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Kapernaum N, Lange A, Ebert M, Grunwald MA, Haege C, Marino S, Zens A, Taubert A, Giesselmann F, Laschat S. Current Topics in Ionic Liquid Crystals. Chempluschem 2021; 87:e202100397. [PMID: 34931472 DOI: 10.1002/cplu.202100397] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/10/2021] [Indexed: 12/20/2022]
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.
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Affiliation(s)
- Nadia Kapernaum
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Alyna Lange
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Golm, Germany
| | - Max Ebert
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Marco A Grunwald
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Christian Haege
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Sebastian Marino
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Anna Zens
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Andreas Taubert
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Golm, Germany
| | - Frank Giesselmann
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Sabine Laschat
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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2
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Bader K, Müller C, Molard Y, Baro A, Ehni P, Knelles J, Laschat S. Fluorenone imidazolium salts as novel de Vries materials. RSC Adv 2020; 10:23999-24016. [PMID: 35517358 PMCID: PMC9055108 DOI: 10.1039/d0ra04650g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/15/2020] [Indexed: 01/09/2023] Open
Abstract
In ionic liquid crystals (ILCs) tilted mesophases such as SmC required for electro-optic devices are quite rare. We report a design concept that induced the SmC phase and enabled de Vries-like behaviour in ILCs. For this purpose, we synthesized and characterized a library of ILC derivatives ImR(On,Ym)X which consist of a rigid central fluorenone core containing an alkoxy or thioether side chain and connected via a flexible spacer to an imidazolium head group. The mesomorphic properties were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). Temperature-dependent measurements of smectic layer spacing d by small-angle X-ray scattering (SAXS) and of optical tilt angles by POM demonstrate that ILCs ImR(On,Ym)X undergo SmA–SmC phase transitions with maximum layer contraction values between 0.4% and 2.1%. The lowest reduction factor R of 0.2 at the reduced temperature T − TAC = −10 K was calculated for Im(O12,S14)Br. Electron density calculations indicated a bilayer structure. Furthermore, temperature dependent emission studies show that self-assembling has a strong influence on the emission intensity of these ILCs. ILCs consisting of cationic head group–spacer–fluorenone central core–side chain show de Vries-like behaviour.![]()
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Affiliation(s)
- Korinna Bader
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Carsten Müller
- Institut für Physikalische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Yann Molard
- CNRS, ISCR-UMR 6226, ScanMAT-UMS 2001, University Rennes 35000 Rennes France
| | - Angelika Baro
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Philipp Ehni
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Jakob Knelles
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Sabine Laschat
- Institut für Organische Chemie, Universität Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
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3
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Anconi CPA. Relative Position and Relative Rotation in Supramolecular Systems through the Analysis of the Principal Axes of Inertia: Ferrocene/Cucurbit[7]uril and Ferrocenyl Azide/β-Cyclodextrin Case Studies. ACS OMEGA 2020; 5:5013-5025. [PMID: 32201787 PMCID: PMC7081398 DOI: 10.1021/acsomega.9b03914] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 02/25/2020] [Indexed: 06/10/2023]
Abstract
Parameters comprising the relative position and relative rotation of molecules can be evaluated when the principal axes of inertia of the entities in a supramolecular association are employed as reference. Such information applies to the characterization and identification of experimental and theoretical nonbonded systems. The parameters are relevant to geometric comparison (for theory and experiment) and, for instance, to monitoring structures by theoretical simulations. This work introduces a software developed to obtain such parameters through the discussion of some intriguing host-guest systems, the ferrocene/cucurbit[7]uril and ferrocenyl azide/β-cyclodextrin. The ideas within this contribution naturally apply to the study of other nonbonded associations beyond host-guest chemistry. A modified version of the software discussed herein serves to obtain user-defined spatial arrangements for two nonbonded entities. Therefore, with a given geometry, for instance, from X-ray data, the parameters can be derived, and with the parameters, from a theoretical perspective, a spatial arrangement can be obtained.
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4
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Swaminathan V, Panov VP, Kocot A, Vij JK. Molecular orientational distribution function of a chiral de Vries smectic liquid crystal from birefringence measurements. J Chem Phys 2019; 150:084901. [PMID: 30823765 DOI: 10.1063/1.5080222] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An alternative method for determining the orientational distribution function and the order parameter from the electric field-induced birefringence measurements of a chiral liquid crystal compound in its Smectic A* is being introduced. A chiral mesogen based on a 5-phenyl-pyrimidine benzoate core terminated by a trisiloxane group on one side and the chiral alkyloxy chain on its opposite side is designed and synthesized to exhibit the "de Vries" smectic characteristics. The compound exhibits first order Smectic A*-Smectic C* phase transition, evidenced by the results of differential scanning calorimetry. The material is being investigated by electro-optical experiment in its smectic phases. We present a model that incorporates the generalised Langevin-Debye model which includes the Maier-Saupe effective mean-field potential term in order to explain the change in birefringence with the electric field. A good agreement between the experimental results and the predictions from the model leads to the determination of the molecular orientational distribution function in Smectic A phase. Furthermore, the temperature dependency of the Saupe orientational order parameter ⟨P2⟩ is obtained using the parameters of the model. Based on the experimental and theoretical results, we show that de Vries Smectic A* phase exhibits a broad volcano-like tilt angle distribution with the two maxima occurring at finite tilt angles closer to the Smectic A*-Smectic C* transition temperature, and a sugarloaf-like distribution occurs in the tilt for temperatures close to the Isotropic-Smectic A* phase transition.
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Affiliation(s)
- V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - A Kocot
- Faculty of Computer Material Sciences, Institute of Technology and Mechatronics, Silesian University, Katowice, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
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5
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Kyrou C, Kralj S, Panagopoulou M, Raptis Y, Nounesis G, Lelidis I. Impact of spherical nanoparticles on nematic order parameters. Phys Rev E 2018; 97:042701. [PMID: 29758630 DOI: 10.1103/physreve.97.042701] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Indexed: 06/08/2023]
Abstract
We study experimentally the impact of spherical nanoparticles on the orientational order parameters of a host nematic liquid crystal. We use spherical core-shell quantum dots that are surface functionalized to promote homeotropic anchoring on their interface with the liquid crystal host. We show experimentally that the orientational order may be strongly affected by the presence of spherical nanoparticles even at low concentrations. The orientational order of the composite system is probed by means of polarized micro-Raman spectroscopy and by optical birefringence measurements as function of temperature and concentration. Our data show that the orientational order depends on the concentration in a nonlinear way, and the existence of a crossover concentration χ_{c}≈0.004pw. It separates two different regimes exhibiting pure-liquid crystal like (χ<χ_{c}) and distorted-nematic ordering (χ>χ_{c}), respectively. In the latter phase the degree of ordering is lower with respect to the pure-liquid crystal nematic phase.
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Affiliation(s)
- C Kyrou
- Faculty of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, Athens 157 84, Greece
| | - S Kralj
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
| | - M Panagopoulou
- Physics Department, National Technical University of Athens, Heroon Polytechniou 9, 15780 Zographou, Athens, Greece
| | - Y Raptis
- Physics Department, National Technical University of Athens, Heroon Polytechniou 9, 15780 Zographou, Athens, Greece
| | - G Nounesis
- Biomolecular Physics Laboratory, National Centre for Scientific Research Demokritos, Aghia Paraskevi, Greece
| | - I Lelidis
- Faculty of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, Athens 157 84, Greece
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6
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Kapernaum N, Wuckert E, Frey W, Marino S, Wahl M, Giesselmann F, Laschat S. Hunting for smectic C in calamitic azobenzene ionic liquid crystals with different cationic head groups. J PHYS ORG CHEM 2017. [DOI: 10.1002/poc.3779] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Nadia Kapernaum
- Institut für Physikalische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Eugen Wuckert
- Institut für Organische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Wolfgang Frey
- Institut für Organische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Sebastian Marino
- Institut für Physikalische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Manuel Wahl
- Institut für Physikalische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Frank Giesselmann
- Institut für Physikalische Chemie; Universität Stuttgart; Stuttgart Germany
| | - Sabine Laschat
- Institut für Organische Chemie; Universität Stuttgart; Stuttgart Germany
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7
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Kocot A, Vij JK, Perova TS, Merkel K, Swaminathan V, Sreenilayam SP, Yadav N, Panov VP, Stevenson PJ, Panov A, Rodriguez-Lojo D. Observation of the de Vries behavior in SmA * phase of a liquid crystal using polarised Raman scattering and infrared spectroscopy. J Chem Phys 2017; 147:094903. [PMID: 28886626 DOI: 10.1063/1.4999792] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Two approaches exist in the literature for describing the orientational distribution function (ODF) of the molecular directors in SmA* phase of liquid crystals, though several models are recently proposed in the literature for explaining the de Vries behaviour. These ODFs correspond to either the conventional unimodal arrangements of molecular directors arising from the mean field theory that leads to the broad or sugar-loaf like distribution or to the "diffuse-cone-shaped" type distribution proposed by de Vries. The hypothesis by de Vries provides for a realistic explanation as to how at a molecular level, a first-order SmA* to SmC* transition can occur where the uniform molecular director azimuthal distributions condense to values lying within a narrow range of angles; finally these condense to a single value while at the same time ensuring a little or no concomitant shrinkage in the layer spacing. The azimuthal distribution of the in-layer directors is probed using IR and polarized Raman spectroscopic techniques. The latter allows us to obtain the ODF and the various order parameters for the uniaxial and the biaxial phases. Based on the results of these measurements, we conclude that the "cone-shaped" (or volcano-shaped) de Vries type of distribution can most preferably describe SmA* where "a first-order phase transition from SmA* to SmC*" and a low layer shrinkage can both be easily explained.
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Affiliation(s)
- A Kocot
- Institute of Physics, Silesian University, Katowice, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - T S Perova
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - K Merkel
- Central Mining Institute, Katowice, Poland
| | - V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - N Yadav
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - P J Stevenson
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
| | - A Panov
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
| | - D Rodriguez-Lojo
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
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8
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Kapernaum N, Müller C, Moors S, Schlick MC, Wuckert E, Laschat S, Giesselmann F. First Examples of de Vries-like Smectic A to Smectic C Phase Transitions in Ionic Liquid Crystals. Chemphyschem 2016; 17:4116-4123. [PMID: 27712023 DOI: 10.1002/cphc.201600829] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 11/07/2022]
Abstract
In ionic liquid crystals, the orthogonal smectic A phase is the most common phase whereas the tilted smectic C phase is rather rare. We present a new study with five novel ionic liquid crystals exhibiting both a smectic A as well as the rare smectic C phase. Two of them have a phenylpyrimidine core whereas the other three are imidazolium azobenzenes. Their phase sequences and tilt angles were studied by polarizing microscopy and their temperature-dependent layer spacing as well as their translational and orientational order parameters were studied by X-ray diffraction. The X-ray tilt angles derived from X-ray studies of the layer contraction and the optically measured tilt angles of the five ionic liquid crystals were compared to obtain their de Vries character. Four of our five mesogens turned out to show de Vries-like behavior with a layer shrinkage that is far less than that expected for conventional materials. These materials can thus be considered as the first de Vries-type materials among ionic liquid crystals.
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Affiliation(s)
- Nadia Kapernaum
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Carsten Müller
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Svenja Moors
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - M Christian Schlick
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Eugen Wuckert
- Institute of Organic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Sabine Laschat
- Institute of Organic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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9
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Jenz F, Osipov MA, Jagiella S, Giesselmann F. Orientational distribution functions and order parameters in "de Vries"-type smectics: A simulation study. J Chem Phys 2016; 145:134901. [PMID: 27782446 DOI: 10.1063/1.4963660] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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.
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Affiliation(s)
- Frank Jenz
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
| | - Mikhail A Osipov
- Department of Mathematics and Statistics, G1 1XH, University of Strathclyde, Glasgow, United Kingdom
| | - Stefan Jagiella
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
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10
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Jenz F, Jagiella S, Glaser MA, Giesselmann F. Reliability of Orientational Order Parameters Determined from Two-dimensional X-ray Diffraction Patterns: A Simulation Study. Chemphyschem 2016; 17:1568-72. [PMID: 26928989 DOI: 10.1002/cphc.201600050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Indexed: 11/09/2022]
Abstract
The orientational order parameter S2 is one of the most important quantities to describe the degree of long-range orientational ordering of liquid crystals. There are several approaches to experimentally measure this order parameter of liquid crystalline phases but every method includes substantial simplifications and assumptions. We present a simulation-based approach to elucidate the reliability of the method of Davidson, Petermann and Levelut to measure S2 via 2D X-ray experiments. We have found that this method slightly underestimates S2 by an absolute value of only 0.05 and thus provides reliable measures of S2 by X-ray diffraction.
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Affiliation(s)
- Frank Jenz
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Stefan Jagiella
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Matthew A Glaser
- Department of Physics, 390 UCB, University of Colorado, Boulder, CO, 80309-0390, USA
| | - Frank Giesselmann
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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11
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Gradišek A, Domenici V, Apih T, Novotná V, Sebastião PJ. 1H NMR Relaxometric Study of Molecular Dynamics in a “de Vries” Liquid Crystal. J Phys Chem B 2016; 120:4706-14. [DOI: 10.1021/acs.jpcb.6b02224] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anton Gradišek
- Jožef Stefan Institute, Jamova
39, SI-1000 Ljubljana, Slovenia
| | - Valentina Domenici
- Dipartimento di Chimica e Chimica Industriale, via Moruzzi 13, 56124 Pisa, Italy
| | - Tomaž Apih
- Jožef Stefan Institute, Jamova
39, SI-1000 Ljubljana, Slovenia
| | - Vladimíra Novotná
- Institute
of Physics, Academy of Sciences of the Czech Republic, Na Slovance
2, 182 21 Prague, Czech Republic
| | - Pedro J. Sebastião
- Center
of Physics and Engineering of Advanced Materials, Instituto Superior
Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Department
of Physics, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
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12
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Bruckner JR, Knecht F, Giesselmann F. Origin of the Director Tilt in the Lyotropic Smectic C* Analog Phase: Hydration Interactions and Solvent Variations. Chemphyschem 2016; 17:86-92. [PMID: 26455909 DOI: 10.1002/cphc.201500673] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Indexed: 11/10/2022]
Abstract
The origin and long-range correlation of the director tilt in the recently discovered Lα'* phase, which is the lyotropic analog of the thermotropic smectic C* (SmC*) liquid crystalline phase, are investigated. Polarized micro-Raman spectroscopy reveals that the director tilt in the Lα'* phase originates from a tilting of the aromatic 2-phenylpyrimidine cores of the surfactant molecules. Optical measurements of the tilt angle show that its magnitude decreases with increasing solvent concentration, suggesting that the long-range inter-lamellar correlation of the tilt directions is reduced at increasing thickness of the solvent layers. The phase diagrams with four different solvents (water, formamide, N-methylformamide, N,N-dimethylformamide) are investigated, showing that the Lα'* phase is only formed with those solvents that exhibit a dense network of hydrogen bonds. This observation suggests that these hydrogen bond networks play an essential role in the long-range correlation of the director tilt between adjacent surfactant layers. To verify this assumption, mixtures with deuterated solvents are investigated, showing that the tilt angle in the Lα'* phase is indeed reduced by this modification of the solvent's hydrogen bond network.
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Affiliation(s)
- Johanna R Bruckner
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Friederike Knecht
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
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13
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Wuckert E, Harjung MD, Kapernaum N, Mueller C, Frey W, Baro A, Giesselmann F, Laschat S. Photoresponsive ionic liquid crystals based on azobenzene guanidinium salts. Phys Chem Chem Phys 2015; 17:8382-92. [DOI: 10.1039/c4cp04783d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The mesomorphic properties and the kinetics of the E/Z-photoisomerization in an ILC matrix of new azobenzene ILCs were investigated.
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Affiliation(s)
- Eugen Wuckert
- Institut für Organische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Marc D. Harjung
- Institut für Physikalische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Nadia Kapernaum
- Institut für Physikalische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Carsten Mueller
- Institut für Physikalische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Wolfgang Frey
- Institut für Organische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Angelika Baro
- Institut für Organische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Frank Giesselmann
- Institut für Physikalische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
| | - Sabine Laschat
- Institut für Organische Chemie
- Universität Stuttgart
- D-70569 Stuttgart
- Germany
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14
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Agra-Kooijman DM, Yoon H, Dey S, Kumar S. Origin of weak layer contraction in de Vries smectic liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032506. [PMID: 24730863 DOI: 10.1103/physreve.89.032506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Indexed: 06/03/2023]
Abstract
Structural investigations of the de Vries smectic-A (SmA) and smectic-C (SmC) phases of four mesogens containing a trisiloxane end segment reveal a linear molecular conformation in the SmA phase and a bent conformation resembling a hockey stick in the SmC phase. The siloxane and the hydrocarbon parts of the molecule tilt at different angles relative to the smectic layer normal and are oriented along different directions. For the compounds investigated, the shape of orientational distribution function (ODF) is found to be sugarloaf shaped and not the widely expected volcano like with positive orientational order parameters: ⟨P2⟩ = 0.53-0.78, ⟨P4⟩ = 0.14-0.45, and ⟨P6⟩∼0.10. The increase in the effective molecular length, and consequently in the smectic layer spacing caused by reduced fluctuations and the corresponding narrowing of the ODF, counteracts the effect of molecular tilt and significantly reduces the SmC layer contraction. Maximum tilt of the hydrocarbon part of the molecule lies between approximately 18° and 25° and between 6° and 12° for the siloxane part. The critical exponent of the tilt order parameter, β∼0.25, is in agreement with tricritical behavior at the SmA-SmC transition for two compounds and has lower value for first-order transition in the other compounds with finite enthalpy of transition.
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Affiliation(s)
| | - HyungGuen Yoon
- TV Development Team, LCD Business, Samsung Display, Chungcheongnam-Do 336-741, Korea
| | - Sonal Dey
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - Satyendra Kumar
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
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Domenici V, Lelli M, Cifelli M, Hamplova V, Marchetti A, Veracini CA. Conformational Properties and Orientational Order of a de Vries Liquid Crystal Investigated through NMR Spectroscopy. Chemphyschem 2014; 15:1485-95. [DOI: 10.1002/cphc.201301036] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Indexed: 11/05/2022]
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