & Pyun, J. (2014). Colloidal Polymers from Dipolar Assembly of Cobalt-Tipped CdSe@CdS Nanorods.. ACS Nano, 8, 3272-3284.
• Hill, L. J., Richey, N. E., Sung, Y., Dirlam, P. T., Griebel, J. J., Shim, I., Pinna, N., Willinger, M., Vogel, W., Char, K., & Pyun, J. (2014). Synthesis of ferromagnetic cobalt nanoparticle tipped CdSe@CdS nanorods: critical role of Pt-activation.. CrystEngComm, 16(40), 9461-9468.
• Hill, L. J., Richey, N. E., Sung, Y., Dirlam, P. T., Griebel, J. J., Shim, I., Pinna, N., Willinger, M., Vogel, W., Char, K., & Pyun, J. (2014). Synthesis of ferromagnetic cobalt nanoparticle tipped CdSe@CdS nanorods: critical role of Pt-activation.. CrystEngComm, 16, 9461-9468.
• Kim, E. T., Chung, W. J., Lim, J., Johe, P., Glass, R. S., Pyun, J., & Char, K. (2014). One-pot synthesis of PbS NP/sulfur-oleylamine copolymer nanocomposites via the copolymerization of elemental sulfur with oleylamine.. Polym. Chem., 5(11), 3617-3623.
• Kim, E. T., Chung, W. J., Lim, J., Johe, P., Glass, R. S., Pyun, J., & Char, K. (2014). One-pot synthesis of PbS NP/sulfur-oleylamine copolymer nanocomposites via the copolymerization of elemental sulfur with oleylamine.. Polymer Chemistry, 5, 3617-3623.
• Namnabat, S., Gabriel, J. J., Pyun, J., & Norwood, R. A. (2014). Optical properties of sulfur copolymers for infrared applications.. Proc. SPIE, 8983(Organic Photonic Materials and Devices XVI), 89830D/1-89830D/8.
• Simmonds, A. G., Griebel, J. J., Park, J., Kim, K. R., Chung, W. J., Oleshko, V. P., Kim, J., Kim, E. T., Glass, R. S., Soles, C. L., Sung, Y., Char, K., & Pyun, J. (2014). Inverse vulcanization of elemental sulfur to prepare polymeric electrode materials for Li-S batteries. ACS Macro Letters, 3(3), 229-232.
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  Abstract: Sulfur-rich copolymers based on poly(sulfur-random-1,3- diisopropenylbenzene) (poly(S-r-DIB)) were synthesized via inverse vulcanization to create cathode materials for lithium-sulfur battery applications. These materials exhibit enhanced capacity retention (1005 mAh/g at 100 cycles) and battery lifetimes over 500 cycles at a C/10 rate. These poly(S-r-DIB) copolymers represent a new class of polymeric electrode materials that exhibit one of the highest charge capacities reported, particularly after extended charge-discharge cycling in Li-S batteries. © 2014 American Chemical Society.
• Chung, W. J., Griebel, J. J., Kim, E. T., Yoon, H., Simmonds, A. G., Ji, H. J., Dirlam, P. T., Glass, R. S., Wie, J. J., Nguyen, N. A., Guralnick, B. W., Park, J., Somogyi, A., Theato, P., MacKay, M. E., Sung, Y., Char, K., & Pyun, J. (2013). The use of elemental sulfur as an alternative feedstock for polymeric materials.. Nat. Chem., 5(6), 518-524.
• Dirlam, P. T., Kim, H. J., Arrington, K. J., Chung, W. J., Sahoo, R., Hill, L. J., Costanzo, P. J., Theato, P., Char, K., & Pyun, J. (2013). Single chain polymer nanoparticles via sequential ATRP and oxidative polymerization. Polymer Chemistry, 4(13), 3765-3773.
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  Abstract: The synthesis of single chain nanoparticles has been achieved by the synthesis of a linear polystyrenic precursor carrying 3,4- propylenedioxythiophene groups via atom transfer radical polymerization followed by intramolecular crosslinking via oxidative polymerization. This methodology enabled the introduction of electroactive inclusions into single chain polymer nanoparticles, while concurrently promoting intramolecular collapse. © 2013 The Royal Society of Chemistry.
• Guoxing, L. i., Wie, J. J., Nguyen, N. A., Chung, W. J., Kim, E. T., Char, K., MacKay, M. E., & Pyun, J. (2013). Synthesis, self-assembly and reversible healing of supramolecular perfluoropolyethers. Journal of Polymer Science, Part A: Polymer Chemistry, 51(17), 3598-3606.
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  Abstract: The synthesis and thermomechanical properties of a novel class of self-healing perfluoropolyethers (PFPEs) is reported. By decoration of 2-ureido-4[1H]-pyrimidone end groups on the termini of low molar mass PFPE, the formation of supramolecular polymers and networks held together via hydrogen bonding associations was achieved. These novel supramolecular polymer materials exhibit a combination of enhanced modulus and elasticity, along with self-healing properties, where rapid self-healing time was demonstrated using dynamic rheological measurements. These types of supramolecular PFPEs are anticipated to be useful for a number of emerging areas in lubrication. © 2013 Wiley Periodicals, Inc.
• Yoo, H., Kim, B. Y., Hill, L. J., Griebel, J. J., Chung, W. J., & Pyun, J. (2013). Polyoctadecyl methacrylate brushes via surface-initiated atom transfer radical polymerization. Applied Organometallic Chemistry, 27(11), 678-682.
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  Abstract: The synthesis of poly(octadecyl methacrylate) brushes on planar Si substrates using surface-initiated atom transfer radical polymerization (SI-ATRP) is reported. SI-ATRP of octadecyl methacrylate from a silane initiator-modified Si substrate yielded well-defined homopolymer brushes of varying molar mass (5000-38 000 g mol-1) and film thickness from around 2 to 20 nm. Correlation of both free polymer molar mass and brush thicknesses confirmed controlled surface-initiated ATRP from these modified surfaces. By optimization of brush molar mass, film thickness and thin-film processing, we observed side chain crystallization of tethered poly(octadecyl methacrylate) chains, resulting in the formation of lamellar morphologies with high-aspect-ratio nanofibers. Copyright © 2013 John Wiley & Sons, Ltd. The synthesis poly(octadecyl meth-acrylate)brushes on planar Si substrates using surface initiated atom transfer radical polymerization (SI-ATRP) is reported. We observed side chain crystallization of tethered PODMA chains resultng in the formation of lamellae morphologies with high aspect ratio nanofibers. Copyright © 2013 John Wiley & Sons, Ltd.
• Benkoski, J. J., Breidenich, J. L., Wei, M. C., Clatterbaughi, G. V., Keng, P. Y., & Pyun, J. (2012). Systems engineering at the nanoscale. Proceedings of SPIE - The International Society for Optical Engineering, 8373.
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  Abstract: Nanomaterials have provided some of the greatest leaps in technology over the past twenty years, but their relatively early stage of maturity presents challenges for their incorporation into engineered systems. Perhaps even more challenging is the fact that the underlying physics at the nanoscale often run counter to our physical intuition. The current state of nanotechnology today includes nanoscale materials and devices developed to function as components of systems, as well as theoretical visions for "nanosystems," which are systems in which all components are based on nanotechnology. Although examples will be given to show that nanomaterials have indeed matured into applications in medical, space, and military systems, no complete nanosystem has yet been realized. This discussion will therefore focus on systems in which nanotechnology plays a central role. Using self-assembled magnetic artificial cilia as an example, we will discuss how systems engineering concepts apply to nanotechnology. © 2012 SPIE.
• Breidenich, J. L., Wei, M. C., Clatterbaugh, G. V., Benkoski, J. J., Keng, P. Y., & Pyun, J. (2012). Controlling length and areal density of artificial cilia through the dipolar assembly of ferromagnetic nanoparticles. Soft Matter, 8(19), 5334-5341.
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  Abstract: Artificial cilia have been explored for use in microrobotics, MEMS, and lab-on-a-chip devices for applications ranging from micromixers, microfluidic pumps, locomotion, acoustic detection, and heat transfer. We have previously demonstrated the ability to assemble dense brushes of magnetically actuated artificial cilia through the dipolar assembly of 24 nm ferromagnetic cobalt nanoparticles. With little more than a strategically placed permanent magnet, the nanoparticles assemble at room temperature in less than 60 s. Despite areal densities exceeding 1 cilium/μm2, diameters below 25 nm, aspect ratios exceeding 400, and flexural rigidities below 3 × 10-28 N m2, these seemingly delicate structures resist collapse upon each other or the underlying substrate. The current study investigates the ability to rationally control their average length and areal density by changing the nanoparticle concentration and the dimensions of the rectangular capillary tube containing the dispersion. We find that the length and areal density obey a simple conservation of mass relationship with concentration and capillary height such that the product of the former is directly proportional to the product of the latter. Detailed statistical analysis supports a mechanism in which the role of the external field is to align pre-existing chains with the external field, assist stacking of chains along the axis of the field, and then draw them towards the ends of the permanent magnets, where the magnetic field gradient is steepest. © 2012 The Royal Society of Chemistry.
• Choi, J., Schattling, P., Jochum, F. D., Pyun, J., Char, K., & Theato, P. (2012). Functionalization and patterning of reactive polymer brushes based on surface reversible addition and fragmentation chain transfer polymerization. Journal of Polymer Science, Part A: Polymer Chemistry, 50(19), 4010-4018.
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  Abstract: We present the synthesis of reactive polymer brushes prepared by surface reversible addition-fragmentation chain transfer polymerization of pentafluorophenyl acrylate. The reactive ester moieties can be used to functionalize the polymer brush film with virtually any functionality by simple post-polymerization modification with amines. Dithiobenzoic acid benzyl-(4-ethyltrimethoxylsilyl) ester was used as the surface chain transfer agent (S-CTA) and the anchoring group onto the silicon substrates. Reactive polymer brushes with adjustable molecular weight, high grafting density, and conformal coverage through the grafting-from approach were obtained. Subsequently, the reactive polymer brushes were converted with amino-spiropyrans resulting in reversible light-responsive polymer brush films. The wetting behavior could be altered by irradiation with ultraviolet (UV) or visible light. Furthermore, a patterned surface of polymer brushes was obtained using a lithography technique. UV irradiation of the S-CTA-modified substrates leads to a selective degradation of S-CTA in the exposed areas and gives patterned activated polymer brushes after a subsequent RAFT polymerization step. Conversion of the patterned polymer brushes with 5-((2-aminoethyl)amino) naphthalene-1-sulfonic acid resulted in patterned fluorescent polymer brush films. The utilization of reactive polymer brushes offers an easy approach in the fabrication of highly functional brushes, even for functionalities whose introduction is limited by other strategies. © 2012 Wiley Periodicals, Inc.
• Hill, L. J., Bull, M. M., Sung, Y., Simmonds, A. G., Dirlam, P. T., Richey, N. E., Derosa, S. E., Shim, I., Guin, D., Costanzo, P. J., Pinna, N., Willinger, M., Vogel, W., Char, K., & Pyun, J. (2012). Directing the deposition of ferromagnetic cobalt onto Pt-tipped CdSe@CdS nanorods: Synthetic and mechanistic insights. ACS Nano, 6(10), 8632-8645.
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  PMID: 22900605;Abstract: A methodology providing access to dumbbell-tipped, metal-semiconductor and metal oxide-semiconductor heterostructured nanorods has been developed. The synthesis and characterization of CdSe@CdS nanorods incorporating ferromagnetic cobalt nanoinclusions at both nanorod termini (i.e., dumbbell morphology) are presented. The key step in the synthesis of these heterostructured nanorods was the decoration of CdSe@CdS nanorods with platinum nanoparticle tips, which promoted the deposition of metallic CoNPs onto Pt-tipped CdSe@CdS nanorods. Cobalt nanoparticle tips were then selectively oxidized to afford CdSe@CdS nanorods with cobalt oxide domains at both termini. In the case of longer cobalt-tipped nanorods, heterostructured nanorods were observed to self-organize into complex dipolar assemblies, which formed as a consequence of magnetic associations of terminal CoNP tips. Colloidal polymerization of these cobalt-tipped nanorods afforded fused nanorod assemblies from the oxidation of cobalt nanoparticle tips at the ends of nanorods via the nanoscale Kirkendall effect. Wurtzite CdS nanorods survived both the deposition of metallic CoNP tips and conversion into cobalt oxide phases, as confirmed by both XRD and HRTEM analysis. A series of CdSe@CdS nanorods of four different lengths ranging from 40 to 174 nm and comparable diameters (6-7 nm) were prepared and modified with both cobalt and cobalt oxide tips. The total synthesis of these heterostructured nanorods required five steps from commercially available reagents. Key synthetic considerations are discussed, with particular emphasis on reporting isolated yields of all intermediates and products from scale up of intermediate precursors. © 2012 American Chemical Society.
• Pyun, J. (2012). Polymer chemistry: Still in control. Nature Materials, 11(9), 753-754.
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  PMID: 22918317;
• Pyun, J. (2012). Self-assembly and colloidal polymerization of polymer-nanoparticle hybrids into mesoscopic chains. Angewandte Chemie - International Edition, 51(50), 12408-12409.
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  PMID: 23161843;Abstract: No, it's not frogspawn! Polymer-coated gold nanoparticles can be assembled into extended mesoscopic chains with precise dimensional control. Here, the conditions can be adjusted to promote the fusion of polymeric ligands into cylindrical micellar aggregates. This type of colloidal polymerization offers a new and versatile route to a variety of mesoscopic assemblies of nanoparticles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Benkoski, J. J., Breidenich, J. L., Uy, O. M., Hayes, A. T., Deacon, R. M., Land, H. B., Spicer, J. M., Keng, P. Y., & Pyun, J. (2011). Dipolar organization and magnetic actuation of flagella-like nanoparticle assemblies. Journal of Materials Chemistry, 21(20), 7314-7325.
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  Abstract: Modeled after the design of eukaryotic protozoa, we fabricated artificial microscopic swimmers through the dipolar assembly of a bidisperse mixture of 250 nm superparamagnetic magnetite colloids and 24 nm ferromagnetic cobalt nanoparticles. The cobalt nanoparticles self-assemble into long, 1-D chains measuring approximately 24 nm × 5 m. These chains then co-assemble with the magnetite beads to form "head" + "tail" structures. These types of asymmetric "flagella-like" colloidal assemblies were formed and maintained solely through dipolar interactions and is the first demonstration using randomly mixed dispersions of disparate magnetic colloids. When actuated by a pair of orthogonal static and sinusoidal magnetic fields, they undergo an asymmetric undulation that is the essential condition for locomotion at low Reynolds numbers. Based upon their shape, size, and articulation, these assemblies are potentially among the smallest structures capable of overcoming Brownian motion to perform useful locomotion. In addition to the head and tail structure, a variety of irregular structures formed that were incapable of swimming. A design of experiments (DOE) study was therefore implemented to optimize the production of artificial swimmers within a large parameter space that included concentration, the amount of sonication, and magnetic field strength. The artificial swimmers were most prevalent for intermediate concentrations of Co and magnetite particles. Statistical analysis suggested that the permanent dipole of the Co nanoparticles stimulated the assembly of the bidisperse mixture into complex, heterogeneous structures. Demonstration of in situ imaging of the magnetic actuation of these dipolar NP assemblies was conducted by optical microscopy. © 2011 The Royal Society of Chemistry.
• Kim, B. Y., Shim, I., L., O., & Pyun, J. (2011). Magnetic self-assembly of gold nanoparticle chains using dipolar core-shell colloids. Chemical Communications, 47(3), 890-892.
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  PMID: 21072399;Abstract: The preparation of gold nanoparticle (AuNP) assemblies was conducted by the synthesis and dipolar assembly of ferromagnetic core-shell nanoparticles composed of AuNP cores and cobalt NP shells. Dissolution of metallic Co phases with mineral acids afforded self-assembled AuNP chains and bracelets.
• Kim, B. Y., Yu, S., Kim, H. S., Lee, D., Shim, I., Derosa, S. E., Sung, Y., & Pyun, J. (2011). Morphological conversion of dipolar core-shell Au-Co nanoparticles into beaded Au-Co₃O₄ nanowires. Journal of Materials Chemistry, 21(37), 14163-14166.
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  Abstract: We report a novel methodology to prepare hierarchical structured Au-Co 3O4 materials composed of Co3O4 nanowires decorated with Au peripheral inclusions. The electrochemical activity of these materials was also demonstrated by fabrication into negative electrodes for rechargeable Li-batteries. © 2011 The Royal Society of Chemistry.
• Pyun, J. (2011). Graphene oxide as catalyst: Application of carbon materials beyond nanotechnology. Angewandte Chemie - International Edition, 50(1), 46-48.
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  PMID: 20979072;Abstract: More hip than nano: Bielawski and co-workers recently demonstrated the remarkable ability of graphene oxide to catalyze the oxidation of a variety of alcohols to the corresponding ketones/aldehydes, alkenes to the corresponding diones, and alkynes to the corresponding hydrates - a process they termed "carbocatalysis". These efficient metal-free reactions mark a promising convergence of heterogeneous catalysis with graphene science. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Pyun, J., & Emrick, T. (2011). Polymer Encapsulation of Metallic and Semiconductor Nanoparticles: Multifunctional Materials with Novel Optical, Electronic and Magnetic Properties. Macromolecular Engineering: Precise Synthesis, Materials Properties, Applications, 4, 2409-2449.
• Benkoski, J. J., Deacon, R. M., Land, H. B., Baird, L. M., Breidenich, J. L., Srinivasan, R., Clatterbaugh, G. V., Keng, P. Y., & Pyun, J. (2010). Dipolar assembly of ferromagnetic nanoparticles into magnetically driven artificial cilia. Soft Matter, 6(3), 602-609.
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  Abstract: Taking inspiration from eukaryotic cilia, we report a method for growing dense arrays of magnetically actuated microscopic filaments. Fabricated from the bottom-up assembly of polymer-coated cobalt nanoparticles, each segmented filament measures approximately 5-15 μm in length and 23.5 nm in diameter, which was commensurate with the width of a single nanoparticle. A custom microscope stage actuates the filaments through orthogonal permanent and alternating magnetic fields. We implemented design of experiments (DOE) to efficiently screen the effects of cobalt nanoparticle concentration, crosslinker concentration, and surface chemistry. The results indicated that the formation of dense, cilia-mimetic arrays could be explained by physical, non-covalent interactions (i.e. dipolar association forces) rather than chemistry. The experiments also determined an optimal Co nanoparticle concentration of approximately 500 μg ml-1 for forming dense arrays near the ends of the permanent magnets, and a critical concentration of approximately 0.3 μg ml-1, below which particle assembly into chains was not observed. © 2010 The Royal Society of Chemistry.
• Bull, M. M., Chung, W. J., Anderson, S. R., Kim, S., Shim, I., Paik, H., & Pyun, J. (2010). Synthesis of ferromagnetic polymer coated nanoparticles on multi-gram scale with tunable particle size. Journal of Materials Chemistry, 20(29), 6023-6025.
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  Abstract: The synthesis of ferromagnetic cobalt nanoparticles with polymeric ligands with tunable particle size is reported on multi-gram scales. End-functional polystyrene ligands were prepared via atom transfer radical polymerization. Mechanistic studies on this system were conducted as well as direct comparisons of polymer vs. small molecule ligand effects on nanoparticle formation. © 2010 The Royal Society of Chemistry.
• Hong, J. S., Pyun, J., Park, Y. W., Kim, C. S., & Shim, I. (2009). Oxidation effect in cobalt nanoparticles magnetic fluids. IEEE Transactions on Magnetics, 45(6), 2464-2466.
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  Abstract: Cobalt nanoparticles were synthesized by modified thermal decomposition and oxidized in the condition of solution. Crystal structure of fabricated cobalt nanoparticles is determined to be cubic of Fm-3m space group from X-ray diffraction (XRD) measurement. Microstructure of cobalt nanoparticles after the oxidation process show core-shell structure. The particle size and thickness of oxide shell can be controlled by oxidation temperature. The shell thickness of cobalt nanoparticles after the oxidation at 300° C is 4.7 nm, when compared to those oxidized at 250° C with the shell thickness of 2.4 nm due to the change in the oxidation temperature. The magnetic properties of cobalt particles have been measured with VSM. Our results show that cobalt metal (core)/cobalt oxide (shell) has two magnetic behaviors of ferromagnetic and antiferromagnetic properties in magnetic fluid. © 2009 IEEE.
• Keng, P. Y., Shim, I., Kim, B. Y., Sahoo, R., Veneman, P. E., Armstrong, N. R., Yoo, H., Pemberton, J. E., Bull, M. M., Griebel, J. J., Ratcliff, E. L., Nebesny, K. W., & Pyun, D. (2009). Colloidal Polymerization of Polymer Coated Ferromagnetic Nanoparticles into Cobalt Oxide Nanowires. ACS Nano, 3, 3143-3157.
• Benkoski, J. J., Bowles, S. E., Jones, R. L., Douglas, J. F., Pyun, J., & Karim, A. (2008). Self-assembly of polymer-coated ferromagnetic nanoparticles into mesoscopic polymer chains. Journal of Polymer Science, Part B: Polymer Physics, 46(20), 2267-2277.
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  Abstract: The self-assembly of dispersed polymer-coated ferromagnetic nanoparticles into micron-sized one-dimensional mesostructures at a liquid-liquid interface was reported. When polystyrene-coated Co nanoparticles (19 nm) are driven to an oil/water interface under zero-field conditions, long (≈ 5 μm) chain-like assemblies spontaneously form because of dipolar associations between the ferromagnetic nano-particles. Direct imaging of the magnetic assembly process was achieved using a recently developed platform consisting of a biphasic oil/water system in which the oil phase was flash-cured within 1 s upon ultraviolet light exposure. The nanoparticle assemblies embedded in the crosslinked phase were then imaged using atomic force microscopy. The effects of time, temperature, and colloid concentration on the self-assembly process of dipolar nanoparticles were then investigated. Variation of either assembly time t or temperature T was found to be an interchangeable effect in the 1D organization process. Because of the dependence of chain length on the assembly conditions, we observed striking similarities between 1D nanoparticle self-assembly and polymerization of small molecule monomers. This is the first in-depth study of the parameters affecting the self-assembly of dispersed, dipolar nanoparticles into extended mesostructures in the absence of a magnetic field. © 2008 Wiley Periodicals, Inc.
• Shim, I., Choi, D. H., Kim, C. S., Pyun, J., & Bowles, S. E. (2008). Fabrication of long CdS nanowires by using a chemical solution process. Journal of the Korean Physical Society, 52(2), 332-336.
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  Abstract: A skein of thread-like cadmium sulfide (CdS) semiconductor nanowires has been successfully fabricated using a high-temperature (360 °C) multiple-injection solution-phase process in a mixture of trioctylphosphine oxide (TOPO), trioctylphosphine (TOP) and n-tetradecylphosphonic acid (TDPA) ligands. The injection method of the sulfide precursor and the holding time were varied and found to be crucial to the fabrication of the long CdS nanowires. The CdS nanowires, with widths of 2.5 nm, formed extended networks over microns long, giving then a skein-type bundle-of-nanowires structure. In addition, we have demonstrated the growth of gold (Au) nanoparticles on the CdS nanowires. The CdS nanowires were characterized by s-ray diffraction (XRD), thermogavimetry-differential thermal analysis (TG-DTA), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometer (XPS) and UV-photoluminecence (PL) spectra.
• Benkoski, J. J., Bowles, S. E., Korth, B. D., Jones, R. L., Douglas, J. F., Karim, A., & Pyun, J. (2007). Field induced formation of mesoscopic polymer chains from functional ferromagnetic colloids. Journal of the American Chemical Society, 129(19), 6291-6297.
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  PMID: 17444645;Abstract: The assembly and direct imaging of ferromagnetic nanoparticles into one-dimensional mesostructures (1-D) are reported. Polymer-coated ferromagnetic colloids (19 nm, 24 nm) were assembled at a crosslinkable oil-water interface under both magnetic field induced and zero-field conditions and permanently fixed into 1-D mesoscopic polymer chains (1-9 μm) in a process referred to as Fossilized Liquid Assembly (FLA). In the FLA process, nanoparticle chains were fixed at the oil interface through photopolymerization, enabling direct visualization of organized mesostructures using atomic force microscopy. Using the FLA methodology, we systematically investigated different conditions and demonstrated that dispersed ferromagnetic colloids possess sufficient dipolar interactions to organize into mesoscopic assemblies. Application of an external magnetic field during assembly enabled the formation of micron-sized chains which were aligned in the direction of the applied field. This universal methodology is an attractive alternative technique to cryogenic transmission electron microscopy (cryo-TEM) for the visualization of nanoparticle assembly in dispersed organic media. © 2007 American Chemical Society.
• Keng, P. Y., Shim, I., Korth, B. D., Douglas, J. F., & Pyun, J. (2007). Synthesis and self-assembly of polymer-coated ferromagnetic nanoparticles. ACS Nano, 1(4), 279-292.
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  PMID: 19206678;Abstract: We describe the synthesis and characterization of polymer-coated ferromagnetic cobalt nanoparticles (CoNPs). The synthesis of end-functionalized polystyrene surfactants possessing amine, carboxylic acid, or phosphine oxide end-groups was accomplished using atom-transfer radical polymerization. This versatile synthetic method enabled the production of multigram quantities of these polymeric surfactants that stabilized ferromagnetic CoNPs when dispersed in organic media. An in-depth investigation into the synthesis of polystyrene-coated ferromagnetic CoNPs was also conducted using various combinations of these polymeric surfactants in the thermolysis of dicobaltoctacarbonyl (Co2(CO) 8). Moreover, the application of a dual-stage thermolysis with Co2 (CO) 8 allowed for the preparation of large samples (200-820 mg) per batch of well-defined and dispersable ferromagnetic nanoparticles. Characterization of these functionalized nanoparticle materials was then done using transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis. Self-assembly of these dipolar nanoparticles was investigated in solutions cast onto supporting substrates, where local nematic-like ordering of nanoparticle chains was observed along with a tendency of adjacent chains to form "zippering" configurations, both phenomena having been predicted by recent simulations of dipolar fluids in conjunction with van der Waals interactions. © 2007 American Chemical Society.
• Pyun, J. (2007). Nanocomposite materials from functional polymers and magnetic colloids. Polymer Reviews, 47(2), 231-263.
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  Abstract: The synthesis of polymer coated magnetic nanoparticles is reviewed. This class of organic/inorganic materials has gained significant attention for potential applications in biomedicine, separations, and magnetic storage. We outline the various approaches that have been investigated to encapsulate discrete magnetic colloids with functional polymer shells. An essential component of this research is the preparation of polymeric surfactants that enable synthesis, passivation, and functionalization of magnetic nanoparticles. Various polymerization techniques, namely, living and controlled polymerizations, such as, ring-opening metathesis polymerization (ROMP) and controlled radical processes have been applied to synthesize core-shell colloids possessing tunable film thickness, composition, and properties.
• Korth, B. D., Keng, P., Shim, I., Bowles, S. E., Tang, C., Kowalewski, T., Nebesny, K. W., & Pyun, J. (2006). Polymer-coated ferromagnetic colloids from well-defined macromolecular surfactants and assembly into nanoparticle chains. Journal of the American Chemical Society, 128(20), 6562-6563.
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  PMID: 16704248;Abstract: A novel synthetic route to polymer-coated ferromagnetic colloids of metallic cobalt has been developed. Well-defined end-functional polystyrenes were synthesized using controlled radical polymerization and used as surfactants in the thermolysis of dicobaltoctacarbonyl to afford uniform ferromagnetic nanoparticles. The presence of the polymer shell enabled prolonged colloidal stability of dispersions in a wide range of organic solvents and formed glassy encapsulating coatings around ferromagnetic cores in the solid state. These polymer-coated colloids assembled into robust, micron-sized nanoparticle chains when cast onto supporting surfaces due to dipolar associations of magnetic cores. Hierarchical assemblies were also prepared by blending polystyrene-coated cobalt colloids with larger silica beads. Copyright © 2006 American Chemical Society.
• Kim, Y., Pyun, J., Fréchet, J. M., Hawker, C. J., & Frank, C. W. (2005). The dramatic effect of architecture on the self-assembly of block copolymers at interfaces. Langmuir, 21(23), 10444-10458.
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  PMID: 16262305;Abstract: Dramatic morphological changes are observed in the Langmuir-Blodgett (LB) film assemblies of poly(ethylene glycol)-b-(styrene-r-benzocyclobutene) block copolymer (PEG-b-(S-r-BCB)) after intramolecular cross-linking of the S-r-BCB block to form a linear-nanoparticle structure. To isolate architectural effects and allow direct comparison, the linear block copolymer precursor and the linear-nanoparticle block copolymer resulting from selective intramolecular cross-linking of the BCB units were designed to have exactly the same molecular weight and chemical composition but different architecture. It was found that the effect of architecture is pronounced with these macromolecular isomers, which self-assemble into dramatically different surface aggregates. The linear block copolymer forms disklike surface assemblies over the range of compression states, while the linear-nanoparticle block copolymer exhibits long (> 10 μm) wormlike aggregates whose length increases as a function of increasing cross-linking density. It is shown that the driving force behind the morphological change is a combination of the altered molecular geometry and the restricted degree of stretching of the nanoparticle block because of the intramolecular cross-linking. A modified approach to interpret the π-A isotherm, which includes presence of the block copolymer aggregates, is also presented, while the surface rheological properties of the block copolymers at the air-water interface provide in-situ evidence of the aggregates' presence at the air-water interface. © 2005 American Chemical Society.
• Pyun, J., Tang, C., Kowalewski, T., M., J., & Hawker, C. J. (2005). Synthesis and direct visualization of block copolymers composed of different macromolecular architectures. Macromolecules, 38(7), 2674-2685.
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  Abstract: A novel approach toward the synthesis of block copolymers composed of architecturally different components, in this case, a nanoparticle covalently attached to a single linear coil is presented. By a synergistic combination of controlled radical polymerization, convergent dendrimer synthesis, and benzocyclobutene (BCB) cross-linking chemistry, strategies for the preparation of a variety of nanoparticle-coil copolymers were developed. Atomic force microscopy (AFM) was used to confirm the formation of architecturally differentiated block copolymers and enabled visualization of individual nanoparticles and their linear chain components for unambiguous characterization of the nanoparticle-coil structures. This confirmed the synthesis of the targeted nanostructure and revealed the dramatic effect that changes in macromolecular architecture can have on the morphology and assembly of these hybrid nanoparticle systems. © 2005 American Chemical Society.
• Peng, W. u., Feldman, A. K., Nugent, A. K., Hawker, C. J., Scheel, A., Voit, B., Pyun, J., M., J., Sharpless, K. B., & Fokin, V. V. (2004). Efficiency and fidelity in a click-chemistry route to triazole dendrimers by the copper(I)-catalyzed ligation of azides and alkynes. Angewandte Chemie - International Edition, 43(30), 3928-3932.
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  PMID: 15274216;Abstract: Components that click: A large number of diverse dendrimers (see scheme) was prepared in almost quantitative yield by the click-chemistry transformation described in the title. In some cases filtration or solvent extraction was the only method required for purification in this highly efficient construction of the triazole units of the dendrimers.
• Pyun, J., Jia, S., Kowalewski, T., & Matyjaszewski, K. (2004). Synthesis and surface attachment of ABC triblock copolymers containing glassy and rubbery segments. Macromolecular Chemistry and Physics, 205(4), 411-417.
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  Abstract: The synthesis of an ABC triblock copolymer containing glassy and rubbery segments was conducted using a combination of living anionic and atom transfer radical polymerizations (ATRP). A poly(dimethylsiloxane) (pDMS) macroinitiator (M̄nSEC = 6 200; M̄w/M̄ n = 1.19) was prepared by living anionic ring-opening polymerization, followed by hydrosilation reactions to incorporate 2-bromoisobutyrate end groups for initiation of ATRP. The ATRP of styrene (S) using the pDMS macroinitiator yielded a diblock copolymer (M̄nSEC = 66730; M̄w/M̄n = 1.38). Chain extension of the pDMS-b-pS macroinitiator with 3-(dimethoxymethylsilyl)propyl acrylate (DMSA) by ATRP yielded an ABC triblock copolymer. The latter reactive segment was covalently attached to silanol groups on a silicon wafer. The presentation of either glassy pS or flexible pDMS segments of the brushes attached to the surface was reversibly controlled by treatment with selective solvents for each segment.
• Pyun, J., Jia, S., Kowalewski, T., Patterson, G. D., & Matyjaszewski, K. (2003). Synthesis and characterization of organic/inorganic hybrid nanoparticles: Kinetics of surface-initiated atom transfer radical polymerization and morphology of hybrid nanoparticle ultrathin films. Macromolecules, 36(14), 5094-5104.
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  Abstract: The synthesis of hybrid nanoparticles was conducted by the atom transfer radical polymerization (ATRP) of styrene and (meth)acrylates from colloidal surfaces. Colloidal initiators were prepared by the functionalization of silica colloids with 2-bromoisobutyrate groups. ATRP from colloidal surfaces was then performed to attach well-defined homopolymers and block copolymers to an inorganic core. Kinetics of the ATRP of styrene (Sty), n-butyl acrylate (BA), and methyl methacrylate (MMA) under identical reaction conditions were investigated. Hybrid nanoparticles containing block copolymers of pSty6-pBA (Mn = 22 300; Mw/Mn = 1.20), pMMA-b-pBA (Mn = 29 400; Mw/Mn = 1.28), and pBA-b-pMMA (Mn = 17 300; Mw/Mn = 1.28) were prepared, and hydrolysis of silica cores by hydrofluoric acid treatment enabled characterization of cleaved copolymers using size exclusion chromatography and 1H NMR. Ultrathin films of hybrid nanoparticles were examined using transmission electron microscopy and atomic force microscopy.
• Pyun, J., Kowalewski, T., & Matyjaszewski, K. (2003). Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization. Macromolecular Rapid Communications, 24(18), 1043-1059.
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  Abstract: Atom transfer radical polymerization (ATRP) is a robust method for the preparation of (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization.
• Pyun, J., Matyjaszewski, K., Jian, W. u., Kim, G., Chun, S. B., & Mather, P. T. (2003). ABA triblock copolymers containing polyhedral oligomeric silsesquioxane pendant groups: Synthesis and unique properties. Polymer, 44(9), 2739-2750.
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  Abstract: The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly (3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.1 3,9.15,15.17,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP = 6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase- separated material exhibits a tensile modulus larger than expected (ca. 2 × 108 Pa) for a continuous rubber phase for temperatures between a pBA-related Tg and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the Tg of the higher Tg phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The Tg of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of Tg in this system. © 2003 Elsevier Science Ltd. All rights reserved.
• Pyun, J., Rees, I., Fréchet, J. M., & Hawker, C. J. (2003). Evaluating the effect of termination by chain-chain coupling in living free-radical polymerizations. Australian Journal of Chemistry, 56(8), 775-782.
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  Abstract: A novel approach based on the reaction of multifunctional star polymers with chromophore-labelled linear polymers is presented for evaluating the extent of termination by chain-chain coupling during living free-radical polymerizations. A mixed initiating system consisting of an unlabelled, multifunctional initiator and an excess of a monofunctional alkoxyamine initiator containing a chromophore, such as pyrene, is used to initiate the living polymerization of vinyl monomers leading to a mixture of star and linear polymers. The occurrence of chain-chain coupling is readily identified and quantified by isolating the star polymer that is obtained and elucidating the level of incorporation of pyrene units by UV/vis spectroscopy. This allows the level of chain-chain coupling to be determined since the inclusion of pyrene into the star structure is a direct result of termination by radical coupling.
• Pyun, J., Zhou, X., Drockenmuller, E., & Hawker, C. J. (2003). Macromolecules of controlled architecture. Journal of Materials Chemistry, 13(11), 2653-2660.
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  Abstract: The recent renaissance in polymer chemistry has resulted in the development of a wide variety of new living polymerisation procedures and the adoption of many synthetic concepts and strategies from organic chemistry, effectively blurring the distinction between organic chemistry and polymer chemistry. A central theme in all of this recent work is the desire to accurately control polymeric structure and functionality to a degree that has previously been solely the domain of natural systems. This has allowed researchers to synthesise a wide range of advanced macromolecular targets with control over shape, size and functional group placement that could not be achieved using traditional procedures and heralds a new era in synthetic polymer chemistry. The scope of this feature article is to provide an insight into the structural diversity that can be accomplished with these recently developed techniques, what challenges still exist and how these advances can impact other related fields in polymer physics and materials science.
• Qin, S., Saget, J., Pyun, J., Jia, S., Kowalewski, T., & Matyjaszewski, K. (2003). Synthesis of Block, Statistical, and Gradient Copolymers from Octadecyl (Meth)acrylates Using Atom Transfer Radical Polymerization. Macromolecules, 36(24), 8969-8977.
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  Abstract: The synthesis of well-defined homopolymers and random, block, and gradient copolymers from octadecyl acrylate (OA) and octadecyl methacrylate (OMA) using atom transfer radical polymerization (ATRP) is reported. Random copolymers were synthesized by the one-pot copolymerization of either tert-butyl acrylate/octadecyl acrylate (Mn,p(tBA-r-OA) = 13 680; M w/Mn = 1.13) or tert-butyl methacrylate/octadecyl methacrylate (Mn,p(tBMA-r-OMA) = 24 250; Mw/Mn = 1.14) monomer pairs. Additionally, gradient copolymers were prepared by the simultaneous copolymerization of either tert-butyl acrylate/octadecyl methacrylate (Mn,p(tBA-co-OMA)) = 21 790; Mw/M n = 1.25) or tert-butyl methacrylate/octadecyl acrylate (M n,p(tBMA-co-OA)) = 21 900; Mw/Mn = 1.20) monomer pairs. AB and ABA triblock copolymers containing octadecyl groups were also prepared with controlled molar mass and composition. The sequence of blocking was varied starting from either poly(tert-butyl (meth)acrylate) or poly(octadecyl (meth)acrylate) macroinitiators. The halogen-exchange technique allowed preparation of various well-defined polyacrylate-polymethacrylate block copolymers. Furthermore, uniform phase-separated structures were formed in ultrathin films cast from AB diblock copolymers of ptBMA-b-pOMA (Mn = 52 000; Mw/Mn = 1.12) and ptBA-b-pOMA (Mn = 28 750; Mw/Mn = 1.20) as determined from AFM. ABA triblock copolymers of pOMA-b-ptBA-b-pOMA (Mn = 75 900; M w/Mn = 1.14) and poly(octadecyl methacrylate)-block-poly(n-butyl acrylate)-block-poly-(octadecyl methacrylate) (Mn = 74 400; Mw/Mn = 1.16) were also analyzed using AFM.
• Matyjaszewski, K., Saget, J., Pyun, J., Schlögl, M., & Rieger, B. (2002). Synthesis of polypropylene-poly(meth)acrylate block copolymers using metallocene catalyzed processes and subsequent atom transfer radical polymerization. Journal of Macromolecular Science - Pure and Applied Chemistry, 39 A(9), 901-913.
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  Abstract: The synthesis of block copolymers containing low molar mass polypropylene and poly(meth)acrylates is reported. Vinyl-terminated polypropylene (MnSEC = 3,100; Mw/Mn = 1.45) was used to prepare a macroinitiator for atom transfer radical polymerization (ATRP) via hydrosilation with 1-(2-bromoisobutyryloxy)propyl-tetramethyldisiloxane. Polar segments were then incorporated to polypropylene by chain extension using either methyl methacrylate, or n-butyl acrylate. While blocking efficiency was limited in this system, well-defined PP-b-PMMA (Mn = 22,220; Mw/Mn = 1.14) was obtained by extraction of unreacted polypropylene with diethyl ether.
• Savin, D. A., Pyun, J., Patterson, G. D., Kowalewski, T., & Matyjaszewski, K. (2002). Synthesis and characterization of silica-graft-polystyrene hybrid nanoparticles: Effect of constraint on the glass-transition temperature of spherical polymer brushes. Journal of Polymer Science, Part B: Polymer Physics, 40(23), 2667-2676.
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  Abstract: The effect of the chain constraint on the glass-transition temperature of polystyrene (pS) was studied in the context of polymer tethering to curved surfaces. The synthesis and characterization of silica-graft-polystyrene (SiO2-g-pS) hybrid nanoparticles is reported. Silica nanoparticles possessing covalently bound pS chains were prepared by the atom transfer radical polymerization of styrene from functionalized colloidal surfaces. These hybrid nanoparticles serve as interesting examples of spherical polymer brushes, as a high density of grafted pS was achieved on the inorganic colloid. The confirmation of a brushlike extension of immobilized chains in a good solvent was obtained with dynamic light scattering in toluene of SiO2-g-pS colloids possessing various molar masses of tethered pS. The solid-state morphology of SiO2-g-pS ultrathin films was assessed with transmission electron microscopy, and this confirmed that the silica colloids were well-dispersed in a matrix of the tethered polymer. Differential scanning calorimetry was used to study the effects of tethering and chain immobilization on the glass-transition temperature of pS. The measured glass-transition temperature of annealed bulk films of the hybrid nanoparticles was elevated with respect to the value for pure bulk pS. The enhancements ranged from 13 to 2 K for SiO2-g-pS brushes possessing tethered pS with number-average molecular weights of 5230 and 32,670 g/mol, respectively. © 2002 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 40.
• Coessens, V., Pyun, J., Miller, P. J., Gaynor, S. G., & Matyjaszewski, K. (2000). Functionalization of polymers prepared by ATRP using radical addition reactions. Macromolecular Rapid Communications, 21(2), 103-109.
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  Abstract: Low molecular weight linear poly(methyl acrylate), star and hyperbranched polymers were synthesized using atom transfer radical polymerization (ATRP) and end-functionalized using radical addition reactions. By adding allyltri-n-butylstannane at the end of the polymerization of poly(methyl acrylate), the polymer was terminated by allyl groups. When at high conversions of the acrylate monomer, allyl alcohol or 1,2-epoxy-5-hexene, monomers which are not polymerizable by ATRP, were added, alcohol and epoxy functionalities respectively were incorporated at the polymer chain end. Functionalization by radical addition reactions was demonstrated to be applicable to multi-functional polymers such as hyperbranched and star polymers. © WILEY-VCH Verlag GmbH, 2000.
• Mather, P. T., Chun, S. B., Pyun, J., Matyjaszewski, K., & Jeon, H. G. (2000). Synthesis and microstructural characterization of POSS-based triblock copolymers prepared using atom transfer radical polymerization. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 582-583.
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  Abstract: A polyhedral silsesquioxane (POSS)-methacrylate and poly(n-butyl acrylate) triblock copolymer (poly(MA-POSS)-b-BA-b-(MA-POSS)) prepared by atom transfer radical polymerization (ATRP) were synthesized and characterized. The molecular weight and composition of the triblock copolymer was determined from size exclusion chromatography and H NMR spectroscopy. The study aims to develop an understanding of the thermoplastic elastomeric properties as influenced by hard-block interactions and nanometer-scale organization in the materials.
• Pyun, J., & Matyjaszewski, K. (2000). Synthesis of hybrid polymers using atom transfer radical polymerization: Homopolymers and block copolymers from polyhedral oligomeric silsesquioxane monomers. Macromolecules, 33(1), 217-220.
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  Abstract: The use of atom transfer radical polymerization (ATRP) of methacrylate functional polyhedral oligomeric silsesquioxanes (POSS) monomers is described to synthesize hybrid homopolymers and block copolymers. From this approach, homopolymers, triblock copolymers, and star-block copolymers containing POSS was prepared. While polymers containing POSS were made by other methods, using ATRP, hybrid-POSS polymers with previously unattainable compositions and drastically lower polydispersities were synthesized.
• Pyun, J., Miller, P. J., & Matyjaszewski, K. (2000). Synthesis of organic/inorganic hybrid materials using atom transfer radical polymerization. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 536-537.
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  Abstract: Atom transfer radical polymerization (ATRP), using inorganic macroinitiators or monomers is a versatile method to prepare organic/inorganic hybrid materials. ATRP was used to synthesize a variety of well-defined (co)polymers from acrylates, methacrylates and styrenes. Due to its radical nature, a wide range of monomers and polymers can be employed, provided that interaction with the catalyst is avoided. By incorporating an activated alkyl halide group into the targeted inorganic polymer or substrate, poly(dimethylsiloxane) and silicon wafers, functionalized with initiator groups, was used as initiator for ATRP. Similarly, polyhedral oligomeric silsesquioxane monomers were used to prepare hybrid materials by ATRP.
• Matyjaszewski, K., Miller, P. J., Pyun, J., Kickelbick, G., & Diamanti, S. (1999). Synthesis and characterization of star polymers with varying arm number, length, and composition from organic and hybrid inorganic/ organic multifunctional initiators. Macromolecules, 32(20), 6526-6535.
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  Abstract: Multifunctional initiators, derived from cyclotriphosphazenes, cyclosiloxanes, and organic polyols, were used in the synthesis of styrenic and (meth)acrylic star polymers by atom transfer radical polymerization (ATRP). Conditions were identified in each system which provided linear first-order kinetics for polymers with narrow, monomodal molecular weight distributions. Molecular weight measurements relative to linear polystyrene standards showed that the star polymers had lower molecular weights than theoretically predicted. Triple detection SEC measured on poly(n-butyl acrylate) samples demonstrated that the absolute molecular weight matched the theoretical value-the smaller relative chain length was due to lower hydrodynamic volumes of the star-branched polymers relative to linear analogues. Kinetic arguments were used to demonstrate that each alkyl halide moiety bound to the initiators was participating in ATRP. Well-defined poly(methyl acrylate) stars of molecular weights Mn > 500 000 and low polydispersity (Mw/Afn < 1.2) have been prepared. Star-block copolymers with a soft poly(methyl acrylate) core and a hard poly(isobornyl acrylate) shell were also synthesized. © 1999 American Chemical Society.
• Miller, P. J., Matyjaszewski, K., Pyun, J., Kickelbick, G., & Diamanti, S. (1999). Synthesis of well-defined star polymers by atom transfer radical polymerization using the core-first approach. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 40(2), 424-425.
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  Abstract: Initiators with functionality from 2 to 6 were synthesized from a variety of organic and inorganic precursors. The atom transfer radical polymerization (ATRP) of styrene, acrylates and methacrylates proceeded in a controlled fashion under a variety of conditions providing well-defined star polymers with molecular weights reaching 500,000 as well as star block copolymers. For butyl acrylate polymerizations from initiators containing 2-bromopropionate groups, kinetic arguments were used to demonstrate that initiation was efficient regardless of the initiator functionality. Triple detection size exclusion chromatography also confirmed that target molecular weights could be obtained in butyl acrylate polymerizations.
• Pyun, J., Miller, P. J., Kickelbick, G., Matyjaszewski, K., Schwab, J., & Lichtenhan, J. (1999). Synthesis of organic/inorganic hybrid materials from polysiloxane precursors using atom transfer radical polymerization. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 40(2), 454-455.
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  Abstract: Hybrid materials from polyhedral oligomeric silsesquioxane (POSS) monomers, using atom transfer radical polymerization (ATRP), were prepared. Well-defined homopolymers, random and block copolymers from controlled radical polymerization, were synthesized.
• Pyun, J., Zhang, X., Nor, S. G., & Matyjaszewski, K. (1999). The synthesis of multifunctional star and hyperbranched polymers using atom transfer radical polymerization and atom transfer radical addition. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 40(2), 452-453.
• Matyjaszewski, K., Pyun, J., & Gaynor, S. G. (1998). Preparation of hyperbranched polyacrylates by atom transfer radical polymerization, 4: The use of zero-valent copper. Macromolecular Rapid Communications, 19(12), 665-670.
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  Abstract: The addition of zero-valent copper to the self-condensing vinyl polymerization (SCVP) of novel AB* (meth)acrylic monomers using atom transfer radical polymerization (ATRP) catalyst systems has allowed for their successful polymerization. Polymerization under homogeneous and heterogeneous catalyst conditions without additional Cu(0) were unsuccessful. The catalyst system that was designed comprised of Cu(I) bromide, 4,4‰-bis(5-nonyl)-2,2‰-bipyridine, and Cu(0) metal (powder or turning). From 1H NMR spectroscopy, the degree of branching was estimated for the acrylic polymers, DB = 0.48. The degree of branching could not be determined for methacrylates by this method due to overlapping signals in the 1H NMR spectra.

Presentations

• Pyun, D. (2017, April 2017). From polymers to particles and back to polymers. American Chemical Society National Meeting. San Francisco, CA: ACS Division of PMSE.
• Pyun, D. (2017, April). Gram-scale synthesis of magnetic-semiconductor Janus nanoparticles: Ramifications for colloidal polymers. American Chemical Society National Meeting. San Francisco, CA: ACS Division of PMSE.
• Pyun, D. (2017, April). Polymerizations with elemental sulfur: Sustainable fossil fuel chemistry. American Chemical Society National Meeting. San Francisco, CA: ACS Division of POLY.
• Pyun, D. (2017, April). Polymerizing Goblins and Brimstone for Energy, Sustainability and Defense. Invited Colloquium. San Luis Obispo: CAL POLY, San Luis Obispo, Department of Chemistry.
• Pyun, D. (2017, August). Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs): A New Class of Materials for Mid-IR Imaging. American Chemical Society National Meeting. Washington, D.C.: ACS Division of POLY.
• Pyun, D. (2017, August). Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs): New Chemistry & Applications for Vulcanization. American Chemical Society National Meeting. Washington, D.C.: ACS Division of POLY.
• Pyun, D. (2017, August). Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs): New Chemistry & Applications for Vulcanization. invited seminar. Daejeon, Korea: Kumho Petrochemicals, Co..
• Pyun, D. (2017, August). Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs): New Chemistry & Applications for Vulcanization. invited seminar. Seoul, Korea: School of Chemical & Biological Engineering, Seoul National University.
• Pyun, D. (2017, August). Dynamic Covalent Polymers from Elemental Sulfur. American Chemical Society National Meeting. Washington, D.C.: ACS Division of PMSE.
• Pyun, D. (2017, August). Fe and CHIPs: New Applications for Controlled Radical Polymerizations in Energy and Optics. invited seminar. Daejeon, Korea: Department of Chemistry, KAIST.
• Pyun, D. (2017, August). From Garbage to Plastics and Beyond: Polymerizations with Elemental Sulfur. invited seminar. Seoul: Department of Chemical Engineering, Seoul Tech.
• Pyun, D. (2017, August). Photoresponisve Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs) via controlled radical polymerization for integrated optics. American Chemical Society National Meeting. Washington, D.C.: ACS Division of POLY.
• Pyun, D. (2017, August). [Fe-Fe] Hydrogenase Mimetic Metallopolymers from ATRP with Long-Lived Electrocatalytic Activity. American Chemical Society National Meeting. Washington, D.C.: ACS Division of POLY.
• Pyun, D. (2017, December). Dancing in the Dark with Se and S. 15th Pacific Polymer Conference. Xiamen, China: Pacific Polymer Society.
• Pyun, D. (2017, January 2017). Polymerizations with Elemental Sulfur. Macro 2017. Kerala, India: Society for Polymer Science, India.
• Pyun, D. (2017, January). From Garbage to Plastics and Beyond. Department of Materials Science & Engineering, Colloquium, University of Washington. Seattle, WA: Department of Materials Science & Engineering, University of Washington.
• Pyun, D. (2017, January). Sulfur Based Polymers for Next Generation IR Optics. invited seminar. Daejeon, Korea: ChemOptics.
• Pyun, D. (2017, July). Fe and CHIPs: New Applications for Controlled Radical Polymerizations in Energy and Optics. Invited Seminar. Busan, Korea: Department of Polymer Science & Engineering, Pusan National University.
• Pyun, D. (2017, July). Fe and CHIPs: New Applications for Controlled Radical Polymerizations in Energy and Optics. invited seminar. Incheon, Korea: Department of Chemical Engineering, Inha University.
• Pyun, D. (2017, May). Dancing in the Dark with S and Se: Next Generation IR Optical Polymers for IR Thermal Imaging. 12th International Conference on Advanced Polymers Macromolecular Engineering. Ghent, Belgium: IUPAC, Belgium Polymer Group.
• Pyun, D. (2017, May). High Refractive Index Sulfur Copolymers for Short Wave and Mid-Wave Infrared Optics and Photonics. AFOSR Program Review. Arlington, VA: AFOSR.
• Pyun, D. (2017, October). Dancing in the Dark with S and Se: Next Generation IR Optical Polymers for IR Thermal Imaging. IUPAC Federation of Asian Polymer Societies 2017 Polymer Congress. Jeju, Korea: IUPAC & Federation of Asian Polymer Societies.
• Pyun, D. (2017, October). Goblins, Brimstone and CHIPs: Unconventional Polymers for Energy, Defense and Sustainability. invited colloquium. Stony Brook, NY: Department of Chemistry, SUNY Stony Brook.
• Pyun, D., & Pyun, D. (2017, July). Goblins, Brimstone and CHIPs: Unconventional Polymers for Energy, Defense and Sustainability. invited seminar. Seoul, Korea: Department of Nanoscience & Engineering, Sejong University.
• Pyun, D. (2004, 2004-present). List of J-Pyun Technical Presentations since 2004. both invited and contributed talks.