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Full-Text Articles in Physics

Elastic Constants And Orientational Viscosities Of A Bent-Core Nematic Liquid Crystal, Madhabi Majumdar, Peter Salamon, Antal Jákli, Jim T. Gleeson, Samuel N. Sprunt Mar 2011

Elastic Constants And Orientational Viscosities Of A Bent-Core Nematic Liquid Crystal, Madhabi Majumdar, Peter Salamon, Antal Jákli, Jim T. Gleeson, Samuel N. Sprunt

Chemical Physics Publications

Using a combination of dynamic light scattering and Freedericksz transitions induced in applied magnetic and electric fields, we have determined the absolute magnitudes of the Frank elastic constants and effective orientational viscosities of the bent-core nematic liquid crystal, 4-chloro-1,3-phenylene bis 4-[4'-(9-decenyloxy)benzoyloxy] benzoate. At a fixed temperature 2 degrees C below the isotropic-nematic transition, we find K(11) = 3.1 x 10(-12) N, K(22) = 0.31 x 10(-12) N, K(33) = 0.88 x 10(-12) N, eta(splay) = 1.1 Pa s, eta(twist) = 0.37 Pa s, and eta(bend) = 1.2 ...


Chirality And Biaxiality In Cholesteric Liquid Crystals, Subas Dhakal, Jonathan Selinger Feb 2011

Chirality And Biaxiality In Cholesteric Liquid Crystals, Subas Dhakal, Jonathan Selinger

Chemical Physics Publications

We investigate the statistical mechanics of chirality and biaxiality in liquid crystals through a variety of theoretical approaches, including Monte Carlo simulations, lattice mean-field theory, and Landau theory. All of these calculations show that there is an important interaction between cholesteric twist and biaxial order: The twist acts as a field on the biaxial order, and conversely, the biaxial order increases the twist, that is, reduces the pitch. We model the behavior of chiral biaxial liquid crystals as a function of temperature and discuss how the predictions can be tested in experiments.


Electro-Optic Effects In Colloidal Dispersion Of Metal Nano-Rods In Dielectric Fluid, Andrii B. Golovin, Jie Xiang, Heung-Shik Park, Luana Tortora, Yuriy A. Nastishin, Sergij V. Shyiyanovskii, Oleg Lavrentovich Feb 2011

Electro-Optic Effects In Colloidal Dispersion Of Metal Nano-Rods In Dielectric Fluid, Andrii B. Golovin, Jie Xiang, Heung-Shik Park, Luana Tortora, Yuriy A. Nastishin, Sergij V. Shyiyanovskii, Oleg Lavrentovich

Chemical Physics Publications

In modern transformation optics, one explores metamaterials with properties that vary from point to point in space and time, suitable for application in devices such as an "optical invisibility cloak" and an "optical black hole". We propose an approach to construct spatially varying and switchable metamaterials that are based on colloidal dispersions of metal nano-rods (NRs) in dielectric fluids, in which dielectrophoretic forces, originating in the electric field gradients, create spatially varying configurations of aligned NRs. The electric field controls orientation and concentration of NRs and thus modulates the optical properties of the medium. Using gold (Au) NRs dispersed in ...


Inelastic Collisions And Anisotropic Aggregation Of Particles In A Nematic Collider Driven By Backflow, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich Jan 2011

Inelastic Collisions And Anisotropic Aggregation Of Particles In A Nematic Collider Driven By Backflow, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich

Chemical Physics Publications

We design a nematic collider for controlled out-of-equilibrium anisotropic aggregation of spherical colloidal particles. The nematic surrounding imparts dipolar interactions among the spheres. A bidirectional backflow of the nematic liquid crystal in a periodic electric field forces the spheres to collide with each other. The inelastic collisions are of two types, head to tail and head to head. Head-to-tail collisions of dipoles result in longitudinal aggregation while head-to-head collisions promote aggregation in the transversal direction. The frequency of head-to-head collisions is set by the impact parameter that controls the resulting shape of aggregates, their anisotropy, and fractal dimension.


Electro-Optic Kerr Effect In Polymer-Stabilized Isotropic Liquid Crystals, Young-Cheol Yang, Deng-Ke Yang Jan 2011

Electro-Optic Kerr Effect In Polymer-Stabilized Isotropic Liquid Crystals, Young-Cheol Yang, Deng-Ke Yang

Chemical Physics Publications

The electro-optic Kerr effect with a high Kerr constant around 10−9 m/V2 was observed in the polymer-stabilized isotropic liquid crystals over a wide temperature range. Optical isotropy at the field-off state was attained with randomly oriented domains of (chiral) nematic liquid crystals formed by a polymer matrix cured in the isotropic phase. Optical birefringence in the field-on state was induced by the reorientation of liquid crystals in the domains. Rapid rising and falling response times of the cells around 0.26 ms (0.52 ms total response time) were achieved. A theoretical model was proposed to explain the ...


The Effect Of Surface Alignment On Analog Control Of Director Rotation In Polarization Stiffened Smc* Devices, Mitya Reznikov, Lena M. Lopatina, Michael J. O'Callaghan, Philip J. Bos Jan 2011

The Effect Of Surface Alignment On Analog Control Of Director Rotation In Polarization Stiffened Smc* Devices, Mitya Reznikov, Lena M. Lopatina, Michael J. O'Callaghan, Philip J. Bos

Chemical Physics Publications

The effect of surface alignment on the achievement of analog ("V"-shaped) electric field control of director rotation in SmC* liquid crystal devices is investigated experimentally and through numerical modeling. Ferroelectric SmC* liquid crystals are intrinsically analog and thresholdless, i.e. the director can be rotated freely around the tilt cone. Whether or not a SmC* liquid crystal cell exhibits thresholdless switching depends strongly on the influence of the cell's alignment layers, on the magnitude of the liquid crystal's spontaneous polarization, and on whether smectic layers adopt a bookshelf or chevron configuration. To study the effect of the ...


Modeling And Simulation Of Liquid-Crystal Elastomers, Wei Zhu, Michael Shelley, Peter Palffy-Muhoray Jan 2011

Modeling And Simulation Of Liquid-Crystal Elastomers, Wei Zhu, Michael Shelley, Peter Palffy-Muhoray

Chemical Physics Publications

We consider a continuum model describing the dynamic behavior of nematic liquid crystal elastomers (LCEs) and implement a numerical scheme to solve the governing equations. In the model, the Helmholtz free energy and Rayleigh dissipation are used, within a Lagrangian framework, to obtain the equations of motion. The free energy consists of both elastic and liquid crystalline contributions, each of which is a function of the material displacement and the orientational order parameter. The model gives dynamics for the material displacement, the scalar order parameter and the nematic director, the latter two of which correspond to the orientational order parameter ...


Lyotropic Chromonic Liquid Crystal Semiconductors For Water-Solution Processable Organic Electronics, V. G. Nazarenko, O. P. Boiko, M. I. Anisimov, A. K. Kadashchuk, Yuriy A. Nastishin, A. B. Golovin, Oleg Lavrentovich Dec 2010

Lyotropic Chromonic Liquid Crystal Semiconductors For Water-Solution Processable Organic Electronics, V. G. Nazarenko, O. P. Boiko, M. I. Anisimov, A. K. Kadashchuk, Yuriy A. Nastishin, A. B. Golovin, Oleg Lavrentovich

Chemical Physics Publications

We propose lyotropic chromonic liquid crystals (LCLCs) as a distinct class of materials for organic electronics. In water, the chromonic molecules stack on top of each other into elongated aggregates that form orientationally ordered phases. The aligned aggregated structure is preserved when the material is deposited onto a substrate and dried. The dried LCLC films show a strongly anisotropic electric conductivity of semiconductor type. The field-effect carrier mobility measured along the molecular aggregates in unoptimized films of LCLC V20 is 0.03 cm(2) V-1 s(-1). Easy processibility, low cost, and high mobility demonstrate the potential of LCLCs for ...


Fabrication And Characterization Of Coupled Metal-Dielectric-Metal Nanoantennas, Bhuwan Joshi, Xuejin Wen, Kai Sun, Wu Lu, Qi-Huo Wei Nov 2010

Fabrication And Characterization Of Coupled Metal-Dielectric-Metal Nanoantennas, Bhuwan Joshi, Xuejin Wen, Kai Sun, Wu Lu, Qi-Huo Wei

Chemical Physics Publications

The authors fabricated two dimensional arrays of metal-dielectric-metal nanoantennas consisting of a thin layer of light-emitting polymers sandwiched between two Ag parallel cuboids and characterized them by measuring the optical transmission through the antenna arrays. The measured transmission spectra show two resonant dips. Numerical simulations reproduce the experimental results and show that the left dip is due to a cavity resonance mode and the right dip is due to the absorption of the polymer. With this vertical antenna design, the dielectric gap can be made much smaller with an extremely small mode volume, making it a potential candidate for single ...


Modeling Elastic Instabilities In Nematic Elastomers, Badel L. Mbanga, Fangfu Ye, Jonathan Selinger, Robin Selinger Nov 2010

Modeling Elastic Instabilities In Nematic Elastomers, Badel L. Mbanga, Fangfu Ye, Jonathan Selinger, Robin Selinger

Chemical Physics Publications

Liquid crystal elastomers are cross-linked polymer networks covalently bonded with liquid crystal mesogens. In the nematic phase, due to strong coupling between mechanical strain and orientational order, these materials display strain-induced instabilities associated with formation and evolution of orientational domains. Using a three-dimensional finite element elastodynamics simulation, we investigate one such instability, the onset of stripe formation in a monodomain film stretched along an axis perpendicular to the nematic director. In our simulation, we observe the formation of striped domains with alternating director rotation. This model allows us to explore the fundamental physics governing dynamic mechanical response of nematic elastomers ...


Surface Alignment, Anchoring Transitions, Optical Properties, And Topological Defects In The Nematic Phase Of Thermotropic Bent-Core Liquid Crystal A131, B. Senyuk, H. Wonderly, M. Mathews, Q. Li, Sergij V. Shiyanovskii, Oleg Lavrentovich Oct 2010

Surface Alignment, Anchoring Transitions, Optical Properties, And Topological Defects In The Nematic Phase Of Thermotropic Bent-Core Liquid Crystal A131, B. Senyuk, H. Wonderly, M. Mathews, Q. Li, Sergij V. Shiyanovskii, Oleg Lavrentovich

Chemical Physics Publications

We study optical, structural, and surface anchoring properties of thermotropic nematic bent-core material A131. The focus is on the features associated with orientational order as the material has been reported to exhibit not only the usual uniaxial nematic but also the biaxial nematic phase. We demonstrate that A131 experiences a surface anchoring transition from a perpendicular to tilted alignment when the temperature decreases. The features of the tilted state are consistent with surface-induced birefringence associated with smectic layering near the surface and a molecular tilt that changes along the normal to the substrates. The surface-induced birefringence is reduced to zero ...


Second-Harmonic Generation In A Bent-Core Nematic Liquid Crystal, Seung Ho Hong, J. C. Williams, Robert J. Twieg, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt, Brett Ellman Oct 2010

Second-Harmonic Generation In A Bent-Core Nematic Liquid Crystal, Seung Ho Hong, J. C. Williams, Robert J. Twieg, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt, Brett Ellman

Chemical Physics Publications

Second-Second-harmonic generation (SHG) is studied in the magnetically aligned nematic phase of a bent-core liquid crystal (BCN) and compared to similar measurements made on a conventional rodlike (calamitic) nematic compound. The second-harmonic (SH) light detected from both materials is predominantly due to scattering and therefore incoherent. Results on the calamitic are consistent with a polarization induced by ordinary director fluctuations in the nematic phase. However, the SH scattering collected in the BCN exhibits a different temperature and angular dependence. We discuss how these differences could arise from the effects of short-range correlated, smectic-C-type molecular clusters, which have been detected in ...


The Ion Capturing Effect Of 5 Degrees Siox Alignment Films In Liquid Crystal Devices, Yi Huang, Philip J. Bos, Achintya Bhowmik Sep 2010

The Ion Capturing Effect Of 5 Degrees Siox Alignment Films In Liquid Crystal Devices, Yi Huang, Philip J. Bos, Achintya Bhowmik

Chemical Physics Publications

We show that SiOx, deposited at 5 degrees to the interior surface of a liquid crystal cell allows for a surprisingly substantial reduction in the ion concentration of liquid crystal devices. We have investigated this effect and found that this type of film, due to its surface morphology, captures ions from the liquid crystal material. Ion adsorption on 5 degrees SiOx film obeys the Langmuir isotherm. Experimental results shown allow estimation of the ion capturing capacity of these films to be more than an order of 10 000/mu m(2). These types of materials are useful for new types ...


Short-Range Smectic Order In Bent-Core Nematic Liquid Crystals, Seung Ho Hong, Rafael Verduzco, J. C. Williams, Robert J. Twieg, E. Dimasi, R. Pindak, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt Aug 2010

Short-Range Smectic Order In Bent-Core Nematic Liquid Crystals, Seung Ho Hong, Rafael Verduzco, J. C. Williams, Robert J. Twieg, E. Dimasi, R. Pindak, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt

Chemical Physics Publications

Small angle X-ray diffraction from the uniaxial nematic phase of certain bent-core liquid crystals is shown to be consistent with the presence of molecular clusters possessing short-range tilted smectic (smectic-C) order. Persistence of these clusters throughout the nematic phase, and even into the isotropic state, likely accounts for the unusual macroscopic behavior previously reported in bent-core nematics, including an anomalously large flexoelectric effect (similar to 1000 times that of conventional calamitic nematics), very large orientational and flow viscosities (similar to 10 100 and similar to 100 1000 times, respectively, typical values for calamitics), and an extraordinary flow birefringence observed in ...


Surface Alignment And Anchoring Transitions In Nematic Lyotropic Chromonic Liquid Crystal, V. G. Nazarenko, O. P. Boiko, H. S. Park, O. M. Brodyn, M. M. Omelchenko, L. Tortora, Yuriy A. Nastishin, Oleg Lavrentovich Jun 2010

Surface Alignment And Anchoring Transitions In Nematic Lyotropic Chromonic Liquid Crystal, V. G. Nazarenko, O. P. Boiko, H. S. Park, O. M. Brodyn, M. M. Omelchenko, L. Tortora, Yuriy A. Nastishin, Oleg Lavrentovich

Chemical Physics Publications

The surface alignment of lyotropic chromonic liquid crystals can not only be planar (tangential) but also homeotropic, with self-assembled aggregates perpendicular to the substrate, as demonstrated by mapping optical retardation and by three-dimensional imaging of the director field. With time, the homeotropic nematic undergoes a transition into a tangential state. The anchoring transition is discontinuous and can be described by a double-well anchoring potential with two minima corresponding to tangential and homeotropic orientation.


Dielectric Properties Of Mixtures Of A Bent-Core And A Calamitic Liquid Crystal, Peter Salamon, Nandor Éber, Agnes Buka, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli Mar 2010

Dielectric Properties Of Mixtures Of A Bent-Core And A Calamitic Liquid Crystal, Peter Salamon, Nandor Éber, Agnes Buka, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli

Chemical Physics Publications

Dielectric spectroscopy measurements have been performed on a bent-core nematic liquid crystal and on its binary mixtures with a calamitic nematic. We have detected more dispersions in the bent-core compound than in the calamitic one, including one at an unusually low frequency of a few kilohertz. The dispersions detected in the mixtures have been identified and the spectra have been split into contributions of the constituents. In order to connect the dielectric increment with the molecular dipole moment we have applied a sophisticated conformational calculation not performed before for a large, flexible mesogen molecule with numerous polar groups.


Bundles Of Fluid Fibers Formed By Bent-Core Molecules, C. Bailey, M. Murphy, A. Eremin, Wolfgang Weissflog, Antal Jakli Mar 2010

Bundles Of Fluid Fibers Formed By Bent-Core Molecules, C. Bailey, M. Murphy, A. Eremin, Wolfgang Weissflog, Antal Jakli

Chemical Physics Publications

The internal structures, stability, and elastic properties of free-standing filament bundles of bent-core smectic liquid crystals are studied using polarizing microscopy, scanning electron microscopy, and a customized cantilever containing, temperature controlled heat stage for force measurements. We find that in bundles, the individual filaments fuse together to form semiseparable filaments with radii approximately two and three times larger than the individual fibers. We also find that the effective surface tension of wide bundles is about 10% smaller than a single filament. Finally, we describe the metastable coexistences of single fibers within the bundles that lead to bending of the bundles ...


Statistical Mechanics Of Splay Flexoelectricity In Nematic Liquid Crystals, Subas Dhakal, Jonathan Selinger Mar 2010

Statistical Mechanics Of Splay Flexoelectricity In Nematic Liquid Crystals, Subas Dhakal, Jonathan Selinger

Chemical Physics Publications

We develop a lattice model for the splay flexoelectric effect in nematic liquid crystals. In this model, each lattice site has a spin representing the local molecular orientation, and the interaction between neighboring spins represents pear-shaped molecules with shape polarity. We perform Monte Carlo simulations and mean-field calculations to find the behavior as a function of interaction parameters, temperature, and applied electric field. The resulting phase diagram has three phases: isotropic, nematic, and polar. In the nematic phase, there is a large splay flexoelectric effect, which diverges as the system approaches the transition to the polar phase. These results show ...


Giant Flexoelectricity In Bent-Core Nematic Liquid Crystal Elastomers, J. Harden, Martin Chambers, Rafael Verduzco, Paul Luchette, Jim T. Gleeson, Samuel N. Sprunt, Antal Jákli Mar 2010

Giant Flexoelectricity In Bent-Core Nematic Liquid Crystal Elastomers, J. Harden, Martin Chambers, Rafael Verduzco, Paul Luchette, Jim T. Gleeson, Samuel N. Sprunt, Antal Jákli

Chemical Physics Publications

Recently ferroelectric ceramic and bent-core nematic liquid crystals have demonstrated flexoelectricity (coupling between curvature strains to electric polarization) up to 10(4) times larger than the previous standards. This may allow for usable electromechanical devices. However, ceramics are too rigid to withstand large bending and bent-core nematic fluids must be physically supported-their technological applicability is still limited. In this paper, we show that novel side-chain bent-core nematic elastomers not only produce giant flexoelectricity but are also robust and flexible enough for microscale parasitic power generation. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3358391]


The Effect Of Siox Alignment Layer Thickness On The Switching Of Smc* Bistable Liquid Crystal Devices, Mitya Reznikov, Philip J. Bos, Michael J. O'Callaghan Jan 2010

The Effect Of Siox Alignment Layer Thickness On The Switching Of Smc* Bistable Liquid Crystal Devices, Mitya Reznikov, Philip J. Bos, Michael J. O'Callaghan

Chemical Physics Publications

SiOx alignment layers have been shown to allow defect-free SmC* devices with near optimum bistable orientation of the director. In this paper we investigate the effect of the thickness of this type of alignment layer on the required amplitude of an applied voltage pulse to cause bistable switching. The results of an experimental investigation and simple model are presented. We find that for thicker layers, the amplitude is controlled by the voltage drop across the alignment layers and by the effect of polar interactions between the liquid crystal (LC) and the alignment layers. For thin alignment layers the amplitude is ...


Electrically Reconfigurable Optical Metamaterial Based On Colloidal Dispersion Of Metal Nanorods In Dielectric Fluid, Andrii B. Golovin, Oleg Lavrentovich Dec 2009

Electrically Reconfigurable Optical Metamaterial Based On Colloidal Dispersion Of Metal Nanorods In Dielectric Fluid, Andrii B. Golovin, Oleg Lavrentovich

Chemical Physics Publications

Optical metamaterials capture the imagination with breathtaking promises of nanoscale resolution in imaging and invisibility cloaking. We demonstrate an approach to construct a metamaterial in which metallic nanorods, of dimension much smaller than the wavelength of light, are suspended in a fluid and placed in a nonuniform electric field. The field controls the spatial distribution and orientation of nanorods because of the dielectrophoretic effect. The field-controlled placement of nanorods causes optical effects such as varying refractive index, optical anisotropy (birefringence), and reduced visibility of an object enclosed by the metamaterial.


Large Flow Birefringence Of Nematogenic Bent-Core Liquid Crystals, C. Bailey, Katalin Fodor-Csorba, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli Dec 2009

Large Flow Birefringence Of Nematogenic Bent-Core Liquid Crystals, C. Bailey, Katalin Fodor-Csorba, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli

Chemical Physics Publications

We have found that bent-core liquid crystalline materials show exceptionally large intrinsic flow birefringence in their isotropic liquid phase. This effect is more than 100 times larger than typical values measured for low molecular weight liquid crystals. The specific flow birefringence (i.e., normalized by the flow viscosity) is an order of magnitude larger than in both side-chain polymeric as well as low molecular weight liquid crystals. We propose that this large enhancement for bent-core compounds may be attributed to nanoscale smecticlike clusters that persist above the nematic-isotropic transition temperature, and shear align under shear flow; however, this mechanism has ...


Optical Waveguiding In Bent-Core Liquid-Crystal Filaments, Jake Fontana, C. Bailey, Wolfgang Weissflog, I. Janossy, Antal Jakli Sep 2009

Optical Waveguiding In Bent-Core Liquid-Crystal Filaments, Jake Fontana, C. Bailey, Wolfgang Weissflog, I. Janossy, Antal Jakli

Chemical Physics Publications

We demonstrate optical waveguiding in recently discovered free-standing bent-core liquid-crystal filaments. The bent-core liquid-crystal molecules in air self-assemble into a cylindrical geometry that is "solidlike" along the radial direction of the filament and liquid in the axial direction of the filament. These filaments are unique not only because they are fluids, but also because they are anisotropic. For this reason, their waveguiding properties not predictable need to be characterized. The light power transmitted through the filament was found to be independent of temperature from 180 degrees C to near room temperature. Initial defects of newly pulled filaments were found to ...


Flexoelectricity Of A Calamitic Liquid Crystal Elastomer Swollen With A Bent-Core Liquid Crystal, Martin Chambers, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli Sep 2009

Flexoelectricity Of A Calamitic Liquid Crystal Elastomer Swollen With A Bent-Core Liquid Crystal, Martin Chambers, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli

Chemical Physics Publications

We have measured the electric current induced by mechanical distortion of a calamitic liquid crystal elastomer (LCE) swollen with a low molecular weight bent-core nematic (BCN) liquid crystal, and have determined, for the first time, the bend flexoelectric coefficient e(3) of such a BCN-LCE composite. In one method, we utilise air-pressure to induce a mechanical bend deformation and flexoelectric polarization in a BCN-LCE film, and then measure the polarization current as a function of time. An alternative technique uses a rotary-motor driven scotch yoke to periodically flex the BCN-LCE; in this case, the magnitude and phase of the induced ...


Cholesteric Liquid-Crystal Displays Illuminated By Diffuse And Partially Diffuse Light, W. D. St. John, Z. J. Lu, J. William Doane, Bahman Taheri Jul 2009

Cholesteric Liquid-Crystal Displays Illuminated By Diffuse And Partially Diffuse Light, W. D. St. John, Z. J. Lu, J. William Doane, Bahman Taheri

Chemical Physics Publications

We report on the photometric and colorimetric properties of surface and polymer network stabilized reflective cholesteric displays. Both diffuse and partially diffuse illumination are used, the latter being an experimental approach to emulating typical room light conditions. It is shown that addition of polymer increases the field of view while decreasing angular dependence of the color quantities: hue, chroma, and lightness. Total luminance and contrast ratio, however, are also decreased. Therefore, it is concluded that optimum polymer concentration is dependent on the viewing geometry. Luminance and contrast ratio of the surface stabilized cells exceeded that of polymer stabilized cell when ...


Design Of A Wide Bandwidth Switchable Mirror Based On A Liquid Crystal Etalon, Enkh-Amgalan Dorjgotov, Philip J. Bos, Achintya Bhowmik May 2009

Design Of A Wide Bandwidth Switchable Mirror Based On A Liquid Crystal Etalon, Enkh-Amgalan Dorjgotov, Philip J. Bos, Achintya Bhowmik

Chemical Physics Publications

We propose the design for a switchable mirror with high efficiency and a 30 nm bandwidth. The device is based on a liquid crystal filled etalon. Broad bandwidth is achieved through the use of integrated half-wave layers into the dielectric stack design, while high efficiency is achieved using a polarization independent liquid crystal effect. Potential applications in the area of displays are also presented.


Theory Of Ferroelectric Nanoparticles In Nematic Liquid Crystals, Lena M. Lopatina, Jonathan Selinger May 2009

Theory Of Ferroelectric Nanoparticles In Nematic Liquid Crystals, Lena M. Lopatina, Jonathan Selinger

Chemical Physics Publications

Recent experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals-increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. To understand these effects, we develop a theory for the statistical mechanics of ferroelectric nanoparticles in liquid crystals. This theory predicts the enhancements of liquid-crystal properties, in good agreement with experiments. These predictions apply even when electrostatic interactions are partially screened by moderate concentrations of ions.


Electro-Optic Technique To Study Biaxiality Of Liquid Crystals With Positive Dielectric Anisotropy: The Case Of A Bent-Core Material, Khoa Van Le, Manoj Mathews, Martin Chambers, John Harden, Quan Li, Hideo Takezoe, Antal Jákli Mar 2009

Electro-Optic Technique To Study Biaxiality Of Liquid Crystals With Positive Dielectric Anisotropy: The Case Of A Bent-Core Material, Khoa Van Le, Manoj Mathews, Martin Chambers, John Harden, Quan Li, Hideo Takezoe, Antal Jákli

Chemical Physics Publications

We propose that, for materials having positive dielectric anisotropy, the biaxiality can be clearly verified or excluded by measuring the transmitted light intensity as a function of electric field. If the material is biaxial and is observed in homeotropically aligned cells, the schlieren texture should not disappear (transmitted intensity is not zero) even at very high fields, since the field does not affect the distribution of the second director normal to the main director. On the other hand, if the material is uniaxial the transmitted intensity should decrease with increasing field and a perfect homeotropic texture can be achieved at ...


Nonphotochemical Laser-Induced Nucleation Of Nematic Phase And Alignment Of Nematic Director From A Supercooled Thermotropic Liquid Crystal, Xiaoying Sun, Bruce A. Garetz, Michele F. Moreira, Peter Palffy-Muhoray Feb 2009

Nonphotochemical Laser-Induced Nucleation Of Nematic Phase And Alignment Of Nematic Director From A Supercooled Thermotropic Liquid Crystal, Xiaoying Sun, Bruce A. Garetz, Michele F. Moreira, Peter Palffy-Muhoray

Chemical Physics Publications

A nonphotochemical laser-induced phase transition was studied in a supercooled 4′‐n-pentyl-4-cyanobiphenyl (5CB, also referred to as PCB and K15) liquid crystal, using linearly polarized 45 ps light pulses at a wavelength of 532 nm. The laser induced nucleation from the metastable supercooled isotropic phase to the nematic phase during slow cooling (0.001 °C∕min) and high light intensity (3.9 MW∕cm2). The resulting nematic director tended to be aligned along the direction of the plane of polarization of the light. At the intensities used, there is no observable laser-induced realignment of the director once the sample ...


Chirality Of Lipids Makes Fluid Lamellar Phases Piezoelectric, John Harden, Nicholas Diorio, Alexander G. Petrov, Antal Jakli Jan 2009

Chirality Of Lipids Makes Fluid Lamellar Phases Piezoelectric, John Harden, Nicholas Diorio, Alexander G. Petrov, Antal Jakli

Chemical Physics Publications

The role of chirality in membrane-forming lipids is not well appreciated at present. Here we demonstrate that the chirality of phospholipids makes fluid lipid bilayers piezoelectric. Thus, chiral lipids would play a central role in the functioning of cell membranes as active mechanotransducers. By periodically shearing and compressing nonaqueous lamellar phases of left (L-alpha-phosphatidylcholine), right (D-alpha-phosphatidylcholine), and racemic (DL-alpha-phosphatidylcholine) lipids, we induced a tilt of the molecules with respect to the bilayer's normal and produced electric current perpendicular to the tilt plane, with the chiral lipids only. This effect is due to the Sm-A(*) phase liquid crystal structure of ...