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471 results on '"Giesselmann, Frank"'

3. Observation of a uniaxial ferroelectric smectic A phase

Author

Chen, Xi, Martinez, Vikina, Nacke, Pierre, Korblova, Eva, Manabe, Atsutaka, Klasen-Memmer, Melanie, Freychet, Guillaume, Zhernenkov, Mikhail, Glaser, Matthew A., Radzihovsky, Leo, Maclennan, Joseph E., Walba, David M., Bremer, Matthias, Giesselmann, Frank, and Clark, Noel A.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We report the smectic $A_F$, a new liquid crystal phase of the ferroelectric nematic realm. The smectic $A_F$ is a phase of small polar, rod-shaped molecules which form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the $\sim 10$ Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field of about $2 \times 10^5$ V/m is observed. The smectic $A_F$ phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic ($N$) -- smectic $Z_A$ (Sm$Z_A$) -- ferroelectric nematic ($N_F$) -- smectic $A_F$ (Sm$A_F$) phase sequence; and 7N/DIO, exhibiting an $N$ -- Sm$Z_A$ -- Sm$A_F$ phase sequence. The latter presents an opportunity to study a transition between two smectic phases having orthogonal systems of layers., Comment: 26 pages, 6 figures

Published
2022
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4. Magnetic Tilting in Nematic Liquid Crystals driven by Self-Assembly

Author

Hähsler, Martin, Nádasi, Hajnalka, Feneberg, Martin, Marino, Sebastian, Giesselmann, Frank, Behrens, Silke, and Eremin, Alexey

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science
Abstract

Self-assembly is one of the crucial mechanisms allowing to design multifunctional materials. Soft hybrid materials contain components of different nature and exhibit competitive interactions which drive self-organisation into structures of a particular function. Here we demonstrate a novel type of a magnetic hybrid material where the molecular tilt can be manipulated through a delicate balance between the topologically-assisted colloidal self-assembly of \rev{magnetic nanoparticles} and the anisotropic molecular interactions in a liquid crystal matrix.

Published
2021
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8. Counterion effects on the mesomorphic and electrochemical properties of guanidinium salts.

Author

Ebert, Max, Lange, Alyna, Müller, Michael, Wuckert, Eugen, Gießelmann, Frank, Klamroth, Tillmann, Zens, Anna, Taubert, Andreas, and Laschat, Sabine

Abstract

Ionic liquid crystals (ILCs) combine the ion mobility of ionic liquids with the order and self-assembly of thermotropic mesophases. To understand the role of the anion in ILCs, wedge-shaped arylguanidinium salts with tetradecyloxy side chains were chosen as benchmark systems and their liquid crystalline self-assembly in the bulk phase as well as their electrochemical behavior in solution were studied depending on the anion. Differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS, SAXS) experiments revealed that for spherical anions, the phase width of the hexagonal columnar mesophase increased with the anion size, while for non-spherical anions, the trends were less clear cut. Depending on the anion, the ILCs showed different stability towards electrochemical oxidation and reduction with the most stable being the PF6 based compound. Cyclic voltammetry (CV) and density functional theory (DFT) calculations suggest a possible contribution of the guanidinium cation to the oxidation processes. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Gelled lyotropic nematic liquid crystals

Author

Herbst, Michael, primary, Dombrowski, Max O., additional, Preisig, Natalie, additional, Dieterich, Sonja, additional, Giesselmann, Frank, additional, Mésini, Philippe, additional, and Stubenrauch, Cosima, additional

Published
2023
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10. Mesogenic Groups Control the Emitter Orientation in Multi‐Resonance TADF Emitter Films**

Author

Chen, Dongyang, primary, Tenopala‐Carmona, Francisco, additional, Knöller, Julius A., additional, Mischok, Andreas, additional, Hall, David, additional, Madayanad Suresh, Subeesh, additional, Matulaitis, Tomas, additional, Olivier, Yoann, additional, Nacke, Pierre, additional, Gießelmann, Frank, additional, Laschat, Sabine, additional, Gather, Malte C., additional, and Zysman‐Colman, Eli, additional

Published
2023
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11. Observation of a uniaxial ferroelectric smectic A phase

Author

Chen, Xi, primary, Martinez, Vikina, additional, Nacke, Pierre, additional, Korblova, Eva, additional, Manabe, Atsutaka, additional, Klasen-Memmer, Melanie, additional, Freychet, Guillaume, additional, Zhernenkov, Mikhail, additional, Glaser, Matthew A., additional, Radzihovsky, Leo, additional, Maclennan, Joseph E., additional, Walba, David M., additional, Bremer, Matthias, additional, Giesselmann, Frank, additional, and Clark, Noel A., additional

Published
2022
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17. Controlling the Emitter Orientation in Solution-processed Films through Introduction of Mesogenic Groups within a Multi-resonance Thermally Activated Delayed Fluorescence Emitter

Author

Chen, Dongyang, primary, Tenopala-Carmona, Francisco, additional, Knöller, Julius, additional, Mischok, Andreas, additional, Hall, David, additional, Suresh, Subeesh, additional, Matulaitis, Tomas, additional, Olivier, Yoann, additional, Nacke, Pierre, additional, Gießelmann, Frank, additional, Laschat, Sabine, additional, Gather, Malte, additional, and Zysman-Colman, Eli, additional

Published
2022
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20. Current Topics in Ionic Liquid Crystals

Author

Kapernaum, Nadia, primary, Lange, Alyna, additional, Ebert, Max, additional, Grunwald, Marco A., additional, Haege, Christian, additional, Marino, Sebastian, additional, Zens, Anna, additional, Taubert, Andreas, additional, Giesselmann, Frank, additional, and Laschat, Sabine, additional

Published
2021
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21. Observation of a uniaxial ferroelectric smectic A phase.

Author

Xi Chen, Martinez, Vikina, Nacke, Pierre, Korblova, Eva, Manabe, Atsutaka, Klasen-Memmer, Melanie, Freychet, Guillaume, Zhernenkov, Mikhail, Glaser, Matthew A., Radzihovsky, Leo, Maclennan, Joseph E., Walba, David M., Bremer, Matthias, Giesselmann, Frank, and Clark, Noel A.

Subjects
LIQUID crystal states, FERROELECTRIC liquid crystals, POLARIZATION (Electricity), ORTHOGONAL systems, BINARY mixtures
Abstract

We report the observation of the smectic AF, a liquid crystal phase of the ferroelectric nematic realm. The smectic AF is a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ~10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ~2 × 105 V/m is observed. The SmAF phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)–smectic ZA (SmZA)–ferroelectric nematic (NF)–SmAF phase sequence, and 7N/DIO, exhibiting an N–SmZA–SmAF phase sequence. The latter presents an opportunity to study a transition between two smectic phases having orthogonal systems of layers. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Cover Feature: Efficient and Spatially Controlled Functionalization of SBA‐15 and Initial Results in Asymmetric Rh‐Catalyzed 1,2‐Additions under Confinement (ChemCatChem 10/2021)

Author

Beurer, Ann‐Katrin, primary, Kirchhof, Manuel, additional, Bruckner, Johanna R., additional, Frey, Wolfgang, additional, Baro, Angelika, additional, Dyballa, Michael, additional, Giesselmann, Frank, additional, Laschat, Sabine, additional, and Traa, Yvonne, additional

Published
2021
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30. Orientational distribution functions and order parameters in "de Vries"-type smectics: A simulation study.

Author

Jenz, Frank, Osipov, Mikhail A., Jagiella, Stefan, and Giesselmann, Frank

Subjects
LIQUID crystal states, SMECTIC liquid crystals, COMPUTER simulation, DISTRIBUTION (Probability theory), DIFFRACTION patterns
Abstract

Simple smectic A liquid crystal phases with different types of prescribed orientational distribution functions have been simulated and compared in order to study the possibility to distinguish between the Maier-Saupe type and cone-like orientational distributions using the popular method of Davidson et al. [J. Phys. II 5, 113 (1995)]. This method has been used to extract the orientational distribution functions from simulated diffraction patterns, and the results have been compared with actual distribution functions which have been prescribed during simulations. It has been shown that it is indeed possible to distinguish between these two qualitatively different types of orientational distribution already from the shape of the 2D diffraction pattern. Moreover, typical experimental diffraction patterns for "de Vries"-type smectic liquid crystals appear to be close to the ones which have been simulated using the prescribed Maier-Saupe orientational distribution function. [ABSTRACT FROM AUTHOR]

Published
2016
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32. Current Topics in Ionic Liquid Crystals.

Author

Kapernaum, Nadia, Lange, Alyna, Ebert, Max, Grunwald, Marco A., Haege, Christian, Marino, Sebastian, Zens, Anna, Taubert, Andreas, Giesselmann, Frank, and Laschat, Sabine

Subjects
IONIC crystals, LIQUID crystal states, IONIC liquids
Abstract

Ionic liquid crystals (ILCs), that is, ionic liquids exhibiting mesomorphism, liquid crystalline phases, and anisotropic properties, have received intense attention in the past years. Among others, this is due to their special properties arising from the combination of properties stemming from ionic liquids and from liquid crystalline arrangements. Besides interesting fundamental aspects, ILCs have been claimed to have tremendous application potential that again arises from the combination of properties and architectures that are not accessible otherwise, or at least not accessible easily by other strategies. The current review highlights recent developments in ILC research, starting with some key fundamental aspects. Further subjects covered include the synthesis and variations of modern ILCs, including the specific tuning of their mesomorphic behavior. The review concludes with reflections on some applications that may be within reach for ILCs and finally highlights a few key challenges that must be overcome prior and during true commercialization of ILCs. [ABSTRACT FROM AUTHOR]

Published
2022
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36. Effects of reducing the free volume in the intercalated bilayers of tricarbosilane liquid crystalline dimers and monomers.

Author

Hosawi, Sarah, Müller, Carsten, Giesselmann, Frank, and Lemieux, Robert P.

Subjects
DIMERS, SMECTIC liquid crystals, FERROELECTRIC liquid crystals, OPTICAL microscopes, FREE energy (Thermodynamics), ALKYLATION
Abstract

Smectic liquid crystals with a low layer contraction of less than 1% upon an SmA to SmC transition are referred to as 'de Vries-like'. These materials have attracted considerable attention as possible alternative to problems with surface-stabilized ferroelectric liquid crystals in liquid crystal displays. The 'de Vries-like' properties of liquid crystals with nanosegregating carbosilane segments are enhanced by lengthening the carbosilane end-groups from mono- to tricarbosilane. The observed enhancement is thought to arise from an increase in the cross-section of the free volume in the hydrocarbon sub-layer. The hypothesis is tested by assuming that dimers with a tricarbosilane linking group have smaller time-averaged cross-sections. This paper reports the synthesis and characterization of two homologous series of liquid crystals and an investigation of their mesogenic properties as model systems employing liquid crystalline monomers (QL39-n) and dimers (QL40-n) comprising 2-phenylpyrimidine cores and tricarbosilane end-groups and spacers, respectively. We find that the QL39-n monomers form only a tilted SmC phase, whereas the QL40-n dimer forms an orthogonal SmA phase due to the tricarbosilane spacer will not have a spherically shape on the time average like that predicted for the tricarbosilane end-group. Results are discussed in the context of the timeaveraged cross-sections of the materials. [ABSTRACT FROM AUTHOR]

Published
2021

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