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Electro-Optical Characteristics of Quasi-Homogeneous Cell in Twisted Nematic Mode. Symmetry (Basel) 2023. [DOI: 10.3390/sym15030597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
A liquid crystal (LC) director distribution was numerically analyzed in 90-degree twisted nematic (TN) LC cells with a symmetric and an asymmetric azimuthal anchoring strength of the alignment substrate and the influence of anchoring strength on the electro-optical property of the TN cell was evaluated. The twist angle decreased with decreasing azimuthal anchoring strength and the LC orientation changed to a homogeneous orientation with the twist angle of 0 degrees in the LC cell with asymmetric azimuthal anchoring strength, specifically with the strong anchoring substrate and the weak anchoring substrate below a critical strength. The asymmetric anchoring LC cell was fabricated by using a poly (vinyl cinnamate) alignment substrate as the weak anchoring surface and a polyimide alignment substrate as the strong anchoring surface. The LC cell performed the dark–bright–dark switching of the transmittance in the crossed polarizers, since the homogeneous LC orientation changed to the TN orientation again with increasing the applied voltage. Therefore, it was experimentally confirmed that LC molecules rotated at 90 degrees in the plane on the alignment surface by the electric field perpendicular to the weak anchoring substrate.
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2
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Tavarone R, Charbonneau P, Stark H. Kinetic Monte Carlo simulations for birefringence relaxation of photo-switchable molecules on a surface. J Chem Phys 2016; 144:104703. [PMID: 26979700 DOI: 10.1063/1.4943393] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Recent experiments have demonstrated that in a dense monolayer of photo-switchable dye methyl-red molecules the relaxation of an initial birefringence follows a power-law decay, typical for glass-like dynamics. The slow relaxation can efficiently be controlled and accelerated by illuminating the monolayer with circularly polarized light, which induces trans-cis isomerization cycles. To elucidate the microscopic mechanism, we develop a two-dimensional molecular model in which the trans and cis isomers are represented by straight and bent needles, respectively. As in the experimental system, the needles are allowed to rotate and to form overlaps but they cannot translate. The out-of-equilibrium rotational dynamics of the needles is generated using kinetic Monte Carlo simulations. We demonstrate that, in a regime of high density and low temperature, the power-law relaxation can be traced to the formation of spatio-temporal correlations in the rotational dynamics, i.e., dynamic heterogeneity. We also show that the nearly isotropic cis isomers can prevent dynamic heterogeneity from forming in the monolayer and that the relaxation then becomes exponential.
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Affiliation(s)
- Raffaele Tavarone
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany
| | - Patrick Charbonneau
- Departments of Chemistry and Physics, Duke University, Durham, North Carolina 27708, USA
| | - Holger Stark
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany
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Du T, Fan F, Tam AMW, Sun J, Chigrinov VG, Sing Kwok H. Complex Nanoscale-Ordered Liquid Crystal Polymer Film for High Transmittance Holographic Polarizer. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:7191-7195. [PMID: 26457810 DOI: 10.1002/adma.201502395] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 07/27/2015] [Indexed: 06/05/2023]
Abstract
A special design of a complex-ordered liquid crystal polymer film is developed into a holographic polarizer. The holographic polarizer shows over 90% transmittance, which provides a simple solution to make LEDs polarized. Furthermore, the holographic polarizer exhibits intensity and polarization maintenance properties, which could be further developed for photonics applications.
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Affiliation(s)
- Tao Du
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
| | - Fan Fan
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
- Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082, China
| | - Alwin Ming Wai Tam
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
| | - Jiatong Sun
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
| | - Vladimir G Chigrinov
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
| | - Hoi Sing Kwok
- Department of Electronic and Computer Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
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Tašič B, Li W, Sánchez-Ferrer A, Čopič M, Drevenšek-Olenik I. Light-Induced Refractive Index Modulation in Photoactive Liquid-Crystalline Elastomers. MACROMOL CHEM PHYS 2013. [DOI: 10.1002/macp.201300493] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Blaž Tašič
- Faculty of Mathematics and Physics; University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia, J. Stefan Institute; Jamova 39 SI1000 Ljubljana Slovenia
| | - Wei Li
- Nankai University, TEDA APS; 23 Hongda Street Tianjin 300457 PR China
| | - Antoni Sánchez-Ferrer
- Department of Health Sciences and Technology; ETH Zurich; Schmelzbergstrasse 9 8091 Zurich Switzerland
| | - Martin Čopič
- Faculty of Mathematics and Physics; University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia, J. Stefan Institute; Jamova 39 SI1000 Ljubljana Slovenia
| | - Irena Drevenšek-Olenik
- Faculty of Mathematics and Physics; University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia, J. Stefan Institute; Jamova 39 SI1000 Ljubljana Slovenia
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5
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Yaroshchuk O, Reznikov Y. Photoalignment of liquid crystals: basics and current trends. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c1jm13485j] [Citation(s) in RCA: 403] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Myhre G, Pau S. Imaging capability of patterned liquid crystals. APPLIED OPTICS 2009; 48:6152-6158. [PMID: 19904311 DOI: 10.1364/ao.48.006152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We demonstrate the ability to make high resolution arbitrary patterned optical retarders using liquid crystal polymer (LCP). Contact lithography is used to define unique LCP alignment domains. Patterned LCP retarders are imaged between crossed polarizers to determine pattern visibility as a function of feature size. It was determined that patterned retarders for wavelengths between 250 nm and 2500 nm can be constructed with feature sizes as small as 4 microm. We also showed that multiple patterns can be created on the same substrate using a combination of patterned LCP and opaque features. Our process has applications in displays, double-patterning lithography, and imaging polarimetry.
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Affiliation(s)
- Graham Myhre
- College of Optical Sciences, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA.
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7
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Ohtake T, Ogawa K. Characteristics of Photoaligned Chemically-Adsorbed Monolayers Having Chalconyl Groups. J PHOTOPOLYM SCI TEC 2009. [DOI: 10.2494/photopolymer.22.719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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8
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Yaroshchuk OV, Kiselev AD, Kravchuk RM. Liquid-crystal anchoring transitions on aligning substrates processed by a plasma beam. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:031706. [PMID: 18517405 DOI: 10.1103/physreve.77.031706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 01/29/2008] [Indexed: 05/26/2023]
Abstract
We have studied a sequence of anchoring transitions observed in nematic liquid crystals (NLCs) sandwiched between hydrophobic polyimide substrates treated with a plasma beam. There is a pronounced continuous transition from a homeotropic to a slightly tilted (nearly planar) alignment with the easy axis parallel to the incidence plane of the plasma beam (the zenithal transition) which takes place as the exposure dose increases. In NLCs with positive dielectric anisotropy, a further increase in the exposure dose results in in-plane reorientation of the easy axis by 90 degrees (the azimuthal transition). This transition occurs through the twofold degenerate alignment characteristic of second-order anchoring transitions. In contrast to the critical behavior of anchoring, the contact angle of the NLC and water on the treated substrates declines monotonically with increasing exposure dose. It follows that the surface concentration of hydrophobic chains decreases continuously. The anchoring transitions under consideration are qualitatively interpreted by using a simple phenomenological model of competing easy axes which is studied by analyzing anchoring diagrams of generalized polar and nonpolar anchoring models.
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Affiliation(s)
- Oleg V Yaroshchuk
- Institute of Physics of National Academy of Sciences of Ukraine, prospekt Nauki 46, 03028 Kyïv, Ukraine.
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9
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Shimizu FM, Volpati D, Giacometti JA, Sworakowski J, Janus K, Luboch E. Kinetics of photoinduced birefringence in the guest–host system of poly(methyl methacrylate) doped with azobenzene-containing crown ethers. J Appl Polym Sci 2007. [DOI: 10.1002/app.26105] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Affiliation(s)
- John L. West
- a Department of Chemistry , Liquid Crystal Institute, Kent State University , Kent , Ohio , 44242 , USA
| | - Linli Su
- a Department of Chemistry , Liquid Crystal Institute, Kent State University , Kent , Ohio , 44242 , USA
| | - Yuri Reznikov
- b Institute of Physics, Ukraine Academy of Science , Kiev , 252022 , Ukraine
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Magyar G, West J, Reznikov Y, Yaroshchuk O. Light Induced LC Alignment on the Isotropic Non-Photosensitive Surface. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259908025927] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- G. Magyar
- a Liquid Crystal Institute, Kent State University , Kent , OH , 44242 , USA
| | - J. West
- a Liquid Crystal Institute, Kent State University , Kent , OH , 44242 , USA
| | - Yu. Reznikov
- b Institute of Physics of National Acad. of Sci. , prospect. Nauky 46, Kyiv , 252022 , Ukraine
| | - O. Yaroshchuk
- b Institute of Physics of National Acad. of Sci. , prospect. Nauky 46, Kyiv , 252022 , Ukraine
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Newsome CJ, O'neill M. Photoinduced Alignment of Liquid Crystals using Polyimide Irradiated with a Polarised Excimer Laser. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259908025982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- C. J. Newsome
- a Department of Physics , The University of Hull , Hull , HU6 7RX , United Kingdom
| | - M. O'neill
- a Department of Physics , The University of Hull , Hull , HU6 7RX , United Kingdom
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13
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Chigrinov V, Pikin S, Verevochnikov A, Kozenkov V, Khazimullin M, Ho J, Huang DD, Kwok HS. Diffusion model of photoaligning in azo-dye layers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 69:061713. [PMID: 15244604 DOI: 10.1103/physreve.69.061713] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2004] [Indexed: 05/24/2023]
Abstract
The model of the rotational diffusion of the azo-dye molecules under the action of polarized uv light was used to explain the formation of the photoinduced order in azo-dye layers. We consider both the approximations of negligible and strong molecular interaction during the process of the reorientation under the field of a polarized light. We constructed an experimental setup, based on a photoelastic modulator, that allows accurate in situ measurements of the phase retardation delta of thin film as a function of the exposure time t(exp) and exposure power W (W/ cm(2) ). A good agreement with experiment was observed. Fitting the experimental curves delta ( t(exp) ) for different power values W, we can estimate the coefficient of rotational diffusion D, azo-dye order parameter S ( t(exp) ), and other parameters of the rotational diffusion model.
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Affiliation(s)
- Vladimir Chigrinov
- Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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Oh-e M, Kim D, Shen YR. Surface anisotropy from photo-induced bond breaking at polymer surfaces: A sum-frequency vibrational spectroscopic study of polyimide. J Chem Phys 2001. [DOI: 10.1063/1.1391480] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Shiyanovskii SV, Glushchenko A, Reznikov Y, Lavrentovich OD, West JL. Tensor and complex anchoring in liquid crystals. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:R1477-R1480. [PMID: 11088707 DOI: 10.1103/physreve.62.r1477] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2000] [Indexed: 05/23/2023]
Abstract
We propose a tensor description of surface anchoring of liquid crystals (LCs). The model allows one to consider both the homogeneous and inhomogeneous parts of LC anchoring and to calculate the cumulative effect of different treatments as a sum of corresponding tensors. For the planar alignment the tensor representation is reduced to the complex azimuthal anchoring coefficient, whose amplitude and phase determine, respectively, the strength of azimuthal anchoring and the azimuthal angle of the easy axis. We predict and experimentally confirm that two consecutive photoalignment treatments with beams of perpendicular polarizations can compensate each other and restore the initial anchoring.
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Affiliation(s)
- SV Shiyanovskii
- Liquid Crystal Institute, Kent State University, Kent, Ohio 44242 and Institute for Nuclear Research, 47 Prospect Nauki, Kyiv, 03039, Ukraine
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16
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Affiliation(s)
- Kunihiro Ichimura
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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17
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Reznikov Y, Ostroverkhova O, Singer KD, Kim JH, Kumar S, Lavrentovich O, Wang B, West JL. Photoalignment of liquid crystals by liquid crystals. PHYSICAL REVIEW LETTERS 2000; 84:1930-1933. [PMID: 11017663 DOI: 10.1103/physrevlett.84.1930] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/1999] [Indexed: 05/23/2023]
Abstract
We observed light-induced alignment of the nematic liquid crystal, 4, 4(')-n-pentylcyanobiphenyl (5CB), on a fused quartz. Irradiation of the adsorbed layer with polarized ultraviolet light produced homogeneous alignment in a 5CB-filled liquid crystal cell with the easy orientation axis perpendicular to the polarization direction. The measured anchoring energy increases with illumination up to 10(-4) erg/cm (2). Phase retardation and pretilt measurements confirmed near homogeneous alignment of the LC in a cell, while the polarization dependence of second harmonic generation suggested a near normal alignment of the adsorbed layer. We believe that light-induced rearrangement or phototransformation of the adsorbed layer causes the observed phenomenon.
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Affiliation(s)
- Y Reznikov
- Institute of Physics of National Academy of Science, Prospect Nauki 46, Kyiv 252022, Ukraine
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Acharya BR, Kim JH, Kumar S. Material-independent determination of anchoring properties on rubbed polyimide surfaces. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 60:6841-6. [PMID: 11970604 DOI: 10.1103/physreve.60.6841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/1999] [Indexed: 04/18/2023]
Abstract
A material-independent method for determining liquid-crystal (LC) anchoring energy on rubbed polyimide (PI) surfaces has been devised. This method exploits the changes in the easy axis of rubbed PI film induced by exposure to linearly polarized UV (LPUV) light. The distribution of PI chains in a rubbed film is approximated by a Gaussian function and its width determined from the measured rotation of the LC easy axis as a function of exposure time. A quasimicroscopic free energy of the LC-substrate interface is used to model LC anchoring properties. The experimental and calculated values of the azimuthal anchoring energy are in good agreement and found to depend inversely on the width of the distribution function. The measurements of the width of the chain distribution function provide a simple LC material-independent method for determining the LC anchoring properties. With this method, it is also possible to calculate the strength of the interaction between PI chains and LC molecules.
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Affiliation(s)
- B R Acharya
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
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Olenik ID, Kim MW, Rastegar A, Rasing T. Characterization of unidirectional photopolymerization in poly(vinyl cinnamate) by surface optical second-harmonic generation. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 60:3120-8. [PMID: 11970119 DOI: 10.1103/physreve.60.3120] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/1999] [Indexed: 04/18/2023]
Abstract
Surface optical second-harmonic generation measurements were used to determine the change in the surface density and the surface orientational order parameter of the trans-cinnamoyl side groups of unidirectionally photopolymerized poly(vinyl cinnamate) (PVCN) films. The observed surface features were compared to the bulk properties of the films, which were probed by their UV absorption spectra and birefringence measurements. We found that the surface and the bulk photoreaction kinetics of the trans cinnamoyl side groups of the PVCN are very similar. The two photoreaction processes (trans-cis photoisomerization and photo-induced cross linking) appear to affect the linear and nonlinear optical properties of the polymer differently. This may explain the discrepancy between the birefringence and the azimuthal anchoring force of the unidirectionally photopolymerized PVCN.
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Affiliation(s)
- I D Olenik
- Research Institute for Materials, University of Nijmegen, Toernooiveld 1, 6525 ED, Nijmegen, The Netherlands
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