Bio


Do Y. Yoon is Adjunct Professor of Chemical Engineering at Stanford University since 2012. He obtained his B.S. in Chemical Engineering from Seoul National University, South Korea (1969), and earned his Ph.D. in Polymer Science and Engineering from University of Massachusetts Amherst, working with Richard S. Stein (1973). He did his postdoctoral study with Paul J. Flory in Chemistry Department of Stanford University (1973-1975). He then worked in IBM Research Laboratory in San Jose, California as Research Staff Member and Manager of Polymer Physics Group (1975-1999). From 1999 to 2012, he was Professor of Chemistry at Seoul National University, South Korea. He was also visiting professor at Max Planck Institute for Polymer Research in Germany (2000–2006) and National Institute of Standards and Technology in U.S. (2006–2012). He published about 260 research papers with h-index of 69 and about 16,000 citations, was elected a fellow of American Physical Society (1985), and received a Senior Humboldt Research Award (1999). His research areas included molecular conformations & dynamics, semicrystalline morphology, liquid crystalline state, surface and thin film characteristics of polymers, and structure-property relationships of polymers for information technology, organic electronics, and clean energy. He is a co-editor of "Selected Works of Paul J. Flory" and "Monte Carlo & Molecular Dynamics Simulations of Polymers," and a co-author of "Paul John Flory: A Life of Science and Friends."

Academic Appointments


Administrative Appointments


  • See the CV, IBM Research Division (1978 - Present)

Honors & Awards


  • See the CV, Alexander Humboldt Foundation

Current Research and Scholarly Interests


See the CV with publication list

2019-20 Courses


All Publications


  • Interface Characteristics of Neat Melts and Binary Mixtures of Polyethylenes from Atomistic Molecular Dynamics Simulations. Polymers Lee, S., Frank, C. W., Yoon, D. Y. 2020; 12 (5)

    Abstract

    Molecular dynamics simulations of free-standing thin films of neat melts of polyethylene (PE) chains up to C150H302 and their binary mixtures with n-C13H28 are performed employing a united atom model. We estimate the surface tension values of PE melts from the atomic virial tensor over a range of temperatures, which are in good agreement with experimental results. Compared with short n-alkane systems, there is an enhanced surface segregation of methyl chain ends in longer PE chains. Moreover, the methyl groups become more segregated in the surface region with decreasing temperature, leading to the conclusion that the surface-segregation of methyl chain ends mainly arises from the enthalpic origin attributed to the lower cohesive energy density of terminal methyl groups. In the mixtures of two different chain lengths, the shorter chains are more likely to be found in the surface region, and this molecular segregation in moderately asymmetric mixtures in the chain length (C13H28 + C44H90) is dominated by the enthalpic effect of methyl chain ends. Such molecular segregation is further enhanced and dominated by the entropic effect of conformational constraints in the surface for the highly asymmetric mixtures containing long polymer chains (C13H28 + C150H3020). The estimated surface tension values of the mixtures are consistent with the observed molecular segregation characteristics. Despite this molecular segregation, the normalized density of methyl chain ends of the longer chain is more strongly enhanced, as compared with the all-segment density of the longer chain itself, in the surface region of melt mixtures. In addition, the molecular segregation results in higher order parameter of the shorter-chain segments at the surface and deeper persistence of surface-induced segmental order into the film for the longer chains, as compared with those in neat melt films.

    View details for DOI 10.3390/polym12051059

    View details for PubMedID 32384644

  • Statistical mechanics of chain molecules in nematic melts of semiflexible polymers and thin polymer films Yoon, D. AMER CHEMICAL SOC. 2019
  • Polyimide-PEG Segmented Block Copolymer Membranes with High Proton Conductivity by Improving Bicontinuous Nanostructure of Ionic Liquid-Doped Films MACROMOLECULAR CHEMISTRY AND PHYSICS Woo, E., Coletta, E., Holm, A., Mun, J., Toney, M. F., Yoon, D. Y., Frank, C. W. 2019; 220 (9)
  • Paul Flory's legacy in polymer science Yoon, D. AMER CHEMICAL SOC. 2018
  • Interfacial and topological effects on the glass transition in free-standing polystyrene films JOURNAL OF CHEMICAL PHYSICS Lyulin, A. V., Balabaev, N. K., Baljon, A. R., Mendoza, G., Frank, C. W., Yoon, D. Y. 2017; 146 (20)

    Abstract

    United-atom molecular-dynamics computer simulations of atactic polystyrene (PS) were performed for the bulk and free-standing films of 2 nm-20 nm thickness, for both linear and cyclic polymers comprised of 80 monomers. Simulated volumetric glass-transition temperatures (Tg) show a strong dependence on the film thickness below 10 nm. The glass-transition temperature of linear PS is 13% lower than that of the bulk for 2.5 nm-thick films, as compared to less than 1% lower for 20 nm films. Our studies reveal that the fraction of the chain-end groups is larger in the interfacial layer with its outermost region approximately 1 nm below the surface than it is in the bulk. The enhanced population of the end groups is expected to result in a more mobile interfacial layer and the consequent dependence of Tg on the film thickness. In addition, the simulations show an enrichment of backbone aliphatic carbons and concomitant deficit of phenyl aromatic carbons in the interfacial film layer. This deficit would weaken the strong phenyl-phenyl aromatic (π-π) interactions and, hence, lead to a lower film-averaged Tg in thin films, as compared to the bulk sample. To investigate the relative importance of the two possible mechanisms (increased chain ends at the surface or weakened π-π interactions in the interfacial region), the data for linear PS are compared with those for cyclic PS. For the cyclic PS, the reduction of the glass-transition temperature is also significant in thin films, albeit not as much as for linear PS. Moreover, the deficit of phenyl carbons in the film interface is comparable to that observed for linear PS. Therefore, chain-end effects alone cannot explain the observed pronounced Tg dependence on the thickness of thin PS films; the weakened phenyl-phenyl interactions in the interfacial region seems to be an important cause as well.

    View details for DOI 10.1063/1.4977042

    View details for Web of Science ID 000401778900016

    View details for PubMedID 28571360

  • Interface characteristics of polystyrene melts in free-standing thin films and on graphite surface from molecular dynamics simulations POLYMER Lee, S., Lyulin, A. V., Frank, C. W., Yoon, D. Y. 2017; 116: 540-548
  • Effects of molecular topology and interface on conformations and dynamics of polymer melts from atomistic molecular dynamics simulations Yoon, D. AMER CHEMICAL SOC. 2017
  • Enhanced ionic conductivity of peg-containing polyimide/ionic liquid membrane upon thermal annealing Frank, C., Woo, E., Lu, J., Coletta, E., Mun, J., Spakowitz, A., Yoon, D., Toney, M. AMER CHEMICAL SOC. 2017
  • Morphology studies of contact optimization in organic electronic devices Richter, L., DeLongchamp, D., Briseno, A., Lee, H., McNeill, C., Gann, E., Yoon, D., Shinn, N. AMER CHEMICAL SOC. 2016
  • Temperature dependence of surface reorganization characteristics of amphiphilic block copolymer in air and in water studied by scanning force microscopy JOURNAL OF PLASTIC FILM & SHEETING Lee, S., Flores, S. M., Berger, R., Gutmann, J. S., Brehmer, M., Conrad, L., Funk, L., Theato, P., Yoon, D. Y. 2015; 31 (4): 434-448
  • Organosilicate polymer e-beam resists with high resolution, sensitivity and stability APPLIED ORGANOMETALLIC CHEMISTRY Lee, S., Sim, J. H., Lee, H., Kasica, R., Kim, H., Soles, C. L., Kim, K., Yoon, D. Y. 2013; 27 (11): 644-651

    View details for DOI 10.1002/aoc.2985

    View details for Web of Science ID 000326332800006

  • Concentration Dependence of Ring Polymer Conformations from Monte Carlo Simulations ACS MACRO LETTERS Reigh, S. Y., Yoon, D. Y. 2013; 2 (4): 296-300

    View details for DOI 10.1021/mz300587v

    View details for Web of Science ID 000317813200004

  • Vertically Segregated Structure and Properties of Small Molecule-Polymer Blend Semiconductors for Organic Thin-Film Transistors ADVANCED FUNCTIONAL MATERIALS Shin, N., Kang, J., Richter, L. J., Prabhu, V. M., Kline, R., Fischer, D. A., DeLongchamp, D. M., Toney, M. F., Satija, S. K., Gundlach, D. J., Purushothaman, B., Anthony, J. E., Yoon, D. Y. 2013; 23 (3): 366–76
  • Hole Injection/Transport Materials Derived from Heck and Sol-Gel Chemistry for Application in Solution-Processed Organic Electronic Devices JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Lim, Y., Park, Y., Kang, Y., Jang, D., Kim, J., Kim, J., Sellinger, A., Yoon, D. Y. 2011; 133 (5): 1375–82

    Abstract

    An organosilicate polymer, based on N,N'-diphenyl-N,N'-bis(4-((E)-2-(triethoxysilyl)vinyl)phenyl)biphenyl-4,4'-diamine (TEVS-TPD) with extended conjugation between the Si atom and the aromatic amine, was prepared under mild conditions via sequential Heck and sol-gel chemistry and used as an alternative to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the most widely used planarizing hole injection/transport layer in solution-processed organic electronic devices. Spin-coating TEVS-TPD polymer solutions yield defect-free, uniform, thin films with excellent adhesion to the ITO electrode. Upon thermal cross-linking at 180 °C, the cross-linked polymer exhibits excellent solvent resistance and electrochemical stability. Solution-processed organic light emitting diode (OLED) devices using iridium-based triplet emitting layers and cross-linked TEVS-TPD films as a hole injection/transport layer show significantly improved performance including lower leakage current, lower turn-on voltage, higher luminance, and stability at high current density, as compared to the control device prepared with PEDOT:PSS.

    View details for DOI 10.1021/ja1061517

    View details for Web of Science ID 000287228500053

    View details for PubMedID 21192680

  • Zone-Refinement Effect in Small Molecule-Polymer Blend Semiconductors for Organic Thin-Film Transistors JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chung, Y. S., Shin, N., Kang, J., Jo, Y., Prabhu, V. M., Satija, S. K., Kline, R. J., Delongchamp, D. M., Toney, M. F., Loth, M. A., Purushothaman, B., Anthony, J. E., Yoon, D. Y. 2011; 133 (3): 412-415

    Abstract

    The blend films of small-molecule semiconductors with insulating polymers exhibit not only excellent solution processability but also superior performance characteristics in organic thin-film transistors (OTFTs) over those of neat small-molecule semiconductors. To understand the underlying mechanism, we studied triethylsilylethynyl anthradithiophene (TESADT) with small amounts of impurity formed by weak UV exposure. OTFTs with neat impure TESADT had drastically reduced field-effect mobility (<10(-5) cm(2)/(V s)), and a disappearance of the high-temperature crystal phase was observed for neat impure TESADT. However, the mobility of the blend films of the UV-exposed TESADT with poly(α-methylstyrene) (PαMS) is recovered to that of a fresh TESADT-PαMS blend (0.040 cm(2)/(V s)), and the phase transition characteristics partly return to those of fresh TESADT films. These results are corroborated by OTFT results on "aged" TIPS-pentacene. These observations, coupled with the results of neutron reflectivity study, indicate that the formation of a vertically phase-separated layer of crystalline small-molecule semiconductors allows the impurity species to remain preferentially in the adjacent polymer-rich layer. Such a "zone-refinement effect" in blend semiconductors effectively removes the impurity species that are detrimental to organic electronic devices from the critical charge-transporting interface region.

    View details for DOI 10.1021/ja108772q

    View details for Web of Science ID 000287553000008

    View details for PubMedID 21155572

  • Surface reorganization of an amphiphilic block copolymer film studied by NEXAFS spectroscopy MACROMOLECULES Theato, P., Brehmer, M., Conrad, L., Frank, C. W., Funk, L., Yoon, D. Y., Luning, J. 2006; 39 (7): 2592-2595

    View details for DOI 10.1021/ma0509964

    View details for Web of Science ID 000236574400026

  • Correlation of surface and bulk order in low surface energy polymers MACROMOLECULES Luning, J., Stohr, J., Song, K. Y., Hawker, C. J., Iodice, P., Nguyen, C. V., Yoon, D. Y. 2001; 34 (5): 1128-1130

    View details for DOI 10.1021/ma0001584

    View details for Web of Science ID 000167136000002

  • Dynamic light scattering studies of cholesteric and polymer-stabilized cholesteric liquid crystals PHYSICAL REVIEW E Borsali, R., Schroeder, U. P., Yoon, D. Y., Pecora, R. 1998; 58 (3): R2717-R2720
  • Determination of splay and twist relaxation modes in nematic liquid crystals from dynamic light scattering experiments JOURNAL OF PHYSICAL CHEMISTRY B Borsali, R., Yoon, D. Y., Pecora, R. 1998; 102 (33): 6337-6341
  • THE INTERPHASE IN LAMELLAR SEMICRYSTALLINE POLYMERS MACROMOLECULES FLORY, P. J., Yoon, D. Y., DILL, K. A. 1984; 17 (4): 862-868
  • AMORPHOUS POLYMERS - GENERAL DISCUSSION FARADAY DISCUSSIONS DILL, K. A., Frank, F. C., SADLER, D. M., DIMARZIO, E. A., GUTTMAN, C. M., Hoffman, J. D., FLORY, P. J., Yoon, D. Y., Dowell, F., Stein, R. S., SAMULSKI, E. T., Windle, A. H., EVERETT, D. H., Rigby, D., STEPTO, R. F., Pechhold, W., FISCHER, E. W., Lovell, R., Mitchell, G. R., ATKINS, E. D., Mandelkern, L., Keller, A., WARD, I. M., UHLMANN, D. R., Champion, J. V., Waring, R., Thomas, E. L., VESELY, D., GRUBB, D. T., FRANK, W. F., Blundell, D. J., Stamm, M., VANDERSANDE, J. B., Stevens, G. C. 1979; 68: 104-?
  • MOLECULAR MORPHOLOGY IN SEMI-CRYSTALLINE POLYMERS NATURE FLORY, P. J., Yoon, D. Y. 1978; 272 (5650): 226-229
  • ANALYSIS OF NUCLEAR MAGNETIC-RESONANCE SPECTRA OF PROTONS IN PREDOMINANTLY ISOTACTIC POLYSTYRENE MACROMOLECULES Yoon, D. Y., FLORY, P. J. 1977; 10 (3): 562-566
  • PERSISTENCE VECTORS FOR POLYPROPYLENE, POLYSTYRENE, AND POLY(METHYL METHACRYLATE) CHAINS JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS Yoon, D. Y., FLORY, P. J. 1976; 14 (8): 1425-1431
  • SMALL-ANGLE NEUTRON AND X-RAY-SCATTERING BY POLY(METHYL METHACRYLATE) CHAINS .2. MACROMOLECULES Yoon, D. Y., FLORY, P. J. 1976; 9 (2): 299-303
  • SMALL-ANGLE X-RAY AND NEUTRON-SCATTERING BY POLYMETHYLENE, POLYOXYETHYLENE, AND POLYSTYRENE CHAINS MACROMOLECULES Yoon, D. Y., FLORY, P. J. 1976; 9 (2): 294-299
  • SMALL-ANGLE NEUTRON AND X-RAY-SCATTERING BY POLY(METHYL METHACRYLATE) CHAINS POLYMER Yoon, D. Y., FLORY, P. J. 1975; 16 (9): 645-648
  • CONFORMATIONAL CHARACTERISTICS OF POLY(METHYL ACRYLATE) MACROMOLECULES Yoon, D. Y., Suter, U. W., Sundararajan, P. R., FLORY, P. J. 1975; 8 (6): 784-789
  • CONFORMATIONAL CHARACTERISTICS OF POLYSTYRENE MACROMOLECULES Yoon, D. Y., Sundararajan, P. R., FLORY, P. J. 1975; 8 (6): 776-783
  • MOMENTS AND DISTRIBUTION FUNCTIONS FOR POLYMER-CHAINS OF FINITE LENGTH .2. POLYMETHYLENE CHAINS JOURNAL OF CHEMICAL PHYSICS Yoon, D. Y., FLORY, P. J. 1974; 61 (12): 5366-5380
  • MOMENTS AND DISTRIBUTION FUNCTIONS FOR POLYMER-CHAINS OF FINITE LENGTH .1. THEORY JOURNAL OF CHEMICAL PHYSICS FLORY, P. J., Yoon, D. Y. 1974; 61 (12): 5358-5365