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Dolganov PV, Kats EI, Dolganov VK, Cluzeau P. Linear defects forming the ground state of polar free standing smectic-C* films. SOFT MATTER 2018; 14:7174-7179. [PMID: 30137094 DOI: 10.1039/c8sm01276h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this paper we report on observations of unusual linear defects forming spontaneously in polar free-standing smectic-C* films near the temperatures of thinning transitions. At high temperature a periodic structure of defects becomes the ground state of the system. We found that the defects are characterized by continuous rotation of the molecular orientation with a change of the sense of the rotation across the defects. We develop a simple theoretical model that describes the observed behavior. The structure of the defects is governed by the competition between two-dimensional quadratic and linear orientational elasticity. The proposed model explains the origin of the linear defects, the periodic structure and their transformation with temperature and chirality of the liquid crystal.
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Affiliation(s)
- Pavel V Dolganov
- Institute of Solid State Physics, Russian Academy of Sciences, Moscow Region, 142432 Chernogolovka, Russia
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2
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Jeon SW, Kim DY, Araoka F, Jeong KU, Choi SW. Nanosegregated Chiral Materials with Self-Assembled Hierarchical Mesophases: Effect of Thermotropic and Photoinduced Polymorphism in Rodlike Molecules. Chemistry 2017; 23:17794-17799. [DOI: 10.1002/chem.201703778] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Indexed: 11/05/2022]
Affiliation(s)
- Sung-Wook Jeon
- Department of Advanced Materials Engineering; for Information and Electronics (BK21Plus); Kyung Hee University; Yongin Kyeonggi 17104 Republic of Korea
| | - Dae-Yoon Kim
- Department of Polymer Nano Science and Technology; Chonbuk National University; Jeonju 54896 Republic of Korea
| | - Fumito Araoka
- Physicochemical Soft Matter Research Unit; RIKEN Center for Emergent Matter Science (CEMS); Wako Saitama 351-0198 Japan
| | - Kwang-Un Jeong
- Department of Polymer Nano Science and Technology; Chonbuk National University; Jeonju 54896 Republic of Korea
| | - Suk-Won Choi
- Department of Advanced Materials Engineering; for Information and Electronics (BK21Plus); Kyung Hee University; Yongin Kyeonggi 17104 Republic of Korea
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3
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Nemitz IR, Ferris AJ, Lacaze E, Rosenblatt C. Chiral oily streaks in a smectic-A liquid crystal. SOFT MATTER 2016; 12:6662-6668. [PMID: 27426740 DOI: 10.1039/c6sm01238h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The liquid crystal octylcyanobiphenyl (8CB) was doped with the chiral agent CB15 and spin-coated onto a substrate treated for planar alignment of the director, resulting in a film of thickness several hundred nm in the smectic-A phase. In both doped and undoped samples, the competing boundary conditions - planar alignment at the substrate and vertical alignment at the free surface - cause the liquid crystal to break into a series of flattened hemicylinders to satisfy the boundary conditions. When viewed under an optical microscope with crossed polarizers, this structure results in a series of dark and light stripes ("oily streaks") of period ∼1 μm. In the absence of chiral dopant the stripes run perpendicular to the substrate's easy axis. However, when doped with chiral CB15 at concentrations up to c = 4 wt%, the stripe orientation rotates by a temperature-dependent angle φ with respect to the c = 0 stripe orientation, where φ increases monotonically with c. φ is largest just below the nematic - smectic-A transition temperature TNA and decreases with decreasing temperature. As the temperature is lowered, φ relaxes to a steady-state orientation close to zero within ∼1 °C of TNA. We suggest that the rotation phenomenon is a manifestation of the surface electroclinic effect: The rotation is due to the weak smectic order parameter and resulting large director tilt susceptibility with respect to the smectic layer normal near TNA, in conjunction with an effective surface electric field due to polar interactions between the liquid crystal and substrate.
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Affiliation(s)
- Ian R Nemitz
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Nemitz IR, Lacaze E, Rosenblatt C. Electroclinic effect in a chiral paranematic liquid-crystal layer above the bulk nematic-to-isotropic transition temperature. Phys Rev E 2016; 93:022701. [PMID: 26986382 DOI: 10.1103/physreve.93.022701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Indexed: 06/05/2023]
Abstract
Electroclinic measurements are reported for two chiral liquid crystals above their bulk chiral isotropic-nematic phase transition temperatures. It is found that an applied electric field E induces a rotation θ [∝Ε] of the director in the very thin paranematic layers that are induced by the cell's two planar-aligning substrates. The magnitude of the electroclinic coefficient dθ/dE close to the transition temperature is comparable to that of a bulk chiral nematic, as well as to that of a parasmectic region above a bulk isotropic-to-chiral smectic-A phase. However, dθ/dE in the paranematic layer varies much more slowly with temperature than in the parasmectic phase, and its relaxation time is slower by more than three orders of magnitude than that of the bulk chiral nematic electroclinic effect.
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Affiliation(s)
- Ian R Nemitz
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
- CNRS UMR 7588, Université Pierre et Marie Curie, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France
- UPMC Université Paris VI, UMR 7588, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France
| | - Emmanuelle Lacaze
- CNRS UMR 7588, Université Pierre et Marie Curie, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France
- UPMC Université Paris VI, UMR 7588, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France
| | - Charles Rosenblatt
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Zappitelli K, Hipolite DN, Saunders K. Modeling the field control of the surface electroclinic effect near continuous and first-order smectic-A* to smectic-C* transitions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:022502. [PMID: 25353484 DOI: 10.1103/physreve.89.022502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Indexed: 06/04/2023]
Abstract
We present and analyze a model for the combination of bulk and surface electroclinic effects in the smectic-A* (Sm-A*) phase near a Sm-A*-Sm-C* transition. As part of our analysis we calculate the dependence of the surface tilt on external electric field and show that it can be eliminated, or even reversed from its zero-field value, as demonstrated in previous experimental work on a system (W415) with a continuous Sm-A*-Sm-C* transition. We also analyze, for the first time, the combination of bulk and surface electroclinic effects in systems with a first-order Sm-A*-Sm-C* transition. The variation of surface tilt with electric field in this case is much more dramatic, with discontinuities and hysteresis. With regard to technological, e.g., display, applications, this could be a feature to be avoided or potentially exploited. Near each type of Sm-A*-Sm-C* transition we obtain the temperature dependence of the field required to eliminate surface tilt. Additionally, we analyze the effect of varying the system's enantiomeric excess, showing that it strongly affects the field dependence of surface tilt, in particular, near a first-order Sm-A*-Sm-C* transition. In this case, increasing enantiomeric excess can change the field dependence of surface tilt from continuous to discontinuous. Our model also allows us to calculate the variation of layer spacing in going from surface to bulk, which in turn allows us to estimate the strain resulting from the difference between the surface and bulk layer spacing. We show that for certain ranges of applied electric field, this strain can result in layer buckling, which reduces the overall quality of the liquid crystal cell. For de Vries materials, with small tilt-induced change in layer spacing, the induced strain for a given surface tilt should be smaller. However, we argue that this may be offset by the fact that de Vries materials, which typically have Sm-A*-Sm-C* transitions near a tricritical point, will generally have larger surface tilt.
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Affiliation(s)
- Kara Zappitelli
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
| | - Dana N Hipolite
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
| | - Karl Saunders
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
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Saunders K, Rudquist P. Surface electroclinic effect near the first-order smectic-A*-smectic-C* transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:051711. [PMID: 21728560 DOI: 10.1103/physreve.83.051711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2011] [Indexed: 05/31/2023]
Abstract
We analyze the surface electroclinic effect (SECE) in a material that exhibits a first-order bulk smectic-A* (Sm-A*)-smectic-C* (Sm-C*) transition. The effect of a continuously varying degree of enantiomeric excess on the SECE is also investigated. We show that due to the first-order nature of the bulk Sm-A*-Sm-C* transition, the SECE can be unusually strong and that as enantiomeric excess is varied, a jump in surface induced tilt is expected. A theoretical state map, in enantiomeric excess-temperature space, features a critical point which terminates a line of first-order discontinuities in the surface induced tilt. This critical point is analogous to that found for the phase diagram (in electric field-temperature space) for the bulk electroclinic effect. Analysis of the decay of the surface induced tilt, as one moves from surface into bulk, shows that for sufficiently high-surface tilt the decay will exhibit a well-defined spatial kink within which it becomes especially rapid. We also propose that the SECE is additionally enhanced by the de Vries nature (i.e., small layer shrinkage at the bulk Sm-A*-Sm-C* transition) of the material. As such, the SECE provides a new means to characterize the de Vries nature of a material. We discuss the implications for using these materials in device applications and propose ways to investigate the predicted features experimentally.
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Affiliation(s)
- Karl Saunders
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA.
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Ferjani S, Choi Y, Pendery J, Petschek RG, Rosenblatt C. Mechanically generated surface chirality at the nanoscale. PHYSICAL REVIEW LETTERS 2010; 104:257801. [PMID: 20867414 DOI: 10.1103/physrevlett.104.257801] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 05/27/2010] [Indexed: 05/29/2023]
Abstract
A substrate coated with an achiral polyimide alignment layer was scribed bidirectionally with the stylus of an atomic force microscope to create an easy axis for liquid crystal orientation. The resulting noncentrosymmetric topography resulted in a chiral surface that manifests itself at the molecular level. To show this unambiguously, a planar-aligned negative dielectric aniostropy achiral nematic liquid crystal was placed in contact with the surface and subjected to an electric field E. The nematic director was found to undergo an azimuthal rotation approximately linear in E. This so-called "surface electroclinic effect" is a signature of surface chirality and was not observed when the polyimide was treated for a centrosymmetric topography, and therefore was nonchiral.
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Affiliation(s)
- Sameh Ferjani
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079, USA
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8
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Bahr C, Fliegner D. The Smectic-C-Smectic-A Transition in Free-Standing Liquid-Crystal Films: An Example for Critical Behaviour Induced by a Confined Geometry. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19930971034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hammarquist A, D'Havé K, Matuszczyk M, Clark NA, Maclennan JE, Rudquist P. V -shaped switching ferroelectric liquid crystal structure stabilized by dielectric surface layers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:031707. [PMID: 18517406 DOI: 10.1103/physreve.77.031707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Indexed: 05/26/2023]
Abstract
The " V -shaped switching" mode in high polarization ferroelectric liquid crystals was studied with the aim of stabilizing the monostable bookshelf structure with the spontaneous polarization parallel to the glass plates. The director field in such cells was confirmed to be sensitive to both the liquid crystal properties and the cell parameters. In cells with only polyimide alignment layers, hysteresis free switching was never obtained, with bistable and asymmetric monostable structures compromising the zero-field dark state and preventing an ideal, hysteresis-free analog response. By incorporating a SiO(2) layer between the ITO electrode and the polyimide, the undesired states were suppressed and essentially hysteresis-free switching was obtained for driving frequencies in the range 0.2-200 Hz . Cells rubbed only on one side give more uniform alignment than cells rubbed on both sides but their inherent asymmetry shifts the long-term dark state away from 0 V and causes the response to gray level voltage modulation to be slightly asymmetric. The formation of different types of states as a function of the values of the surface parameters, and the observed stabilization of the V -shaped switching structure by the dielectric surface layers, are in good agreement with an earlier analysis by Copic [Phys. Rev. E 65, 021701 (2002)].
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Affiliation(s)
- A Hammarquist
- Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-412 96 Göteborg, Sweden
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Sigarev AA, Vij JK, Hall AW, Cowling SJ, Goodby JW. Molecular orientational properties of a high-tilt chiral smectic liquid crystal determined from its infrared dichroism. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:051707. [PMID: 18233673 DOI: 10.1103/physreve.76.051707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Revised: 08/02/2007] [Indexed: 05/25/2023]
Abstract
The orientational characterisitics and the temperature dependencies of the molecular apparent tilt angle of a partly fluorinated chiral smectic liquid crystal (/S/)-4-(1-methylheptyloxycarbonyl)phenyl 4'-[6-(3,4,4,4-tetrafluoro-3-trifluoromethylbutylcarbonyloxy)hexyloxy] biphenyl-4-carboxylate (acronym MHPHFHHOBC) are studied using the polarized Fourier transform infrared (FTIR) spectroscopy. The molecular orientational distributions and the orientational order parameters for a homogeneously aligned liquid crystalline sample at various temperatures and external electric fields are examined. The analysis uses the dichroic parameters of the phenyl and the carbonyl bands. For a temperature range of 65-80 degrees C corresponding to the antiferroelectric SmCA* phase, the molecular apparent tilt angle lies within the range 43 degrees -44 degrees; antiferroelectric smectic structure being rather close to the orthoconic SmCA* phase. An application of sufficiently high dc field across the cell in its SmA* phase surprisingly shows that the dichroism first increases slowly and then rapidly in two stages and finally a saturated apparent tilt angle of approximately 30 degrees is reached. The IR dichroic data is used to estimate the polar angles and the degree of rotational biasing of the carbonyl groups with respect to the molecular long axis. In the SmA* phase, the sample appears to demonstrate some of the typical properties of a de Vries material.
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Affiliation(s)
- A A Sigarev
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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11
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Kiselev AD, Chigrinov VG, Pozhidaev EP. Switching dynamics of surface stabilized ferroelectric liquid crystal cells: effects of anchoring energy asymmetry. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:061706. [PMID: 17677282 DOI: 10.1103/physreve.75.061706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Indexed: 05/16/2023]
Abstract
We study both theoretically and experimentally switching dynamics in asymmetric surface stabilized ferroelectric liquid crystal cells where the bounding surfaces are treated differently to produce asymmetry in their anchoring properties. Our electro-optic measurements of the switching voltage thresholds, V+ and -V{-}, that are determined by the peaks of the reversal polarization current reveal the frequency dependent shift of the hysteresis loop, V{+}-V{-}. We examine the predictions of the uniform dynamic model with the anchoring energy taken into account. It is found that the asymmetry effects are dominated by the polar contribution to the anchoring energy. Frequency dependence of the voltage thresholds is studied by analyzing the properties of time-periodic solutions to the dynamic equation (cycles). For this purpose, we apply the method linking the cycles and the fixed points of the composition of two parametrized half-period mappings for the approximate model. It is found that the cycles are unstable and can only be formed if the driving frequency is lower than its critical value. The polar anchoring parameter is estimated by making a comparison between the results of modeling and the experimental data for the shift vs frequency curve.
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Affiliation(s)
- Alexei D Kiselev
- Institute of Physics of National Academy of Sciences of Ukraine, Prospekt Nauki 46, 03028 Kyïv, Ukraine
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12
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Kimura M, Yamada M, Ishihara H, Akahane T. Numerical Calculatiqns of Electroclinic Effect: Effect of the Polar Anchoring Strength. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259708041829] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Munehiro Kimura
- a Department of Electrical Engineering, Faculty of Engineering , Nagaoka University of Technology , Kamitomioka 1603, Nagaoka, Niigata , 940-21 , Japan
| | - Masataka Yamada
- a Department of Electrical Engineering, Faculty of Engineering , Nagaoka University of Technology , Kamitomioka 1603, Nagaoka, Niigata , 940-21 , Japan
- b SEIKO EPSON Co
| | - Hideo Ishihara
- a Department of Electrical Engineering, Faculty of Engineering , Nagaoka University of Technology , Kamitomioka 1603, Nagaoka, Niigata , 940-21 , Japan
| | - Tadashi Akahane
- a Department of Electrical Engineering, Faculty of Engineering , Nagaoka University of Technology , Kamitomioka 1603, Nagaoka, Niigata , 940-21 , Japan
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Lee SD, Kim JH, Patel JS, Goodby JW. The Anomaly in Layer Ordering and Electro-Optic Properties of Smectic a Liquid Crystals. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259308030959] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Sin-Doo Lee
- a Physics Department , Sogang University , C. P. O. Box 1142, Seoul , Korea
| | - Jae-Hoon Kim
- a Physics Department , Sogang University , C. P. O. Box 1142, Seoul , Korea
| | | | - J. W. Goodby
- c School of Chemistry , The University , Hull , HU6 7RX , England
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Lagerwall JPF, Kane AA, Clark NA, Walba DM. Polarity-directed analog electro-optic switching in a low-polarization chiral smectic liquid crystal with positive dielectric anisotropy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:031703. [PMID: 15524539 DOI: 10.1103/physreve.70.031703] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Indexed: 05/24/2023]
Abstract
We describe an analog electro-optic (EO) switching mechanism occurring in thin cells filled with a low-polarization ferroelectric liquid crystal mixture with positive dielectric anisotropy. The mixture is composed of an achiral nonpolar smectic-C (Sm-C) host doped with a small amount of a commercially available unichiral compound. The switching mechanism provides analog EO behavior, and thus could be attractive for information display applications. The process is polarization-driven for weak fields, while for higher field strength the dielectric coupling dominates the process.
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Affiliation(s)
- Jan P F Lagerwall
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
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Maclennan JE, Muller D, Shao RF, Coleman D, Dyer DJ, Walba DM, Clark NA. Field control of the surface electroclinic effect in chiral smectic-A liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 69:061716. [PMID: 15244607 DOI: 10.1103/physreve.69.061716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Indexed: 05/24/2023]
Abstract
The surface electroclinic effect, which causes an azimuthal deviation of the layer normal from the surface rubbing direction in cells of chiral smectic- A liquid crystals, can be eliminated (and even reversed) by applying an electric field during cooling from the isotropic phase. The observed dependence of layer orientation on field strength leads to a model in which the surface electroclinic tilt results from an effective surface electric field. The experiements suggest a general method for controlling the azimuthal layer alignment of chiral smectic cells.
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Affiliation(s)
- Joseph E Maclennan
- Department of Physics, and Ferroelectric Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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16
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Fokin YG, Murzina TV, Aktsipetrov OA, Soria S, Marowsky G. Ferroelectric ordering and electroclinic effect in chiral smectic liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 69:031701. [PMID: 15089304 DOI: 10.1103/physreve.69.031701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Indexed: 05/24/2023]
Abstract
Ferroelectric ordering, the electroclinic effect, and chiral smectic C(SmC*)-smectic A phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electro-optic and second harmonic generation (SHG) techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied dc electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the SHG switching behavior in reflection and transmission geometries allows one to distinguish the contributions from the bulk and the subsurface layers of the cell. The analysis of SHG temperature dependences shows the existence of a strong surface coupling. The temperature-dependent nonlinear polarization shows a critical behavior with the exponent approximately 0.3 in SmC* phase.
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Affiliation(s)
- Yu G Fokin
- Physics Department, Moscow State University, Moscow 119992, Russia.
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17
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Vaupotic N, Copic M. Effect of spontaneous polarization and polar surface anchoring on the director and layer structure in surface-stabilized ferroelectric liquid crystal cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 68:061705. [PMID: 14754223 DOI: 10.1103/physreve.68.061705] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Indexed: 11/07/2022]
Abstract
We use the Landau-de Gennes model to study theoretically the effect of the magnitude of the spontaneous polarization (P(S)), the ratio (r) between the equilibrium layer tilt and the smectic cone angle, the thickness of the insulating alignment layers and the strength of the polar and nonpolar surface anchoring on the director and layer structure in surface-stabilized ferroelectric liquid crystal cells with the chevron structure of smectic layers. The system shows a surprising number of stable structures, accompanied by one or two metastable ones. At P(S) greater than the critical value only quasimonostable structures, which can exhibit the thresholdless (V-shaped) switching, exist at all r and both at weak and strong polar surface anchoring. At lower P(S) bistable and monostable structures can coexist. Bistable structures can be expected at high r, low P(S) and if polar surface anchoring is weaker than the nonpolar one. Lowering the ratio r and/or increasing the strength of polar anchoring promotes the stability of monostable structures. Thicker insulating alignment layers also drive the system into the monostable state. Polar surface anchoring induces a large surface electroclinic effect. As a result the nematic deformations close to the surfaces are very strong and the stress is relieved by bending of the smectic layers. This leads to the formation of a double chevron structure which is stable at very large polar anchoring and due to the surface electroclinic effect it is metastable also at lower values of polar anchoring.
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Affiliation(s)
- Natasa Vaupotic
- Department of Physics, Faculty of Education, University of Maribor, Koroska 160, 2000 Maribor, Slovenia
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18
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Coleman D, Mueller D, Clark NA, Maclennan JE, Shao RF, Bardon S, Walba DM. Control of molecular orientation in electrostatically stabilized ferroelectric liquid crystals. PHYSICAL REVIEW LETTERS 2003; 91:175505. [PMID: 14611359 DOI: 10.1103/physrevlett.91.175505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Revised: 10/10/2002] [Indexed: 05/24/2023]
Abstract
The continuously reorientable (XY-like) ferroelectric polarization density of a chiral smectic liquid crystal is shown experimentally to produce nearly complete screening of the applied electric field in an appropriate cell geometry. This screening, combined with the expulsion of polarization charge for large polarization materials, is shown to produce electrostatic control of the orientation of a uniform optic axis or polarization field.
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Affiliation(s)
- D Coleman
- Department of Physics and Ferroelectric Liquid Crystal Materials Research Center, University of Colorado at Boulder, Boulder, CO 80309, USA
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19
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Syed IM, Rosenblatt C. Surface-induced molecular tilt above the smectic-A-smectic-C phase transition in a nonchiral liquid crystal. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2003; 68:031701. [PMID: 14524782 DOI: 10.1103/physreve.68.031701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2003] [Indexed: 05/24/2023]
Abstract
A polyimide-coated substrate was rubbed in such a way as to possess two competing easy axes for liquid crystal alignment. On cooling a homeotropically aligned liquid crystal through the smectic-A phase toward the smectic-C phase transition, an increasing tilt of the molecules relative to the layer normal was observed. The tilt was localized to within a smectic-C correlation length of the interface, and was found to increase monotonically with the rubbing strength associated with the preparation of the polyimide surface. The results are discussed in light of the dual easy axis model [T. Shioda et al., Phys. Rev. E 67, 041706 (2003)], and suggest that the two easy axes are not mutually orthogonal.
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Affiliation(s)
- Ishtiaque M Syed
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079, USA
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Coleman D, Bardon S, Radzihovsky L, Danner G, Clark NA. Liquid-crystal-solid interface structure at the antiferroelectric-ferroelectric phase transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 66:061709. [PMID: 12513307 DOI: 10.1103/physreve.66.061709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2002] [Indexed: 05/24/2023]
Abstract
Total internal reflection is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented.
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Affiliation(s)
- D Coleman
- Condensed Matter Laboratory, Department of Physics, University of Colorado, Boulder, CO 80309, USA
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Spector MS, Prasad SK, Weslowski BT, Kamien RD, Selinger JV, Ratna BR, Shashidhar R. Chiral twisting of a smectic-A liquid crystal. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:3977-3983. [PMID: 11088179 DOI: 10.1103/physreve.61.3977] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/1999] [Indexed: 05/23/2023]
Abstract
Chiral twisting of the molecular orientation within the layer of a smectic-A liquid crystal has been investigated using circular dichroism spectroscopy. The results indicate that a rotation of the layers away from the alignment direction is induced by the surface electroclinic effect. This leads to an interfacial region where the molecular director twists from the alignment direction until it reaches the layer normal direction. A theory is presented to explain the observed field and temperature dependence of the circular dichroism.
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Affiliation(s)
- MS Spector
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6950, Washington, D.C. 20375-5348, USA
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Sprunt S, Selinger JV, Crawford GP, Ratna BR, Shashidhar R. New fluctuation mode in a chiral smectic-A liquid crystal with a uniaxial layer modulation. PHYSICAL REVIEW LETTERS 1995; 74:4671-4674. [PMID: 10058569 DOI: 10.1103/physrevlett.74.4671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Crandall KA, Tripathi S, Rosenblatt C. Surface-mediated electroclinic effect in a chiral nematic liquid crystal. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 46:R715-R718. [PMID: 9908230 DOI: 10.1103/physreva.46.r715] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Zhuang Z, Clark NA, Meadows MR. Orientational plasticity at a smectic-liquid-crystal-anisotropic-solid interface. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 45:R6981-R6984. [PMID: 9906851 DOI: 10.1103/physreva.45.r6981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Chen W, Ouchi Y, Moses T, Shen YR, Yang KH. Surface electroclinic effect on the layer structure of a ferroelectric liquid crystal. PHYSICAL REVIEW LETTERS 1992; 68:1547-1550. [PMID: 10045159 DOI: 10.1103/physrevlett.68.1547] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Lee SD, Patel JS, Goodby JW. Nature of the surface-induced order above the direct isotropic to chiral-smectic-A transition. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1991; 44:2749-2751. [PMID: 9906261 DOI: 10.1103/physreva.44.2749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Patel JS, Lee SD, Goodby JW. Nature of smectic ordering at a solid-liquid-crystal interface and its influence on layer growth. PHYSICAL REVIEW LETTERS 1991; 66:1890-1893. [PMID: 10043336 DOI: 10.1103/physrevlett.66.1890] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Lee SD, Patel JS, Goodby JW. Anomalous electroclinic effect associated with molecular conformation distributions in chiral smectic-A liquid crystals. PHYSICAL REVIEW LETTERS 1991; 66:449-452. [PMID: 10043810 DOI: 10.1103/physrevlett.66.449] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Lee SD, Patel JS. Symmetry-breaking effect of interfacial interactions on electro-optical properties of liquid crystals. PHYSICAL REVIEW LETTERS 1990; 65:56-59. [PMID: 10042171 DOI: 10.1103/physrevlett.65.56] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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