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848 results on '"Komber, Hartmut"'

1. Indacenodithiophene homopolymers via direct arylation: direct polycondensation versus polymer analogous reaction pathways

Author

Adamczak, Desiree, Komber, Hartmut, Illy, Anna, Scaccabarozzi, Alberto D., Caironi, Mario, and Sommer, Michael

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Indacenodithiophene (IDT) based materials are emerging high performance conjugated polymers for use in efficient organic photovoltaics and transistors. However, their preparation generally suffers from long reaction sequences and is often accomplished using disadvantageous Stille couplings. Herein, we present detailed synthesis pathways to IDT homopolymers using C-H activation for all C-C coupling steps. Polyketones are first prepared by direct arylation polycondensation (DAP) in quantitative yield and further cyclized polymer analogously. This protocol is suitable for obtaining structurally well-defined IDT homopolymers, provided that the conditions for cyclization are chosen appropriately and that side reactions are suppressed. Moreover, this polymer analogous pathway gives rise to asymmetric side chain patterns, which allows to fine tune physical properties. Alternatively, IDT homopolymers can be obtained via oxidative direct arylation polycondensation of IDT monomers (oxDAP), leading to IDT homopolymers with similar properties but at reduced yield. Detailed characterization by NMR, IR, UV-vis and PL spectroscopy, and thermal properties, is used to guide synthesis and to explain varying field-effect transistor hole mobilities in the range of 10-6- 10-3 cm2/Vs.

Published
2019
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2. A Defect-Free Naphthalene Diimide Bithiazole Copolymer via Regioselective Direct Arylation Polycondensation

Author

Matsidik, Rukiya, Giorgio, Michele, Luzio, Alessandro, Caironi, Mario, Komber, Hartmut, and Sommer, Michael

Subjects
Condensed Matter - Materials Science
Abstract

An optimized direct arylation polycondensation (DAP) protocol for the synthesis of a novel naphthalene diimide (NDI) 2,2'-bithiazole (2-BTz) copolymer (PNDI-2-BTz) is presented. The regioselective C-H activation of 2-BTz at the 5-positions allows for the synthesis of fully regioregular and homocoupling-free PNDI-2-BTz of high molecular weight in less than 1 h in quantitative yield. Complete end group assignment shows functionalities according to monomer structures or to nucleophilic substitution, and allows for the reliable determination of absolute molecular weight. Compared to the well-known bithiophene analog PNDIT2, an exceptionally high thermal stability, a hypsochromically shifted charge transfer absorption band and a lower-lying LUMO energy level is found, making PNDI-2-BTz an interesting candidate for applications in organic electronic devices. In contrast to the selective and high yielding C-H activation of 2-BTz at the 5-position, the regioisomer 5,5'-bithiazole is inactive under a variety of conditions.

Published
2018

4. Cove-Edged Chiral Graphene Nanoribbons with Chirality-Dependent Bandgap and Carrier Mobility

Author

Sub Nanophotonics, Nanophotonics, Liu, Kun, Zheng, Wenhao, Osella, Silvio, Qiu, Zhen Lin, Böckmann, Steffen, Niu, Wenhui, Meingast, Laura, Komber, Hartmut, Obermann, Sebastian, Gillen, Roland, Bonn, Mischa, Hansen, Michael Ryan, Maultzsch, Janina, Wang, Hai I., Ma, Ji, Feng, Xinliang, Sub Nanophotonics, Nanophotonics, Liu, Kun, Zheng, Wenhao, Osella, Silvio, Qiu, Zhen Lin, Böckmann, Steffen, Niu, Wenhui, Meingast, Laura, Komber, Hartmut, Obermann, Sebastian, Gillen, Roland, Bonn, Mischa, Hansen, Michael Ryan, Maultzsch, Janina, Wang, Hai I., Ma, Ji, and Feng, Xinliang

Published
2024

10. Vinyl methyl oxazolidinone as reactive diluent to overcome the solubility limitations of highly polar unsaturated polyesters.

Author

Wylezek, Maciej, Kalinkin, Chris, Gläser, Kristin, Adermann, Torben, García Romero, Iván, D'Andola, Giovanni, Komber, Hartmut, Lorenz, Reinhard, and Voit, Brigitte

Subjects
UNSATURATED polyesters, GLYCOLS, DYNAMIC mechanical analysis, SOLUBILITY, POLYESTERS
Abstract

Vinyl methyl oxazolidinone (VMOX®) is studied as a new reactive diluent (RD) for highly polar unsaturated polyesters (UPs). Molecules with special structure properties are extensively investigated as components for unsaturated polyester resins (UPRs) and thermosets, particularly for high‐temperature applications. Special diols with a cyclic structure like isosorbide and tricyclodecanedimethanol or special diols with side groups like 2‐methyl‐2‐propyl‐1,3‐propanediol and 2‐ethyl‐2‐butyl‐1,3‐propanediol can provide interesting properties. Bio‐based diols such as isosorbide and 1,3‐butanediol improve the sustainability profile. However, UPs based on such special diols have a higher polarity, limiting their solubility in styrene. This demands a RD, which provides adequate solubility and is suitable for high‐temperature applications. Therefore, our study compares the solubility of highly polar UPs based on special diols in styrene and VMOX®. UPs with different formulations, polarities, and Hansen parameters were synthesized and characterized. The solubility sphere of styrene was determined experimentally with the synthesized UPs. The influence of the special diols on the thermoset properties was investigated in dynamic mechanical analysis measurements. In conclusion, VMOX® as a RD enables full utilization of special diols properties due to the wide solubility window. Moreover, a new class of high‐temperature styrene‐free UP resin was developed. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Verstärkung von chiroptischen Eigenschaften in helikalen Nanographenen durch geometrische Anpassung von Doppel‐[7]Helicenen.

Author

Niu, Wenhui, Fu, Yubin, Deng, Qingsong, Qiu, Zhen‐Lin, Liu, Fupin, Popov, Alexey A., Komber, Hartmut, Ma, Ji, and Feng, Xinliang

Subjects
SERVER farms (Computer network management), AUTHOR-reader relationships, ENANTIOMERS, GRAPHENE, LUMINESCENCE
Abstract

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2024
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13. Cove-Edged Chiral Graphene Nanoribbons with Chirality-Dependent Bandgap and Carrier Mobility

Author

Liu, Kun, primary, Zheng, Wenhao, additional, Osella, Silvio, additional, Qiu, Zhen-Lin, additional, Böckmann, Steffen, additional, Niu, Wenhui, additional, Meingast, Laura, additional, Komber, Hartmut, additional, Obermann, Sebastian, additional, Gillen, Roland, additional, Bonn, Mischa, additional, Hansen, Michael Ryan, additional, Maultzsch, Janina, additional, Wang, Hai I., additional, Ma, Ji, additional, and Feng, Xinliang, additional

Published
2023
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27. Partially Bio‐Based Polyester Bead Foams via Extrusion Foaming of Poly(butylene terephthalate)/Poly(butylene furanoate) Blends.

Author

Mielke, Christian, Pospiech, Doris, Kuhnigk, Justus, Korwitz, Andreas, Komber, Hartmut, Bernhardt, Ricardo, Krebs, Nico, Boldt, Regine, Ruckdäschel, Holger, and Voit, Brigitte

Subjects
FOAM, POLYBUTENES, POLYMER blends, BUTENE, POLYESTERS, NUCLEAR magnetic resonance, DIELS-Alder reaction, EXTRUSION process
Abstract

The interest in bio‐based alternatives to classical polyesters such as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) is steadily growing to achieve a more sustainable approach to polymer materials. In this study, PBT/poly(butylene furanoate) (PBF) blends are prepared, characterized and extrusion foamed. PBF as a bio‐based polyester offers two advantages. The ecological footprint of the material is reduced, and additionally, it can be used in Diels‐Alder reactions at the blend surface to support fusion of the foamed beads. The blending behavior of the polyesters is investigated using samples prepared in a microcompounder, particularly focused on the miscibility of the blends and transesterification reactions. The blends are thermodynamically immiscible but show a certain degree of transesterification according to nuclear magnetic resonance (NMR) spectroscopy. The morphology of blend beads produced by an extrusion foaming process is analyzed regarding their cell density, cell size distribution, and open‐cell content. It is shown that PBF has a positive effect on the bead foam morphology. The use of a bifunctional linker designed for chemical fusion of the bead surfaces allows to obtaining of molded parts, in contrast to beads containing pure PBT. [ABSTRACT FROM AUTHOR]

Published
2023
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31. Substituent-controlled energetics and barriers of mechanochromic spiropyran-functionalized Poly(ɛ-caprolactone)

Author

Kempe, Fabian, Metzler, Lukas, Brügner, Oliver, Buchheit, Hannah, Walter, Michael, Komber, Hartmut, Sommer, Michael, and Publica

Subjects
polycaprolactone, mechanochromic polymer, mechanochemistry, force-induced reactions, spiropyran
Abstract

In a joint theoretical and experimental study, it is shown that the onset of the mechanically-induced spiropyran (SP) to merocyanine (MC) isomerization can be controlled by both the regiochemistry and the substitution pattern of SP. Four SP-based bifunctional initiators with consistently varied polymer chain anchor point and substituent are used to synthesize poly-ε-caprolactone (PCL). Theoretical calculations (1S and 3S COGEF methods) and in-situ visible light absorption measurements of films during uniaxial stress-strain experiments consistently show varying activation barriers of the force-induced ring-opening reaction of SP to give MC. SPs with PCL chains attached in ortho-position to the pyran oxygen isomerize at lower stress than their para-analogs. NO2-substituted SP mechanophores exhibit a lower activation barrier compared with H-substituted ones, but only if the -NO2 substituent is located in para-position relative to the O at the pyran half. These results are consistent with theoretical loading rate-dependent rupture forces required to break the C-O bond of SP and may guide mechanophore design.

Published
2023

46. Helical Bilayer Nonbenzenoid Nanographene Bearing a [10]Helicene with Two Embedded Heptagons

Author

Yang, Lin, Ju, Yang-Yang, Medel, Miguel A., Fu, Yubin, Komber, Hartmut, Dmitrieva, Evgenia, Zhang, Jin-Jiang, Obermann, Sebastian, Campaña, Araceli G., Ma, Ji, Feng, Xinliang, Yang, Lin, Ju, Yang-Yang, Medel, Miguel A., Fu, Yubin, Komber, Hartmut, Dmitrieva, Evgenia, Zhang, Jin-Jiang, Obermann, Sebastian, Campaña, Araceli G., Ma, Ji, and Feng, Xinliang

Abstract

The precision synthesis of helical bilayer nanographenes (NGs) with new topology is of substantial interest because of their exotic physicochemical properties. However, helical bilayer NGs bearing non-hexagonal rings remain synthetically challenging. Here we present the efficient synthesis of the first helical bilayer nonbenzenoid nanographene (HBNG1) from a tailor-made azulene-embedded precursor, which contains a novel [10]helicene backbone with two embedded heptagons. Single-crystal X-ray analysis reveals its highly twisted bilayer geometry with a record small interlayer distance of 3.2 Å among the reported helical bilayer NGs. Notably, the close interlayer distance between the two layers offers intramolecular through-space conjugation as revealed by in situ spectroelectrochemistry studies together with DFT simulations. Furthermore, the chiroptical properties of the P/M enantiomers of HBNG1 are also evaluated by circular dichroism and circularly polarized luminescence.

Published
2022

47. Solution Synthesis and Characterization of a Long and Curved Graphene Nanoribbon with Hybrid Cove–Armchair–Gulf Edge Structures

Author

Yang, Lin, Zheng, Wenhao, Osella, Silvio, Droste, Jörn, Komber, Hartmut, Liu, Kun, Böckmann, Steffen, Beljonne, David, Hansen, Michael Ryan, Bonn, Mischa, Wang, Hai I., Liu, Junzhi, Feng, Xinliang, Ma, Ji, Yang, Lin, Zheng, Wenhao, Osella, Silvio, Droste, Jörn, Komber, Hartmut, Liu, Kun, Böckmann, Steffen, Beljonne, David, Hansen, Michael Ryan, Bonn, Mischa, Wang, Hai I., Liu, Junzhi, Feng, Xinliang, and Ma, Ji

Abstract

Curved graphene nanoribbons (GNRs) with hybrid edge structures have recently attracted increasing attention due to their unique band structures and electronic properties as a result of their nonplanar conformation. This work reports the solution synthesis of a long and curved multi-edged GNR (cMGNR) with unprecedented cove–armchair–gulf edge structures. The synthesis involves an efficient A2B2-type Diels–Alder polymerization between a diethynyl-substituted prefused bichrysene monomer (3b) and a dicyclopenta[e,l]pyrene-5,11-dione derivative (6) followed by FeCl3-mediated Scholl oxidative cyclodehydrogenation of the obtained polyarylenes (P1). Model compounds 1a and 1b are first synthesized to examine the suitability and efficiency of the corresponding polymers for the Scholl reaction. The successful formation of cMGNR from polymer P1 bearing prefused bichrysene units is confirmed by FTIR, Raman, and solid-state NMR analyses. The cove-edge structure of the cMGNR imparts the ribbon with a unique nonplanar conformation as revealed by density functional theory (DFT) simulation, which effectively enhances its dispersibility in solution. The cMGNR has a narrow optical bandgap of 1.61 eV, as estimated from the UV–vis absorption spectrum, which is among the family of low-bandgap solution-synthesized GNRs. Moreover, the cMGNR exhibits a carrier mobility of ≈2 cm2 V−1 s−1 inferred from contact-free terahertz spectroscopy.

Published
2022

48. Benzo-Extended Cyclohepta[def]fluorene Derivatives with Very Low-Lying Triplet States

Author

Wu, Fupeng, Ma, Ji, Lombardi, Federico, Fu, Yubin, Liu, Fupin, Huang, Zhijie, Liu, Renxiang, Komber, Hartmut, Alexandropoulos, Dimitris I., Dmitrieva, Evgenia, Lohr, Thorsten G., Israel, Noel, Popov, Alexey A., Liu, Junzhi, Bogani, Lapo, Feng, Xinliang, Wu, Fupeng, Ma, Ji, Lombardi, Federico, Fu, Yubin, Liu, Fupin, Huang, Zhijie, Liu, Renxiang, Komber, Hartmut, Alexandropoulos, Dimitris I., Dmitrieva, Evgenia, Lohr, Thorsten G., Israel, Noel, Popov, Alexey A., Liu, Junzhi, Bogani, Lapo, and Feng, Xinliang

Abstract

Open-shell non-alternant polycyclic hydrocarbons (PHs) are attracting increasing attention due to their promising applications in organic spintronics and quantum computing. Herein we report the synthesis of three cyclohepta[def]fluorene-based diradicaloids (1–3), by fusion of benzo rings on its periphery for the thermodynamic stabilization, as evidenced by multiple characterization techniques. Remarkably, all of them display a very narrow optical energy gap (Egopt=0.52–0.69 eV) and persistent stability under ambient conditions (t1/2=11.7–33.3 h). More importantly, this new type of diradicaloids possess a low-lying triplet state with an extremely small singlet–triplet energy gap, as low as 0.002 kcal mol−1, with a clear dependence on the molecular size. This family of compounds thus offers a new route to create non-alternant open-shell PHs with high-spin ground states, and opens up novel possibilities and insights into understanding the structure–property relationships.

Published
2022

49. Benzo‐Extended Cyclohepta[def]fluorene Derivatives with Very Low‐Lying Triplet States

Author

Wu, Fupeng, primary, Ma, Ji, additional, Lombardi, Federico, additional, Fu, Yubin, additional, Liu, Fupin, additional, Huang, Zhijie, additional, Liu, Renxiang, additional, Komber, Hartmut, additional, Alexandropoulos, Dimitris I., additional, Dmitrieva, Evgenia, additional, Lohr, Thorsten G., additional, Israel, Noel, additional, Popov, Alexey A., additional, Liu, Junzhi, additional, Bogani, Lapo, additional, and Feng, Xinliang, additional

Published
2022
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