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Nacke P, Manabe A, Klasen-Memmer M, Chen X, Martinez V, Freychet G, Zhernenkov M, Maclennan JE, Clark NA, Bremer M, Giesselmann F. New examples of ferroelectric nematic materials showing evidence for the antiferroelectric smectic-Z phase. Sci Rep 2024; 14:4473. [PMID: 38396051 DOI: 10.1038/s41598-024-54832-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 02/16/2024] [Indexed: 02/25/2024] Open
Abstract
We present a new ferroelectric nematic material, 4-((4'-((trans)-5-ethyloxan-2-yl)-2',3,5,6'-tetrafluoro-[1,1'-biphenyl]-4-yl)difluoromethoxy)-2,6-difluorobenzonitrile (AUUQU-2-N) and its higher homologues, the molecular structures of which include fluorinated building blocks, an oxane ring, and a terminal cyano group, all contributing to a large molecular dipole moment of about 12.5 D. We observed that AUUQU-2-N has three distinct liquid crystal phases, two of which were found to be polar phases with a spontaneous electric polarization Ps of up to 6 µC cm-2. The highest temperature phase is a common enantiotropic nematic (N) exhibiting only field-induced polarization. The lowest-temperature, monotropic phase proved to be a new example of the ferroelectric nematic phase (NF), evidenced by a single-peak polarization reversal current response, a giant imaginary dielectric permittivity on the order of 103, and the absence of any smectic layer X-ray diffraction peaks. The ordinary nematic phase N and the ferroelectric nematic phase NF are separated by an antiferroelectric liquid crystal phase which has low permittivity and a polarization reversal current exhibiting a characteristic double-peak response. In the polarizing light microscope, this antiferroelectric phase shows characteristic zig-zag defects, evidence of a layered structure. These observations suggest that this is another example of the recently discovered smectic ZA (SmZA) phase, having smectic layers with the molecular director parallel to the layer planes. The diffraction peaks from the smectic layering have not been observed to date but detailed 2D X-ray studies indicate the presence of additional short-range structures including smectic C-type correlations in all three phases-N, SmZA and NF-which may shed new light on the understanding of polar and antipolar order in these phases.
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Affiliation(s)
- Pierre Nacke
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Atsutaka Manabe
- Display Solutions, Merck Electronics KGaA, 64293, Darmstadt, Germany
- Individual researcher (Since 01.01.22), 64625, Bensheim, Germany
| | | | - Xi Chen
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA
| | - Vikina Martinez
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA
| | - Guillaume Freychet
- Brookhaven National Laboratory, National Synchrotron Light Source-II, Upton, NY, 11973, USA
| | - Mikhail Zhernenkov
- Brookhaven National Laboratory, National Synchrotron Light Source-II, Upton, NY, 11973, USA
| | - Joseph E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA
| | - Noel A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA
| | - Matthias Bremer
- Display Solutions, Merck Electronics KGaA, 64293, Darmstadt, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
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2
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Chowdhury RA, Green AAS, Park CS, Maclennan JE, Clark NA. Topological defect coarsening in quenched smectic-C films analyzed using artificial neural networks. Phys Rev E 2023; 107:044701. [PMID: 37198757 DOI: 10.1103/physreve.107.044701] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 01/17/2023] [Indexed: 05/19/2023]
Abstract
Mechanically quenching a thin film of smectic-C liquid crystal results in the formation of a dense array of thousands of topological defects in the director field. The subsequent rapid coarsening of the film texture by the mutual annihilation of defects of opposite sign has been captured using high-speed, polarized light video microscopy. The temporal evolution of the texture has been characterized using an object-detection convolutional neural network to determine the defect locations, and a binary classification network customized to evaluate the brush orientation dynamics around the defects in order to determine their topological signs. At early times following the quench, inherent limits on the spatial resolution result in undercounting of the defects and deviations from expected behavior. At intermediate to late times, the observed annihilation dynamics scale in agreement with theoretical predictions and simulations of the 2D XY model.
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Affiliation(s)
- Ravin A Chowdhury
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Adam A S Green
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Cheol S Park
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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3
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Chen X, Martinez V, Korblova E, Freychet G, Zhernenkov M, Glaser MA, Wang C, Zhu C, Radzihovsky L, Maclennan JE, Walba DM, Clark NA. The smectic Z A phase: Antiferroelectric smectic order as a prelude to the ferroelectric nematic. Proc Natl Acad Sci U S A 2023; 120:e2217150120. [PMID: 36791101 PMCID: PMC9974471 DOI: 10.1073/pnas.2217150120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 12/19/2022] [Indexed: 02/16/2023] Open
Abstract
We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to the almost perfectly polar-ordered ferroelectric nematic. This intermediate phase, which fills a 100-y-old void in the taxonomy of smectic LCs and which we term the "smectic ZA," is antiferroelectric, with the nematic director and polarization oriented parallel to smectic layer planes, and the polarization alternating in sign from layer to layer with a 180 Å period. A Landau free energy, originally derived from the Ising model of ferromagnetic ordering of spins in the presence of dipole-dipole interactions, and applied to model incommensurate antiferroelectricity in crystals, describes the key features of the nematic-SmZA-ferroelectric nematic phase sequence.
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Affiliation(s)
- Xi Chen
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Vikina Martinez
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Eva Korblova
- Department of Chemistry and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Guillaume Freychet
- Brookhaven National Laboratory, National Synchrotron Light Source-II, Upton, NY11973
| | - Mikhail Zhernenkov
- Brookhaven National Laboratory, National Synchrotron Light Source-II, Upton, NY11973
| | - Matthew A. Glaser
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Cheng Wang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Leo Radzihovsky
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Joseph E. Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - David M. Walba
- Department of Chemistry and Soft Materials Research Center, University of Colorado, Boulder, CO80309
| | - Noel A. Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO80309
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4
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Dolganov PV, Shuravin NS, Dolganov VK, Kats EI, Stannarius R, Harth K, Trittel T, Park CS, Maclennan JE. Transient hexagonal structures in sheared emulsions of isotropic inclusions on smectic bubbles in microgravity conditions. Sci Rep 2021; 11:19144. [PMID: 34580344 PMCID: PMC8476617 DOI: 10.1038/s41598-021-98166-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 08/19/2021] [Indexed: 11/08/2022] Open
Abstract
We describe the collective behavior of isotropic droplets dispersed over a spherical smectic bubble, observed under microgravity conditions on the International Space Station (ISS). We find that droplets can form two-dimensional hexagonal structures changing with time. Our analysis indicates the possibility of spatial and temporal periodicity of such structures of droplets. Quantitative analysis of the hexagonal structure including the first three coordination circles was performed. A peculiar periodic-in-time ordering of the droplets, related to one-dimensional motion of droplets with non-uniform velocity, was found.
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Affiliation(s)
- P V Dolganov
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia
| | - N S Shuravin
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia
| | - V K Dolganov
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia.
| | - E I Kats
- L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, 142432, Chernogolovka, Moscow Region, Russia
| | - R Stannarius
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - K Harth
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - T Trittel
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - C S Park
- Department of Physics, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - J E Maclennan
- Department of Physics, University of Colorado Boulder, Boulder, CO, 80309, USA
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5
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Chen D, Coleman DA, Zhu C, Chattham N, Jenz F, Cheng X, Tschierske C, Glaser MA, Maclennan JE, Clark NA. Frustration between two- and three-dimensional smectic ordering leads to a biaxial nematic phase. Soft Matter 2020; 16:747-753. [PMID: 31825443 DOI: 10.1039/c9sm01809c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The bola-amphiphilic, T-shaped mesogen CT2 has an aromatic, biphenyl core terminated on both ends by hydrophilic groups and a semi-perfluorinated, aliphatic side chain. Upon cooling from the isotropic phase, the fluorinated tails and the polar, rod-like cores nanophase-segregate to form a fluid lamellar phase. At high temperatures, the biphenyl cores are orientationally disordered in two dimensions (2D) in the lamellar planes but on further cooling the cores order orientationally, giving a biaxial lamellar phase with 2D nematic in-plane ordering. At lower temperature, the aromatic and hydrophilic parts of the cores nanosegregate within the lamellae and 2D smectic correlations of the head groups develop. X-ray diffraction shows that this 2D smectic ordering is incompatible with the initial lamellar structure, with both structures becoming short-ranged, resulting in a 3D biaxial nematic phase with macroscopic orthorhombic symmetry featuring strong smectic correlations in two orthogonal spatial dimensions. Freeze-fracture transmission electron microscopy enables direct visualization of the resulting short-ranged periodic structures.
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Affiliation(s)
- Dong Chen
- Institute of Process Equipment, College of Energy Engineering, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
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6
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Klopp C, Trittel T, Eremin A, Harth K, Stannarius R, Park CS, Maclennan JE, Clark NA. Structure and dynamics of a two-dimensional colloid of liquid droplets. Soft Matter 2019; 15:8156-8163. [PMID: 31595938 DOI: 10.1039/c9sm01433k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Droplet arrays in thin, freely suspended liquid-crystalline smectic A films can form two-dimensional (2D) colloids. The droplets interact repulsively, arranging locally in a more or less hexagonal arrangement with only short-range spatial and orientational correlations and local lattice cell parameters that depend on droplet size. In contrast to quasi-2D colloids described earlier, there is no 3D bulk liquid subphase that affects the hydrodynamics. Although the films are surrounded by air, the droplet dynamics are genuinely 2D, the mobility of each droplet in its six-neighbor cage being determined by the ratio of cage and droplet sizes, rather than by the droplet size as in quasi-2D colloids. These experimental observations are described well by Saffman's model of a diffusing particle in a finite 2D membrane. The experiments were performed in microgravity, on the International Space Station.
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Affiliation(s)
- Christoph Klopp
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Torsten Trittel
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Alexey Eremin
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Kirsten Harth
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Ralf Stannarius
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Cheol S Park
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
| | - Joseph E Maclennan
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
| | - Noel A Clark
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
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7
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Alshomrany AS, Nguyen Z, Maclennan JE, Clark NA. Scanned conical illumination as a probe of electro-optic retro-reflection. Opt Express 2019; 27:18383-18398. [PMID: 31252783 DOI: 10.1364/oe.27.018383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 05/19/2019] [Indexed: 06/09/2023]
Abstract
We describe a prototype element for use in probing electro-optic retro-reflection in sensor applications, illuminating a planar-aligned nematic liquid crystal electro-optic cell with convergent light having a single, tunable angle of incidence (tunable conical illumination). This illumination is generated using a 100X, high numerical aperture, long working-distance microscope objective under conditions of extreme spherical aberration. The electro-optic effect observed is multiple-beam optical interference between polarized reflections from the two bounding plates of the cell, rendered tunable with voltage-controlled refractive index changes induced by molecular reorientation of the liquid crystal. Characterization of the reflectivity vs. angle of incidence and applied voltage enables identification of conditions of high-contrast, low power, electro-optic reflectivity control applicable to fiber optics.
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8
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Green AAS, Tuchband MR, Shao R, Shen Y, Visvanathan R, Duncan AE, Lehmann A, Tschierske C, Carlson ED, Guzman E, Kolber M, Walba DM, Park CS, Glaser MA, Maclennan JE, Clark NA. Chiral Incommensurate Helical Phase in a Smectic of Achiral Bent-Core Mesogens. Phys Rev Lett 2019; 122:107801. [PMID: 30932628 DOI: 10.1103/physrevlett.122.107801] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Indexed: 06/09/2023]
Abstract
An achiral, bent-core mesogen forms several tilted smectic liquid crystal phases, including a nonpolar, achiral de Vries smectic A which transitions to a chiral, ferroelectric state in applied electric fields above a threshold. At lower temperature, a chiral, ferrielectric phase with a periodic, supermolecular modulation of the tilt azimuth, indicated by a Bragg peak in carbon-edge resonant soft x-ray scattering, is observed. The absence of a corresponding resonant umklapp peak identifies the superlayer structure as a twist-bend-like helix that is only weakly modulated by the smectic layering.
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Affiliation(s)
- Adam A S Green
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Michael R Tuchband
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Renfan Shao
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Yongqiang Shen
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Rayshan Visvanathan
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Alexandra E Duncan
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Anne Lehmann
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
| | - Carsten Tschierske
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
| | - Eric D Carlson
- Department of Chemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0215, USA
| | - Edward Guzman
- Department of Chemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0215, USA
| | - Maria Kolber
- Department of Chemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0215, USA
| | - David M Walba
- Department of Chemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0215, USA
| | - Cheol S Park
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Matthew A Glaser
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Joseph E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
| | - Noel A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado, 80309-0390, USA
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9
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Radzihovsky SP, Cranfill C, Nguyen Z, Park CS, Maclennan JE, Glaser MA, Clark NA. Two-dimensional island emulsions in ultrathin, freely-suspended smectic liquid crystal films. Soft Matter 2017; 13:6314-6321. [PMID: 28849846 DOI: 10.1039/c7sm01584d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report a novel type of two-dimensional colloidal emulsion, in which arrays of disc-shaped liquid crystal domains are created in ultrathin, freely-suspended, fluid smectic C liquid crystal films. After a film has been drawn across an aperture, an island emulsion is produced by repeatedly compressing and expanding the film while maintaining vigorous shear and extensional air flow across its area. Once formed, these emulsions restructure over a period of a few minutes to a stable state that then changes only slowly, over the course of several days. This stability enables study of the sedimentation of the emulsion under in-plane gravitation produced by tilting the film, during which the original island emulsion segregates into regions with different kinds of emulsions distinguished by the size, density, and degree of order of the islands. We observe a rich array of phenomena that includes the formation of chains of islands organized into two-dimensional smectics in the dilute phase, and island deformation and coalescence in the condensed phase.
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Affiliation(s)
- Sarah P Radzihovsky
- Soft Materials Research Center and Department of Physics, University of Colorado Boulder, Boulder, CO 80309, USA.
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10
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Shi Y, Sun Z, Chen R, Zhu C, Shoemaker RK, Tsai E, Walba DM, Glaser MA, Maclennan JE, Chen D, Clark NA. Effect of Conformational Chirality on Optical Activity Observed in a Smectic of Achiral, Bent-Core Molecules. J Phys Chem B 2017; 121:6944-6950. [DOI: 10.1021/acs.jpcb.7b04033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yue Shi
- State
Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Zeyong Sun
- State
Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
- Institute
of Process Equipment, College of Energy Engineering, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
| | - Ran Chen
- State
Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
- Institute
of Process Equipment, College of Energy Engineering, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
| | - Chenhui Zhu
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Richard K. Shoemaker
- Department
of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Ethan Tsai
- Department
of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0215, United States
- Department
of Chemistry, Metropolitan State University of Denver, Denver, Colorado 80217, United States
| | - David M. Walba
- Department
of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Matthew A. Glaser
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Joseph E. Maclennan
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Dong Chen
- State
Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
- Institute
of Process Equipment, College of Energy Engineering, Zhejiang University, Zheda Road No. 38, Hangzhou, 310027, China
| | - Noel A. Clark
- Department
of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
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11
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Qi Z, Ferguson K, Sechrest Y, Munsat T, Park CS, Glaser MA, Maclennan JE, Clark NA, Kuriabova T, Powers TR. Active microrheology of smectic membranes. Phys Rev E 2017; 95:022702. [PMID: 28297876 DOI: 10.1103/physreve.95.022702] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Indexed: 11/07/2022]
Abstract
Thin fluid membranes embedded in a bulk fluid of different viscosity are of fundamental interest as experimental realizations of quasi-two-dimensional fluids and as models of biological membranes. We have probed the hydrodynamics of thin fluid membranes by active microrheology using small tracer particles to observe the highly anisotropic flow fields generated around a rigid oscillating post inserted into a freely suspended smectic liquid crystal film that is surrounded by air. In general, at distances more than a few Saffman lengths from the meniscus around the post, the measured velocities are larger than the flow computed by modeling a moving disklike inclusion of finite extent by superposing Levine-MacKintosh response functions for pointlike inclusions in a viscous membrane. The observed discrepancy is attributed to additional coupling of the film with the air below the film that is displaced directly by the shaft of the moving post.
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Affiliation(s)
- Zhiyuan Qi
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Kyle Ferguson
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Yancey Sechrest
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Tobin Munsat
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Cheol Soo Park
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Matthew A Glaser
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.,Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Tatiana Kuriabova
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
| | - Thomas R Powers
- School of Engineering and Department of Physics, Brown University, Providence, Rhode Island 02912, USA
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12
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Kuriabova T, Powers TR, Qi Z, Goldfain A, Park CS, Glaser MA, Maclennan JE, Clark NA. Hydrodynamic interactions in freely suspended liquid crystal films. Phys Rev E 2016; 94:052701. [PMID: 27967127 DOI: 10.1103/physreve.94.052701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Indexed: 06/06/2023]
Abstract
Hydrodynamic interactions play an important role in biological processes in cellular membranes, a large separation of length scales often allowing such membranes to be treated as continuous, two-dimensional (2D) fluids. We study experimentally and theoretically the hydrodynamic interaction of pairs of inclusions in two-dimensional, fluid smectic liquid crystal films suspended in air. Such smectic membranes are ideal systems for performing controlled experiments as they are mechanically stable, of highly uniform structure, and have well-defined, variable thickness, enabling experimental investigation of the crossover from 2D to 3D hydrodynamics. Our theoretical model generalizes the Levine-MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. We describe in detail the theoretical and computational approach previously outlined in Z. Qi et al., Phys. Rev. Lett. 113, 128304 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.128304 and extend the method to study the mutual mobilities of inclusions with asymmetric shapes. The model predicts well the observed mutual mobilities of pairs of circular inclusions in films and the self-mobility of a circular inclusion in the vicinity of a linear boundary.
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Affiliation(s)
- Tatiana Kuriabova
- Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
| | - Thomas R Powers
- School of Engineering and Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - Zhiyuan Qi
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Aaron Goldfain
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Cheol Soo Park
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Matthew A Glaser
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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13
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Zhu C, Tuchband MR, Young A, Shuai M, Scarbrough A, Walba DM, Maclennan JE, Wang C, Hexemer A, Clark NA. Resonant Carbon K-Edge Soft X-Ray Scattering from Lattice-Free Heliconical Molecular Ordering: Soft Dilative Elasticity of the Twist-Bend Liquid Crystal Phase. Phys Rev Lett 2016; 116:147803. [PMID: 27104729 DOI: 10.1103/physrevlett.116.147803] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Indexed: 05/16/2023]
Abstract
Resonant x-ray scattering shows that the bulk structure of the twist-bend liquid crystal phase, recently discovered in bent molecular dimers, has spatial periodicity without electron density modulation, indicating a lattice-free heliconical nematic precession of orientation that has helical glide symmetry. In situ study of the bulk helix texture of the dimer CB7CB shows an elastically confined temperature-dependent minimum helix pitch, but a remarkable elastic softness of pitch in response to dilative stresses. Scattering from the helix is not detectable in the higher temperature nematic phase.
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Affiliation(s)
- Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Michael R Tuchband
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA
| | - Anthony Young
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Min Shuai
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA
| | - Alyssa Scarbrough
- Department of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0215, USA
| | - David M Walba
- Department of Chemistry and Biochemistry and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0215, USA
| | - Joseph E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA
| | - Cheng Wang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Alexander Hexemer
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Noel A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado Boulder, Boulder, Colorado 80309-0390, USA
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14
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Shuai M, Klittnick A, Shen Y, Smith GP, Tuchband MR, Zhu C, Petschek RG, Mertelj A, Lisjak D, Čopič M, Maclennan JE, Glaser MA, Clark NA. Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates. Nat Commun 2016; 7:10394. [PMID: 26817823 PMCID: PMC4738347 DOI: 10.1038/ncomms10394] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/08/2015] [Indexed: 11/18/2022] Open
Abstract
Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field. Ferromagnetism has been known as a material property of solids since the time of the ancient Greeks. Here, Shuai et al. report that magnetic nanoplates suspended in a simple solvent can spontaneously align to form a ferromagnetic liquid, capable of both producing and sensing magnetic fields.
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Affiliation(s)
- M Shuai
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - A Klittnick
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Y Shen
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - G P Smith
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - M R Tuchband
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - C Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - R G Petschek
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - A Mertelj
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - D Lisjak
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - M Čopič
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia.,Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - J E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - M A Glaser
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - N A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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15
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Qi Z, Park CS, Glaser MA, Maclennan JE, Clark NA. Experimental realization of an incompressible Newtonian fluid in two dimensions. Phys Rev E 2016; 93:012706. [PMID: 26871134 DOI: 10.1103/physreve.93.012706] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Indexed: 06/05/2023]
Abstract
The Brownian diffusion of micron-scale inclusions in freely suspended smectic-A liquid crystal films a few nanometers thick and several millimeters in diameter depends strongly on the air surrounding the film. Near atmospheric pressure, the three-dimensionally coupled film-gas system is well described by Hughes-Pailthorpe-White hydrodynamic theory but at lower pressure (p≲70 torr), the diffusion coefficient increases substantially, tending in high vacuum toward the two-dimensional limit where it is determined by film size. In the absence of air, the films are found to be a nearly ideal physical realization of a two-dimensional, incompressible Newtonian fluid.
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Affiliation(s)
- Zhiyuan Qi
- Department of Physics and the Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Cheol Soo Park
- Department of Physics and the Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Matthew A Glaser
- Department of Physics and the Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics and the Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics and the Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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16
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Chen D, Wang H, Li M, Glaser MA, Maclennan JE, Clark NA. Chiral random grain boundary phase of achiral hockey-stick liquid crystals. Soft Matter 2014; 10:9105-9109. [PMID: 25310113 DOI: 10.1039/c4sm01814a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A disordered chiral conglomerate, the random grain boundary (RGB) phase, has been observed below the smectic A liquid crystal phase of an achiral, hockey-stick molecule. In cells, the RGB phase appears dark between crossed polarizers but decrossing the polarizers reveals large left- and right-handed chiral domains with opposite optical rotation. Freeze-fracture transmission electron microscopy reveals that the RGB phase is an assembly of randomly oriented blocks of smectic layers, an arrangement that distinguishes the RGB from the dark, chiral conglomerate phases of bent-core mesogens. X-ray diffraction indicates that there is significant layer shrinkage at the SmA-RGB phase transition, which is marked by the collapse of layers with long-range order into small, randomly oriented smectic blocks.
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Affiliation(s)
- Dong Chen
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309-0390, USA.
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17
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Qi Z, Nguyen ZH, Park CS, Glaser MA, Maclennan JE, Clark NA, Kuriabova T, Powers TR. Mutual diffusion of inclusions in freely suspended smectic liquid crystal films. Phys Rev Lett 2014; 113:128304. [PMID: 25279649 DOI: 10.1103/physrevlett.113.128304] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Indexed: 06/03/2023]
Abstract
We study experimentally and theoretically the hydrodynamic interaction of pairs of circular inclusions in two-dimensional, fluid smectic membranes suspended in air. By analyzing their Brownian motion, we find that the radial mutual mobilities of identical inclusions are independent of their size but that the angular coupling becomes strongly size dependent when their radius exceeds a characteristic hydrodynamic length. These observations are described well for arbitrary inclusion separations by a model that generalizes the Levine-MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent.
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Affiliation(s)
- Zhiyuan Qi
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Zoom Hoang Nguyen
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Cheol Soo Park
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Matthew A Glaser
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Tatiana Kuriabova
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Thomas R Powers
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA and Department of Physics, Brown University, Providence, Rhode Island 02912, USA
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18
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Shi Y, Fang G, Glaser MA, Maclennan JE, Korblova E, Walba DM, Clark NA. Phase winding of a nematic liquid crystal by dynamic localized reorientation of an azo-based self-assembled monolayer. Langmuir 2014; 30:9560-9566. [PMID: 25019612 DOI: 10.1021/la501983u] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Azobenzene-based molecules forming a self-assembled monolayer (SAM) tethered to a glass surface are highly photosensitive and readily reorient liquid crystals in contact with them when illuminated with polarized actinic light. We probe the coupling of such monolayers to nematic liquid crystal in a hybrid cell by studying the dynamics of liquid crystal reorientation in response to local orientational changes of the monolayer induced by a focused actinic laser with a rotating polarization. The steady increase in the azimuth of the mean molecular orientation of the SAM around the laser beam locally reorients the nematic, winding up an extended set of nested rings of splay-bend nematic director reorientation until the cumulative elastic torque exceeds that of the surface coupling within the beam, after which the nematic director starts to slip. Quantitative analyses of the ring dynamics allow measurements of the anchoring strength of the azo-SAM and its interaction with the nematic liquid crystal.
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Affiliation(s)
- Yue Shi
- Department of Physics, Liquid Crystal Materials Research Center, University of Colorado , Boulder, Colorado 80309, United States
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19
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Chen D, Nakata M, Shao R, Tuchband MR, Shuai M, Baumeister U, Weissflog W, Walba DM, Glaser MA, Maclennan JE, Clark NA. Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:022506. [PMID: 25353488 DOI: 10.1103/physreve.89.022506] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Indexed: 06/04/2023]
Abstract
The chiral, heliconical (twist-bend) nematic ground state is reported in an achiral, rigid, bent-core mesogen (UD68). Similar to the nematic twist-bend (N(TB)) phase observed in bent molecular dimers, the N(TB) phase of UD68 forms macroscopic, smecticlike focal-conic textures and exhibits nanoscale, periodic modulation with no associated modulation of the electron density, i.e., without a detectable lamellar x-ray reflection peak. The N(TB) helical pitch is p(TB) ∼ 14 nm. When an electric field is applied normal to the helix axis, a weak electroclinic effect is observed, revealing 50-μm-scale left- and right-handed domains in a chiral conglomerate.
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Affiliation(s)
- Dong Chen
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Michi Nakata
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Renfan Shao
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Michael R Tuchband
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Min Shuai
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Ute Baumeister
- Institut für Chemie, Physikalische Chemie, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz, D-06120 Halle (Saale), Germany
| | - Wolfgang Weissflog
- Institut für Chemie, Physikalische Chemie, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz, D-06120 Halle (Saale), Germany
| | - David M Walba
- Department of Chemistry and Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309-0215, USA
| | - Matthew A Glaser
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Joseph E Maclennan
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
| | - Noel A Clark
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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20
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Chen D, Shen Y, Aguero J, Korblova E, Walba DM, Kapernaum N, Giesselmann F, Watanabe J, Maclennan JE, Glaser MA, Clark NA. Chiral Isotropic Sponge Phase of Hexatic Smectic Layers of Achiral Molecules. Chemphyschem 2013; 15:1502-7. [DOI: 10.1002/cphc.201300912] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2013] [Revised: 10/31/2013] [Indexed: 11/08/2022]
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21
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Shen Y, Wang L, Shao R, Gong T, Zhu C, Yang H, Maclennan JE, Walba DM, Clark NA. Generalized Langevin-Debye model of the field dependence of tilt, birefringence, and polarization current near the de Vries smectic-A* to smectic-C* liquid crystal phase transition. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:062504. [PMID: 24483465 DOI: 10.1103/physreve.88.062504] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Indexed: 06/03/2023]
Abstract
In chiral smectic-A (Sm-A) liquid crystals, an applied electric field induces a tilt of the optic axis from the layer normal. When these materials are of the de Vries type, the electroclinic tilt susceptibility is unusually large, with the field-induced director reorientation accompanied by a substantial increase in optical birefringence with essentially no change in the smectic layer spacing. In order to account for the observed electro-optic behavior, we assume that the molecular orientation distribution in the Sm-A has two degrees of freedom: azimuthal orientation and tilt of the molecular long axis from the layer normal, with the tilt confined to a narrow range of angles. We present a generalized Langevin-Debye model of the response of this orientational distribution to applied field that gives a field-induced optic axis tilt, birefringence, and polarization dependence that agrees well with experimental measurements and reproduces the double-peaked polarization current response characteristic of a first-order Sm-A(*)-Sm-C(*) transition. Additionally, we find that the measured field-induced polarization and the Langevin-Debye model predictions can be quantitatively described as pre-transitional behavior near the tricritical point of a recently published generalized 3D XY model of interacting hard rods confined to reorient on a cone in the presence of an applied field.
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Affiliation(s)
- Yongqiang Shen
- Department of Physics, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Lixing Wang
- Department of Chemistry and Biochemistry, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Renfan Shao
- Department of Physics, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Tao Gong
- Department of Chemistry and Biochemistry, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Chenhui Zhu
- Department of Physics, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Hong Yang
- Department of Chemistry and Biochemistry, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Joseph E Maclennan
- Department of Physics, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - David M Walba
- Department of Chemistry and Biochemistry, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Noel A Clark
- Department of Physics, and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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22
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Zhu C, Shao R, Reddy RA, Chen D, Shen Y, Gong T, Glaser MA, Korblova E, Rudquist P, Maclennan JE, Walba DM, Clark NA. Topological Ferroelectric Bistability in a Polarization-Modulated Orthogonal Smectic Liquid Crystal. J Am Chem Soc 2012; 134:9681-7. [DOI: 10.1021/ja3009314] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chenhui Zhu
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Renfan Shao
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - R. Amaranatha Reddy
- Department of Chemistry and
Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United
States
| | - Dong Chen
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Yongqiang Shen
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Tao Gong
- Department of Chemistry and
Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United
States
| | - Matthew A. Glaser
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Eva Korblova
- Department of Chemistry and
Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United
States
| | - Per Rudquist
- Department of Microtechnology
and Nanoscience, Chalmers University of Technology, S-41269 Göteborg, Sweden
| | - Joseph E. Maclennan
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - David M. Walba
- Department of Chemistry and
Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United
States
| | - Noel A. Clark
- Department
of Physics and Liquid
Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
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23
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Nakata M, Chen D, Shao R, Korblova E, Maclennan JE, Walba DM, Clark NA. Electro-optic response of the anticlinic, antiferroelectric liquid-crystal phase of a biaxial bent-core molecule with tilt angle near 45∘. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 85:031704. [PMID: 22587111 DOI: 10.1103/physreve.85.031704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Indexed: 05/31/2023]
Abstract
We describe the unusual electro-optic response of a biaxial bent-core liquid crystal molecule that exhibits an anticlinic, antiferroelectric smectic phase (Sm-C(A)P(A)) with a molecular tilt angle close to 45°. In the ground state, the sample shows very low birefringence. A weak applied electric field distorts the antiferroelectric ground state, inducing a small azimuthal reorientation of the molecules on the tilt cone. This results in only a modest increase in the birefringence but an anomalously large (∼40°) analog rotation of the extinction direction. This unusual electro-optic response is shown to be a consequence of the molecular biaxiality.
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Affiliation(s)
- Michi Nakata
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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24
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Chen D, Heberling MS, Nakata M, Hough LE, Maclennan JE, Glaser MA, Korblova E, Walba DM, Watanabe J, Clark NA. Cover Picture: Structure of the B4 Liquid Crystal Phase near a Glass Surface (ChemPhysChem 1/2012). Chemphyschem 2012. [DOI: 10.1002/cphc.201290000] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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25
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Eremin A, Baumgarten S, Harth K, Stannarius R, Nguyen ZH, Goldfain A, Park CS, Maclennan JE, Glaser MA, Clark NA. Two-dimensional microrheology of freely suspended liquid crystal films. Phys Rev Lett 2011; 107:268301. [PMID: 22243186 DOI: 10.1103/physrevlett.107.268301] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 08/21/2011] [Indexed: 05/31/2023]
Abstract
Smectic liquid crystals form freely-suspended, fluid films of highly uniform structure and thickness, making them ideal systems for studies of hydrodynamics in two dimensions. We have measured particle mobility and shear viscosity by direct observation of the gravitational drift of silica spheres and smectic islands included in these fluid membranes. In thick films, we observe a hydrodynamic regime dominated by lateral confinement effects, with the mobility of the inclusion determined predominantly by coupling of the fluid flow to the fixed boundaries of the film. In thin films, the mobility of inclusions is governed primarily by coupling of the fluid to the surrounding air, as predicted by Saffman-Delbrück theory.
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Affiliation(s)
- A Eremin
- Otto-von-Guericke Universität Magdeburg, Institute for Experimental Physics, D-39016 Magdeburg, Germany
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26
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Chen D, Heberling MS, Nakata M, Hough LE, Maclennan JE, Glaser MA, Korblova E, Walba DM, Watanabe J, Clark NA. Structure of the B4 Liquid Crystal Phase near a Glass Surface. Chemphyschem 2011; 13:155-9. [DOI: 10.1002/cphc.201100589] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Indexed: 11/05/2022]
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27
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Fang G, Shi Y, Maclennan JE, Walba DM, Clark NA. Photodegradation of azobenzene-based self-assembled monolayers characterized by in-plane birefringence. Langmuir 2011; 27:10407-10411. [PMID: 21812419 DOI: 10.1021/la201306a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Azobenzene-based self-assembled monolayers (azo-SAMs) are photoactive and become orientationally ordered when illuminated with linearly polarized light (LPL), making them attractive as dynamic alignment layers in liquid crystal cells. Azo-SAMs, however, are chemically unstable when exposed to both air and light. We have characterized the photodegradation of a methyl red-based SAM by measuring with a high-sensitivity polarimeter the optical anisotropy induced by illumination with linearly polarized actinic light after the sample is irradiated with circularly polarized light (CPL) in air. The number of unbleached, photoactive molecules in the SAM decays exponentially with CPL exposure time, lowering the reorientation rate during photowriting with LPL. Azo-SAMs in an argon atmosphere, in contrast, are chemically stable and remain photoactive even after exposure to CPL.
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Affiliation(s)
- Guanjiu Fang
- Departments of Physics, University of Colorado, Boulder, Colorado 80309, USA
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28
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Shen Y, Gong T, Shao R, Korblova E, Maclennan JE, Walba DM, Clark NA. Effective conductivity due to continuous polarization reorientation in fluid ferroelectrics. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 84:020701. [PMID: 21928940 DOI: 10.1103/physreve.84.020701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 05/06/2011] [Indexed: 05/31/2023]
Abstract
A smectic-A (SmA) liquid crystal phase of fluid layers with in-plane polarization P is shown to exhibit effective conductivity in the semiconducting range during electric-field-induced polarization reorientation, but becomes insulating once the polarization is aligned with the field. Such fluid ferroelectrics sandwiched between highly insulating layers enable electro-optic devices with long-term dc electrostatic control of polarization and optic axis orientation.
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Affiliation(s)
- Yongqiang Shen
- Department of Physics, Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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Chen D, Maclennan JE, Shao R, Yoon DK, Wang H, Korblova E, Walba DM, Glaser MA, Clark NA. Chirality-Preserving Growth of Helical Filaments in the B4 Phase of Bent-Core Liquid Crystals. J Am Chem Soc 2011; 133:12656-63. [DOI: 10.1021/ja203522x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dong Chen
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Joseph E. Maclennan
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Renfan Shao
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Dong Ki Yoon
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
- Graduate School of Nanoscience and Technology, World Class University, KAIST, Daejeon 305-701, Korea
| | - Haitao Wang
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
- Key Laboratory of Automobile Materials (MOE) and College of Materials Science and Engineering, Jilin University, Changchun 130012, China
| | - Eva Korblova
- Department of Chemistry and Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - David M. Walba
- Department of Chemistry and Biochemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Matthew A. Glaser
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
| | - Noel A. Clark
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, United States
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Yi Y, Maclennan JE, Clark NA. Cooperative liquid-crystal alignment generated by overlaid topography. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:051708. [PMID: 21728557 DOI: 10.1103/physreve.83.051708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 04/18/2011] [Indexed: 05/31/2023]
Abstract
Nematic and smectic liquid crystals were introduced into μm-scale gaps between plates coated with polymer films nanoimprinted with parallel arrays of rectangular channels. Overlaying the channels on the two plates close enough at a slight angle produces a mosaic of alternating planar and homeotropic alignments and hybrid alignment, showing that complex liquid-crystal orientation patterns can be achieved by combining two simple topographic patterns. These alignment patterns are attributed to spatial variation of surface roughness and 3D topographic structure created by a sufficient proximity of the two patterns.
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Affiliation(s)
- Youngwoo Yi
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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31
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Reddy RA, Zhu C, Shao R, Korblova E, Gong T, Shen Y, Garcia E, Glaser MA, Maclennan JE, Walba DM, Clark NA. Spontaneous ferroelectric order in a bent-core smectic liquid crystal of fluid orthorhombic layers. Science 2011; 332:72-7. [PMID: 21454782 DOI: 10.1126/science.1197248] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Macroscopic polarization density, characteristic of ferroelectric phases, is stabilized by dipolar intermolecular interactions. These are weakened as materials become more fluid and of higher symmetry, limiting ferroelectricity to crystals and to smectic liquid crystal stackings of fluid layers. We report the SmAP(F), the smectic of fluid polar orthorhombic layers that order into a three-dimensional ferroelectric state, the highest-symmetry layered ferroelectric possible and the highest-symmetry ferroelectric material found to date. Its bent-core molecular design employs a single flexible tail that stabilizes layers with untilted molecules and in-plane polar ordering, evident in monolayer-thick freely suspended films. Electro-optic response reveals the three-dimensional orthorhombic ferroelectric structure, stabilized by silane molecular terminations that promote parallel alignment of the molecular dipoles in adjacent layers.
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Affiliation(s)
- R Amaranatha Reddy
- Department of Chemistry and Biochemistry, Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309-0215, USA
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32
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Fang G, Koral N, Zhu C, Yi Y, Glaser MA, Maclennan JE, Clark NA, Korblova ED, Walba DM. Effect of concentration on the photo-orientation and relaxation dynamics of self-assembled monolayers of mixtures of an azobenzene-based triethoxysilane with octyltriethoxysilane. Langmuir 2011; 27:3336-3342. [PMID: 21401057 DOI: 10.1021/la104457v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Self-assembled monolayers (SAMs) were prepared from solutions with different proportions of a photoactive, azobenzene-based, silanized derivative of disperse red one (dDR1), and octyltriethoxysilane (OTE), a shorter, nonphotoactive molecule. The in-plane photoinduced orientational ordering of the resulting two component monolayers was monitored via precision measurement of in-plane birefringence using a dedicated high-extinction polarimeter. Measurements of contact angle, absorption, and birefringence show that introduction of OTE into the dDR1 deposition solution produces a continuous reduction of the surface density of dDR1 in the SAM, enabling the study of photowriting and relaxation dynamics in monolayers ranging from 100% dDR1 to samples where the dDR1 coverage is about 35%. The orientational dynamics depend strongly on the areal density of dDR1. As the fractional area of dDR1 is reduced, the rates of photowriting, photoerasing, and thermal relaxation increase, and the local orientational confinement of the molecules becomes more heterogeneous.
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Affiliation(s)
- Guanjiu Fang
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
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33
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Fang G, Shi Y, Maclennan JE, Clark NA, Farrow MJ, Walba DM. Photo-reversible liquid crystal alignment using azobenzene-based self-assembled monolayers: comparison of the bare monolayer and liquid crystal reorientation dynamics. Langmuir 2010; 26:17482-17488. [PMID: 20929215 DOI: 10.1021/la102788j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Photosensitive surfaces treated to have in-plane structural anisotropy by illumination with polarized light can be used to orient liquid crystals (LCs). Here we report a detailed study of the dynamic behavior of this process at both short and long times, comparing the ordering induced in the bare active surface with that of the LC in contact with the surface using a high-sensitivity polarimeter that enables detailed characterization of the anisotropy of the active surface. The experiments were carried out using self-assembled monolayers (SAMs) made from dimethylaminoazobenzene covalently bonded to a glass surface through a triethoxysilane terminus. This surface gives planar alignment of the liquid crystal director with an azimuthal orientation that can be controlled by the polarization of actinic light. We find a remarkable long-term collective interaction between the orientationally ordered SAM and the director field of the LC: while an azobenzene based SAM in contact with an isotropic gas or liquid relaxes to an azimuthally isotropic state in the absence of light due to thermal fluctuations, an orientationally written SAM in contact with LC in the absence of light can maintain the LC director twist permanently, that is, the SAM is capable of providing azimuthal anchoring to the LC even in the presence of a torque about the surface normal. We find that the short-time, transient LC reorientation is limited by the weak azimuthal anchoring strength of the SAM and by the LC viscosity.
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Affiliation(s)
- Guanjiu Fang
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
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Chen D, Zhu C, Shoemaker RK, Korblova E, Walba DM, Glaser MA, Maclennan JE, Clark NA. Pretransitional orientational ordering of a calamitic liquid crystal by helical nanofilaments of a bent-core mesogen. Langmuir 2010; 26:15541-15545. [PMID: 20809598 DOI: 10.1021/la101849h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Mixtures of 8CB (a calamitic mesogen) and NOBOW (P-9-O-PIMB, a bent-core mesogen) have been investigated using differential scanning calorimetry, nuclear magnetic resonance spectroscopy, and freeze fracture transmission electron microscopy. On cooling the isotropic mixture, the NOBOW component phase separates, forming a dilute, random network of helical nanofilaments in the B4 phase with isotropic 8CB material filling the interstitial volume. At lower temperature, but still far above the bulk isotropic-nematic transition of pure 8CB, a significant fraction of the 8CB becomes prealigned on the filament surfaces. We propose that this pretransitional ordering is induced by short-range interactions of the polar 8CB molecules with the NOBOW filaments, leading to the formation of an adsorbed film of orientationally frozen 8CB around each filament.
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Affiliation(s)
- Dong Chen
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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35
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Fang G, Maclennan JE, Clark NA. High extinction polarimeter for the precision measurement of the in-plane optical anisotropy of molecular monolayers. Langmuir 2010; 26:11686-11689. [PMID: 20568821 DOI: 10.1021/la101117n] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A polarimeter using selected Glan-Thompson polarizers, a spatially filtered probe laser beam, precision polarizer orientation, and spatially filtered output coupling into an optical fiber achieves a static extinction ratio between crossed and parallel polarizer and analyzer orientations of I(perpendicular)/I(parallel) approximately = 2 x 10(-10). This instrument allows the detection of retardance as small as 0.0015 nm to better than 1%, enabling the first detailed study of the in-plane birefringence of molecular monolayers. We demonstrate the performance of the polarimeter with measurements of the photoinduced birefringence of azobenzene-based monolayers self-assembled on glass.
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Affiliation(s)
- Guanjiu Fang
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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Abstract
Among the condensed phases, those of lowest point group symmetry are the triclinic crystals, which have only the identity element or the identity and inversion elements. Such low symmetry is stabilized by the specificity of molecular interaction, which is weakened with increasing disorder, so that known phases with fluid degrees of freedom are more symmetric. Here we report triclinic order, appearing as a broken symmetry in a single, isolated, fluid smectic liquid crystal layer freely suspended in air, showing that none of its principal dielectric axes lies either normal or parallel to the layer plane.
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Affiliation(s)
- Nattaporn Chattham
- Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
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37
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Zhu C, Chen D, Shen Y, Jones CD, Glaser MA, Maclennan JE, Clark NA. Nanophase segregation in binary mixtures of a bent-core and a rodlike liquid-crystal molecule. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 81:011704. [PMID: 20365388 DOI: 10.1103/physreve.81.011704] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Indexed: 05/29/2023]
Abstract
We studied mixtures of the achiral bent-core mesogen NOBOW 1,3-phenylene bis[4-(4-9-alkoxyphenyliminonetyl)benzoates] (P-9-O-PIMB) and the small, rodlike liquid crystal 8CB using high-resolution synchrotron x-ray diffraction, freeze fracture transmission electron microscopy, and differential scanning calorimetry. NOBOW and 8CB mix in an isotropic state at high temperatures but phase separate at lower temperatures when NOBOW transforms into the B4 phase and forms chiral helical nanofilaments. In pure NOBOW, the nanofilaments are close packed but at moderate 8CB concentrations, they are separated by nanosized gaps filled by 8CB. At higher concentrations of 8CB, macroscopic phase separation occurs.
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Affiliation(s)
- Chenhui Zhu
- Department of Physics and the Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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38
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Silvestre NM, Patrício P, Telo da Gama MM, Pattanaporkratana A, Park CS, Maclennan JE, Clark NA. Modeling dipolar and quadrupolar defect structures generated by chiral islands in freely suspended liquid crystal films. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:041708. [PMID: 19905326 DOI: 10.1103/physreve.80.041708] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Indexed: 05/28/2023]
Abstract
We report a detailed theoretical analysis of quadrupolar interactions observed between islands, which are disklike inclusions of extra layers, floating in thin, freely suspended smectic- C liquid crystal films. Strong tangential anchoring at the island boundaries results in a strength +1 chiral defect in each island and a companion -1 defect in the film--these forming a topological dipole. While islands of the same handedness form linear chains with the topological dipoles pointing in the same direction, as reported in the literature, islands with different handedness form compact quadrupolar structures with the associated dipoles pointing in opposite directions. The interaction between such heterochiral-island-defect pairs is complex, with the defects moving to minimize the director field distortion as the distance between the islands changes. The details of the interisland potential and the trajectories of the -1 defects depend strongly on the elastic anisotropy of the liquid crystal, which can be modified in the experiments by varying the material chirality of the liquid crystal. A Landau model that describes the energetics of freely mobile defects is solved numerically to find equilibrium configurations for a wide range of parameters.
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Affiliation(s)
- N M Silvestre
- Departamento de Física da Faculdade de Ciências, Universidade de Lisboa, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa Codex, Portugal.
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39
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Yi Y, Lombardo G, Ashby N, Barberi R, Maclennan JE, Clark NA. Topographic-pattern-induced homeotropic alignment of liquid crystals. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:041701. [PMID: 19518244 DOI: 10.1103/physreve.79.041701] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Indexed: 05/27/2023]
Abstract
Polymer films nanoimprinted with checkerboard patterns of square wells align calamitic (rodlike) liquid crystals vertically, horizontally, or tilted depending on the depth/width ratio of the wells. The liquid crystal prefers planar orientation on polymer films that are smooth but when the films are topographically patterned, the increasing elastic energy density as the wells become narrower eventually overcomes the surface anchoring of the polymer and the liquid crystal director field makes a transition from planar to homeotropic. Similar effects have been demonstrated in both nematics and smectics, and the behavior is confirmed by theory and computer simulation.
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Affiliation(s)
- Youngwoo Yi
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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40
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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. Phys Rev E Stat Nonlin Soft Matter Phys 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] [What about the content of this article? (0)] [Affiliation(s)] [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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41
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Lieber SI, Hendershott MC, Pattanaporkratana A, Maclennan JE. Self-organization of bouncing oil drops: two-dimensional lattices and spinning clusters. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 75:056308. [PMID: 17677165 DOI: 10.1103/physreve.75.056308] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Indexed: 05/16/2023]
Abstract
Multiple oil drops bouncing on the surface of a vertically vibrating bath of the same oil exhibit self-organization behavior in two dimensions [S. Protière, Y. Couder, E. Fort, and A. Boudaoud, J. Phys.: Condens. Matter 17, S3529 (2005)]. We describe further the morphology and dynamic behavior of stable assemblies of large bouncing oil drops, for which we find that both the spacing and the lattice structure itself change with frequency, with variants of both square and hexagonal structures being observed. Large "rafts" of drops form soft triangular lattices with faceted boundaries. Small clusters of drops are unstable to coherent, collective spinning under certain driving conditions, manifesting spontaneous rotational symmetry breaking.
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Affiliation(s)
- Suzanne I Lieber
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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42
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Kane A, Shao RF, Maclennan JE, Wang L, Walba DM, Clark NA. Cover Picture: Electric-Field-Driven Deracemization (ChemPhysChem 1/2007). Chemphyschem 2007. [DOI: 10.1002/cphc.200690041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
We demonstrate, both theoretically and experimentally, that it is possible to use an electric field to drive the formation of macroscopic chiral (conglomerate) domains from an initially homogeneous fluid racemate. Field-induced segregation is exhibited in a fluid smectic liquid-crystal phase of a racemic mesogen, wherein enantiomerically-enriched domains are readily identifiable by their chiral electro-optical response. The sharp field-generated boundaries that form between opposite-handed domains broaden by diffusion in the absence of field, but reform rapidly if the field is switched on again, providing unambiguous evidence for the field-driven physical separation of enantiomers. A mean-field model successfully describes the steady-state and the dynamic evolution of conglomerate formation.
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Affiliation(s)
- Alexander Kane
- Department of Physics, University of Colorado, Boulder, CO 80309, USA
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44
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Nakata M, Shao RF, Maclennan JE, Weissflog W, Clark NA. Electric-field-induced chirality flipping in smectic liquid crystals: the role of anisotropic viscosity. Phys Rev Lett 2006; 96:067802. [PMID: 16606050 DOI: 10.1103/physrevlett.96.067802] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Indexed: 05/08/2023]
Abstract
We demonstrate the homogeneous and permanent reversal of the chirality of a condensed phase by an applied electric field. Tilted chiral smectic layers exhibit a coupled polarization density and molecular orientation fields which reorient about the layer normal as couple of fixed handedness in response to small applied electric fields. Experiments on some bent-core smectics show that above a threshold field the induced rotation can occur instead about the molecular long axis and that, as a result, the handedness of the phase can be flipped. The effect is quantitatively described by a nonequilibrium dissipative model of chiral smectic dynamics with anisotropic rotational viscosities.
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Affiliation(s)
- M Nakata
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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45
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Fernsler J, Hough L, Shao RF, Maclennan JE, Navailles L, Brunet M, Madhusudana NV, Mondain-Monval O, Boyer C, Zasadzinski J, Rego JA, Walba DM, Clark NA. Giant-block twist grain boundary smectic phases. Proc Natl Acad Sci U S A 2005; 102:14191-6. [PMID: 16176991 PMCID: PMC1242277 DOI: 10.1073/pnas.0500664102] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Study of a diverse set of chiral smectic materials, each of which has twist grain boundary (TGB) phases over a broad temperature range and exhibits grid patterns in the Grandjean textures of the TGB helix, shows that these features arise from a common structure: "giant" smectic blocks of planar layers of thickness l(b) > 200 nm terminated by GBs that are sharp, mediating large angular jumps in layer orientation between blocks (60 degrees < Delta < 90 degrees ), and lubricating the thermal contraction of the smectic layers within the blocks. This phenomenology is well described by basic theoretical models applicable in the limit that the ratio of molecular tilt penetration length-to-layer coherence length is large, and featuring GBs in which smectic ordering is weak, approaching thin, melted (nematic-like) walls. In this limit the energy cost of change of the block size is small, leading to a wide variation of block dimension, depending on preparation conditions. The models also account for the temperature dependence of the TGB helix pitch.
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Affiliation(s)
- J Fernsler
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309-0390, USA
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46
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Link DR, Chattham N, Maclennan JE, Clark NA. Effect of high spontaneous polarization on defect structures and orientational dynamics of tilted chiral smectic freely suspended films. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 71:021704. [PMID: 15783337 DOI: 10.1103/physreve.71.021704] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Indexed: 05/24/2023]
Abstract
The director structure around topological defects and in 2pi walls in the two-dimensional orientation field of thin freely suspended films of tilted chiral smectic liquid crystal is observed to minimize splay of the spontaneous polarization. Concentric ring patterns in the director field unwind more slowly in higher polarization films. These experiments confirm that polarization space charge increases the effective elasticity of static polarization-splay distortions and that it attracts ionic charge, leading to an increase in the effective orientational viscosity of the director field.
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Affiliation(s)
- Darren R Link
- Department of Physics, and Ferroelectric Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309-0390, USA
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47
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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. Phys Rev E Stat Nonlin Soft Matter Phys 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] [What about the content of this article? (0)] [Affiliation(s)] [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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48
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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. Phys Rev Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Coleman DA, Fernsler J, Chattham N, Nakata M, Takanishi Y, Körblova E, Link DR, Shao RF, Jang WG, Maclennan JE, Mondainn-Monval O, Boyer C, Weissflog W, Pelzl G, Chien LC, Zasadzinski J, Watanabe J, Walba DM, Takezoe H, Clark NA. Polarization-modulated smectic liquid crystal phases. Science 2003; 301:1204-11. [PMID: 12947191 DOI: 10.1126/science.1084956] [Citation(s) in RCA: 272] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or "splayed." However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.
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Affiliation(s)
- D A Coleman
- Department of Physics and Ferroelectric Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO80309 - 0390, USA
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Tian P, Bedrov D, Smith GD, Glaser M, Maclennan JE. A molecular-dynamics simulation study of the switching dynamics of a nematic liquid crystal under an applied electrical field. J Chem Phys 2002. [DOI: 10.1063/1.1516190] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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