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412 results on '"Bock, Harald"'

1. Using 4D STEM to probe mesoscale order in molecular glass films prepared by physical vapor deposition

Author

Chatterjee, Debaditya, Huang, Shuoyuan, Gu, Kaichen, Ju, Jianzhu, Yu, Junguang, Bock, Harald, Yu, Lian, Ediger, M. D., and Voyles, Paul M.

Subjects
Condensed Matter - Materials Science
Abstract

Physical vapor deposition can be used to prepare highly stable organic glass systems where the molecules show orientational and translational ordering at the nanoscale. We have used low-dose four-dimensional scanning transmission electron microscopy (4D STEM), enabled by a fast direct electron detector, to map columnar order in glassy samples of a discotic mesogen using a 2 nm probe. Both vapor deposited and liquid cooled glassy films show domains of similar orientation, but their size varies from tens to hundreds of nanometers, depending on processing. Domain sizes are consistent with surface diffusion mediated ordering during film deposition. These results demonstrate the ability of low-dose 4D STEM to characterize mesoscale structure in a molecular glass system which may be relevant to organic electronics.

Published
2023
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3. Vapor-to-glass preparation of biaxially aligned organic semiconductors.

Author

Ju, Jianzhu, Chatterjee, Debaditya, Voyles, Paul M., Bock, Harald, and Ediger, Mark D.

Subjects
ORGANIC semiconductors, PHYSICAL vapor deposition, GLASS transition temperature, MOLECULAR orientation, EMISSION control
Abstract

Physical vapor deposition (PVD) provides a route to prepare highly stable and anisotropic organic glasses that are utilized in multi-layer structures such as organic light-emitting devices. While previous work has demonstrated that anisotropic glasses with uniaxial symmetry can be prepared by PVD, here, we prepare biaxially aligned glasses in which molecular orientation has a preferred in-plane direction. With the collective effect of the surface equilibration mechanism and template growth on an aligned substrate, macroscopic biaxial alignment is achieved in depositions as much as 180 K below the clearing point TLC−iso (and 50 K below the glass transition temperature Tg) with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The preparation of biaxially aligned organic semiconductors adds a new dimension of structural control for vapor-deposited glasses and may enable polarized emission and in-plane control of charge mobility. [ABSTRACT FROM AUTHOR]

Published
2023
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5. System Innovations in Inter Data Center Transport Networks

Author

Paraschis, Loukas, Bock, Harald, Kandappan, Parthiban, Sommerkorn-Krombholz, Bernd, Pedro, Joao, Sadasivarao, Abhinava, Syed, Sharfuddin, Rahn, Jeff, Doolan, Paul, Lu, Biao, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Tzanakaki, Anna, editor, Varvarigos, Manos, editor, Muñoz, Raul, editor, Nejabati, Reza, editor, Yoshikane, Noboru, editor, Anastasopoulos, Markos, editor, and Marquez-Barja, Johann, editor

Published
2020
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6. Nanoscale View of Alignment and Domain Growth in a Hexagonal Columnar Liquid Crystal

Author

Huang, Shuoyuan, Cheng, Shinian, Ju, Jianzhu, Chatterjee, Debaditya, Yu, Junguang, Bock, Harald, Yu, Lian, Ediger, Mark D., and Voyles, Paul M.

Abstract

Highly ordered liquid crystalline (LC) phases have important potential for organic electronics. We studied the molecular alignment and domain structure in a columnar LC thin film with nanometer resolution during in situ heating using four-dimensional scanning transmission electron microscopy (4D STEM). The initial disordered vapor-deposited LC glass thin film rapidly ordered at its glass transition temperature into a hexagonal columnar phase with small (<10 nm), well-aligned, planar domains (columns oriented parallel to the surface). Upon further heating, the domains coarsen via bulk diffusion, then the film crystallizes, then finally transforms back to an LC phase at an even higher temperature. The LC phase at high temperature shows straight columns of molecules, which we attribute to structure inherited from the intermediate crystalline phase. Nanoscale 4D STEM offers direct insight into the mechanisms of domain reorganization, and intermediate crystallization is a potential approach to manipulate orientational order and texture at the nano- to mesoscale in LC thin films.

Published
2024
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7. Thermotropic Orientational Order of Discotic Liquid Crystals in Nanochannels: An Optical Polarimetry Study and a Landau-de Gennes Analysis

Author

Kityk, Andriy V., Busch, Mark, Rau, Daniel, Calus, Sylwia, Cerclier, Carole V., Lefort, Ronan, Morineau, Denis, Bock, Harald, Grelet, Eric, Krause, Christina, Schoenhals, Andreas, Frick, Bernhard, and Huber, Patrick

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Optical polarimetry measurements of the orientational order of a discotic liquid crystal based on a pyrene derivative and confined in parallel-aligned nanochannels of monolithic mesoporous alumina, silica, and silicon as a function of temperature, channel radius (3 - 22 nm) and surface chemistry reveal a competition of radial and axial columnar order. The evolution of the orientational order parameter of the confined systems is continuous, in contrast to the discontinuous transition in the bulk. For channel radii larger than 10 nm we suggest several, alternative defect structures, which are compatible both with the optical experiments on the collective molecular orientation presented here and with a translational, radial columnar order reported in previous diffraction studies. For smaller channel radii our observations can semi-quantitatively be described by a Landau-de Gennes model with a nematic shell of radially ordered columns (affected by elastic splay deformations) that coexists with an orientationally disordered, isotropic core. For these structures, the cylindrical phase boundaries are predicted to move from the channel walls to the channel centres upon cooling, and vice-versa upon heating, in accord with the pronounced cooling/heating hystereses observed and the scaling behavior of the transition temperatures with channel diameter. The absence of experimental hints of a paranematic state is consistent with a biquadratic coupling of the splay deformations to the order parameter., Comment: 14 pages, 8 figures

Published
2015
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8. Engineering the glass structure of a discotic liquid crystal by multiple kinetic arrests.

Author

Yu, Junguang, Chen, Zhenxuan, Fatina, Caroline, Chatterjee, Debaditya, Bock, Harald, Richert, Ranko, Voyles, Paul, Ediger, M. D., and Yu, Lian

Subjects
DISCOTIC liquid crystals, GLASS structure, STRUCTURAL engineering, THERMAL expansion, X-ray scattering
Abstract

X-ray scattering has been used to characterize the columnar packing and the π stacking in a glass-forming discotic liquid crystal. In the equilibrium liquid state, the intensities of the scattering peaks for π stacking and columnar packing are proportional to each other, indicating concurrent development of the two orders. Upon cooling into the glassy state, the π–π distance shows a kinetic arrest with a change in the thermal expansion coefficient (TEC) from 321 to 109 ppm/K, while the intercolumnar spacing exhibits a constant TEC of 113 ppm/K. By changing the cooling rate, it is possible to prepare glasses with a wide range of columnar and π stacking orders, including zero order. For each glass, the columnar order and the π stacking order correspond to a much hotter liquid than its enthalpy and π–π distance, with the difference between the two internal (fictive) temperatures exceeding 100 K. By comparison with the relaxation map obtained by dielectric spectroscopy, we find that the δ mode (disk tumbling within a column) controls the columnar order and the π stacking order trapped in the glass, while the α mode (disk spinning about its axis) controls the enthalpy and the π–π spacing. Our finding is relevant for controlling the different structural features of a molecular glass to optimize its properties. [ABSTRACT FROM AUTHOR]

Published
2023
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10. Aromaticity in Semi‐Condensed Figure‐Eight Molecules.

Author

Artigas, Albert, Carissan, Yannick, Hagebaum‐Reignier, Denis, Bock, Harald, Durola, Fabien, and Coquerel, Yoann

Subjects
AROMATICITY, DIHEDRAL angles, ELECTRON delocalization, MOLECULES, POLYCYCLIC aromatic hydrocarbons
Abstract

Electron delocalization and aromaticity was comparatively evaluated in recently synthesized figure‐eight molecules made of two condensed U‐shaped polycyclic aromatic hydrocarbon moieties connected either by two single bonds or by two para‐phenylene groups. The selected examples include molecules that incorporate eight‐membered and sixteen‐membered rings, as well as a doubly [5]helicene‐bridged (1,4)cyclophane. We probe whether some electron delocalization could occur through the stereogenic single bonds in these molecules: Is aromaticity purely (semi‐)local, or possibly also global in these molecules? It was concluded that the situation can go from a purely (semi‐)local character when the dihedral angle at the connecting single bonds is large, such as in biphenyl, to a predominantly (semi‐)local character with a minor global contribution when the dihedral angle is small, such as in the para‐phenylene connectors of the [5] helicene‐bridged cyclophane. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Charge carrier transport in perylene-based and pyrene-based columnar liquid crystals

Author

Alves, Alessandro L, primary, Bernardino, Simone V, additional, Stadtlober, Carlos H, additional, Girotto, Edivandro, additional, Farias, Giliandro, additional, do Nascimento, Rodney M, additional, Curcio, Sergio F, additional, Cazati, Thiago, additional, Dotto, Marta E R, additional, Eccher, Juliana, additional, Furini, Leonardo N, additional, Gallardo, Hugo, additional, Bock, Harald, additional, and Bechtold, Ivan H, additional

Published
2023
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16. System Innovations in Inter Data Center Transport Networks

Author

Paraschis, Loukas, primary, Bock, Harald, additional, Kandappan, Parthiban, additional, Sommerkorn-Krombholz, Bernd, additional, Pedro, Joao, additional, Sadasivarao, Abhinava, additional, Syed, Sharfuddin, additional, Rahn, Jeff, additional, Doolan, Paul, additional, and Lu, Biao, additional

Published
2020
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17. Dissymmetric Triaryltriazines: Small Mass Columnar Glasses

Author

Nunes da Silva, Fabrícia, primary, Marchi Luciano, Hugo, additional, Stadtlober, Carlos H., additional, Farias, Giliandro, additional, Durola, Fabien, additional, Eccher, Juliana, additional, Bechtold, Ivan H., additional, Bock, Harald, additional, Gallardo, Hugo, additional, and Vieira, André A., additional

Published
2023
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18. A Triply [5]Helicene‐Bridged (1,3,5)Cyclophane

Author

Aribot, Frédéric, primary, Merle, Amélie, additional, Dechambenoit, Pierre, additional, Bock, Harald, additional, Artigas, Albert, additional, Vanthuyne, Nicolas, additional, Carissan, Yannick, additional, Hagebaum‐Reignier, Denis, additional, Coquerel, Yoann, additional, and Durola, Fabien, additional

Published
2023
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23. Data for paper 'Vapor-to-glass preparation of biaxially aligned organic semiconductors'

Author

Ju, Jianzhu, Chatterjee, Debaditya, Voyles, Paul, Bock, Harald, and Ediger, Mark

Subjects
PVD, solid-state, mesogens
Abstract

Physical vapor deposition (PVD) provides a route to prepare anisotropic organic glasses which are utilized in multi-layer structures such as organic light emitting devices (OLEDs). While previous work has demonstrated that anisotropic glasses with uniaxial symmetry can be prepared by PVD, here we prepare biaxially aligned glasses in which molecular orientation has a preferred in-plane direction. With the collective effect of the surface equilibration mechanism and template growth on an aligned substrate, macroscopic biaxial alignment is achieved in depositions as much as 180 K below clearing point (and 50 K below ) with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The preparation of biaxially aligned organic semiconductors may enable polarized emission and in-plane control of charge mobility.

Published
2023
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25. Columnar Liquid Crystalline Glasses by Combining Configurational Flexibility with Moderate Deviation from Planarity: Extended Triaryltriazines

Author

Nunes da Silva, Fabrícia, primary, Marchi Luciano, Hugo, additional, Stadtlober, Carlos H., additional, Farias, Giliandro, additional, Durola, Fabien, additional, Eccher, Juliana, additional, Bechtold, Ivan H., additional, Bock, Harald Reinhart, additional, Gallardo, Hugo, additional, and Vieira, André A., additional

Published
2023
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28. A carboxyfunctionalized ([2.sub.40])-1,6-pyrenophane-tetraene by glyoxylic Perkin condensation

Author

Robert, Antoine, Dechambenoit, Pierre, Bock, Harald, and Durola, Fabien

Subjects
Condensation -- Observations, Aromatic compounds -- Chemical properties, Chemistry
Abstract

Abstract: Without employing high dilution conditions, the fourfold 2+2 Perkin reaction of 1,6-pyrenylene-diglyoxylic acid with its reduction product 1,6-pyrenylene-diacetic acid yields the corresponding tetrameric conjugated macrocycle in 25% overall yield [...]

Published
2017
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30. Characterizing Antimicrobial Resistance in Clinically Relevant Bacteria Isolated at the Human/Animal/Environment Interface Using Whole-Genome Sequencing in Austria

Author

Cabal, Adriana, primary, Rab, Gerhard, additional, Daza-Prieto, Beatriz, additional, Stöger, Anna, additional, Peischl, Nadine, additional, Chakeri, Ali, additional, Mo, Solveig Sølverød, additional, Bock, Harald, additional, Fuchs, Klemens, additional, Sucher, Jasmin, additional, Rathammer, Krista, additional, Hasenberger, Petra, additional, Stadtbauer, Silke, additional, Caniça, Manuela, additional, Strauß, Peter, additional, Allerberger, Franz, additional, Wögerbauer, Markus, additional, and Ruppitsch, Werner, additional

Published
2022
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34. Columnar Liquid Crystals

Author

Bock, Harald, Lam, Lui, editor, Guyon, Etienne M., editor, Langevin, Dominique, editor, Stanley, H. Eugene, editor, Kitzerow, Heinz-Siegfried, editor, and Bahr, Christian, editor

Published
2001
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40. Des rubans aromatiques aux anneaux de Möbius par l'approche de Perkin

Author

Bock, Harald, Durola, Fabien, Centre de Recherche Paul Pascal (CRPP), Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Teulet, Nadine

Subjects
helicenes, [CHIM.MATE] Chemical Sciences/Material chemistry, macrocycles, polycyclic aromatic compounds, Organic synthesis, nano-ribbons, [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; Une nouvelle stratégie pour la synthèse de grands composés aromatiques polycycliques a récemment été développée. Elle fait intervenir une variante de la réaction de Perkin dont le rôle est d'assembler des briques élémentaires, des acides aryle-glyoxyliques et des acides aryle-acétiques, en précurseurs flexibles conjugués et substitués par des fonctions carboxyliques. L'étape finale de rigidification, en formant les liaisons CC manquantes, aboutit alors à des composés aromatiques polycycliques entièrement ou partiellement condensés. La méthode est maintenant au point avec un grand nombre de briques élémentaires accessibles, des techniques de protection des fonctions réactives, et plusieurs exemples de composés finaux de structures très diverses : rubans plans, hélicènes, macrocycles. Mots-clés : Synthèse organique, composés aromatiques polycycliques, nano-rubans, macrocycles, hélicènes.

Published
2021

44. Cyclic tris-[5]helicenes with single and triple twisted Möbius topologies and Möbius aromaticity† †Electronic supplementary information (ESI) available: Synthetic procedures, NMR spectra, 2D NMR spectra, single crystal X-ray diffraction, ACID plots, orbital plots, cartesian coordinates of B3LYP/6-31G* optimized structures. CCDC 1826373 and 1826374. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc02877j

Author

Naulet, Guillaume, Sturm, Ludmilla, Robert, Antoine, Dechambenoit, Pierre, Röhricht, Fynn, Herges, Rainer, Bock, Harald, and Durola, Fabien

Subjects
Chemistry
Abstract

Synthesis and theoretical study of rigid conjugated macrocycles having persistent geometries of single and triple twisted Möbius strips., A number of singly (180°) twisted, largely single-stranded and thus conformationally rather fragile, Möbius molecules have been synthesized within the last 15 years, which are aromatic with 4n electrons, thus violating the Hückel rule. Annulenes with significantly higher twist (e.g. 540°) that retain a full cyclic conjugation path have been elusive, mainly because of the high strain and loss of orbital overlap. Recently, a topological strategy was devised to project the “twist” into “writhe”, thus reducing the strain. However, orbital overlap was still severely reduced within the flexible building blocks. We now present a single and a triple twisted annulene with fully conjugated peripheries. They are unique in their pronounced band shape and conformational robustness as they are made up of three fully kata-condensed [5]helicene fragments. The triple twisted molecule exhibits a strong diatropic ring current in the outer periphery, even though the π system includes 4n electrons. The diatropic current is counterbalanced by a paratropic current in the σ system, resulting in no net manifestation of macrocyclic aromaticity. The key step of the synthesis of both Möbius compounds is a Perkin condensation of complementary bifunctional bismaleates leading to a flexible macrocycle containing alternating benzene and biphenyl fragments. Subsequent photocyclization yields a separable mixture of rigid diastereomeric tris-helicene macrocycles of the above topologies.

Published
2018

45. Organic Light-Emitting Diodes Based on a Columnar Liquid-Crystalline Perylene Emitter

Author

Keum, Changmin, Becker, David, Archer, Emily, Bock, Harald, Kitzerow, Heinz, Gather, Malte C., Murawski, Caroline, Keum, Changmin, Becker, David, Archer, Emily, Bock, Harald, Kitzerow, Heinz, Gather, Malte C., and Murawski, Caroline

Abstract

Liquid crystalline materials possess great potential as emitters in organic light-emitting diodes (OLEDs) due to their self-assembling property, which may lead to anisotropic films and improved charge transport. Here, the key photophysical properties of the columnar liquid crystalline emitter perylene-3,4,9,10-tetracarboxylic tetraethyl ester (PTCTE) are investigated and the material is implemented into OLEDs. It is found that vacuum-deposited PTCTE films exhibit preferential horizontal orientation of the transition dipole moment. Embedding the emitter into different host materials leads to increased photoluminescence quantum yield but reduces molecular orientation compared to the neat film. OLEDs containing PTCTE doped into an exciplex-forming co-host achieve very high luminance exceeding 10 000 cd m(-2)at 5.7 V, which is among the best performances of OLEDs based on columnar liquid crystalline emitters reported so far.

Published
2020

48. System innovations in open WDM DCI networks

Author

Paraschis, Loukas, primary, Bock, Harald, additional, Sadasivarao, Abhinava Shivakumar, additional, Syed, Sharfuddin, additional, Sommerkorn-Krombholz, Bernd, additional, Rahn, Jeff, additional, Lu, Biao, additional, Pedro, Joao, additional, Doolan, Paul, additional, and Kandappan, Parthiban, additional

Published
2020
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