Science.gov

Sample records for polymer liquid crystal

  1. Liquid crystal-templated conducting organic polymers

    DOEpatents

    Stupp, Samuel I.; Hulvat, James F.

    2004-01-20

    A method of preparing a conductive polymeric film, includes providing a liquid crystal phase comprising a plurality of hydrophobic cores, the phase on a substrate, introducing a hydrophobic component to the phase, the component a conductive polymer precursor, and applying an electric potential across the liquid crystal phase, the potential sufficient to polymerize the said precursor.

  2. Patterned cholesteric liquid crystal polymer film.

    PubMed

    Hsu, Wei-Liang; Ma, Ji; Myhre, Graham; Balakrishnan, Kaushik; Pau, Stanley

    2013-02-01

    Herein, the ability to create arbitrarily patterned circular polarized optical devices is demonstrated by using cholesteric liquid crystal polymer. Photoalignment with polarized ultraviolet light is utilized to create aligned cholesteric liquid crystal films. Two different methods, thermal annealing and solvent rinse, are utilized for patterning cholesteric liquid crystal films over large areas. The patterned cholesteric liquid crystal films are measured using a Mueller matrix imaging polarimeter, and the polarization properties, including depolarization index, circular diattenuation (CD), and circular retardance are derived. Patterned nonlinearly polarized optical devices can be fabricated with feature sizes as small as 20 μm with a CD of 0.812±0.015. Circular polarizing filters based on polymer cholesteric liquid crystal films have applications in three-dimensional displays, medical imaging, polarimetry, and interferometry. PMID:23456060

  3. Polymer's anchoring behavior in liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Cui, Yue

    The current dissertation mainly discusses about the polymers anchoring behavior in liquid crystal cells in two aspects: surface interaction and bulk interaction. The goal of the research is to understand the fundamental physics of anchoring strength and apply the knowledge to liquid crystal display devices. Researchers proposed two main contributors to the surface anchoring strength: the micro grooves generated by external force and the polymer chain's alignment. Both of them has experimental proofs. In the current study, explorations were made to understand the mechanisms of surface anchoring strength and easy axis of surface liquid crystal provided by rubbed polymer alignment layer. The work includes not only the variation of the alignment layer itself such as thickness(Chapter 3) and polymer side chain (Chapter 5), but also the variation of external conditions such as temperature (Chapter 4) and rubbing condition (Chapter 6). To determine the polar and azimuthal anchoring strengths, Rapini-Papoular's expression was applied. However, it was discovered that higher order terms may be required in order to fit the experimental result or theoretically predict unique anchoring behaviors (Chapter 2, Chapter 6). SEM and AFM technologies were introduced to gather the actual structures of polymer alignment layer and extrapolate the alignment of liquid crystal in a micro scale. The result shows that the anchoring strength can be adjusted by the layer thickness, side chain structure, while the easy axis direction can be adjusted by a second rubbing direction. In addition, different anchoring conditions combined with liquid crystal's elastic energy can generate quite different forms of liquid crystals (Chapter 7). In the study of bulk alignment, the main contrition from the current dissertation is applying the understanding of anchoring behavior to optimizing actual switchable devices. Conventional PDLC performance can be tuned with the knowledge of the polymer and the liquid

  4. Photosensitive Polymers for Liquid Crystal Alignment

    NASA Astrophysics Data System (ADS)

    Mahilny, U. V.; Stankevich, A. I.; Trofimova, A. V.; Muravsky, A. A.; Murauski, A. A.

    The peculiarities of alignment of liquid crystal (LC) materials by the layers of photocrosslinkable polymers with side benzaldehyde groups are considered. The investigation of mechanism of photostimulated alignment by rubbed benzaldehyde layer is performed. The methods of creation of multidomain aligning layers on the basis of photostimulated rubbing alignment are described.

  5. Polymer Crystallization at Curved Liquid/Liquid Interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda

    Liquid/liquid interface, either flat or curved, is a unique template for studying self-assembly of a variety of nanomaterials such as nanoparticles and nanorods. The resultant monolayer films can be ordered or disordered depending on the regularity of the nanomaterials. Integration of nanoparticles into two-dimensional structure leads to intriguing collective properties of the nanoparticles. Crystallization can also be guided by liquid/liquid interface. Due to the particular shape of the interface, crystallization can happen in a different manner comparing to the normal solution crystallization. In this dissertation, liquid/liquid interface is employed to guide the crystallization of polymers, mainly focusing on using curved liquid/liquid interface. Due to the unique shape of the interface and feasibility to control the curvature, polymer crystallization can take place in different manner and lead to the formation of curved or vesicular crystals. Curved liquid/liquid interface is typically created through o/w emulsions. With the presence of surfactant, the emulsions are controlled to be stable at least for the polymer crystallization periods. The difference to normal solution crystallization is: the nuclei will diffuse to the curved interface due to the Pickering effect and guide the crystallization along the curved liquid/liquid interface. If the supercooling can be controlled to be very small, crystal growth in the bulk droplets can be avoided. The advantages of this strategy are: 1) the formation process of vesicular type crystals can be monitored by controlling the polymer supply; 2) curved crystals, bowl-like structures and enclosed capsules can be easily obtained comparing to the self-assembly method for vesicle formation; 3) the obtained vesicles will be made of polymer crystals, which will possess the extraordinary mechanical properties. Based on the nucleation type, this dissertation is divided into two parts. The first part is focused on the self

  6. Polymer single crystal membrane from liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group-Drexel University Team

    2013-03-01

    Vesicles, mimicking the structure of cell membrane at the molecular scale, are small membrane-enclosed sacks that can store or transport substances. The weak mechanical properties and the nature of environment-sensitivity of the current available vesicles: liposomes, polymersomes, colloidsomes limit their applications as an excellent candidate for targeting delivery of drugs/genes in biomedical engineering and treatment. Recently, we developed an emulsion-based method to grow curved polymer single crystals. Varying the polymer concentration and/or the emulsification conditions (such as surfactant concentration, water-oil volume ratio), curved crystals with different sizes and different openness could be obtained. This growing process was attributed to polymer crystal growth along the liquid/liquid interface. In addition, the liquid/liquid interfacial crystal growth is promising for synthesis of enclosed hollow sphere.

  7. Polymer-dispersed liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  8. Shear-Sensitive Monomer/Polymer Liquid Crystal System

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Eftekhari, Abe; Parmar, D. S.

    1993-01-01

    Report describes preliminary investigation of new monomer/polymer liquid crystal system, thin film of shear-sensitive cholesteric monomer liquid crystal (TI 511) on Xydar (STR800) (or equivalent) liquid crystal polymer substrate. Monomer/polymer liquid crystal films applied to surfaces provide quantitative indications of shear stresses caused by winds blowing along surfaces. Effects of shear stresses reversible in new coating system. System provides quantitative data on flows in wind tunnels.

  9. Investigation of Polymer Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.

    1996-01-01

    The positron annihilation lifetime spectroscopy (PALS) using a low energy flux generator may provide a reasonably accurate technique for measuring molecular weights of linear polymers and characterization of thin polyimide films in terms of their dielectric constants and hydrophobity etc. Among the tested samples are glassy poly arylene Ether Ketone films, epoxy and other polyimide films. One of the proposed techniques relates the free volume cell size (V(sub f)) with sample molecular weight (M) in a manner remarkably similar to that obtained by Mark Houwink (M-H) between the inherent viscosity (eta) and molecular wieght of polymer solution. The PALS has also demonstrated that free-volume cell size in thermoset is a versatile, useful parameter that relates directly to the polymer segmental molecular weight, the cross-link density, and the coefficient of thermal expansion. Thus, a determination of free volume cell size provides a viable basis for complete microstructural characterization of thermoset polyimides and also gives direct information about the cross-link density and coefficient of expansion of the test samples. Seven areas of the research conducted are reported here.

  10. Polymer Crystallization at Curved Liquid-Liquid Interface

    NASA Astrophysics Data System (ADS)

    Li, Christopher; Wang, Wenda; Qi, Hao; Huang, Ziyin

    2013-03-01

    Curved space is incommensurate with typical ordered structures with three-dimensional (3D) translational symmetry. However, upon assembly, soft matter, including colloids, amphiphiles, and block copolymers (BCPs), often forms structures depicting curved surface/interface. Examples include liposomes, colloidosomes, spherical micelles, worm-like micelles, and vesicles (also known as polymersomes). For crystalline BCPs, crystallization oftentimes overwrites curved geometries since the latter is incommensurate with crystalline order. On the other hand, twisted and curved crystals are often observed in crystalline polymers. Various mechanisms have been proposed for these non-flat crystalline morphologies. In this presentation, we will demonstrate that curved liquid/liquid (L/L) interface can guide polymer single crystal growth. The crystal morphology is strongly dependent on the nucleation mechanism. A myriad of controlled curved single crystals can be readily obtained.

  11. Partially exposed polymer dispersed liquid crystals for boundary layer investigations

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Singh, Jag J.

    1992-01-01

    A new configuration termed partially exposed polymer dispersed liquid crystal in which the liquid crystal microdroplets dispersed in a rigid polymer matrix are partially entrapped on the free surface of the thin film deposited on a glass substrate is reported. Optical transmission characteristics of the partially exposed polymer dispersed liquid crystal thin film in response to an air flow induced shear stress field reveal its potential as a sensor for gas flow and boundary layer investigations.

  12. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, S.D.; Marshall, K.L.; Cerqua, K.A.

    1991-10-08

    Composite optical devices are disclosed using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T[sub g]) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device. 7 figures.

  13. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, Stephen D.; Marshall, Kenneth L.; Cerqua, Kathleen A.

    1991-01-01

    Composite optical devices using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T.sub.g) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device.

  14. Polymer-dispersed liquid crystal elastomers

    PubMed Central

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-01-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations. PMID:27713478

  15. Photorefractive conjugated polymer-liquid crystal composites

    SciTech Connect

    Wasielewski, M. R.; Yoon, B. A.; Fuller, M.; Wiederrecht, G. P.; Niemczyk, M. P.; Svec, W. A.

    2000-05-15

    A new mechanism for space-charge field formation in photorefractive liquid crystal composites containing poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N{prime}-dioctyl-1,4:5,8-naphthalenediimide, NI, is observed. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 {micro}m. The authors show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PEV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  16. Novel ion-containing liquid crystals and liquid crystalline polymers

    SciTech Connect

    Cheng, P.

    1992-01-01

    The properties of main chain polymeric liquid crystals (PLC's) based on trans-1,2-bis(4,4[prime]-pyridyl)ethylene mesogens, alkyl spacers and various counterions are described. The mesomorphic properties of model compounds are also described. Some of these are based on [open quotes]Siamese twin[close quotes] systems with the 4-alkoxystilbazole mesogen similar to the trans-1,2-bis(4,4[prime]-pyridyl)ethylene used in the polymer. Some model compounds are low molecular mass monomer analogues of the polymer. The structural parameters investigated were the length of the flexible spacer, the nature of the mesogen, the ionic density of the system and the nature and size of the counterion. The introduction of ionic sites into a main chain PLC's far from inhibiting appears to promote mesophase formation and enhance the stability of the mesophase. The phenomena described here involve high transition temperatures strong odd-even oscillations and supercooling effects. The twins and polymers display a great variety of smectic mesophases, the nature of which depends strongly on the nature of the counterion. Large organic counterions such as methylsulfonates promote the formation of smectic mesophases, sometimes of lower order (S[sub A] or S[sub C]) whilst toluenesulfonate promote often higher order smectic polymorphism. The polymers display also lyotropic liquid crystallinity.

  17. Theory of polymer-dispersed cholesteric liquid crystals

    SciTech Connect

    Matsuyama, Akihiko

    2013-11-07

    A mean field theory is presented to describe cholesteric phases in mixtures of a polymer and a cholesteric liquid crystal. Taking into account an anisotropic coupling between a polymer and a liquid crystal, we examine the helical pitch, twist elastic constant, and phase separations. Analytical expressions of the helical pitch of a cholesteric phase and the twist elastic constant are derived as a function of the orientational order parameters of a polymer and a liquid crystal and two intermolecular interaction parameters. We also find isotropic-cholesteric, cholesteric-cholesteric phase separations, and polymer-induced cholesteric phase on the temperature-concentration plane. We demonstrate that an anisotropic coupling between a polymer and a liquid crystal can stabilize a cholesteric phase in the mixtures. Our theory can also apply to mixtures of a nematic liquid crystal and a chiral dopant. We discuss the helical twisting power, which depends on temperature, concentration, and orientational order parameters. It is shown that our theory can qualitatively explain experimental observations.

  18. Holographic polymer-dispersed liquid crystals: Physics and applications

    NASA Astrophysics Data System (ADS)

    Qi, Jun

    Holographic polymer-dispersed liquid crystals are composite materials that are rich in physical phenomena and useful for electrically or thermally switchable hologram and grating applications. They are formed through a self-diffusion process using an interference pattern to initiate and drive the kinetics of formation, which is generated through two or more coherent laser beams. The information from the interference pattern is permanently recorded through a phase separation process or optical alignment of polymer in liquid crystal/polymer composites. The recorded holograms are erasable or tunable by applying sufficient external field or temperature variation. The formation kinetics of holographic polymer-dispersed liquid crystals can be modeled by a set of reaction-diffusion equations. By analyzing the optical performance of resulting gratings, we found that the phase separation process is dominated by a photo-polymerization induced diffusion in the fast polymerization regime rather than the thermal diffusion in the slow polymerization regime. The effective diffusion constant of oligomers can be enhanced by two orders of magnitude. This diffusion model is verified by in-situ spectroscopy measurements of reflective holographic polymer-dispersed liquid crystals. Through experiments and modeling, the shrinkage of the polymer matrix is determined. In addition, we have expanded our diffusion formalism to model two-dimensional and three-dimensional cases and temporally multiplexed systems. The Freedericksz transition, based on the elastic theory of liquid crystals, is used to model various morphologies of confined liquid crystals. A polymer scaffolding model and a cylindrical cavity model are proposed, which enable us to make an order of magnitude estimation of the surface anchoring strength of liquid crystal/polymer interfaces in different systems. From the applied physics standpoint, we have also made a number of valuable contributions to optical and photonic

  19. Electro-optic phase modulation by polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Vicari, L.

    1997-05-01

    We present a mathematical model to describe the optical phase shift induced by polymer dispersed liquid crystals (PDLCs) on light impinging transversely on the sample. PDLCs are dispersions of liquid crystal microdroplets in a polymeric binder. Droplets appear as optically uniaxial spheres randomly oriented so that the material is optically isotropic. The application of an external electric field results in a reorientation of the liquid crystal and therefore in an electrically controllable optical uniaxicity of the material. The model is discussed by comparison with experimental data and with previous theory [F. Basile, F. Bloisi, L. Vicari, and F. Simoni, Phys. Rev. E 48, 432 (1993)].

  20. Photorefractivity in crosslinked polymer-stabilized nematic liquid crystals.

    SciTech Connect

    Wiederrecht, G. P.; Wasielewski, M. R.; Chemistry; Northwestern Univ.

    1999-03-01

    The observation of photorefractive gratings in new crosslinked polymer-stabilized liquid crystals (PSLCs) is discussed and compared to previous PSLCs. The PSLCs easily incorporate reduced or oxidized molecules that are present in a nematic liquid crystal at a concentration of 2 mol%. The PSLCs that are crosslinked provide improved photo-refractive grating resolution, due to their improved functionality as an immobile electron trap. These materials are capable of functioning well into the Bragg diffraction regime. Photoconductivity experiments that support the photorefractive mechanism and a different charge transport mechanism than neat liquid crystals are also performed.

  1. Polymer single crystal membranes from curved liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group Team

    2014-03-01

    The weak mechanical properties of the current available vesicles such as liposomes, polymersomes, colloidosomes limit their applications for targeting delivery of drugs/genes. Recently, we developed an emulsion-crystallization method to grow polymer curved single crystals. Using polyethylene and poly(l-lactic acid)as the model systems, enclosed or partially open polymer single crystals have been obtained. Electron diffraction and XRD results confirmed their crystalline structure. The single crystal hollow sphere is structurally close to polymersomes, but with thinner wall and higher modulus.

  2. Photorefractivity in polymer-stabilized nematic liquid crystals

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R. |

    1998-07-01

    Polymer-stabilized liquid crystals, consisting of low concentrations of a polymeric electron acceptor, are shown to exhibit significantly enhanced photorefractive properties. The charge generation and transport properties of these composite systems are strongly modified from nematic liquid crystals doped with electron donors and acceptors. The new composites are produced by polymerizing a small quantity of a 1,4:5,8-naphthalenediimide electron acceptor functionalized with an acrylate group in an aligned nematic liquid crystal. Photopolymerization creates an anisotropic gel-like medium in which the liquid crystal is free to reorient in the presence of a space charge field, while maintaining charge trapping sites in the polymerized regions of the material. The presence of these trapping sites results in the observation of longer lived, higher resolution holographic gratings in the polymer-stabilized liquid crystals than observed in nematic liquid crystals alone. These gratings display Bragg regime diffraction. Asymmetric beam coupling, photo-conductivity, and four-wave mixing experiments are performed to characterize the photophysics of these novel materials.

  3. Photorefractivity in polymer-stabilized nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wiederrecht, Gary P.; Wasielewski, Michael R.

    1998-10-01

    Polymer-stabilized liquid crystals, consisting of low concentrations of a polymeric electron acceptor, are shown to exhibit significantly enhanced photorefractive properties. The charge generation and transport properties of these composite systems are strongly modified from nematic liquid crystals doped with electron donors and acceptors. The new composites are produced by polymerizing a small quantity of a 1,4:5,8-naphthalenediimide electron acceptor functionalized with an acrylate group in an aligned nematic liquid crystal. Photopolymerization creates an anisotropic gel-like medium in which the liquid crystal is free to reorient in the presence of a space charge field, while maintaining charge trapping sites in the polymerized regions of the material. The presence of these trapping sites results in the observation of longer lived, higher resolution holographic gratings in the polymer-stabilized liquid crystals than observed in nematic liquid crystals alone. These gratings display Bragg regime diffraction. Asymmetric beam coupling, photo-conductivity, and four-wave mixing experiments are performed to characterize the photophysics of these novel materials.

  4. LIQUID CRYSTAL POLYMERS (LCP) USED AS A MACHINING FLUID CD

    EPA Science Inventory

    This interactive CD was produced to present the science, research activities, and beneficial environmental and machining advantages for utilizing Liquid Crystal Polymers (LCPs) as a machine fluid in the manufacturing industry.

    In 1995, the USEPA funded a project to cut flu...

  5. Electrically tunable holographic polymer templated blue phase liquid crystal grating

    NASA Astrophysics Data System (ADS)

    He, Zheng-Hong; Chen, Chao-Ping; Zhu, Ji-Liang; Yuan, Ya-Chao; Li, Yan; Hu, Wei; Li, Xiao; Li, Hong-Jing; Lu, Jian-Gang; Su, Yi-Kai

    2015-06-01

    In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications. Project supported by the National Basic Research Program of China (Grant No. 2013CB328804), the National Natural Science Foundation of China (Grant No. 61307028), the Funds from the Science and Technology Commission of Shanghai Municipality (Grant Nos. 11JC1405300, 13ZR1420000, and 14ZR1422300), and the Fundamental Research Funds for the Central Universities, China (Grant No. XDJK 2011C047).

  6. Novel Microstructures for Polymer-Liquid Crystal Composite Materials

    NASA Technical Reports Server (NTRS)

    Magda, Jules J.

    2004-01-01

    There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.

  7. Interaction between lyotropic chromonic liquid crystals and polymers

    NASA Astrophysics Data System (ADS)

    Yao, Xuxia; Park, Jung; Srinivasarao, Mohan

    2010-03-01

    Lyotropic chromonic liquid crystals (LCLCs) consist of various dyes, drugs, etc., so their importance is self-evident. The interaction of chromonic molecules and polymers is involved in their real applications, such as the dyeing process of fibers, textiles and food, and the functionalization of drugs in vivo. In our research, polymer dispersed LCLC droplets and polymer coated LCLC cells have been fabricated. Effect of interaction was observed by optical texture of LCLCs, as the different polymers induce different director configuration of LCLCs. A textile dye-Benzopurpurine 4B, food dye-Sunset Yellow FCF, and drug-Disodium Cromoglycate mixed with water soluble polymers, proteins and textile polymers have been all studied and compared.

  8. Well-defined liquid crystal gels from telechelic polymers.

    PubMed

    Xia, Yan; Verduzco, Rafael; Grubbs, Robert H; Kornfield, Julia A

    2008-02-01

    Well-defined liquid crystal networks with controlled molecular weight between cross-links and cross-link functionality were prepared by "click" cross-linking of telechelic polymers produced by ring-opening metathesis polymerization (ROMP). The networks readily swell in a small molecule liquid crystal, 5CB, to form LC gels with high swelling ratios. These gels exhibit fast, reversible, and low-threshold optic switching under applied electric fields when they are unconstrained between electrodes. For a given electric field, the LC gels prepared from shorter telechelic polymers showed a reduced degree of switching than their counterparts made from longer polymer strands. The reported approach provides control over important parameters for LC networks, such as the length of the network strands between cross-links, cross-linker functionality, and mesogen density. Therefore, it allows a detailed study of relationships between molecular structure and macroscopic properties of these scientifically and technologically interesting networks. PMID:18197667

  9. Fluorinated Azobenzenes for Shape-Persistent Liquid Crystal Polymer Networks.

    PubMed

    Iamsaard, Supitchaya; Anger, Emmanuel; Aßhoff, Sarah Jane; Depauw, Alexis; Fletcher, Stephen P; Katsonis, Nathalie

    2016-08-16

    Liquid crystal polymer networks respond with an anisotropic deformation to a range of external stimuli. When doped with molecular photoswitches, these materials undergo complex shape modifications under illumination. As the deformations are reversed when irradiation stops, applications where the activated shape is required to have thermal stability have been precluded. Previous attempts to incorporate molecular switches into thermally stable photoisomers were unsuccessful at photogenerating macroscopic shapes that are retained over time. Herein, we show that to preserve photoactivated molecular deformation on the macroscopic scale, it is important not only to engineer the thermal stability of the photoswitch but also to adjust the cross-linking density in the polymer network and to optimize the molecular orientations in the material. Our strategy resulted in materials containing fluorinated azobenzenes that retain their photochemical shape for more than eight days, which constitutes the first demonstration of long-lived photomechanical deformation in liquid-crystal polymer networks. PMID:27430357

  10. Fast switching of polymer-stabilized liquid crystal pi cells

    NASA Astrophysics Data System (ADS)

    Huang, Chi Yen; Fung, Ri Xin; Lin, Ying Ging; Hsieh, Chia Ting

    2007-04-01

    This work demonstrates a dual-frequency polymer-stabilized liquid crystal pi cell with zero bias and a short response time. The high curing voltage and low curing intensity give the cell a low dark state and a high bright state, such that the transmittance against the applied voltage curve is steep. The response time is under 1ms and is independent of monomer concentration because a strong electric torque is exerted on the liquid crystals. The cell is useful in field-sequential color systems, and the low operating voltage of ˜5V makes the cell compatible with conventional thin film transistor driving voltages.

  11. Polymer-dispersed liquid crystal displays: switching times effect

    NASA Astrophysics Data System (ADS)

    Mucha, Maria; Nastal-Grosicka, E.

    1998-02-01

    Electrooptical and switching properties of polyester resin/nematic liquid crystal composite films have been studied by varying composition, temperature and UV curing time of the matrix. The PDLC films were formed by LC separation in UV polymerization process of the thin layer of oligoester resin between ITO coated glass plates. The electrooptical and response behavior based on the electric field controlled light scattering of the composite films was recorded. The result were interpreted in terms of effective anchoring strength at the interface of polymer and liquid crystal.

  12. Chromonic liquid crystals and their dispersion in polymers

    NASA Astrophysics Data System (ADS)

    Park, Jung; Yao, Xuxia; Srinivasarao, Mohan

    2010-03-01

    Chromonic liquid crystals can self-assemble into an ordered complex fluid, potentially applicable for biosensor, polarizers, optical compensetors and organic solar cells. Different from common amphiphilic lyotropic mesophases, aggregation of the chromonic liquid crystals is thought to be isodesmic and without optimum aggregation size. We studied the aggregation behavior by Vis-spectroscopy, and the phase behavior by polarizing optical microscopy and differential scanning calorimetry. We also used capillary flow to achieve uniform planar alignment in a flat capillary, and measured polarized Raman scattering, from which the temperature and concentration dependence of order parameters, both and , and the orientation distribution were deduced. Order parameters increase as concentration increases and decrease as temperature increases. Polymer dispersed chromonic droplets with different director configurations were obtained by using different water soluble polymers and those anchoring phenomena were compared.

  13. Holographic polymer dispersed liquid crystal enhanced by introducing urethane trimethacrylate.

    PubMed

    Nataj, Nahid Hosein; Mohajerani, Ezeddin; Jashnsaz, Hossein; Jannesari, Ali

    2012-02-20

    This work characterizes holographic polymer dispersed liquid crystals (HPDLC) composite material based on a new monomer, urethane trimethacrylate, by fabricating switchable diffraction grating. The highest diffraction efficiency achieved was 90.3%. Details of the fabrication and preliminary results of electro-optical switching of the HPDLC diffraction gratings are presented and discussed based on the functionality of the monomer. These experimental results are explained by means of morphological scanning electron microscopy analyses. PMID:22358158

  14. Anchoring of a nematic liquid crystal at a polymer surface

    NASA Astrophysics Data System (ADS)

    Bagheri-Hamaneh, Mehdi; Taylor, Philip L.

    2003-03-01

    A commonly used technique to orient liquid crystal molecules in contact with a polymer is to rub the polymer surface with a soft cloth. This has the effect of both digging grooves and aligning polymeric chains in the surface. The relative importance of these two effects has long been debated. To study this question we have performed atomistic molecular dynamic simulations of molecules of 5CB in contact with polyvinyl alcohol. In this way it is possible to investigate the effects of interchain spacing, tacticity, chain orientation, and surface topography on the preferred orientation. The resulting preferred direction of planar anchoring appears to depend on all of these factors.

  15. Effect of Frustration in Liquid Crystals and Polymers

    NASA Astrophysics Data System (ADS)

    Kléman, Maurice

    1987-01-01

    We assign the term of frustration to the general case in which the interactions which compete on short distances in the stability of some material lead to local configurations of molecules which are incompatible on large scales. The standard example in liquid crystals are the blue phases, whose ground state is an assembly of frustrated domains with specific double twist order and characteristic size, separated by defect lines (disclinations). Blue phases are modifications of cholesteric phases with small molecules; the same considerations extend to cholesteric liquid crystal polymers where frustration is also documented. In particular, we discuss observations made in solutions of biological liquid crystal polymers, and in biological objects, like some proteins and the chromosome of dinoflagellate; this last example provides a geometry of double twist different to that one theorized in blue phases. In this model, the finite size of the chromosome is directly related to the characteristic size of the unfrustrated domain of double twist. Finally, we extend the consideration of a space of constant positive curvature already used for blue phases to the case of crystalline arrangements of chiral molecules. The frustration is entirely relieved in such a space. We argue that the same model of curved space could describe short range correlations in chiral or non-chiral amorphous polymers.

  16. A polarization independent liquid crystal phase modulation adopting surface pinning effect of polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Tsou, Yu-Shih

    2011-12-01

    A polarization-independent liquid crystal (LC) phase modulation using the surface pinning effect of polymer dispersed liquid crystals (SP-PDLC) is demonstrated. In the bulk region of the SP-PDLC, the orientations of LC directors are randomly dispersed; thus, any polarization of incident light experiences the same averaged refractive index. In the regions near glass substrates, the LC droplets are pinned. The orientations of top and bottom droplets are orthogonal. Two eigen-polarizations of an incident light experience the same phase shift. As a result, the SP-PDLC is polarization independent. Polarizer-free microlens arrays of SP-PDLC are also demonstrated. The SP-PDLC has potential for application in spatial light modulators, laser beam steering, and electrically tunable microprisms.

  17. Photocontrol of fluid slugs in liquid crystal polymer microactuators

    NASA Astrophysics Data System (ADS)

    Lv, Jiu-An; Liu, Yuyun; Wei, Jia; Chen, Erqiang; Qin, Lang; Yu, Yanlei

    2016-09-01

    The manipulation of small amounts of liquids has applications ranging from biomedical devices to liquid transfer. Direct light-driven manipulation of liquids, especially when triggered by light-induced capillary forces, is of particular interest because light can provide contactless spatial and temporal control. However, existing light-driven technologies suffer from an inherent limitation in that liquid motion is strongly resisted by the effect of contact-line pinning. Here we report a strategy to manipulate fluid slugs by photo-induced asymmetric deformation of tubular microactuators, which induces capillary forces for liquid propulsion. Microactuators with various shapes (straight, ‘Y’-shaped, serpentine and helical) are fabricated from a mechanically robust linear liquid crystal polymer. These microactuators are able to exert photocontrol of a wide diversity of liquids over a long distance with controllable velocity and direction, and hence to mix multiphase liquids, to combine liquids and even to make liquids run uphill. We anticipate that this photodeformable microactuator will find use in micro-reactors, in laboratory-on-a-chip settings and in micro-optomechanical systems.

  18. Photocontrol of fluid slugs in liquid crystal polymer microactuators.

    PubMed

    Lv, Jiu-An; Liu, Yuyun; Wei, Jia; Chen, Erqiang; Qin, Lang; Yu, Yanlei

    2016-01-01

    The manipulation of small amounts of liquids has applications ranging from biomedical devices to liquid transfer. Direct light-driven manipulation of liquids, especially when triggered by light-induced capillary forces, is of particular interest because light can provide contactless spatial and temporal control. However, existing light-driven technologies suffer from an inherent limitation in that liquid motion is strongly resisted by the effect of contact-line pinning. Here we report a strategy to manipulate fluid slugs by photo-induced asymmetric deformation of tubular microactuators, which induces capillary forces for liquid propulsion. Microactuators with various shapes (straight, 'Y'-shaped, serpentine and helical) are fabricated from a mechanically robust linear liquid crystal polymer. These microactuators are able to exert photocontrol of a wide diversity of liquids over a long distance with controllable velocity and direction, and hence to mix multiphase liquids, to combine liquids and even to make liquids run uphill. We anticipate that this photodeformable microactuator will find use in micro-reactors, in laboratory-on-a-chip settings and in micro-optomechanical systems. PMID:27604946

  19. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber.

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG, are discussed. Experimental data presented here demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, and is discussed further. PMID:23988927

  20. Photorefractivity in liquid crystals doped with a soluble conjugated polymer.

    SciTech Connect

    Niemczyk, M. P.; Svec, W. A.; Wasielewski, M. R.; Wiederrecht, G. P.

    1999-07-07

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N{prime}-dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 {micro}m. We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  1. Photorefractivity in liquid crystals doped with a soluble conjugated polymer

    NASA Astrophysics Data System (ADS)

    Wiederrecht, Gary P.; Svec, Walter A.; Niemczyk, Mark P.; Wasielewski, Michael R.

    1999-10-01

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2'-ethylhexyloxy)-1,4- phenylenevinylene) (BEH-PPV) and the electron acceptor N,N'- dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 micrometers . We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile spaces due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  2. Intrinsic response of polymer liquid crystals in photochemical phase transition

    SciTech Connect

    Ikeda, Tomiki; Sasaki, Takeo; Kim, Haengboo )

    1991-01-24

    Time-resolved measurements were performed on the photochemically induced isothermal phase transition of polymer liquid crystals (PLC) with mesogenic side chains of phenyl benzoate (PAPB3) and cyanobiphenyl (PACB3) under conditions wherein the photochemical reaction of the doped photoresponsive molecule (4-butyl-4-{prime}-methoxyazobenzene, BMAB) was completed within {approximately} 10 ns, and the subsequent phase transition of the matrix PLC from nematic (N) to isotropic (I) state was followed by time-resolved measurements of the birefringence of the system. Formation of a sufficient amount of the cis isomer of BMAB with a single pulse of a laser lowered the N-I phase transition temperature of the mixture, inducing the N-I phase transition of PLCs isothermally in a time range of {approximately} 200 ms. This time range is comparable to that of low molecular weight liquid crystals, indicating that suppression in mobility of mesogens in PLCs does not affect significantly the thermodynamically controlled process.

  3. Skin friction measurement with partially exposed polymer dispersed liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Partially exposed polymer dispersed liquid crystal thin film (10-25 microns) deposited on a flat glass substrate has been used for the first time to measure skin friction. Utilizing the shear-stress-induced director reorientation in the partially exposed liquid-crystal droplets, optical transmission under crossed polarization has been measured as a function of the air flow differential pressure. Direct measurement of the skin friction with a skin friction drag balance, under the same aerodynamic conditions, lets us correlate the skin friction with optical transmission. This provides a unique technique for the direct measurement of skin friction from the transmitted light intensity. The results are in excellent agreement with the model suggested in this paper.

  4. Exploring Motion Reversal in Polymer Cholesteric-Liquid-Crystal Devices

    SciTech Connect

    Kosc, T.Z.; Coon, C.J.; Babcock, G.V.; Marshall, K.L.; Trajkovska-Petkoska, Jacobs, S.D.

    2006-12-13

    Polymer cholesteric-liquid-crystal (PCLC) flakes suspended in a fluid are used as the active medium in a novel particle-based, electro-optic technology. The motion of PCLC flakes is controlled with an electric field so that PCLC flake devices are brightly reflective in their “off” state and appear dark when an electric field is applied, causing the flakes to reorient 90º. We seek to control flake orientation by designing waveforms that follow the initial drive voltage. Shaped pulses were investigated to accelerate flake relaxation.

  5. Thermal tunability of photonic bandgaps in liquid crystal filled polymer photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Wang, Doudou; Chen, Guoxiang; Wang, Lili

    2016-05-01

    A highly tunable bandgap-guiding polymer photonic crystal fiber is designed by infiltrating the cladding air holes with liquid crystal 5CB. Structural parameter dependence and thermal tunability of the photonic bandgaps, mode properties and confinement losses of the designed fiber are investigated. Bandgaps red shift as the temperature goes up. Average thermal tuning sensitivity of 30.9 nm/°C and 20.6 nm/°C is achieved around room temperature for the first and second photonic bandgap, respectively. Our results provide theoretical references for applications of polymer photonic crystal fiber in sensing and tunable fiber-optic devices.

  6. Thick polymer-stabilized liquid crystal films for microwave phase control

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Kuki, Takao; Nomoto, Toshihiro; Tsuchiya, Yuzuru; Utsumi, Yozo

    2001-05-01

    This article describes the use of thick polymer-stabilized liquid crystal films in a new design for microwave variable phase shifters. A fine μm-order sized polymer network was formed in a 100-μm-thick liquid crystal film, using a photopolymerization-induced phase-separation method to stabilize the molecular alignment of the liquid crystal. Measurement of the electro-optic properties of the liquid crystal film revealed that the relaxation response time of the liquid crystal alignment was drastically decreased by doping the polymer at a concentration of several wt %. A new variable phase shifter composed of a microstrip transmission line (length: 193 mm, width: 200 μm) was also fabricated by using the liquid crystal film as the dielectric material. This device exhibited a microwave phase shift of -80° at a frequency of 20 GHz, when a drive voltage of 70Vrms was applied vertically to the liquid crystal film.

  7. Ultra-fast solid state electro-optical modulator based on liquid crystal polymer and liquid crystal composites

    SciTech Connect

    Ouskova, Elena; Sio, Luciano De Vergara, Rafael; Tabiryan, Nelson; White, Timothy J.; Bunning, Timothy J.

    2014-12-08

    A different generation of polymer-dispersed liquid crystals (PDLCs) based on a liquid crystalline polymer host is reported wherein the fluid behavior of the reactive mesogenic monomer is an enabler to concentration windows (liquid crystal polymer/liquid crystal) (and subsequent morphologies) not previously explored. These liquid crystal (LC) polymer/LC composites, LCPDLCs, exhibit excellent optical and electro-optical properties with negligible scattering losses in both the ON and OFF states. These systems thus have application in systems where fast phase modulation of optical signal instead of amplitude control is needed. Polarized optical microscopy and high resolution scanning electron microscopy confirm a bicontinuous morphology composed of aligned LC polymer coexisting with a phase separated LC fluid. Operating voltages, switching times, and spectra of LCPDLCs compare favourably to conventional PDLC films. The LCPDLCs exhibit a low switching voltage (4–5 V/μm), symmetric and submillisecond (200 μs) on/off response times, and high transmission in both the as formed and switched state in a phase modulation geometry.

  8. Surface dynamics and mechanics in liquid crystal polymer coatings

    NASA Astrophysics Data System (ADS)

    Liu, Danqing; Broer, Dirk J.

    2015-03-01

    Based on liquid crystal networks we developed `smart' coatings with responsive surface topographies. Either by prepatterning or by the formation of self-organized structures they can be switched on and off in a pre-designed manner. Here we provide an overview of our methods to generate coatings that form surface structures upon the actuation by light. The coating oscillates between a flat surface and a surface with pre-designed 3D micro-patterns by modulating a light source. With recent developments in solid state lighting, light is an attractive trigger medium as it can be integrated in a device for local control or can be used remotely for flood or localized exposure. The basic principle of formation of surface topographies is based on the change of molecular organization in ordered liquid crystal polymer networks. The change in order leads to anisotropic dimensional changes with contraction along the director and expansion to the two perpendicular directions and an increase in volume by the formation of free volume. These two effects work in concert to provide local expansion and contraction in the coating steered by the local direction of molecular orientation. The surface deformation, expressed as the height difference between the activated regions and the non-activated regions divided by the initial film thickness, is of the order of 20%. Switching occurs immediately when the light is switched `on' and `off' and takes several tens of seconds.

  9. Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Rai, Kashma; Shriyan, Sameet; Fontecchio, Adam

    2008-03-01

    Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique.

  10. Polymer-dispersed liquid crystal devices with graphene electrodes.

    PubMed

    Chung, Seok-Hwan; Noh, Hee Yeon

    2015-12-14

    Although polymer-dispersed liquid crystal (PDLC) devices have considerable potential application in smart windows, the high material cost of the indium tin oxide (ITO) electrodes conventionally used in these devices hinders their wide usage. In this work, we explore the use of graphene electrodes as a potential substitute for ITO electrodes in PDLC devices. The fabricated PDLC devices with graphene electrodes exhibit higher contrast and faster response than PDLC devices with ITO electrodes fabricated using the same chemical formulation and polymerization process. However, they also exhibit higher operation voltage and haze, which is primarily attributed to the inherently large resistance and inhomogeneity of the large-area graphene sheets initially transferred onto the transparent substrates. PDLC devices with graphene electrodes are robust under standard operating conditions and also have the advantage of flexibility and stretchability, unlike PDLCs with ITO electrodes. PMID:26699005

  11. Nematic polymer liquid-crystal wave plate for high-power lasers at 1054 nm

    SciTech Connect

    Kreuzer, F. ); Korenic, E.M.; Jacobs, S.D.; Houghton, J.K.; Schmid, A. )

    1994-04-01

    A nematic polymer liquid crystal is used to construct wave plates for use at 1054 nm. Three methods of wave-plate construction are discussed: double substrate with fiber spacers in homogeneous distribution, double substrate with fiber spacers in annular distribution, and single substrate. The polymer liquid crystal shows high laser-damage resistance, making it particularly useful for high-peak-power laser applications. Alignment techniques and measurement of birefringence for the highly viscous polymer are described.

  12. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystal with orthogonal alignment layers

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih; Lin, Yi-Hsin

    2012-10-01

    A polarization-independent liquid crystal (LC) phase modulation using polymer-network liquid crystals with orthogonal alignments layers (T-PNLC) is demonstrated. T-PNLC consists of three layers. LC directors in the two layers near glass substrates are orthogonal to each other. In the middle layer, LC directors are perpendicular to the glass substrate. The advantages of such T-PNLC include polarizer-free, larger phase shift (~0.4π rad) than the residual phase type (<0.05π rad), and low operating voltage (< 30Vrms). It does not require bias voltage for avoiding scattering because the refractive index of liquid crystals matches that of polymers. The phase shift of T-PNLC is affected by the cell gap and the curing voltages. The potential applications are laser beam steering, spatial light modulators and electrically tunable micro-lens arrays.

  13. Shear Flow Induced Transition from Liquid-Crystalline to Polymer Behavior in Side-Chain Liquid Crystal Polymers

    SciTech Connect

    Noirez, L.; Lapp, A.

    1997-01-01

    We determine the structure and conformation of side-chain liquid-crystalline polymers subjected to shear flow in the vicinity of the smectic phase by neutron scattering on the velocity gradient plane. Below the nematic-smectic transition we observe a typical liquid-crystal behavior; the smectic layers slide, leading to a main-chain elongation parallel to the velocity direction. In contrast,a shear applied above the transition induces a tilted main-chain conformation which is typical for polymer behavior. {copyright} {ital 1996} {ital The American Physical Society}

  14. Switchable Solar Window Devices Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Murray, Joseph; Ma, Dakang; Munday, Jeremy

    Windows are an interesting target for photovoltaics due to the potential for large area of deployment and because glass is already a ubiquitous component of solar cell devices. Many demonstrations of solar windows in recent years have used photovoltaic devices which are semitransparent in the visible region. Much research has focused on enhancing device absorption in the UV and IR ranges as a means to circumvent the basic tradeoff between efficiency and transparency to visible light. Use of switchable solar window is a less investigated alternative approach; these windows utilize the visible spectrum but can toggle between high transparency and high efficiency as needed. We present a novel switchable solar window device based on Polymer Dispersed Liquid Crystals (PDLC). By applying an electric field to the PDLC layer, the device can be switched from an opaque, light diffusing, efficient photovoltaic cell to a clear, transparent window. In the off state (i.e. scattering state), these devices have the added benefits of increased reflectivity for reduced lighting and cooling costs and haze for privacy. Further, we demonstrate that these windows have the potential for self-powering due to the very low power required to maintain the on, or high transparency, state. Support From: University of Maryland and Maryland Nano-center and its Fablab.

  15. Exploratory development of foams from liquid crystal polymers

    NASA Technical Reports Server (NTRS)

    Chung, T. S.

    1985-01-01

    Two types of liquid crystal polymer (LCP) compositions were studied and evaluated as structural foam materials. One is a copolymer of 6-hydroxy-2-naphthoic acid, terephthalic acid, and p-acetoxyacetanilide (designed HNA/TA/AAA), and the other is a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (designated HBA/HNA). Experimental results showed that the extruded HNA/TA/AA foams have better mechanical quality and appearance than HBA/HNA foams. Heat treatment improved foam tensile strength and break elongation, but reduced their modulus. The injection molding results indicated that nitrogen foaming agents with a low-pressure process gave better void distribution in the injection molded LCP foams than those made by the conventional injection-molding machine and chemical blowing agents. However, in comparing LCP foams with other conventional plastic foams, HBA/HNA foams have better mechanical properties than foamed ABS and PS, but are comparable to PBT and inferior to polycarbonate foams, especially in heat-deflection temperature and impact resistance energy. These deficiencies are due to LCP molecules not having been fully oriented during the Union-Carbide low-pressure foaming process.

  16. Piezoelectric properties of polymers containing bent-shape liquid crystal molecules

    NASA Astrophysics Data System (ADS)

    Diorio, N.; Varga, M.; Carif, A.; Puskas, J. E.; Fodor-Csorba, K.; Sprunt, S.; Gleeson, J. T.; Jakli, A.

    2013-03-01

    Recently, bent-core liquid crystal elastomers have shown to exhibit large values of flexoelectricity as many as 3 orders of magnitude larger than liquid crystal elastomers containing rod-shaped molecules. These unusual high responses are attributed to have piezoelectric origin. Motivated by this, in this study, two bent-core liquid crystals were used to make various types of materials; low molecular weight bent-core nematic fluid, side chain bent-core liquid crystal polymer, low molecular liquid crystal dispersed in a polyisobutylene-based thermoplastic elastomer, and side-chain bent-core elastomers. Liquid crystal elastomers combine elasticity and flexibility inherent to rubbers and the optical and electrical properties of liquid crystals, and are promising materials for applications such as electro-optics, flexible electronics and actuator technologies for biomedical applications. Most conventional liquid crystal elastomers have rod-shaped liquid crystal molecules chemically attached to a crosslinked polymer network. Converse piezoelectric responses were measured by a Mirau interferometer and the direct piezoelectric signals were studied by home-made device where the stress is provided by an audio speaker. The results will be analyzed in terms of ferroelectric clusters of the materials in the nematic phase and will be compared with other piezoelectric materials. Supported by Grants NSF-DMR -0964765 and NSF-DMR -0804878.

  17. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm‑2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm‑2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  18. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal.

    PubMed

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm(-2), which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm(-2)). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  19. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm-2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm-2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  20. Polymer stabilized liquid crystals: Topology-mediated electro-optical behavior and applications

    NASA Astrophysics Data System (ADS)

    Weng, Libo

    There has been a wide range of liquid crystal polymer composites that vary in polymer concentration from as little as 3 wt.% (polymer stabilized liquid crystal) to as high as 60 wt.% (polymer dispersed liquid crystals). In this dissertation, an approach of surface polymerization based on a low reactive monomer concentration about 1 wt.% is studied in various liquid crystal operation modes. The first part of dissertation describes the development of a vertical alignment (VA) mode with surface polymer stabilization, and the effects of structure-performance relationship of reactive monomers (RMs) and polymerization conditions on the electro-optical behaviors of the liquid crystal device has been explored. The polymer topography plays an important role in modifying and enhancing the electro-optical performance of stabilized liquid crystal alignment. The enabling surface-pinned polymer stabilized vertical alignment (PSVA) approach has led to the development of high-performance and fast-switching displays with controllable pretilt angle, increase in surface anchoring energy, high optical contrast and fast response time. The second part of the dissertation explores a PSVA mode with in-plane switching (IPS) and its application for high-efficiency and fast-switching phase gratings. The diffraction patterns and the electro-optical behaviors including diffraction efficiency and response time are characterized. The diffraction grating mechanism and performance have been validated by computer simulation. Finally, the advantages of surface polymerization approach such as good optical contrast and fast response time have been applied to the fringe-field switching (FFS) system. The concentration of reactive monomer on the electro-optical behavior of the FFS cells is optimized. The outstanding electro-optical results and mechanism of increase in surface anchoring strength are corroborated by the director field simulation. The density and topology of nanoscale polymer protrusions

  1. The effect of the temperature on the bandgaps based on the chiral liquid crystal polymer

    NASA Astrophysics Data System (ADS)

    Wang, Jianhua; Shi, Shuhui; Wang, Bainian

    2015-10-01

    Chiral side-chain liquid crystal polymer is synthesized from polysiloxanes and liqud crystal monomer 4-(Undecenoic-1- yloxybenzoyloxy)-4'-benzonitrile and 6-[4-(4- Undecenoic -1-yloxybenzoyloxy)- hydroxyphenyl] cholesteryl hexanedioate. The optical and thermal property of the monomer and polymer are shown by POM and DSC. As the unique optical property of the polymer, the bandgaps are shifted for heating temperature. The reflection bandgaps is shifted from 546nm to 429nm with temperature increase. As a photonic material, the chiral polymer which sensitive responses under the outfield is widely studied for reflection display, smart switchable reflective windows and defect model CLC laser etc.

  2. Langmuir Films of Flexible Polymers Transferred to Aqueous/Liquid Crystal Interfaces Induce Uniform Azimuthal Alignment of the Liquid Crystal

    PubMed Central

    Kinsinger, Michael I.; Buck, Maren E.; Meli, Maria-Victoria; Abbott, Nicholas L.; Lynn, David M.

    2009-01-01

    We reported recently that amphiphilic polymers can be assembled at interfaces created between aqueous phases and thermotropic liquid crystals (LCs) in ways that (i) couple the organization of the polymer to the order of the LC and (ii) respond to changes in the properties of aqueous phases that can be characterized as changes in the optical appearance of the LC. This investigation sought to characterize the behavior of aqueous-LC interfaces decorated with uniaxially compressed thin films of polymers transferred by Langmuir-Schaefer (LS) transfer. Here, we report physicochemical characterization of interfaces created between aqueous phases and the thermotropic LC 4-cyano-4’-pentylbiphenyl (5CB) decorated with Langmuir films of a novel amphiphilic polymer (polymer 1), synthesized by the addition of hydrophobic and hydrophilic side chains to poly(2-vinyl-4,4’-dimethylazlactone). Initial characterization of this system resulted in the unexpected observation of uniform azimuthal alignment of 5CB after LS transfer of the polymer films to aqueous-5CB interfaces. This paper describes characterization of Langmuir films of polymer 1 hosted at aqueous-5CB interfaces as well as the results of our investigations into the origins of the uniform ordering of the LC observed upon LS transfer. Our results, when combined, support the conclusion that uniform azimuthal alignment of 5CB is the result of long-range ordering of polymer chains in the Langmuir films (in a preferred direction orthogonal to the direction of compression) that is generated during uniaxial compression of the films prior to LS transfer. Although past studies of Langmuir films of polymers at aqueous-air interfaces have demonstrated that in-plane alignment of polymer backbones can be induced by uniaxial compression, these past reports have generally made use of polymers with rigid backbones. One important outcome of this current study is thus the observation of anisotropy and long-range order in Langmuir films

  3. Polymer-Layer-Free Alignment for Fast Switching Nematic Liquid Crystals by Multifunctional Nanostructured Substrate.

    PubMed

    Jung, Woo-Bin; Jeong, Hyeon Su; Jeon, Hwan-Jin; Kim, Yun Ho; Hwang, Jeong Yeon; Kim, Jae-Hoon; Jung, Hee-Tae

    2015-11-01

    A novel polymer-layer-free system for liquid-crystal alignment is demonstrated by various shaped indium tin oxide (ITO) patterns. Liquid crystals are aligned along the ITO line pattern and secondary sputtering lithography can change the shape of the ITO line pattern. Different shapes can control the direction and size of the pretilt angle. This effect eliminates defects and reduces the response time.

  4. Hysteresis-free and submillisecond-response polymer network liquid crystal.

    PubMed

    Lee, Yun-Han; Gou, Fangwang; Peng, Fenglin; Wu, Shin-Tson

    2016-06-27

    We demonstrate a polymer network liquid crystal (PNLC) with negligible hysteresis while keeping submillisecond response time. By doping about 1% dodecyl acrylate (C12A) into the liquid crystal/monomer precursor, both hysteresis and residual birefringence are almost completely eliminated. The operating voltage and scattering properties remain nearly intact, but the tradeoff is enhanced double relaxation. This hysteresis-free PNLC should find applications in spatial light modulators, laser beam control, and optical communications in infrared region.

  5. Dielectric Permittivity of Polymer Composites with Encapsulated Liquid Crystals in Strong Electric Fields

    NASA Astrophysics Data System (ADS)

    Zhdanov, K. R.; Romanenko, A. I.; Zharkova, G. M.; Suslyaev, V. I.; Zhuravlev, V. A.

    2013-12-01

    It is demonstrated that the threshold value of the electric Fredericks transition in the composite based on polyvinyl acetate with 35% weight content of nematic liquid crystal 5СВ (4-pentyl-4'-cyanobiphenyl) is observed at a voltage of 60 V. A cell and a circuit for measuring the dielectric permittivity of polymer composites with encapsulated liquid crystals in strong electric fields are described.

  6. Hysteresis-free and submillisecond-response polymer network liquid crystal.

    PubMed

    Lee, Yun-Han; Gou, Fangwang; Peng, Fenglin; Wu, Shin-Tson

    2016-06-27

    We demonstrate a polymer network liquid crystal (PNLC) with negligible hysteresis while keeping submillisecond response time. By doping about 1% dodecyl acrylate (C12A) into the liquid crystal/monomer precursor, both hysteresis and residual birefringence are almost completely eliminated. The operating voltage and scattering properties remain nearly intact, but the tradeoff is enhanced double relaxation. This hysteresis-free PNLC should find applications in spatial light modulators, laser beam control, and optical communications in infrared region. PMID:27410631

  7. Shape-Selectivity with Liquid Crystal and Side-Chain Liquid Crystalline Polymer SAW Sensor Interfaces

    SciTech Connect

    FRYE-MASON,GREGORY CHARLES; OBORNY,MICHAEL C.; PUGH,COLEEN; RICCO,ANTONIO; THOMAS,ROSS C.; ZELLERS,EDWARD T.; ZHANG,GUO-ZHENG

    1999-09-23

    A liquid crystal (LC) and a side-chain liquid crystalline polymer (SCLCP) were tested as surface acoustic wave (SAW) vapor sensor coatings for discriminating between pairs of isomeric organic vapors. Both exhibit room temperature smectic mesophases. Temperature, electric-field, and pretreatment with self-assembled monolayers comprising either a methyl-terminated or carboxylic acid-terminated alkane thiol anchored to a gold layer in the delay path of the sensor were explored as means of affecting the alignment and selectivity of the LC and SCLCP films. Results for the LC were mixed, while those for the SCLCP showed a consistent preference for the more rod-like isomer of each isomer pair examined.

  8. Liquid-Crystal Thermosets, a New Generation of High-Performance Liquid-Crystal Polymers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theo; Weiser, Erik; Hou, Tan; Jensen, Brian; St. Clair, Terry

    2004-01-01

    One of the major challenges for NASA's next-generation reusable-launch-vehicle (RLV) program is the design of a cryogenic lightweight composite fuel tank. Potential matrix resin systems need to exhibit a low coefficient of thermal expansion (CTE), good mechanical strength, and excellent barrier properties at cryogenic temperatures under load. In addition, the resin system needs to be processable by a variety of non-autoclavable techniques, such as vacuum-bag curing, resin-transfer molding (RTM), vacuum-assisted resin-transfer molding (VaRTM), resin-film infusion (RFI), pultrusion, and advanced tow placement (ATP). To meet these requirements, the Advanced Materials and Processing Branch (AMPB) at NASA Langley Research Center developed a new family of wholly aromatic liquid-crystal oligomers that can be processed and thermally cross-linked while maintaining their liquid-crystal order. All the monomers were polymerized in the presence of a cross-linkable unit by use of an environmentally benign melt-condensation technique. This method does not require hazardous solvents, and the only side product is acetic acid. The final product can be obtained as a powder or granulate and has an infinite shelf life. The obtained oligomers melt into a nematic phase and do not exhibit isotropization temperatures greater than the temperatures of decomposition (Ti > T(sub dec)). Three aromatic formulations were designed and tested and included esters, ester-amides, and ester-imides. One of the major advantages of this invention, named LaRC-LCR or Langley Research Center-Liquid Crystal Resin, is the ability to control a variety of resin characteristics, such as melting temperature, viscosity, and the cross-link density of the final part. Depending on the formulation, oligomers can be prepared with melt viscosities in the range of 10-10,000 poise (100 rad/s), which can easily be melt-processed using a variety of composite-processing techniques. This capability provides NASA with custom

  9. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih

    2012-07-01

    A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell (T-PNLC) is demonstrated. T-PNLC consists of three layers. Liquid crystal (LC) directors in the two layers near glass substrates are orthogonal to each other and those two layers modulate two eigen-polarizations of an incident light. As a result, two eigen-polarizations of an incident light experience the same phase shift. In the middle layer, LC directors are perpendicular to the glass substrate and contribute no phase shift. The phase shift of T-PNLC is electrically tunable and polarization-independent. T-PNLC does not require any bias voltage for operation. The phase shift is 0.28 π rad for the voltage of 30 Vrms. By measuring and analyzing the optical phase shift of T-PNLC at the oblique incidence of transverse magnetic wave, the pretilt angle of LC directors and the effective thickness of three layers are obtained and discussed. The potential applications are spatial light modulators, laser beam steering, and micro-lens arrays.

  10. Random lasing in dye-doped polymer dispersed liquid crystal film

    NASA Astrophysics Data System (ADS)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  11. Random lasing in dye-doped polymer dispersed liquid crystal film

    NASA Astrophysics Data System (ADS)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575–590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  12. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field.

    PubMed

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant. PMID:25399158

  13. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field

    SciTech Connect

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant.

  14. Effect of dopant nanoparticles on reorientation process in polymer-dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Zobov, K. V.; Zharkova, G. M.; Syzrantsev, V. V.

    2016-01-01

    The analysis of the experimental data of the nanoscale powders application for doping polymer-dispersed liquid crystals (PDLC) was represented in this work. A model based on the separation of the liquid crystals reorientation process on the surface mode and the volume mode was proposed and tested. In the research the wide-spread model mixture PDLC were used. But alumina nanoparticles were the distinctive ones obtained by electron beam evaporation. The proposed model allowed to conclude that the nanoparticles localization at the surface of the droplets (as in the Pickering emulsion) lead to the variation of the connection force between the liquid crystals and the polymer. The effect of nanoparticles resulted in an acceleration of the reorientation process near the surface when the control field is turned on and in a deceleration when it is turned off. The effect for the different size particles was confirmed.

  15. A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, Jag J.; Eftekhari, Abe

    1992-01-01

    Characteristics of a liquid crystal system, comprised of a shear-sensitive cholesteric-monomer liquid crystal thin-film coated on a liquid-crystal polymer substrate, are described. The system provides stable Grandjean texture, a desirable feature for shear-stress measurements using selective reflection from the monomer liquid-crystal helix structure. Impingement of gas or air flow on the monomer liquid-crystal free surface changes the wavelength of the selective reflection for an incident white light from red toward blue with increase in the rate of gas flow. The contrast of the selectively reflected light improves considerably by providing a thin black coating of about 5 microns at the monomer-polymer interface. The coating thickness is such that the steric interactions are still sufficiently strong to maintain Grandjean texture. For a small angle of incidence of a monochromatic light, the measurement of the reflected light intensity normal to the monomer-polymer liquid-crystal interface enables the determination of the wavelength for selective reflection as a function of the gas-flow differential pressure applied in the plane of the interface. The variation of the wavelength with the pressure is linear with a slope of about 2 nm/mmHg. Furthermore, the shear-stress effects are reversible unlike for monomer liquid crystal-metal systems used for flow visualization on wind-tunnel model surfaces. The present system offers a suitable method for direct on-line measurement of shear stress field from measurements of the wavelength for selective reflection for an incident white light.

  16. Complex Nanoscale-Ordered Liquid Crystal Polymer Film for High Transmittance Holographic Polarizer.

    PubMed

    Du, Tao; Fan, Fan; Tam, Alwin Ming Wai; Sun, Jiatong; Chigrinov, Vladimir G; Sing Kwok, Hoi

    2015-11-25

    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.

  17. Study of a Holographic Grating based on Dye-Doped Polymer-Ball-Type Polymer-Dispersed Liquid Crystal Films

    NASA Astrophysics Data System (ADS)

    Fuh, Andy Ying-Guey; Lee, Chia-Rong; Ho, Ya-Hui; Mo, Ting-Shan; Liu, Pin-Miao

    2001-12-01

    This study investigates the characteristics of the holographic grating formed in polymer-ball-type polymer-dispersed-liquid crystal (PBT-PDLC) films, doped with a diazo dye (G206). A dye-doped PBT-PDLC sample was fabricated, and used to write a holographic grating. Experimental results indicated that the grating had memory of the polarization of the writing beams. This polarization memory effect was inerasable if the sample was heated to the isotropic phase, and then cooled down to room temperature. Based on these observations, we believe that the memory of the grating effect does not relate to the intrinsic memory in the transmission versus applied voltage curve of PBT-PDLC films, which is thermally erasable. Rather, the effect is due to a feature of the grating, resulting from the reorientation of the liquid crystals through their interaction with the photo-induced adsorption of the doped dyes on the surface of the polymer balls.

  18. Enhanced contrast ratio and viewing angle of polymer-stabilized liquid crystal via refractive index matching between liquid crystal and polymer network.

    PubMed

    Lee, Ji-Hoon; Lee, Jung Jin; Lim, Young Jin; Kundu, Sudarshan; Kang, Shin-Woong; Lee, Seung Hee

    2013-11-01

    Long standing electro-optic problems of a polymer-dispersed liquid crystal (PDLC) such as low contrast ratio and transmittances decrease in oblique viewing angle have been challenged with a mixture of dual frequency liquid crystal (DFLC) and reactive mesogen (RM). The DFLC and RM molecules were vertically aligned and then photo-polymerized using a UV light. At scattering state under 50 kHz electric field, DFLC was switched to planar state, giving greater extraordinary refractive index than the normal PDLC cell. Consequently, the scattering intensity and the contrast ratio were increased compared to the conventional PDLC cell. At transparent state under 1 kHz electric field, the extraordinary refractive index of DFLC was simultaneously matched with the refractive index of vertically aligned RM so that the light scattering in oblique viewing angles was minimized, giving rise to high transmittance in all viewing angles.

  19. Enhanced contrast ratio and viewing angle of polymer-stabilized liquid crystal via refractive index matching between liquid crystal and polymer network.

    PubMed

    Lee, Ji-Hoon; Lee, Jung Jin; Lim, Young Jin; Kundu, Sudarshan; Kang, Shin-Woong; Lee, Seung Hee

    2013-11-01

    Long standing electro-optic problems of a polymer-dispersed liquid crystal (PDLC) such as low contrast ratio and transmittances decrease in oblique viewing angle have been challenged with a mixture of dual frequency liquid crystal (DFLC) and reactive mesogen (RM). The DFLC and RM molecules were vertically aligned and then photo-polymerized using a UV light. At scattering state under 50 kHz electric field, DFLC was switched to planar state, giving greater extraordinary refractive index than the normal PDLC cell. Consequently, the scattering intensity and the contrast ratio were increased compared to the conventional PDLC cell. At transparent state under 1 kHz electric field, the extraordinary refractive index of DFLC was simultaneously matched with the refractive index of vertically aligned RM so that the light scattering in oblique viewing angles was minimized, giving rise to high transmittance in all viewing angles. PMID:24216913

  20. Polymer-stabilized blue-phase liquid crystal grating cured with interfered visible light.

    PubMed

    Yuan, Yachao; Li, Yan; Chen, Chao Ping; Liu, Shuxin; Rong, Na; Li, Weihuan; Li, Xiao; Zhou, Pengcheng; Lu, Jiangang; Liu, Ruili; Su, Yikai

    2015-07-27

    In this paper, we demonstrate a holographic polymer-stabilized blue-phase liquid crystal grating fabricated using a visible laser. As blue phase is stabilized by the interfered light, polymer-concentration gradient is achieved simultaneously. With the application of a uniform vertical electric field, periodic index distribution is obtained due to polymer-concentration gradient. The grating exhibits several attractive features such as polarization-independency, a broad temperature range, sub-millisecond response, simple fabrication, and low cost, thus holding great potential for photonics applications. PMID:26367659

  1. Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

    NASA Technical Reports Server (NTRS)

    Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

    1994-01-01

    Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

  2. Field-induced Bragg diffraction in polymer stabilized cholesteric liquid crystal bubbles

    NASA Astrophysics Data System (ADS)

    Varanytsia, Andrii; Chien, Liang-Chy

    2015-03-01

    Cholesteric liquid crystals (CLC) with a specific confinement conditions are known to form bubble domain (BD) texture. We have developed the CLC BD texture stabilized with a small amount of polymer. CLC bubbles of a BD texture self-assemble into domains with a hexagonal ordering and optically perform as a diffraction grating. By stabilization of the BD texture with a polymer we have improved optical quality of the diffractive CLC layer and have increased its mechanical stability. We discuss details about samples preparation, Bragg diffraction, electro-optical performance and present results of scanning electron microscopy (SEM) morphological study of the polymer network formed in the bulk of the diffractive liquid crystal layer.

  3. Observation of shear-induced nematic-isotropic transition in side-chain liquid crystal polymers

    NASA Astrophysics Data System (ADS)

    Pujolle-Robic, Caroline; Noirez, Laurence

    2001-01-01

    Flow-induced phase transitions are a fundamental (but poorly understood) property of non-equilibrium systems, and are also of practical importance for tuning the processing conditions for plastics, petroleum products, and other related materials. Recognition that polymers may exhibit liquid crystal properties has led to the discovery of the first tailored side-chain liquid crystal polymers (SCLCPs), which are formed by inserting a spacer between the main polymer chain and the lateral mesogen liquid-crystalline graftings. Subsequent research has sought to understand the nature of the coupling between the main polymer chain and the mesogens, with a view to obtaining better control of the properties of these tailored structures. We show here that the parallel or perpendicular orientation of the mesogens with respect to the main chain can be reversed by the application of an external field produced by a shear flow, demonstrating the existence of an isotropic nematic phase transition in SCLCPs. Such a transition, which was theoretically predicted for low-molecular-weight liquid crystals but never observed, is shown to be a general property of SCLCPs too. We expect that these SCLCPs will prove to be good candidate systems for the experimental study of these non-equilibrium phenomena.

  4. Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

  5. Holographically formed, acoustically switchable gratings based on polymer-dispersed liquid crystals.

    PubMed

    Liu, Yan Jun; Lu, Mengqian; Ding, Xiaoyun; Leong, Eunice S P; Lin, Sz-Chin Steven; Shi, Jinjie; Teng, Jing Hua; Wang, Lin; Bunning, Timothy J; Huang, Tony Jun

    2013-08-01

    We report holographic polymer-dispersed liquid crystal (H-PDLC) gratings driven by surface acoustic waves (SAWs). Our experiments show that upon applying SAWs, the H-PDLC grating exhibited switchable properties: The diffraction of the H-PDLC grating decreased, whereas the transmission increased. This acoustically switchable behavior is due to the acoustic streaming-induced realignment of liquid crystals as well as absorption-resulted thermal diffusion. Such SAW-driven H-PDLC gratings are potentially useful in many photonic applications, such as optical switches, spatial light modulators, and switchable add/drop filters. PMID:22909448

  6. Effects of Polymers on the Rotational Viscosities of Nematic Liquid Crystals and Dynamics of Field Alignment.

    NASA Astrophysics Data System (ADS)

    Kim, Du-Rim

    Many of the important physical phenomena exhibited by the nematic phase, such as its unusual flow properties and its responses to the electric and the magnetic fields, can be discussed regarding it as a continuous medium. The Leslie-Erickson dynamic theory has the six dissipative coefficients from continuum model of liquid crystal. Parodi showed that only five of them are independent, when Onsagar's reciprocal relations are used. One of these, which has no counterpart in the isotropic liquids, is the rotational viscosity coefficient, gamma_1. The main objective of this project is to study the rotational viscosities of selected micellar nematic systems and the effect of dissolved polymers in micellar and thermotropic liquid crystals. We used rotating magnetic field method which allows one to determine gamma _1 and the anisotropic magnetic susceptibility, chi_{a}. For the ionic surfactant liquid crystals of SDS and KL systems used in this study, the rotational viscosity exhibited an extraordinary drop after reaching the highest value gamma_1 as the temperature was lowered. This behavior is not observed in normal liquid crystals. But this phenomena can be attributed to the existence of nematic biaxial phase below the rod-like nematic N_{c} phase. The pretransitional increase in gamma _1 near the disk-like nematic to smectic -A phase transition of the pure CsPFO H_2O systems are better understood with the help of mean-field models of W. L. McMillan. He predicted a critical exponent nu = -{1over 2} for the divergence of gamma_1. The polymer (PEO, molecular weight = 10 ^5) dissolved in CsPFO H_2O system (which has 0.6% critical polymer concentration), suppressed the nematic to lamellar smectic phase transition in concentrated polymer solutions (0.75% and higher). In dilute polymer solutions with lower than 0.3% polyethylene-oxide, a linear increase of gamma_1 is observed, which agrees with Brochard theory. The polymer solutions in thermotropic liquid crystal solvents

  7. Mechanisms of liquid crystal and biopolymer alignment on highly-oriented polymer thin films

    NASA Astrophysics Data System (ADS)

    Dennis, John Raymond

    1998-12-01

    Molecular order can strongly enhance material properties, or produce materials which perform advanced functions. Many materials, from small crystals to large macromolecules, may be aligned on highly-oriented poly(tetrafluoroethylene) (PTFE) or high-density polyethylene (HDPE) thin films, prepared by a simple shear deposition procedure. Here, processes by which these films produce order are examined, first in a well- characterized liquid crystal, then in two more complex polymer liquid crystals, and finally in an adsorbed motor protein system. Optical second harmonic generation (SHG) was used to study surface molecular order in the liquid crystal 4'-n-octyl-4-cyano-biphenyl (8CB) on PTFE and HDPE films. In nematic 8CB cells with bulk alignment along the polymer orientation axis, the surface monolayers of 8CB were also aligned, and showed C2ν symmetry. In the isotropic phase, the surface monolayer alignment was lost. Monolayers of 8CB evaporated onto either polymer showed little or no alignment. The bulk 8CB alignment appears to be primarily caused by surface ridges through an elastic, bulk- mediated mechanism, unlike the epitaxy-like alignment found on some cloth-rubbed polymer surfaces. For the polymer liquid crystal poly-γ-benzyl- glutamate (PBG), uniform homogeneous surface alignment was observed on PTFE films; this is the first report of PBG surface alignment. However, liquid crystalline samples of microtubules were not aligned. PTFE films show promise for aligning some other polymer liquid crystals via elastic interactions. The motor protein kinesin, adsorbed to PTFE films, transported fluorescently labeled microtubules predominantly in straight lines along the films' orientation axis, not in random directions as observed on glass surfaces. As the kinesin surface density was increased, the degree of alignment peaked and then declined. The results indicate that directed motion occurs because active kinesin preferentially adsorbs to surface sites along linear

  8. Pattern Polymerization-Induced Phase Separation in a Polymer-Dispersed Liquid Crystal System

    NASA Astrophysics Data System (ADS)

    Kyu, Thein

    2002-03-01

    Liquid crystal (LC)/polymer composite films have gained attention increasingly due to their applications in flat panel displays and shutters. Photopolymerization is a preferred method to produce LC/polymer composite films from mixtures of reactive monomers and LCs. On the basis of the combined Flory-Huggins free energy for isotropic mixing and Maier-Saupe free energy for nematic ordering along with the elastic free energy of the network, phase diagrams have been established by solving self-consistently. A theoretical simulation has been modeled by incorporating the kinetics of crosslinking reaction into the time-dependent Ginzburg-Landau (TDGL-model C) equations to elucidate the emergence of nematic domains during photopolymerization induced phase separation in electrically switchable holographic polymer-dispersed liquid crystals (H-PDLC). The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid crystal droplets alternating periodically with polymer network-rich layers. Furthermore, we recognized the potential for producing electrically tunable microlens from PDLC systems through pattern-photopolymerization-induced phase separation by means of the interference of two horizontal waves and two vertical waves. Our simulation revealed that the emerged LC microlens are of the order of a few hundred nanometers. These LC microlens are not only uniformed in size, but also form in regular arrays, reminiscence of the compound eyes found in flies, ants, and wasps. Supported by ALCOM, NSF DMR 99-03519, and OBR.

  9. Dual frequency addressing of polymer-dispersed liquid-crystal films

    NASA Astrophysics Data System (ADS)

    Vaz, Nuno A.; Montgomery, G. Paul, Jr.

    1989-06-01

    We report the feasibility of using dual frequency addressing (DFA) to switch polymer-dispersed liquid crystal (PDLC) films between their on- and off-states. In this scheme, the on-state is activated with an applied voltage of low frequency while the off-state is activated with a high-frequency voltage. We find that DFA increases the forward-scattering efficiency of PDLC films in the off-state without decreasing their on-state transmittance. Consequently, DFA can be used to improve the contrast ratio of PDLC films in projection displays and similar devices. We also find that the addressing frequency required to activate the off-state in a PDLC film has the same exponential temperature dependence observed in conventional liquid-crystal devices not employing microdispersed liquid crystals; this limits the use of DFA in PDLC films to applications which do not require operation over a wide temperature range.

  10. Molecular dynamics in azobenzene liquid crystal polymer films measured by time-resolved techniques.

    PubMed

    Fujii, T; Kuwahara, S; Katayama, K; Takado, K; Ube, T; Ikeda, T

    2014-06-14

    Photo-induced molecular motion in a liquid crystal polymer film including azobenzene was studied by the heterodyne transient grating method. The film was confined in a liquid crystal cell, where it is a photomobile film under free-standing conditions. By observation of the refractive index change induced by a laser pulse, contraction of the film was observed on the order of several hundreds of nanoseconds, and the subsequent reorientation and molecular rotation dynamics were observed from a few microseconds to a hundred milliseconds. Finally, the cis isomer of azobenzene was thermally returned back to the trans isomer in about ten seconds because the film could not be bent in the liquid crystal cell. Since the contraction, reorientation and molecular rotation took place before the cis to trans back-transformation, these processes correspond to the preliminary molecular motion preceding the macroscopic bending of the film. PMID:24736859

  11. Dielectric and electro-optical properties of polymer-stabilized liquid crystal. II. Polymer PiBMA dispersed in MBBA

    NASA Astrophysics Data System (ADS)

    Tripathi, Pankaj Kumar; Pande, Mukti; Singh, Shri

    2016-09-01

    In continuation of our earlier work (Pande et al. in Appl Phys A 122:217-226, 2016), we report the results of dielectric and electro-optical properties of pure MBBA and PSLC (polymer PiBMA dispersed in MBBA) systems. The polymer networks domains formed are found to be anisotropic and are oriented in the direction of electric field for both the planar and homeotropic alignment cells. The dielectric anisotropy, optical anisotropy, response time, threshold voltage, splay elastic constant and rotational viscosity were observed for both the LC and PSLC systems with electric field. The liquid crystal properties are affected significantly with increasing concentration of polymer in pure LC material. It has been observed that the polymer networks interaction plays a major role in changing the properties of PSLC system. The effect of dielectric loss and dielectric permittivity on both pure LC and PSLC systems is also discussed.

  12. Improvement of dichroic polymer dispersed liquid crystal performance using lift-off technique

    NASA Astrophysics Data System (ADS)

    Masutani, A.; Roberts, T.; Schüller, B.; Hollfelder, N.; Kilickiran, P.; Nelles, G.; Yasuda, A.; Sakaigawa, A.

    2006-10-01

    A lift-off method has been developed for the fabrication of polymer dispersed liquid crystal (PDLC) displays. A polymer matrix template can be prefabricated by lifting off a PDLC film from a fluorosilanized antisticking substrate. Desirable liquid crystal can then be backfilled/infiltrated into the template. Applying this technique to fabricate dichroic PDLC yielded a reflectivity of 66% and a contrast ratio of 13.8:1 in 3.8in. quarter video graphics array reflective thin film transistor (TFT) displays. A diffuse layer with melamine-formaldehyde nanoparticles was employed to suppress the metallic glare caused by the reflective back plane. The technique is suitable for various back planes such as flexible, solvent/UV-sensitive, organic TFTs.

  13. Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

    PubMed Central

    Wang, Wenda; Qi, Hao; Zhou, Tian; Mei, Shan; Han, Lin; Higuchi, Takeshi; Jinnai, Hiroshi; Li, Christopher Y.

    2016-01-01

    Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery. PMID:26837260

  14. Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Qi, Hao; Zhou, Tian; Mei, Shan; Han, Lin; Higuchi, Takeshi; Jinnai, Hiroshi; Li, Christopher Y.

    2016-02-01

    Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ~148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery.

  15. Rewritable Optical Storage with a Spiropyran Doped Liquid Crystal Polymer Film.

    PubMed

    Petriashvili, Gia; De Santo, Maria Penelope; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Gary, Ramla; Barberi, Riccardo

    2016-03-01

    Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. PMID:26864876

  16. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal.

    PubMed

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-10

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at gamma = 1.55 microm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 microm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms.

  17. Fast flexoelectric switching in a cholesteric liquid crystal cell with surface-localized polymer network

    NASA Astrophysics Data System (ADS)

    Kim, Sang Hwa; Shi, Lei; Chien, Liang-Chy

    2009-10-01

    We developed an electro-optical device based on the flexoelectric effect of a polymer-stabilized cholesteric liquid crystal with a uniform lying helix. Using a dual-frequency switchable nematic, a small amount of chiral dopant and a small amount of phase-separated polymer localized at the substrate surfaces, we were able to create a device that operates in both the amplitude (flexoelectric) and phase (dielectric) modes. Using a high-frequency voltage we were able to suppress the phase mode and preserve the amplitude mode.

  18. Tunable liquid crystal microlenses with crater polymer prepared by droplet evaporation.

    PubMed

    Hwang, Shug-June; Liu, Yi-Xiang; Porter, Glen Andrew

    2013-12-16

    A simple and low-cost technique is proposed to construct a tunable liquid crystal (LC) microlens with a crater polymer structure, which is prepared using micro-drop technology and 2-step UV polymerization. The dimensions and the geometric profile of the restructured polymer surface significantly depend on the volume of the micro droplet, and the UV irradiation dose. In this work, the focal length of the LC microlens is controlled electrically from infinity to 7.8 cm. Such a microlens has prospective applications in optical communications, image processing, and switchable 2D/3D displays.

  19. Nanoparticle free polymer blends for light scattering films in liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Takei, Satoshi; Mochiduki, Kazuhide; Kubo, Naoya; Yokoyama, Yoshiyuki

    2012-06-01

    This paper reports an approach using nanoparticle free polymer blends for light scattering films in liquid crystal displays. The ability to create the regularly structured circle of approximately 200 nm diameter in the light scattering film by blending two specified polymers with carboxylic acid groups and epoxy groups was demonstrated. The developed light scattering film based on thermosetting system indicated regularly structured nanomorphology, high light scattering rates of more than 3.9% at 300-600 nm of wavelength, and fast thermal cross-linking reaction at 150 °C and 60 s in thermosetting conditions for high productivity.

  20. Progress in the Development of Polymer Cholesteric Liquid Crystal Flakes for Display Applications

    SciTech Connect

    Kosc, T.Z.; Marshall, K.L.; Trajkovska-Petkoska, A.; Kimball, E.; Jacobs, S.D.

    2004-12-31

    Polymer cholesteric liquid crystal (PCLC) flake technology is being developed as an alternative display technology for flexible, reflective particle displays. The motion of PCLC flakes suspended in a host fluid can be controlled with an electric field, creating means to electrically control for the flakes ability to brightly reflect light that is circularly polarized. The PCLC flake/host fluid dispersion has been successfully micro-encapsulated both in a polymer matrix and in gelatin micro-capsules. Micro-encapsulation will not only expand the applications scope of the technology, but also may aid in addressing some potential problem areas that are inherent to many forms of particle display technology.

  1. Crystallization of Polymers at liquid/liquid interface templated by single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher

    2012-02-01

    Nanosized single-walled carbon nanotube rings were fabricated by using a Pickering emulsion-based method. By tuning a water/oil/SWNT miniemulsion system, SWNT rings with a diameter of ˜200 nm can be readily achieved. The formation mechanism is attributed to the bending force induced by the curved liquid/liquid interface. Crystallization of polyethylene homo- and copolymers using this unique SWNT rings as the nucleation agent was conducted at the curved liquid/liquid interface. Crystal structure, hybrid morphology and crystallization kinetics were systematically studied. The structure of controlled alternating patterns on SWNT rings has great potential in various applications in large-scale integrated circuits and single-electron devices.

  2. Photorefractivity in polymer-stabilized liquid crystals films.

    SciTech Connect

    Wasielewski, M. R.

    1998-05-08

    We have shown that PSLCs are capable of forming photorefractive gratings that operate in the thick grating regime. Polymer stabilization alters the charge transport and trapping characteristics of LCs, resulting in longer lived gratings, while maintaining the advantages of high orientational birefringence within LCs. Furthermore, very low applied electric fields (800 V/cm) and low optical intensities (100 mW/cm{sup 2}) are required to create large photorefractive effects in these materials. It is expected that optimization of the redox potentials of the chromophores within the PSLCs will continue to improve the performance of these materials.

  3. Enhanced Solar Cell Conversion Efficiency Using Birefringent Liquid Crystal Polymer Homeotropic Films from Reactive Mesogens

    PubMed Central

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  4. Enhanced solar cell conversion efficiency using birefringent liquid crystal polymer homeotropic films from reactive mesogens.

    PubMed

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  5. Electrical addressing of polymer stabilized hyper-twisted chiral nematic liquid crystals with interdigitated electrodes: Experiment and model

    NASA Astrophysics Data System (ADS)

    Lorenz, A.; Gardiner, D. J.; Morris, S. M.; Castles, F.; Qasim, M. M.; Choi, S. S.; Kim, W.-S.; Coles, H. J.; Wilkinson, T. D.

    2014-02-01

    Electro-optic switching in short-pitch polymer stabilized chiral nematic liquid crystals was studied and the relative contributions of flexoelectric and dielectric coupling were investigated: polymer stabilization was found to effectively suppress unwanted textural transitions of the chiral nematic liquid crystal and thereby enhance the electro-optical performance (high optical contrast for visible light, a near ideal optical hysteresis, fast electro-optic response). Test cells were studied that possessed interdigitated electrodes to electrically address the liquid crystal. Based on simulations, a well-fitted phenomenological description of the electro-optic response was derived considering both flexoelectro-optic and Kerr-effect based electro-optic response.

  6. In situ prepared polymer films as alignment layers for nematic liquid crystals

    SciTech Connect

    Pires, David; Galerne, Yves

    2006-12-15

    By means of UV-visible irradiations and convenient photoinitiators, we realize the cross-linked polymerization of a triacrylate monomer in solution in a nematic liquid crystal (p-pentyl-p{sup '}-cyanobiphenyl) at low concentrations (a few wt %), i.e., under conditions opposite to the synthesis of polymer-dispersed liquid crystals. As atomic force microscope measurements show, when operating close to, but below, the percolation transition, a thin polymer layer is synthesized in situ, directly covering and coating all the substrate. These observations therefore confirm that the properties of anchoring and of alignment memory previously observed in such nematic cells effectively originate from the synthesized polymer film. According to the photoinitiator used, bulk or surface polymerizations dominate and respectively produce continuous or discontinuous films (i.e., with separate clusters). In the former case, polymer aggregates are first synthesized. They then diffuse in the volume until they meet a surface, where they definitely stick if they are large enough. An estimate of the entropy and interaction energy differences between the two states, stuck or free, shows that the aggregates stick on the substrates if their size exceeds the length of about three monomers, i.e., if they contain more than 20-30 monomers. Interestingly, these films may be used to replicate nonuniform alignment patterns that are difficult to realize otherwise. The method may be considered as an imprinting method.

  7. Optical diffractometry of highly anisotropic holographic gratings formed by liquid crystal and polymer phase separation.

    PubMed

    Kakiuchida, Hiroshi; Tazawa, Masato; Yoshimura, Kazuki; Ogiwara, Akifumi

    2012-12-01

    Optical diffractometry is proposed as a practical method of quantitatively analyzing the microscopic structural origins of a wide range of highly efficient and linearly polarized optical diffraction grating produced from holographic polymer-dispersed liquid crystal. The structure is organized by a spatially periodical distribution of submicrometer-scale liquid crystal (LC) droplets in a polymer matrix. Six independent Bragg diffraction spectra were obtained at two orthogonal polarization states at temperatures below, at, and above the nematic-to-isotropic phase transition point. These spectra were simultaneously analyzed by employing anisotropic diffraction theory under the restraint of a simple and widely useful structural model constructed on the basis of the previously reported microscopic observations. The refractive indices of spatially periodic LC- and polymer-rich phases were analyzed using Cauchy's equation as a function of optical wavelength. The present diffractometry was demonstrated for a variety of holographic structures, and the structural parameters were discussed such as the filling ratio of LC droplets to polymer matrix, the orientational order in the droplets, and the thermo-optic properties in the LC droplets. Furthermore, the higher order Bragg diffractions were measured and discussed. The proposed method was examined in consistency by comparisons with polarizing optical microscopy and scanning electron microscopy. PMID:23367963

  8. Electrically switchable polymer liquid crystal and polymer birefringent flake in fluid host systems and optical devices utilizing same

    DOEpatents

    Marshall, Kenneth L.; Kosc, Tanya Z.; Jacobs, Stephen D.; Faris, Sadeg M.; Li, Le

    2003-12-16

    Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotation about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.

  9. Conducting polymers as driving electrodes for Polymer-Dispersed Liquid-Crystals display devices: on the electro-optical efficiency.

    PubMed

    Roussel, F; Chan-Yu-King, R; Buisine, J-M

    2003-07-01

    Intrinsically conducting polymer (ICP) thin films are used as driving electrodes for Polymer-Dispersed Liquid-Crystals (PDLC) display devices. In order to investigate the electro-optical efficiency of these organic electrodes, three different kinds of conducting polymers, i.e. polyaniline doped with 10-camphorsulfonic acid (PANI(HCSA)), polypyrrole doped with dodecylbenzenesulfonic acid (PPY(DBSA)), and polyethylenedioxythiophene doped with polystyrenesulfonate (PEDOT(PSS)), were prepared or purchased, and coated either on glass or plastic substrates. Optical absorption studies in the UV-Vis range of the conducting polymer-coated substrates were first performed showing the presence of conducting species for the three types of polymers. The electrical characteristics of the resulting films were measured with the four-probes technique. PANI(HCSA) exhibits a higher conductivity sigma approximately 122 S x cm(-1) (RS=1.2x10(3) Omega x (-1)) compared to PPY(DBSA) sigma approximately 2.6 S x cm(-1) (RS=150.7x10(3) Omega x (-1)), and PEDOT(PSS) sigma approximately 1.6 S x cm(-1) (RS=637.3x10(3) Omega x (-1)). It is also shown that for a given conducting polymer, its electrical conductivity decreases when a plastic substrate is used. These observations have been related to significant morphological changes observed by scanning electron microscopy (SEM). A mixture of Norland Optical Adhesive 65 and nematic liquid-crystal E7 in the weight ratio (35:65) was used as precursor of the PDLC material. Better electro-optical responses (transmission properties, drive voltages and switching times) of PDLC films were obtained for devices prepared with (PPY(DBSA))-based electrodes. The electro-optical performances of the PDLC display devices also depend on the nature of the ICP substrate used. PMID:15011049

  10. Conducting polymers as driving electrodes for Polymer-Dispersed Liquid-Crystals display devices: On the electro-optical efficiency

    NASA Astrophysics Data System (ADS)

    Roussel, F.; Chan-Yu-King, R.; Buisine, J.-M.

    2003-07-01

    Intrinsically conducting polymer (ICP) thin films are used as driving electrodes for Polymer-Dispersed Liquid-Crystals (PDLC) display devices. In order to investigate the electro-optical efficiency of these organic electrodes, three different kinds of conducting polymers, i.e. polyaniline doped with 10-camphorsulfonic acid (PANI(HCSA)), polypyrrole doped with dodecylbenzenesulfonic acid (PPY(DBSA)), and polyethylenedioxythiophene doped with polystyrenesulfonate (PEDOT(PSS)), were prepared or purchased, and coated either on glass or plastic substrates. Optical absorption studies in the UV-Vis range of the conducting polymer-coated substrates were first performed showing the presence of conducting species for the three types of polymers. The electrical characteristics of the resulting films were measured with the four-probes technique. PANI(HCSA) exhibits a higher conductivity σsim 122\\un{S\\cdot cm^{-1}} (R_S=1.2 ; 10^3; Ω\\cdotBox^{ -1}) compared to PPY(DBSA) σsim 2.6\\un{S\\cdot cm^{-1}} (R_S=150.7 ;10^3;Ω\\cdotBox^{-1}), and PEDOT(PSS) σsim 1.6\\un{S\\cdot cm^{-1}} (R_S=637.3 ; 10^3; Ω\\cdotBox^{-1}). It is also shown that for a given conducting polymer, its electrical conductivity decreases when a plastic substrate is used. These observations have been related to significant morphological changes observed by scanning electron microscopy (SEM). A mixture of Norland Optical Adhesive 65 and nematic liquid-crystal E7 in the weight ratio (\\chem{35:65}) was used as precursor of the PDLC material. Better electro-optical responses (transmission properties, drive voltages and switching times) of PDLC films were obtained for devices prepared with (PPY(DBSA))-based electrodes. The electro-optical performances of the PDLC display devices also depend on the nature of the ICP substrate used.

  11. Immobilization of Polymer-Decorated Liquid Crystal Droplets on Chemically Tailored Surfaces

    PubMed Central

    Kinsinger, Michael I.; Buck, Maren E.; Abbott, Nicholas L.; Lynn, David M.

    2010-01-01

    We demonstrate that the assembly of an amphiphilic polyamine on the interfaces of micrometer-sized droplets of a thermotropic liquid crystal (LC) dispersed in aqueous solutions can be used to facilitate the immobilization of LC droplets on chemically functionalized surfaces. Polymer 1 was designed to contain both hydrophobic (alkyl-functionalized) and hydrophilic (primary and tertiary amine-functionalized) side chain functionality. The assembly of this polymer at the interfaces of aqueous dispersions of LC droplets was achieved by spontaneous adsorption of polymer from aqueous solution. Polymer adsorption triggered transitions in the orientational ordering of the LCs, as observed by polarized light and bright-field microscopy. We demonstrate that the presence of polymer 1 on the interfaces of these droplets can be exploited to immobilize LC droplets on planar solid surfaces through covalent bond formation (e.g., for surfaces coated with polymer multilayers containing reactive azlactone functionality) or through electrostatic interactions (e.g., for surfaces coated with multilayers containing hydrolyzed azlactone functionality). Characterization of immobilized LC droplets by polarized, fluorescence, and laser scanning confocal microscopy revealed the general spherical shape of the polymer-coated LC droplets to be maintained after immobilization, and that immobilization led to additional ordering transitions within the droplets that was dependent on the nature of the surfaces with which they were in contact. Polymer 1-functionalized LC droplets were not immobilized on polymer multilayers treated with poly(ethylene imine) (PEI). We demonstrate that the ability to design surfaces that promote or prevent the immobilization of polymer-functionalized LC droplets can exploited to pattern the immobilization of LC droplets on surfaces. The results of this investigation provide the basis of an approach that could be used to tailor the properties of dispersed LC emulsions and

  12. Photoluminescence properties of cadmium-selenide quantum dots embedded in a liquid-crystal polymer matrix

    SciTech Connect

    Tselikov, G. I. Timoshenko, V. Yu.; Plenge, J.; Ruehl, E.; Shatalova, A. M.; Shandryuk, G. A.; Merekalov, A. S.; Tal'roze, R. V.

    2013-05-15

    The photoluminescence properties of cadmium-selenide (CdSe) quantum dots with an average size of {approx}3 nm, embedded in a liquid-crystal polymer matrix are studied. It was found that an increase in the quantum-dot concentration results in modification of the intrinsic (exciton) photoluminescence spectrum in the range 500-600 nm and a nonmonotonic change in its intensity. Time-resolved measurements show the biexponential decay of the photoluminescence intensity with various ratios of fast and slow components depending on the quantum-dot concentration. In this case, the characteristic lifetimes of exciton photoluminescence are 5-10 and 35-50 ns for the fast and slow components, respectively, which is much shorter than the times for colloidal CdSe quantum dots of the same size. The observed features of the photoluminescence spectra and kinetics are explained by the effects of light reabsorption, energy transfer from quantum dots to the liquid-crystal polymer matrix, and the effect of the electronic states at the CdSe/(liquid crystal) interface.

  13. Liquid crystal polymer networks: preparation, properties, and applications of films with patterned molecular alignment.

    PubMed

    Liu, Danqing; Broer, Dirk J

    2014-11-18

    Monolithically ordered liquid crystal polymer networks are formed by the photoinitiated polymerization of multifunctional liquid crystal monomers. This paper describes the relevant principles and methods, the basic structure-property relationships in terms of mesogenic properties of the monomers, and the mechanical and optical properties of the polymers. Strategies are discussed to control the molecular orientation by various means and in all three dimensions. The versatility of the process is demonstrated by two examples of films with a patterned molecular order. It is shown that patterned retarders can be made by a two-step polymerization process which is successfully employed in a transflective display principle. A transflective display is a liquid crystal display that operates in both a reflective mode using ambient light and a transmissive mode with light coming from a backlight system. Furthermore, a method is discussed to create a patterned film in a single polymerization process. This film has alternating planar chiral nematic areas next to perpendicularly oriented (so-called homeotropic) areas. When applied as a coating to a substrate, the film changes its surface texture. During exposure to UV light, it switches from a flat to a corrugated state. PMID:24707811

  14. Liquid crystal polymer networks: preparation, properties, and applications of films with patterned molecular alignment.

    PubMed

    Liu, Danqing; Broer, Dirk J

    2014-11-18

    Monolithically ordered liquid crystal polymer networks are formed by the photoinitiated polymerization of multifunctional liquid crystal monomers. This paper describes the relevant principles and methods, the basic structure-property relationships in terms of mesogenic properties of the monomers, and the mechanical and optical properties of the polymers. Strategies are discussed to control the molecular orientation by various means and in all three dimensions. The versatility of the process is demonstrated by two examples of films with a patterned molecular order. It is shown that patterned retarders can be made by a two-step polymerization process which is successfully employed in a transflective display principle. A transflective display is a liquid crystal display that operates in both a reflective mode using ambient light and a transmissive mode with light coming from a backlight system. Furthermore, a method is discussed to create a patterned film in a single polymerization process. This film has alternating planar chiral nematic areas next to perpendicularly oriented (so-called homeotropic) areas. When applied as a coating to a substrate, the film changes its surface texture. During exposure to UV light, it switches from a flat to a corrugated state.

  15. Polymer/(liquid crystal) composite systems for novel electro-optical effects

    NASA Astrophysics Data System (ADS)

    Kajiyama, Tisato; Kikuchi, Hirotsugu; Takahara, Atsushi

    1992-06-01

    Aggregation states and electro-optical effects based on light scattering have been investigated for polymer (liquid crystal) composite films. The composite film was prepared by a solvent- evaporation method. Since a continuous liquid crystalline domain is embedded in a three- dimensional spongy network of polymer matrix, the liquid crystalline material is self- supported in the composite film in spite of its very low viscosity. The composite film composed of poly(methyl methacrylate) and a nematic LC(E44) with positive dielectric- anisotropy exhibited remarkable and reversible light scattering-light transmission switching under the modulation of an ac electric field. A light scattering state was dependent on optical heterogeneities such as a spatial distribution of nematic directors and/or mismatching in refractive indices of the components. Reversible and bistable electro-optical effects were also recognized for a smectic phase of a binary composite system composed of liquid crystalline polymer (LCP) and nematic LC. A light-addressed optical information storage of the LCP/nematic LC/(photoresponsive molecule) ternary composite membrane has also been demonstrated.

  16. Photochemical switching behavior of azofunctionalized polymer liquid crystal/SiO{sub 2} composite photonic crystal

    SciTech Connect

    Moritsugu, M.; Kim, S. N.; Ogata, T.; Nonaka, T.; Kurihara, S.; Kubo, S.; Segawa, H.; Sato, O.

    2006-10-09

    A photochemically tunable photonic crystal was prepared by infiltrating azopolymer liquid crystal in a SiO{sub 2} inverse opal structure. The SiO{sub 2} inverse opal film obtained reflected a light corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation shifted the reflection band to longer wavelength more than 15 nm. This is caused by the formation of anisotropic molecular orientation of the azopolymer. The switched state was stable in the dark, and the reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiations.

  17. Neutron scattering as a probe of liquid crystal polymer-reinforced composite materials

    SciTech Connect

    Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C.; Langlois, D.A.

    1995-12-31

    This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This research project sought to obtain nanoscale and molecular level information on the mechanism of reinforcement in liquid crystal polymer (LCP)-reinforced composites, to realize molecular-reinforced LCP composites, and to test the validity of the concept of molecular reinforcement. Small-angle neutron scattering was used to study the structures in the ternary phase diagram of LCP with liquid crystal thermosets and solvent on length scales ranging from 1-100 nm. The goal of the scattering measurements is to understand the phase morphology and degree of segregation of the reinforcing and matrix components. This information helps elucidate the physics of self assembly in these systems. This work provides an experimental basis for a microengineering approach to composites of vastly improved properties.

  18. Discontinuous anchoring transition and photothermal switching in composites of liquid crystals and conducting polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Zuhail, K. P.; Manda, R.; Paik, P.; Haase, W.; Dhara, Surajit

    2014-05-01

    We prepared nanocomposites of a nematic liquid crystal and nanofibers of a conducting polymer (polyaniline). All the nanocomposites exhibit a discontinuous surface anchoring transition from planar to homeotropic in the nematic phase on a perfluoropolymer coated surface with a thermal hysteresis (≈5.3∘C). We observe a relatively large bistable conductivity and demonstrate a light driven switching of conductivity and dielectric constant in dye doped nanocomposites in the thermal hysteresis (bistable) region. The experimental results have been explained based on the reorientation of the nanofibers driven by the anchoring transition of the nematic liquid crystal. We show a significant enhancement of the bistable temperature range (≈13∘C) by an appropriate choice of compound in the binary system.

  19. An electrically switchable surface free energy on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chu, Ting-Yu; Tsou, Yu-Shih; Chang, Kai-Han; Chiu, Ya-Ping

    2012-12-01

    An electrically switchable surface free energy on a liquid crystal and polymer composite film (LCPCF) resulting from the orientations of liquid crystal molecules is investigated. By modification of Cassie's model and the measurement based on the Chibowski's film pressure model (E. Chibowski, Adv. Colloid Interface Sci. 103, 149 (2003)), the surface free energy of LCPCF is electrically switchable from 36×10-3J/ m2 to 51×10-3J/ m2 while the average tilt angle of LC molecules changes from 0° to 32° with the applied pulsed voltage. The switchable surface free energy of LCPCF can help us to design biosensors and photonics devices, such as electro-optical switches, blood sensors, and sperm testers.

  20. Formation of temperature dependable holographic memory using holographic polymer-dispersed liquid crystal.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-04-01

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization controllable optical devices, such as the holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) that the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is discussed with two types of LC composites comprised of isotropic and LC diacrylate monomers. The holographic memory formed by the LC and LC diacrylate monomer performs precise reconstruction of the context information for ORGAs at high temperatures more than 150°C. PMID:23546276

  1. Single-mode lasing from dye-doped holographic polymer-dispersed liquid crystal transmission gratings

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Liu, Quan; Xuan, Li; Chen, Linsen

    2014-12-01

    We demonstrate single-mode laser operation in dye-doped holographic polymer-dispersed liquid crystal (HPDLC) transmission gratings. The gratings are fabricated in cells made from specifically chosen glass substrates to decrease the refractive index difference between the waveguide core layer and cladding layer. The phase separation degree of liquid crystal after holographic recording is further optimized to confine only the lowest propagation mode in the device. The mode selection mechanism is explained under the framework of the waveguide distributed feedback (DFB) theory. The wavelength of single-mode lasing can be tuned between 620 and 660 nm by varying the grating period. Our results show the HPDLC technique could provide single-mode organic DFB lasers in a tunable, simple, and large-area manner.

  2. Temperature dependence of anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-09-10

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC. PMID:24085129

  3. Improvement of decay time in nematic-liquid-crystal-loaded coplanar-waveguide-type microwave phase shifter by polymer stabilizing method

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh; Umeno, Shuhei; Higuchi, Hiroki; Kikuchi, Hirotsugu; Moritake, Hiroshi

    2014-01-01

    Polymer stabilization by UV light irradiation in nematic liquid crystals is proposed to improve the decay time of coplanar-waveguide-type microwave phase shifters. The effect of polymer concentration on the decay time of polymer-stabilized nematic liquid crystals is confirmed by a dielectric experiment on a liquid-crystal-sandwiched indium-tin-oxide (ITO) glass cell before loading into a coplanar-waveguide-type microwave phase shifter. The decay time, phase shift value, and insertion loss of microwave phase shifters with different polymer concentrations are measured. The decay time of polymer-stabilized nematic liquid crystals in the microwave phase shifter markedly decreases compared with that of pure nematic liquid crystals. It is confirmed that the use of polymer-stabilized nematic liquid crystals is effective to improve the response time of microwave phase shifters.

  4. Photomechanical bending mechanics of polydomain azobenzene liquid crystal polymer network films

    SciTech Connect

    Cheng Liang; Torres, Yanira; Oates, William S.; Lee, Kyung Min; McClung, Amber J.; Baur, Jeffery; White, Timothy J.

    2012-07-01

    Glassy, polydomain azobenzene liquid crystal polymer networks (azo-LCNs) have been synthesized, characterized, and modeled to understand composition dependence on large amplitude, bidirectional bending, and twisting deformation upon irradiation with linearly polarized blue-green (440-514 nm) light. These materials exhibit interesting properties for adaptive structure applications in which the shape of the photoresponsive material can be rapidly reconfigured with light. The basis for the photomechanical output observed in these materials is absorption of actinic light by azobenzene, which upon photoisomerization dictates an internal stress within the local polymer network. The photoinduced evolution of the underlying liquid crystal microstructure is manifested as macroscopic deformation of the glassy polymer film. Accordingly, this work examines the polarization-controlled bidirectional bending of highly concentrated azo-LCN materials and correlates the macroscopic output (observed as bending) to measured blocked stresses upon irradiation with blue-green light of varying polarization. The resulting photomechanical output is highly dependent on the concentration of crosslinked azobenzene mesogens employed in the formulation. Experiments that quantify photomechanical bending and photogenerated stress are compared to a large deformation photomechanical shell model to quantify the effect of polarized light interactions with the material during static and dynamic polarized light induced deformation. The model comparisons illustrate differences in internal photostrain and deformation rates as a function of composition and external mechanical constraints.

  5. Responsive ionic liquid-polymer 2D photonic crystal gas sensors.

    PubMed

    Smith, Natasha L; Hong, Zhenmin; Asher, Sanford A

    2014-12-21

    We developed novel air-stable 2D polymerized photonic crystal (2DPC) sensing materials for visual detection of gas phase analytes such as water and ammonia by utilizing a new ionic liquid, ethylguanidine perchlorate (EGP) as the mobile phase. Because of the negligible ionic liquid vapor pressure these 2DPC sensors are indefinitely air stable and, therefore, can be used to sense atmospheric analytes. 2D arrays of ~640 nm polystyrene nanospheres were attached to the surface of crosslinked poly(hydroxyethyl methacrylate) (pHEMA)-based polymer networks dispersed in EGP. The wavelength of the bright 2D photonic crystal diffraction depends sensitively on the 2D array particle spacing. The volume phase transition response of the EGP-pHEMA system to water vapor or gaseous ammonia changes the 2DPC particle spacing, enabling the visual determination of the analyte concentration. Water absorbed by EGP increases the Flory-Huggins interaction parameter, which shrinks the polymer network and causes a blue shift in the diffracted light. Ammonia absorbed by the EGP deprotonates the pHEMA-co-acrylic acid carboxyl groups, swelling the polymer which red shifts the diffracted light.

  6. Asymmetric tunable Fabry-Perot cavity using switchable polymer stabilized cholesteric liquid crystal optical Bragg mirror

    NASA Astrophysics Data System (ADS)

    Sathaye, Kedar S.; Dupont, Laurent; de Bougrenet de la Tocnaye, Jean-Louis

    2012-03-01

    Optical properties of an asymmetric Fabry-Perot (FP) cavity interferometer made up of a conventional metallic mirror and a polymer stabilized cholesteric liquid crystal (PSCLC) Bragg mirror have been investigated. The first FP cavity design comprises a gold mirror, an isotropic layer made up of the polymer glue, a quarter wave plate to convert the input linearly polarized modes into the circularly polarized modes inside the cavity, and the PSCLC Bragg mirror, all sandwiched between two indium tin oxide glass plates. The second FP cavity has a layer of conducting polymer deposited on the quarter-wave plate to apply the electric field only to the cholesteric stack. To have reflectivity above 95% in visible range we implement 30 layers of cholesteric liquid crystal in a planar Grandjean texture. The device compactness and the mirror parallelism due to the monolithic fabrication of FP are advantageous from the technical point of view. We test the FP tunability by shifting the resonance wavelength through an entire period; by applying electric field and/or by varying the temperature.

  7. Theoretical approach to study the effect of free volumes on the physical behavior of polymer stabilized ferroelectric liquid crystal molecules

    NASA Astrophysics Data System (ADS)

    Lahiri, T.; Majumder, T. Pal

    2011-06-01

    It was clearly indicative that the polymer chains make a tremendous interaction with the tilt angle in case of a polymer stabilized ferroelectric liquid crystal (PSFLC). After suitable consideration of such interaction, we expanded the Landau free energy for a PSFLC system. We theoretically demonstrated the effect of free volumes, which expected to create bulk self-energy, on the physical functionalities of a PSFLC system. Then we obtained spontaneous polarization, tilt angle, rotational viscosity and dielectric constant strongly correlated with the assumed interactions. We also observed a shift of transition temperature highly influenced by this interaction between polymer network and liquid crystal molecules. A microscopical picture of this polymer-liquid crystal interaction is provided in view of the free volume charge density present in the composite system.

  8. Photosensitivity of reflection notch tuning and broadening in polymer stabilized cholesteric liquid crystals.

    PubMed

    Lee, Kyung Min; Tondiglia, Vincent P; White, Timothy J

    2016-01-28

    The position or bandwidth of the selective reflection of polymer stabilized cholesteric liquid crystals (PSCLCs) prepared from negative dielectric anisotropy ("-Δε") liquid crystalline hosts can be shifted by applying a DC voltage. The underlying mechanism of the tuning or broadening of the reflection of PSCLCs detailed in these recent efforts is ion-facilitated, electromechanical deformation of the structurally chiral, polymer stabilizing network in the presence of a DC bias. Here, we show that these electro-optic responses can also be photosensitive. The photosensitivity is most directly related to the presence of photoinitiator, which is a known ionic contaminant to liquid crystal devices. Measurement of the ion density of a series of control compositions before, during, and after irradiation with UV light confirms that the ion density in compositions that exhibit photosensitivity is increased by irradiation and correlates to not only the concentration of the photoinitiator but also the type. Thus, the magnitude of the electrically tuned or broadened reflection of PSCLC of certain compositions when subjected to DC field is further increased in the presence of UV light. While interesting and potentially useful in applications such as architectural windows, the effect may be deleterious to some device implementations. Accordingly, compositions in which photosensitivity is not observed are identified. PMID:26593860

  9. Surface-polymer stabilized liquid crystals with dual-frequency control.

    PubMed

    Minasyan, Amalya; Galstian, Tigran

    2013-08-01

    Dual-frequency control liquid crystal (LC) and thin reactive mesogen (RM) films, cast on internal surfaces of cell substrate, are used to build surface polymer stabilized structures. Electric field of high frequency is used to orient the LC molecules by the negative dielectric torque prior to the photopolymerization of RM films. Electro-optic characterization results show that the contrasts of light scatter modulation and polarization dependence are noticeably improved by the dual-frequency control. However, there is no significant shortening in the full cycle duration of excitation-relaxation-excitation.

  10. Low voltage polymer-stabilized blue phase liquid crystal reflective display by doping ferroelectric nanoparticles.

    PubMed

    Xu, X W; Zhang, X W; Luo, D; Dai, H T

    2015-12-14

    Low driving voltage is achieved in full color reflective display based on polymer-stabilized blue phase liquid crystal (PS-PBLC), by doping a small amount of ferroelectric nanoparticles. Both reflectance spectra of PS-PBLC with and without BaTiO₃ ferroelectric nanoparticles are studied under different applied external voltages. Superior to PS-PBLC without ferroelectric nanoparticles, the vertical driving electric fields of PS-PBLC with 0.4 wt.% BaTiO₃ ferroelectric nanoparticles are dramatically reduced by more than 70% for red, green and blue cells. The proposed approach would accelerate the practical application of full color PS-BPLC reflective display.

  11. Effect of polarization on dielectric behaviour of PET/0.8PHB polymer liquid crystals

    NASA Astrophysics Data System (ADS)

    Yarramaneni, Sridharbabu; Sharma, Anu; Quamara, J. K.

    2014-04-01

    Dielectric constant and loss behaviour of pristine and polarized samples of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) polymer liquid crystals were studied at continuous temperatures ranging from 20 °C to 250 °C, polarized at potentials 500V and 2000V with high precision d.c. power supply. Dielectric constant appears to be almost linearly dependent in the lower temperature region and is independent in the higher temperature region. Dielectric loss becomes approximately ten times lower at higher temperatures.

  12. Faraday waves on finite thickness smectic A liquid crystal and polymer gel materials

    SciTech Connect

    Ovando-Vazquez, C.; Rodriguez, O. Vazquez; Hernandez-Contreras, M.

    2008-11-13

    We studied with linear stability theory the Faraday waves on the surface of a smectic A liquid crystal and polymer gel-vapor systems of finite thicknesses. Model smectic A material exhibits alternating subharmonic-harmonic patterns of stability curves in a plot of driving acceleration versus wave number. For the case of highly viscoelastic gel media there are coexisting surface modes of harmonic and subharmonic types that correspond to peaks in the plot of the critical acceleration as a function of wave frequency. Larger frequencies lead to subsequent peaks of coexisting subharmonic waves only.

  13. Effect of polarization on dielectric behaviour of PET/0.8PHB polymer liquid crystals

    SciTech Connect

    Yarramaneni, Sridharbabu; Sharma, Anu; Quamara, J. K.

    2014-04-24

    Dielectric constant and loss behaviour of pristine and polarized samples of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) polymer liquid crystals were studied at continuous temperatures ranging from 20 °C to 250 °C, polarized at potentials 500V and 2000V with high precision d.c. power supply. Dielectric constant appears to be almost linearly dependent in the lower temperature region and is independent in the higher temperature region. Dielectric loss becomes approximately ten times lower at higher temperatures.

  14. Optical rotatory power of polymer-stabilized blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Liu, Yifan; Lan, Yi-fen; Zhang, Hongxia; Zhu, Ruidong; Xu, Daming; Tsai, Cheng-Yeh; Lu, Jen-Kuei; Sugiura, Norio; Lin, Yu-Chieh; Wu, Shin-Tson

    2013-04-01

    Macroscopically, a polymer-stabilized blue phase liquid crystal (BPLC) is assumed to be an optically isotropic medium. Our experiment challenges this assumption. Our results indicate that the optical rotatory power (ORP) of some nano-scale double-twist cylinders in a BPLC composite causes the polarization axis of the transmitted light to rotate a small angle, which in turn leaks through the crossed polarizers. Rotating the analyzer in azimuthal direction to correct this ORP can greatly improve the contrast ratio. A modified De Vries equation based on a thin twisted-nematic layer is proposed to explain the observed phenomena.

  15. Small-angle light scattering from polymer-dispersed liquid-crystal films

    SciTech Connect

    Loiko, V. A. Maschke, U.; Zyryanov, V. Ya.; Konkolovich, A. V.; Misckevich, A. A.

    2008-10-15

    A method is developed for modeling and computing the angular distribution of light scattered forward from a single-layer polymer-dispersed liquid-crystal (PDLC) film. The method is based on effective-medium approximation, anomalous diffraction approximation, and far-field single-scattering approximation. The angular distribution of forward-scattered light is analyzed for PDLC films with droplet size larger than the optical wavelength. The method can be used to study field-and temperature-induced phase transitions in LC droplets with cylindrical symmetry by measuring polarized scattered light intensity.

  16. Surface-polymer stabilized liquid crystals with dual-frequency control.

    PubMed

    Minasyan, Amalya; Galstian, Tigran

    2013-08-01

    Dual-frequency control liquid crystal (LC) and thin reactive mesogen (RM) films, cast on internal surfaces of cell substrate, are used to build surface polymer stabilized structures. Electric field of high frequency is used to orient the LC molecules by the negative dielectric torque prior to the photopolymerization of RM films. Electro-optic characterization results show that the contrasts of light scatter modulation and polarization dependence are noticeably improved by the dual-frequency control. However, there is no significant shortening in the full cycle duration of excitation-relaxation-excitation. PMID:23913090

  17. Holographic polymer-dispersed liquid crystal memory for optically reconfigurable gate array using subwavelength grating mask.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru; Mabuchi, Takayuki; Kobayashi, Fuminori

    2011-12-01

    Holographic polymer-dispersed liquid crystal (HPDLC) memory formed by a subwavelength grating (SWG) mask is presented for new optical information processing. The SWG structure in a photomask is formed on the SiO(2) plate using the anisotropic reactive ion etching technique. The configuration contexts for optically reconfigurable gate arrays (ORGAs) are stored in the HPDLC memory by polarization modulation property based on the form birefringence of the SWG plate. The configuration context pattern in the HPDLC memory is reconstructed to write it for the ORGAs under parallel programmability. PMID:22192988

  18. Electro-optical characteristics of holographic polymer dispersed liquid crystal gratings doped with nanosilver.

    PubMed

    Zhang, Menghua; Zheng, Jihong; Gui, Kun; Wang, Kangni; Guo, Caihong; Wei, Xiaopeng; Zhuang, Songlin

    2013-11-01

    We report on the synthesis and characteristics of a holographic polymer dispersed liquid crystal (H-PDLC) switchable grating based on nano-Ag particles. The influence of doping different concentrations of nano-Ag on the diffraction efficiency, driving voltage, and response time of the H-PDLC grating is investigated. The best grating characteristics were achieved with 0.05% nano-Ag doping. Calculated and experimental results reveal that the improvement of the characteristics is likely due to the surface plasmon effect of nano-Ag. PMID:24216639

  19. Electrically tunable liquid-crystal wave plate using quadripolar electrode configuration and transparent conductive polymer layers.

    PubMed

    Fraval, Nicolas; Joffre, Pascal; Formont, Stéphane; Chazelas, Jean

    2009-10-01

    We present the realization of an electrically tunable wave plate, which uses a nematic liquid-crystal (LC) phase retarder that allows fast and continuous control of the polarization state. This device is built using a quadripolar electrode design and transparent conductive polymer layers in order to obtain a uniform electric field distribution in the interelectrode area. With this realization, we obtain a high degree of control of the orientation of the electric field and, consequently, of the LC director. Indeed, this modulator outperforms classical bipolar LC cells in both optical path variation (>4 microm) and LC rotation speed (0.4 degrees/micros). PMID:19798369

  20. Polymer stabilized vertical alignment liquid crystal display: effect of monomer structures and their stabilizing characteristics

    NASA Astrophysics Data System (ADS)

    Kwon, You Ri; Choi, Young Eun; Wen, Pushen; Lee, Byeong Hoon; Kim, Jong Chan; Lee, Myong-Hoon; Jeong, Kwang-Un; Lee, Seung Hee

    2016-04-01

    A polymer-stabilized vertical alignment (PS-VA) mode using a new type of photoreactive monomer for polymer stabilization of the liquid crystal (LC) director was developed. Conventional reactive mesogens having a higher molecular weight than those of the host LC tend to aggregate and form large-sized polymer grains when exposed to ultraviolet (UV) light, subsequently deteriorating the quality of the dark state. To address these problems, bis(4-hydroxyphenyl) diacrylates were synthesized with four different linking groups as stabilizing monomers (SMs) which have molecular weights similar to that of the host LC. Their stabilizing characteristics with respect to the molecular size and polarity of SMs were evaluated by examining the electro-optic characteristics of LC cells after UV irradiation. The results showed that the SM containing a small linking group in size between biphenyls with high polarity was favored to achieve excellent polymer stabilization. The SM containing an ether linkage showed excellent electro-optic characteristics with no large-sized polymer grains even in the absence of a photo-initiator. Consequently, we anticipate that SMs, polar and smaller in size, can improve the electro-optic characteristics in PS-VA mode.

  1. Phase Behavior of Blends of Polymers and Smectic-A Liquid Crystals.

    PubMed

    Benmouna; Coqueret; Maschke; Benmouna

    1998-07-28

    The phase behavior of blends of polymers and smectic-A liquid crystals (LCs) is investigated using Flory-Huggins and Maier-Saupe-McMillan theories. Various examples are considered to depict the effects of the architecture and the size of the polymer together with the nature of anisotropic ordering forces on the phase diagram. The strength of these forces is characterized by a parameter alpha which is directly related to the temperature of the smectic-nematic transition. Three cases are considered depending on the value of alpha, and the corresponding phase diagrams are constructed. Substantial differences are observed in these diagrams, and the reasons for these differences are discussed. A comparative study is performed between mixtures of polymers and LCs, where the polymer is made of linear and crosslinked chains. The LC consists either of molecules with nematic ordering only or of molecules presenting both nematic and smectic-A ordering. Blends where polymer matrices are cross-linked networks are also examined. Remarkable properties are found in the nature of the phase diagrams for such mixtures. In general, it is observed that the ordering forces favor unmixing with a stronger effect for the higher smectic-A ordering. Spinodal curves are also reported for these mixtures. The effects of fluctuations near the transition temperatures are briefly discussed.

  2. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal

    NASA Astrophysics Data System (ADS)

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-01

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at lambda=1.55 μm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 μm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms.

  3. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal.

    PubMed

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-10

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at gamma = 1.55 microm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 microm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms. PMID:16045229

  4. Electrically tunable birefringence of a polymer composite with long-range orientational ordering of liquid crystals.

    PubMed

    Choi, Byeongdae; Song, Seongkyu; Jeong, Soon Moon; Chung, Seok-Hwan; Glushchenko, Anatoliy

    2014-07-28

    We report an optical film with electrically tunable birefringence in which the liquid crystals (LCs), mixed with the host polymer, form long-range ordering. The film was prepared through polymerization without phase separation between the LCs and polymers. Driving voltage below 30 V for full switching of birefringence is achieved in a 6 μm-thick film. Electro-optical investigations for the film suggest that the long-range ordering of the LCs mixed in the film caused by polymerization lead to rotations of the LCs as well as optical anisotropy in the film. These films with electrically tunable birefringence could have applications as flexible light modulators and phase retardation films for 2D-3D image switching. PMID:25089422

  5. Theory and characteristics of holographic polymer dispersed liquid crystal transmission grating with scaffolding morphology.

    PubMed

    Huang, Wenbin; Liu, Yonggang; Diao, Zhihui; Yang, Chengliang; Yao, Lishuang; Ma, Ji; Xuan, Li

    2012-06-20

    We have performed a detailed characterization of the optical properties of a holographic polymer dispersed liquid crystal (LC) transmission grating with polymer scaffolding morphology, which was fabricated with conventional high-functionality acrylate monomer under low curing intensity. Temporal evolution of the grating formation was investigated, and the amount of phase-separated LC was determined by birefringence investigation. A grating model combined with anisotropic coupled-wave theory yielded good agreement with experimental data without any fitting parameter. The results in this study demonstrate the non droplet scaffolding morphology grating is characterized by a high degree of phase separation (70%), high anisotropy, low scattering loss (<6%), and high diffraction efficiency (95%). PMID:22722275

  6. Long-term evaluation of a liquid crystal polymer (LCP)-based retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Jeong, Joonsoo; Bae, So Hyun; Seo, Jong-Mo; Chung, Hum; Kim, Sung June

    2016-04-01

    Objective. The aim of this study is to evaluate the long-term reliability of a recently presented liquid crystal polymer (LCP) -based retinal prosthesis in vitro as well as in vivo. Because an all-polymer implant introduces another intrinsic leak type due to gas permeation, for which the traditional helium leak test for metallic packages was not designed to quantify, a new method to investigate its durability is required. Approach. We designed and carried out a series of reliability tests specifically for all-polymer implants by quantitatively investigating moisture ingress through various pathways of the polymer surface, and the polymer-polymer and polymer-metal adhesions. Moisture permeation through the bulk material was estimated by analytic calculation, while water ingress through the adhesively sealed LCP-LCP and LCP-metal interfaces was investigated using the separate parts of an electrode array and a package in an accelerated aging condition. In vivo tests were done in rabbits to examine the long-term biocompatibility and implantation stability by fundus observation and optical coherence tomography (OCT) imaging. Main results. The analytic calculation estimated good barrier properties of the LCP. Samples of the LCP-based electrode array failed after 114 days in 87 °C saline as a result of water penetration through the LCP-metal interface. An eye-conformable LCP package survived for 87 days in an accelerated condition at 87 °C. The in vivo results confirmed that no adverse effects were observed around the retina 2.5 years after the implantation of the device. Significance. These long-term evaluation results show the potential for the chronic use of LCP-based biomedical implants to provide an alternative to traditional metallic packages.

  7. Semiconductor nanorod liquid crystals

    SciTech Connect

    Li, Liang-shi; Walda, Joost; Manna, Liberato; Alivisatos, A. Paul

    2002-01-28

    Rodlike molecules form liquid crystalline phases with orientational order and positional disorder. The great majority of materials in which liquid crystalline phases have been observed are comprised of organic molecules or polymers, even though there has been continuing and growing interest in inorganic liquid crystals. Recent advances in the control of the sizes and shapes of inorganic nanocrystals allow for the formation of a broad class of new inorganic liquid crystals. Here we show the formation of liquid crystalline phases of CdSe semiconductor nanorods. These new liquid crystalline phases may have great importance for both application and fundamental study.

  8. Photorefractivity in nematic liquid crystals doped with a conjugated polymer: Mechanisms for enhanced charge transport

    SciTech Connect

    Wiederrecht, G.P.; Niemczyk, M.P.; Svec, W.A.; Wasielewski, M.R. |

    1999-06-01

    New organic materials that exhibit photorefractive effects are of wide interest for potential optical signal processing applications. The authors report on a photorefractive nematic liquid crystal composite containing the conjugated polymer poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene), BEH-PPV that exhibits a novel fringe spacing dependent inversion of the polarity of the space-charge field due to competition between the ionic diffusion and charge drift transport mechanisms. A eutectic mixture of 35% (wt %) 4{prime}-(n-octyloxy)-4-cyanobiphenyl, 8OCB, and 65% 4{prime}(n-pentyl)-4-cyanobiphenyl, 5CB, was doped with 10{sup {minus}5} M BEH-PPV (200 kD by GPC), as the electron donor. The molecular weight of the BEH-PPV polymer implies that 500 repeat units of the monomer are present with an extended chain length of 0.35 {micro}m. N,N{prime}-Dioctyl-1,4:5,8-naphthalenediimide, NI, 8 {times} 10{sup {minus}3} M, was added as the electron acceptor. The free energy change for the photoinduced electron-transfer reaction, (BEH-PPV) + NI {yields} (BEH-PPV){sup +} + NI{sup {minus}}, is {minus}1.0 eV. Two other liquid-crystal composites were also studied as controls.

  9. Fast-response IR spatial light modulators with a polymer network liquid crystal

    NASA Astrophysics Data System (ADS)

    Peng, Fenglin; Chen, Haiwei; Tripathi, Suvagata; Twieg, Robert J.; Wu, Shin-Tson

    2015-03-01

    Liquid crystals (LC) have widespread applications for amplitude modulation (e.g. flat panel displays) and phase modulation (e.g. beam steering). For phase modulation, a 2π phase modulo is required. To extend the electro-optic application into infrared region (MWIR and LWIR), several key technical challenges have to be overcome: 1. low absorption loss, 2. high birefringence, 3. low operation voltage, and 4. fast response time. After three decades of extensive development, an increasing number of IR devices adopting LC technology have been demonstrated, such as liquid crystal waveguide, laser beam steering at 1.55μm and 10.6 μm, spatial light modulator in the MWIR (3~5μm) band, dynamic scene projectors for infrared seekers in the LWIR (8~12μm) band. However, several fundamental molecular vibration bands and overtones exist in the MWIR and LWIR regions, which contribute to high absorption coefficient and hinder its widespread application. Therefore, the inherent absorption loss becomes a major concern for IR devices. To suppress IR absorption, several approaches have been investigated: 1) Employing thin cell gap by choosing a high birefringence liquid crystal mixture; 2) Shifting the absorption bands outside the spectral region of interest by deuteration, fluorination and chlorination; 3) Reducing the overlap vibration bands by using shorter alkyl chain compounds. In this paper, we report some chlorinated LC compounds and mixtures with a low absorption loss in the near infrared and MWIR regions. To achieve fast response time, we have demonstrated a polymer network liquid crystal with 2π phase change at MWIR and response time less than 5 ms.

  10. Localised polymer networks in chiral nematic liquid crystals for high speed photonic switching

    NASA Astrophysics Data System (ADS)

    Tartan, Chloe C.; Salter, Patrick S.; Booth, Martin J.; Morris, Stephen M.; Elston, Steve J.

    2016-05-01

    Self-assembled periodic structures based upon chiral liquid crystalline materials have significant potential in the field of photonics ranging from fast-switching optoelectronic devices to low-threshold lasers. The flexoelectro-optic effect, which is observed in chiral nematic liquid crystals (LCs) when an electric field is applied perpendicular to the helical axis, has significant potential as it exhibits analogue switching in 10-100 μs. However, the major technological barrier that prohibits the commercial realisation of this electro-optic effect is the requirement of a uniform, in-plane alignment of the helix axis between glass substrates. Here, it is shown that periodic polymer structures engineered in the nematic phase of a chiral nematic LC device using direct laser writing can result in the spontaneous formation of the necessary uniform lying helix (ULH) state. Specifically, two-photon polymerization is used in conjunction with a spatial light modulator so as to correct for aberrations introduced by the bounding glass substrates enabling the polymer structures to be fabricated directly into the device. The ULH state appears to be stable in the absence of an externally applied electric field, and the optimum contrast between the bright and dark states is obtained using polymer structures that have periodicities of the order of the device thickness.

  11. Single molecule spectroscopy of conjugated polymer chains in an electric field-aligned liquid crystal.

    PubMed

    Chang, Wei-Shun; Link, Stephan; Yethiraj, Arun; Barbara, Paul F

    2008-01-17

    Using single molecule polarization spectroscopy, we investigated the alignment of a polymer solute with respect to the liquid crystal (LC) director in an LC device while applying an external electric field. The polymer solute is poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (or MEH-PPV), and the LC solvent is 5CB. The electric field induces a change in the LC director orientation from a planar alignment (no electric field) to a perpendicular (homeotropic) alignment with an applied field of 5.5 x 103 V/cm. We find that the polymer chains align with the LC director in both planar and homeotropic alignment when measured in the bulk of the LC solution away from the device interface. Single molecule polarization distributions measured as a function of distance from the LC device interface reveal a continuous change of the MEH-PPV alignment from planar to homeotropic. The observed polarization distributions are modeled using a conventional elastic model that predicts the depth profile of the LC director orientation for the applied electric field. The excellent agreement between experiment and simulations shows that the alignment of MEH-PPV follows the LC director throughout the LC sample. Furthermore, our results suggest that conjugated polymers such as MEH-PPV can be used as sensitive local probes to explore complex (and unknown) structures in anisotropic media. PMID:17975912

  12. Liquid Crystals

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  13. Nonvolatile memory effects in an orthoconic smectic liquid crystal mixture doped with polymer-capped gold nanoparticles.

    PubMed

    Marino, L; Marino, S; Wang, D; Bruno, E; Scaramuzza, N

    2014-06-01

    Promising applications of liquid crystal nanocomposites have driven extensive efforts to achieve non-volatile memory effects for the realization of electronic storage devices. In this context, non-volatile memory effects in an orthoconic smectic liquid crystal mixture, with and without polymer capped gold nanoparticles, were investigated. The dielectric spectroscopy technique was performed by applying a d.c. bias during the measurement or a d.c. potential before the start of the measurement in order to obtain pre-conditioning of the sample. Both techniques showed the presence of non-volatile memory effects in the pure orthoconic smectic liquid crystal mixture similar to the doped one. The results demonstrate that the addition of gold nanoparticles enhances the memory effect making it permanent. Our experimental evidence underlines the importance of the structure of the host liquid crystal and clearly suggests that the prolonged time memory effect, observed in the doped liquid crystal, is due to the electric field inducing charge transfer from the liquid crystal molecules to the gold nanoparticles, thanks to the polymer-capping which acts as an ionic charge trapper. Such an ionic trap effect is also responsible for strong reduction of total conductivity of the doped system.

  14. Third-harmonic generation enhancement in polymer-dispersed liquid crystal grating

    NASA Astrophysics Data System (ADS)

    Wicharn, S.; Buranasiri, P.

    2014-09-01

    In this paper, the enhancement of third-harmonic generation in one-dimensional periodic grating structure with lowindex contrast, which is produced by holographic illuminated liquid crystal droplets and called polymer-dispersed liquid crystal grating, with near-infrared pumping has been demonstrated. The observed enhancement process is theoretically explained and modeled with a multi-scale perturbation analysis and split-step Fourier transform technique, respectively. We show that the third-harmonic generation has been enhanced by setting the fundamental frequency wavelength to the long-wavelength band-edge of the first photonic band-gap of this periodic structure and satisfying band-edge phasematched condition. The numerical results show that a dramatic enhancement of the third-harmonic field is observed near the long-wavelength band-edge of the second photonic band-gap. Furthermore, the conversion efficiency of thirdharmonic field of forward-propagating direction is more than of backward-propagating direction by a factor of 600.

  15. Fabrication of sisal fibers/epoxy composites with liquid crystals polymer grafted on sisal fibers

    NASA Astrophysics Data System (ADS)

    Luo, Q. Y.; Lu, S. R.; Song, L. F.; Li, Y. Q.

    2016-07-01

    In this word, microcrystalline cellulose fibers (MCFs), extracted from sisal fibers, were treated with function end-group hyperbranched liquid crystals (HLP). This work brought some insights into the successful surface modification in epoxy composite with HLP. The HLP-MCFs/epoxy composites are studied systematically. The HLP - MCFs/epoxy composites were studied by Fourier transform infrared spectroscopy (FT-IR), polarizing microscope (POM), X-ray photoelectron spectroscopy (XPS) and mechanical properties analysis. The results reveal that the reinforcement of EP composites was carried out by adding HLP-MCFs. In particular, with 1.0 wt% filler loading, the flexural strength, tensile strength, impact strength and flexural modulus of the HLP-MCFs/EP composites were increased by 60%, 69%, 130%, and 192%, respectively. It anticipates that our current work exploits more efficient methods to overcome the few nature fiber/polymer (NPC) adhesion in the interface region and provides implications for the engineering applications of the development of NPC.

  16. Distributed feedback lasing from electrically tunable dye-doped polymer-liquid crystal transmission gratings

    NASA Astrophysics Data System (ADS)

    Sakhno, O. V.; Gritsai, Y.; Stumpe, J.

    2014-11-01

    In the present work we report low-threshold distributed feedback (DFB) lasing from electrically tunable holographic polymer-liquid crystal transmission gratings of POLIPHEM type doped with pyrromethene 567. Due to their uniform droplet-free micro-morphology, the POLIPHEM gratings possess high diffraction efficiency and excellent optical quality. Second-order lasing with a threshold of ~0.8 µJ/pulse and a bandwidth of ~1 nm was achieved under the excitation of a frequency-doubled Nd:YAG laser operating at 532 nm. The laser emission wavelength was tuned from 572-625 nm by varying the grating period. Application of an electric field switches off or tunes the lasing intensity. An electrically-induced blue-shift of the output laser emission was observed.

  17. Molecular dynamics in azobenzene liquid crystal polymer films studied by transient grating technique

    NASA Astrophysics Data System (ADS)

    Katayama, Kenji; Fujii, Tomomi; Kuwahara, Shota; Takado, Kiyohide; Ikeda, Tomiki

    2014-10-01

    We studied the effect of the ratio between the monomer and cross-linker molecules in the azobenene included liquid crystal polymer films by using the heterodyne transient grating (HD-TG) technique, which is one of the time-resolved measurement techniques. Depending on the ratio, the magnitude of the refractive index change, its anisotropy, and the lifetime of the cis isomer of azobenzene, generated by a UV pulse irradiation. By increasing the cross-linker ratio, the refractive index change and its anisotropy was reduced, indicating less ability for the motion, while slower lifetime was observed by increasing the monomer ratio, indicating that the film is difficult to return the original shape by a visiblelight irradiation. The obtained dynamics was consistent with the functionality of the films.

  18. Dual-period tunable phase grating using polymer stabilized blue phase liquid crystal.

    PubMed

    Yan, Jing; Xing, Yufei; Li, Qing

    2015-10-01

    Dual-period tunable phase grating using polymer stabilized blue phase liquid crystal is demonstrated by controlling its driving scheme. High efficiencies of 35.3% for the small-period phase grating and 28.7% for the large-period phase grating have been achieved because of the rectangular-like phase profile which shows good agreement with the simulation results. The diffraction angle can be alternatively tuned, as well as the diffraction efficiency. Moreover, this device also possesses polarization independency and fast response with a rise time of 826 μs and a decay time of 1.143 ms which shows great potential for diffractive optics. PMID:26421571

  19. Merged vector gratings recorded in a photocrosslinkable polymer liquid crystal film for polarimetry

    SciTech Connect

    Sasaki, Tomoyuki Wada, Takumi; Noda, Kohei; Ono, Hiroshi; Kawatsuki, Nobuhiro

    2014-01-14

    A merged vector grating, which is holographically fabricated in an anisotropic medium by irradiation with interference light with intensity modulation and polarization modulation, was designed to detect the polarization of light. The merged vector grating is recorded by the interference of two elliptically polarized beams with equal intensities, parallel azimuths, equal ellipticities, and different directions of rotation. We clarified theoretically that the Stokes parameters of the incident light beam are described by the diffraction efficiency of the merged vector grating. Also, to apply this property to formation of a polarimeter without any moving parts or mechanisms, two merged vector gratings with different grating vectors were recorded in a photocrosslinkable polymer liquid crystal film by angle-multiplexed holography. By investigation of the diffraction properties of the gratings obtained, we demonstrated the applicability of the merged vector gratings for use in polarimetry.

  20. Electro-optical properties of low viscosity driven holographic polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Moon, K. R.; Bae, S. Y.; Kim, B. K.

    2015-04-01

    Relative diffraction efficiency (RDE), operating voltage, and response times are most important performance characteristics of holographic polymer dispersed liquid crystals (HPDLC). Two types of triallyl isocyanurate (TI) having different structures were incorporated into the conventional transmission grating of HPDLC. Premix viscosity decreased by 13-18% with up to 3% TI, beyond which it increased. TI eliminated induction period and augmented initial grating formation rate at all contents. Saturation RDE increased over 200% while threshold voltage and rise time decreased to about half and 2/3, respectively up to 3% TI, beyond which the tendencies were reversed. Among the two TIs, low viscosity monomer (TA) showed high RDE, while high miscibility monomer (TE) low characteristic voltages and short response times. It is concluded that grating formation is largely favored by low viscosity, while interface tensions and electro-optical performances by miscibility at similar viscosities.

  1. Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

    PubMed

    Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

    2015-08-19

    A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows. PMID:26192469

  2. Structural studies of polymers and polymer liquid crystals by X-ray scattering, thermal analysis and ellipsometric studies through polarized light microscopy

    NASA Astrophysics Data System (ADS)

    Georgiev, Georgi Yordanov

    We have studied the phase transformation behavior and structure of binary polymer blends and polymer liquid crystalline materials, to understand the formation of long and short-range ordered structures. We investigated their crystallization, melting and liquid crystalline behavior using Small Angle X-ray Scattering (SAXS), Wide Angle X-ray Scattering (WAXS), Modulated Differential Scanning Calorimetry (MDSC), Polarized Light Microcopy (PLM), and Scanning Probe Microscopy (SPM). Materials selected for the study were: (1) a miscible blend of semicrystalline poly(etheretherketone), PEEK, and noncrystallizable poly(etherimide), PEI; (2) an immiscible blend of poly(ethyleneterephtalate), PET, and liquid crystalline polymer, Vectra RTM; (3) a thermotropic liquid crystalline random copolyester HIQ-40; and (4) new biological collagen model peptides. We explore the phenomenon of multiple melting endotherms seen through MDSC after thermal pre-treatment of PEEK/PEI blend at different crystallization temperatures. Multiple melting endotherms have several possible origins, including melting of several populations of crystals with different lamellar thicknesses, melting of different crystallographic forms, or melting and recrystallization of the same population of crystals. The location of the amorphous phase, whether it is interlamellar, interfibrillar or interspherulite is addressed, by comparing the total crystallinity of the sample obtained by DSC and the linear stack crystallinity obtained by SAXS. Also by the temperature dependence of the smaller thickness determined from the SAXS correlation function, we were able to assign it to the crystalline thickness of the lamellae. We studied the effect of Vectra on the crystallization behavior of PET, and found that it slows the nucleation time for crystallization, and decreases the sample viscosity. By X-ray scattering and Differential Scanning Calorimetry and optical measurements we showed that the liquid crystalline component

  3. Possible enhancement of physical properties of nematic liquid crystals by doping of conducting polymer nanofibres

    NASA Astrophysics Data System (ADS)

    Manda, R.; Dasari, V.; Sathyanarayana, P.; Rasna, M. V.; Paik, P.; Dhara, Surajit

    2013-09-01

    We report on the preparation and physical characterization of the colloidal suspension of conducting polyaniline (PANI) nanofibres and a nematic liquid crystal (5CB). The ac electrical conductivity anisotropy increases significantly and the rotational viscosity decreases with increasing wt. % of PANI nanofibres, while other physical properties such as birefringence, dielectric anisotropy, splay, and bend elastic constants are changed moderately. The high conductivity anisotropy of liquid crystal nano-composites is very useful for magnetically steered liquid crystal-nanofibre switch.

  4. Grafting of a functionalized side-chain liquid crystal polymer on carbon fiber surfaces: Novel coupling agents for fiber/polymer matrix composites

    SciTech Connect

    Le Bonheur, V.; Stupp, S.I. )

    1993-09-01

    The authors studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces, offering a mechanism to control composite properties not only through bonding but also through their [open quotes]spontaneous[close quotes] molecular orientation in interfacial regions. The grafting methodology for both monomer and polymer to fiber surfaces involved esterification through carbodiimide chemistry in solution. Carboxylic acid groups found on functionalized carbon fiber surfaces were esterified to phenolic functions in the side chains of the experimental polymer. Following grafting procedures the fibers were analyzed by scanning electron microscopy (SEM) and by contact angle measurements. SEM micrographs of fibers grafted with polymer revealed the presence of strongly attached polymeric material on the graphitic surface after rigorous extraction with polymer solvent. Contact angle measurements and polar/dispersive free energy analysis indicated also a smaller polar component of the surface free energy of fibers possibly due to the hydrophobic polymer backbone grafted on the carbon surfaces. On the basis of results, it is concluded that the esterification reaction grafted the polyphenolic liquid-crystal polymer on graphite fiber surfaces. 24 refs., 8 figs., 4 tabs.

  5. Large birefringence and polarization holographic gratings formed in photocross-linkable polymer liquid crystals comprising bistolane mesogenic side groups

    SciTech Connect

    Emoto, Akira; Matsumoto, Taro; Shioda, Tatsutoshi; Ono, Hiroshi; Yamashita, Ayumi; Kawatsuki, Nobuhiro

    2009-10-01

    Polarization gratings with large birefringence are formed in photoreactive polymer liquid crystals with bistolane moiety and terminal cinnamic acid moiety by the use of polarized ultraviolet interference light and subsequent annealing. The polarized ultraviolet light causes the axis-selective photoreaction between the cinnamic acid groups and subsequent annealing induce the reorientation of peripheral molecules without cross-linking along the cross-linked groups. Long bistolane mesogenic moiety exhibits large birefringence in comparison with a biphenyl mesogenic moiety, the value of the induced birefringence in the bistolane mesogenic liquid crystalline (LC) polymer is strongly dependent on both the grating constant and the wavelength of the reconstruction light.

  6. A flexible liquid crystal polymer MEMS pressure sensor array for fish-like underwater sensing

    NASA Astrophysics Data System (ADS)

    Kottapalli, A. G. P.; Asadnia, M.; Miao, J. M.; Barbastathis, G.; Triantafyllou, M. S.

    2012-11-01

    In order to perform underwater surveillance, autonomous underwater vehicles (AUVs) require flexible, light-weight, reliable and robust sensing systems that are capable of flow sensing and detecting underwater objects. Underwater animals like fish perform a similar task using an efficient and ubiquitous sensory system called a lateral-line constituting of an array of pressure-gradient sensors. We demonstrate here the development of arrays of polymer microelectromechanical systems (MEMS) pressure sensors which are flexible and can be readily mounted on curved surfaces of AUV bodies. An array of ten sensors with a footprint of 60 (L) mm × 25 (W) mm × 0.4 (H) mm is fabricated using liquid crystal polymer (LCP) as the sensing membrane material. The flow sensing and object detection capabilities of the array are illustrated with proof-of-concept experiments conducted in a water tunnel. The sensors demonstrate a pressure sensitivity of 14.3 μV Pa-1. A high resolution of 25 mm s-1 is achieved in water flow sensing. The sensors can passively sense underwater objects by transducing the pressure variations generated underwater by the movement of objects. The experimental results demonstrate the array’s ability to detect the velocity of underwater objects towed past by with high accuracy, and an average error of only 2.5%.

  7. Influence of virtual surfaces on Frank elastic constants in a polymer-stabilized bent-core nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Madhuri, P. Lakshmi; Hiremath, Uma S.; Yelamaggad, C. V.; Madhuri, K. Priya; Prasad, S. Krishna

    2016-04-01

    Effect of a polymer network on the threshold voltage of the Fréedericksz transition, Frank elastic constants, switching speed, and the rotational viscosity are investigated in a polymer-stabilized bent-core nematic liquid crystal with different polymer concentrations. These polymer networks form virtual surfaces with a finite anchoring energy. The studies bring out several differences in comparison to similar studies with a calamitic liquid crystal as the nematic host. For example, on varying the polymer content the threshold voltage decreases initially, but exhibits a drastic increase above a critical concentration. A similar feature—reaching a minimum before rising—is seen for the bend elastic constant, which gets enhanced by an order of magnitude for a polymer content of 2.5 wt %. In contrast, the splay elastic constant has a monotonic variation although the overall enhancement is comparable to that of the bend elastic constant. The behavior changing at a critical concentration is also seen for the switching time and the associated rotational viscosity. The presence of the polymer also induces a shape change in the thermal dependence of the bend elastic constant. We explain the features observed here on the basis of images obtained from the optical and atomic force microscopy.

  8. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  9. Development of polymer cholesteric liquid crystal flake technology for electro-optic devices and particle displays

    NASA Astrophysics Data System (ADS)

    Kosc, T. Z.; Marshall, K. L.; Trajkovska-Petkoska, A.; Coon, C. J.; Hasman, K.; Babcock, G. V.; Howe, R.; Leitch, M.; Jacobs, S. D.

    2007-02-01

    Liquid crystals have had a large presence in the display industry for several decades, and they continue to remain at the forefront of development as the industry delves into flexible displays and electronic paper. Among the emerging technologies trying to answer this call are polymer cholesteric liquid crystal (PCLC) flakes. The motion of PCLC flakes suspended in a host fluid is controlled with an electric field, whereby the flakes reorient to align parallel with the applied field. A PCLC device easily switches from a bright state, where light of a given wavelength and polarizationis selectively reflected, to a dark, non-reflective state. The device returns to a bright state when the flakes relax to their original orientation after removal of the applied field. Progress has been made in addressing several key device issues: the need to switch flakes back to a reflective state quickly, the development of bistability, the ability to produce flexible devices, and the necessity to produce both high brightness and a large contrast ratio. Improvements in the technology have been made by addressing the optical, mechanical, chemical, and electrical features and characteristics of the PCLC flake/fluid host system. The manufacture of "custom" flakes by the process of formation of specific flake shapes, the addition of dopants, or the formation of layered flake composites results in particles with improved reflectivity and response times along with the ability to respond to both AC and DC fields. Specially designed driving waveforms provide a new means for controlling flake motion. PCLC flake micro-encapsulation allows for the possibility of flexible and potentially bistable devices. Here we report on the wide variety of approaches toward improving PCLC flake devices and their results.

  10. Photoalignment and resulting holographic vector grating formation in composites of low molecular weight liquid crystals and photoreactive liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Sasaki, Tomoyuki; Shoho, Takashi; Goto, Kohei; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2015-08-01

    Polarization holographic gratings were formed in liquid crystal (LC) cells fabricated from a mixture of low molecular weight nematic LC and a photoreactive liquid crystalline polymer (PLCP) with 4-(4-methoxycinnamoyloxy)biphenyl side groups. The diffraction properties of the gratings were analyzed using theoretical models which were determined based on the polarization patterns of the polarization holography. The results demonstrated that vector gratings comprised of periodic orientation distributions of the LC molecule were induced in the cells based on the axis-selective photoreaction of the PLCP. The vector gratings were erased by applying a sufficiently high voltage to the cells and then were reformed with no hysteresis after the voltage was removed. This phenomenon suggested that the PLCP molecules were stabilized based on the axis-selective photocrosslink reaction and that the LC molecules were aligned by the photocrosslinked PLCP. This LC composite with axis-selective photoreactivity is useful for various optical applications, because of their stability, transparency, and response to applied voltage.

  11. Thermally stimulated polarization currents of pristine poly (p-hydroxybenzoic acid - co - ethylene terephthalate) polymer liquid crystals

    NASA Astrophysics Data System (ADS)

    Yarramaneni, Sridharbabu; Anu, Sharma; Quamara, J. K.

    2016-05-01

    Thermally stimulated polarization currents (TSPC) of pristine PET/0.8PHB polymer liquid crystals have been studied at various polarizing fields ranging from 38.5 kV/cm to 153.8 kV/cm at continuous temperatures ranging from 20 °C to 250 °C. The charge transport phenomena, responsible mechanisms can be investigated by studying TSP current spectra of these polymer liquid crystals. The TSP current spectra consists of two maxima one at low temperature region and the other at high temperature region and a linear variation in the temperature region from 70°C to 190°C. The relaxation behaviour of this PLC is results from various mechanisms associated with crystalline and amorphous phases.

  12. Liquid crystal alignment at macroscopically isotropic polymer surfaces: Effect of an isotropic-nematic phase transition

    NASA Astrophysics Data System (ADS)

    Aryasova, Natalie; Reznikov, Yuri

    2016-09-01

    We study the effect of an isotropic-nematic (I -N ) phase transition on the liquid crystal alignment at untreated polymer surfaces. We demonstrate that the pattern at the untreated substrate in the planar cell where the other substrate is uniformly rubbed strongly depends on the temperature gradient across the cell during the I -N phase transition, being macroscopically isotropic if the untreated substrate is cooled faster, but becoming almost homogeneous along the rubbing direction in the opposite temperature gradient. We interpret the observed effect using complementary models of heat transfer and nematic elasticity. Based on the heat transfer model we show that the asymmetric temperature conditions in our experiments provide unidirectional propagation of the I -N interface during the phase transition and determine the initial director orientation pattern at the test's untreated surface. Using the Frank-Oseen model of nematic elasticity, we represent the three-dimensional director field in the nematic cell as a two-dimensional (2D) pattern at the untreated surface and perform 2D numeric simulations. The simulations explain the experimental results: Different initial director orientations at the untreated surface evolve into different stationary patterns.

  13. Non-symmetric broadening of the reflection notch in polymer stabilized cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Natarajan, Lalgudi V.; Voss, Jimmy R.; Tondiglia, Vincent P.; Yang, Deng-Ke; White, Timothy J.; Bunning, Timothy J.

    2010-08-01

    Non-symmetric broadening (to the blue side) of a cholesteric reflection notch was observed when a cell containing diacrylate and monoacrylate nematic LC monomers, a chiral dopant, nematic LC and a photoinitiator was exposed to very low intensity (microwatts) of 335 nm UV light. At very low intensity, the polymerization rate is very slow and takes a long time to complete as observed by real-time monitoring experiments. The polymerized scaffold templates the original liquid crystal helical structure. The 335 nm light is highly absorbed by the system which generates an intensity gradient throughout the thickness of the cell. This gradient produces a free radical density gradient in the later stage of the polymerization when diffusion is slowed by the growing polymer network. Since more monomer is consumed at the front half of the cell, a counter diffusion of chiral dopant towards the cell backside is observed. This leads to a local increase in the HTP causing a local blue shift of the notch wavelength. The net result observed in transmission is a broadening of the reflection bandwidth from 70 nm to 200 nm where the broadening occurs only to the blue side of the original notch. By varying the intensity of the UV source on one side of the substrate, the broadening magnitude could be controlled. Simultaneous UV illumination from both sides of the cell reduced the broadening considerably. The broadened notch was switchable at high electrical field (20V/μm).

  14. Varied-line-spacing switchable holographic grating using polymer-dispersed liquid crystal.

    PubMed

    Wang, Kangni; Zheng, Jihong; Lu, Feiyue; Gao, Hui; Palanisamy, Aswin; Zhuang, Songlin

    2016-06-20

    A varied-line-spacing switchable holographic grating is demonstrated through a changeable interference pattern recorded in polymer-dispersed liquid crystal. The pattern is generated by the interference between one plane wave and another cylindrical wave. The line spacing and the period of grating can be controlled by varying the distance between the cylindrical lens and the grating sample and by changing the exposure angle between the two beams. Experimental period measurements and calculations show good agreement with the theoretical results. High diffraction efficiency of more than 80% for the middle period of the grating has been achieved under appropriate exposure time of 120 s and intensity of 19.1  mW/cm2. In addition, the diffraction can be switched on and off by virtue of the external driving voltage of approximately 120 V. The grating also possesses a fast response with a rise time of 300 μs and a fall time of 750 μs. This grating, which can change the period in the grating structure to allow switchable diffraction of transmitted light, shows great potential application for diffractive optics. PMID:27409124

  15. Biomimetic Submicroarrayed Cross-Linked Liquid Crystal Polymer Films with Different Wettability via Colloidal Lithography.

    PubMed

    Zhan, Yuanyuan; Zhao, Jianqiang; Liu, Wendong; Yang, Bai; Wei, Jia; Yu, Yanlei

    2015-11-18

    Photoresponsive cross-linked liquid crystal polymer (CLCP) films with different surface topographies, submicropillar arrays, and submicrocone arrays were fabricated through colloidal lithography technique by modulating different types of etching masks. The prepared submicropillar arrays were uniform with an average pillar diameter of 250 nm and the cone bottom diameter of the submicrocone arrays was about 400 nm, which are much smaller than previously reported CLCP micropillars. More interestingly, these two species of films with the same chemical structure represented completely different wetting behavior of water adhesion and mimicked rose petal and lotus leaf, respectively. Both the submicropillar arrayed film and the submicrocone arrayed film exhibited superhyrophobicity with a water contact angle (CA) value of 144.0 ± 1.7° and 156.4 ± 1.2°, respectively. Meanwhile, the former demonstrated a very high sliding angle (SA) greater than 90°, and thus, the water droplet was pinned on the surface as rose petal. On the contrary, the SA of the submicrocone arrayed CLCP film consisting of micro- and nanostructure was only 3.1 ± 2.0°, which is as low as that of lotus leaf. Furthermore, the change on the wettability of the films was also investigated under alternating irradiation of visible light with two different wavelengths, blue light and green light.

  16. Effect of cell gap on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-07-01

    Polymer dispersed liquid crystal (PDLC) lenses with a cell gap of 11 μm and 30 μm were made from a uniformly dispersed mixture of 40% prepolymer (NOA 65, Norland optical adhesive 65) and 60% E7 liquid crystal. PDLC's mixture between two ITO coated glasses was polymerized by UV (ultraviolet) curing in the polymerization induced phase separation (PIPS) process. Decline of cell gap is a physical approach to improve the electrooptical properties, while cooling or doping of SiO2 nanoparticles is the microstructural approach to enhance the properties, because the electric field applied to the liquid crystal molecules in LC droplets is inversely proportional to the cell gap. A smaller cell gap significantly and effectively increases the electric field applied to PDLCD devices. The driving voltages and slope for the sample with a cell gap of 11 μm and 30 μm were drastically improved. The driving voltage and the slope of the linear region of PDLC lens with narrow cell gap of 11 μm were drastically enhanced compared to those of the samples with 30 μm cell gap and the cooled and doped samples. These improvements were due to the increase of the applied electric field. However, the response time and contrast ratio were deteriorated. It seems that this deterioration was caused by the sticking or fixing of liquid crystal molecules in LC (liquid crystal) droplets by the intensive electric field applied to the PDLC device.

  17. Negative dispersion of birefringence of smectic liquid crystal-polymer composite: dependence on the constituent molecules and temperature.

    PubMed

    Yang, Seungbin; Lee, Hyojin; Lee, Ji-Hoon

    2015-02-01

    We investigated the dependence of the negative dispersion of birefringence of smectic liquid crystal-polymer composites on the constituent molecules and temperature. The dispersion of birefringence was significantly varied from positive dispersion to negative dispersion by the change of the relative fraction of the constituent monomers. For the temperature dependence of the dispersion, a composite with more fraction of monomers located at the inter-layer space showed a wider temperature range of the negative dispersion of birefringence.

  18. Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals

    SciTech Connect

    Fally, Martin; Ellabban, Mostafa A.; Drevensek-Olenik, Irena; Pranzas, Klaus P.; Vollbrandt, Juergen

    2006-10-20

    We report strong diffraction of cold neutrons from an only 30 {mu}m thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10{sup -6}, i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

  19. Collapse of homeotropic liquid-crystal alignment by increased molecular packing on comb-like polymer surfaces.

    PubMed

    Sohn, Eun-Ho; Kang, Hyo; Kim, Dong-Gyun; Song, Kigook; Lee, Jong-Chan

    2012-06-01

    We report an unusual alignment behavior of liquid crystals (LCs) on well-ordered comb-like poly(oxyethylene) surfaces. The homeotropic LC alignments that are observed on as-coated surfaces of the polymers are transformed to the random planar type after annealing treatment, even though the molecular structure of the polymer surface becomes more ordered and the surface energy decreases. Studies of the surface properties, such as molecular structure, morphology, and wettability, reveal that such an unexpected alteration of the LC alignment originates from the density of the alkyl side chains being enhanced by localized packing. PMID:22511283

  20. Holographic polymer dispersed liquid crystal system utilizing the co-polymerizations with siloxane compounds and polypropylene glycol derivatives

    NASA Astrophysics Data System (ADS)

    Takanokura, Tomoe; Kurashige, Makio; Ishida, Kazutoshi; Ohyagi, Yasuyuki; Watanabe, Masachika; Cho, Yeong Hee

    2011-03-01

    Holographic polymer dispersed liquid crystal (HPDLC) has a feature that can control diffraction of light by applying electric field. HPDLC can be used for optical elements such as an optical switch, or a polarized beam splitter etc. One of the reactive systems for making HPDLC is well known photopolymerization-induced phase separation (PIPS). The performance of HPDLC by PIPS is dependent on distribution of oriented liquid crystal (LC) molecules, or size and shape of LC droplets. These are controlled by chemical structure or functional group of polymer matrix. In this report, Organic-inorganic hybrid materials having sensitivity at 532 nm were synthesized. Polymer matrix was formed with co-polymerization of siloxane-containing materials and poly (propylene glycol) derivatives functionalized with methacrylate groups. Siloxane chain was introduced in polymer matrix to encourage phase separation of LC and stabilize grating structure. In addition, poly (propylene glycol) derivatives were designed to control polymerization rate and extent of phase separation of LC. The characterization of HPDLC was evaluated in terms of diffraction efficiency, contrast between diffraction and transparency modes by applying voltage, and switch speed. As a result, the separation ratio of p-polarized light and s-polarized light was 100:1. The value of ▵n was 0.075, and the index matching of both polymer-rich layer and LC-rich layer was completed at voltage of 17V/μm.

  1. The effect of fluorine-substituted monomers on the electrooptical and morphological properties of polymer-dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Schulte, Michael Dominic

    Polymer dispersed liquid crystals (PDLCs) with semi-fluorinated host matrices have been investigated. Films were formed by photopolymerization-induced phase separation using floodlit and holographic techniques from an initially isotropic solution of monomer and liquid crystal. The electro-optical and morphological properties that resulted from the systematic addition of fluorinated additives to a pentaacrylate-based prepolymer solution are reported. The rational for pursuing partially fluorinated systems is based on the hypothesis that these materials may decrease the chemical compatibility and liquid crystal (LC) interfacial anchoring strength, thereby improving electro-optical and morphological characteristics. Real-time transmittance monitoring and polarized optical microscopy (POM) revealed that the incorporation of additives generally resulted in a delay in the appearance of a LC phase with increasing additive concentration. This was due to an accompanying decrease in average system functionality. However, this delay was less pronounced as the degree of additive fluorination increased. This was interpreted as an indication of lower LC solubility in semi-fluorinated polymer matrices. An improvement in contrast ratio was observed with partial matrix fluorination while chemically-similar, non-fluorinated systems resulted in no appreciable change in contrast ratio and an increase in relaxation time. General increases in polymer network phase separation were observed using low-voltage, high-resolution scanning electron microscopy (SEM) in fluorinated floodlit and holographic films. Film morphologies ranged from highly interconnected, porous networks to spherical bead-like structures dispersed throughout a semi-continuous liquid crystal medium. In order to determine the effect of additive functionality and chemical structure on PDLC properties, difunctional additives were investigated. The synthesis and characterization of several novel fluorinated difunctional

  2. Fabrication of twisted nematic structure and vector grating cells by one-step exposure on photocrosslinkable polymer liquid crystals.

    PubMed

    Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2012-03-15

    We present a simple yet efficient method to automatically fabricate the twisted nematic structure by one-step exposure on an empty glass cell coated with photocrosslinkable polymer liquid crystal (PCLC) films. The resultant photoalignment directions of two substrates can be orthogonal to each other by controlling the difference between the exposure energy for upper and lower PCLC films and the twisted nematic (TN) structure can be automatically fabricated. The vector grating liquid crystalline cell with TN structure was also fabricated by means of a developed method, and the diffraction properties were well explained by the theoretical calculation on the basis of Jones calculus. PMID:22446243

  3. Coordinative nanoporous polymers synthesized with hydrogen-bonded columnar liquid crystals.

    PubMed

    Ishihara, Shinsuke; Furuki, Yusuke; Hill, Jonathan P; Ariga, Katsuhiko; Takeoka, Shinji

    2012-10-01

    In this paper, we report the development of nanoporous polymer which demonstrates the coordination property toward zinc porphyrin. A hydrogen-bonded columnar liquid crystalline precursor composed of a triphenylene template and three equivalent of the surrounding dendric amphiphile bearing a pyridyl head group and a polymerizable aliphatic chain, was covalently fixed by photopolymerization, and then the subsequent selective removal of the template successively resulted in a nanoporous polymer in which the pore wall is modified with pyridyl groups. The nanoporous polymer reflected the conformation of template, and displayed considerable coordination ability of the pyridyl groups towards zinc porphyrin. The coordinative nanoporous polymer is promising as a nano-scaled scaffold for the organization of dyes into functional supramolecular architectures.

  4. The existence region and composition of a polymer-induced liquid precursor phase for DL-glutamic acid crystals.

    PubMed

    Jiang, Yuan; Gower, Laurie; Volkmer, Dirk; Cölfen, Helmut

    2012-01-14

    The existence region of a polymer-induced liquid precursor (PILP) phase for crystals of an organic compound (DL-glutamic acid, Glu) was determined for the first time in the phase diagram of the Glu-polyethyleneimine-water-ethanol system. The existence region and the amount of PILP phase relative to the thermodynamically stable crystal phase were very small. Other phases detected in the phase diagram were coacervates, homogenous mixtures, and crystals obtained via a clear solution. The PILP phase is rich in the polymeric additive, which helps to explain the long induction period of PILP before crystallization occurs. Volume measurements indicated that its amount is <1 vol%, showing that this precursor phase is only a minor component.

  5. Microencapsulation effects on the electro-optical behavior of polymer cholesteric liquid crystal flakes

    NASA Astrophysics Data System (ADS)

    Cox, Gerald Philip

    A modeling method is introduced for predicting the effect of microencapsulation on the electro-optical behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid. The electric field acting on the flakes is significantly altered as various materials and boundary conditions are explored. The modeling predicts that test cells with multiple materials in the electric field path can have a wide range of electro-optic responses in AC electric fields. For DC drive conditions at high field strengths and test cell materials with low dielectric constants, electrophoretic behavior is observed for PCLC flakes. Prototype test cells for several encapsulation configurations are characterized for their resulting electro-optical behavior. The observed flake motions are in good agreement with the predicted results. This modeling method is shown to be a useful predictive tool for developing switchable particle devices utilizing microencapsulated dielectric particles in a host fluid medium. This work further builds on previous research on flake motion in a host fluid suspension, exploring flake doping effects, both internal and surface coated. Host fluids were also doped for increased conductivity and are explored for their effect on PCLC flake motion. A low dielectric property host fluid doped with an aqueous salt solution and a surfactant is found to enable Maxwell-Wagner reorientation in a DC electric field. In an AC electric field the doped host fluid is found to have dual-frequency response enabling a reverse drive for PCLC flakes. Below the turnover frequency, flakes align parallel to the electric field and above the turnover frequency the flakes align perpendicular.

  6. Liquid Crystal Devices.

    ERIC Educational Resources Information Center

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  7. Liquid Crystal Inquiries.

    ERIC Educational Resources Information Center

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

  8. Characterization of submillisecond response optical addressing phase modulator based on low light scattering polymer network liquid crystal

    SciTech Connect

    Xiangjie, Zhao E-mail: zxjdouble@gmail.com; Cangli, Liu; Jiazhu, Duan; Dayong, Zhang; Yongquan, Luo

    2015-01-07

    Optically addressed conventional nematic liquid crystal spatial light modulator has attracted wide research interests. But the slow response speed limited its further application. In this paper, polymer network liquid crystal (PNLC) was proposed to replace the conventional nematic liquid crystal to enhance the response time to the order of submillisecond. The maximum light scattering of the employed PNLC was suppressed to be less than 2% at 1.064 μm by optimizing polymerization conditions and selecting large viscosity liquid crystal as solvent. The occurrence of phase ripple phenomenon due to electron diffusion and drift in photoconductor was found to deteriorate the phase modulation effect of the optical addressed PNLC phase modulator. The wavelength effect and AC voltage frequency effect on the on state dynamic response of phase change was investigated by experimental methods. These effects were interpreted by electron diffusion and drift theory based on the assumption that free electron was inhomogeneously distributed in accordance with the writing beam intensity distribution along the incident direction. The experimental results indicated that the phase ripple could be suppressed by optimizing the wavelength of the writing beam and the driving AC voltage frequency when varying the writing beam intensity to generate phase change in 2π range. The modulation transfer function was also measured.

  9. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  10. Tunable liquid crystal lens array by encapsulation with a photo-reactive polymer for short focal length

    NASA Astrophysics Data System (ADS)

    Kim, Se-Um; Lee, Sanghun; Na, Jun-Hee; Lee, Sin-Doo

    2014-02-01

    We demonstrated an electrically tunable liquid crystal (LC) lens array with a short focal length by self-encapsulation with a polymer layer of photo-reactive mesogens (RMs). The underlying concept relies primarily on the encapsulation of the LC with a thin curvilinear polymer layer in contact with air for the reduction of the focal length. The polymer-encapsulated (PE)-LC lens array was produced on a patterned substrate by selective wetting inscription through the phase separation of the LC and the RMs. In the field-off state, the focal length of the PE-LC lens was measured to be about 3 mm which is shorter than a conventional case by a factor of three (about 9 mm). The wettability inscription by ultraviolet light enables to build up any size of the LC lens in array over large-area without using a wet-chemical etching process for flexible optoelectronic and photonic applications.

  11. Dielectric properties of liquid-crystal azomethine polymer with a side alkyl-substituted chain, doped with fullerene C60

    NASA Astrophysics Data System (ADS)

    Kovalev, D. S.; Kostromin, S. V.; Musteaţa, V.; Cozan, V.; Bronnikov, S. V.

    2016-04-01

    We studied the actual and imaginary components of the dielectric constant of liquid-crystal azomethine polymer with a side chain, doped with 0.5 wt % of fullerene C60, over a wide range of temperatures and frequencies; measurements were made by means of dielectric spectroscopy. By analyzing the frequency dependence of the dielectric constant, we detected the relaxation processes (α, β1, and β2) in the nanocomposite, corresponding to certain modes of molecular motion and described them by the Arrhenius equations (β1- and β2-processes) and the Vogel-Fulcher-Tamman equation (α-process). An antiplasticization effect is discovered after doping the polymer with fullerene C60, which manifests itself in increasing the glass transition temperature of the nanocomposite compared to this parameter typical of pure polymer.

  12. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  13. Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix.

    PubMed

    Yu, Ji Hoon; Chen, Hung-Shan; Chen, Po-Ju; Song, Ki Hoon; Noh, Seong Cheol; Lee, Jae Myeong; Ren, Hongwen; Lin, Yi-Hsin; Lee, Seung Hee

    2015-06-29

    Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast~5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality.

  14. An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes.

    PubMed

    Zong, Wen; Li, Gao-Wei; Cao, Jiang-Ming; Lei, Xinxiang; Hu, Mao-Lin; Sun, Han; Griesinger, Christian; Tan, Ren Xiang

    2016-03-01

    Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π-conjugated molecules. Moreover, sonication-induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement.

  15. Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix.

    PubMed

    Yu, Ji Hoon; Chen, Hung-Shan; Chen, Po-Ju; Song, Ki Hoon; Noh, Seong Cheol; Lee, Jae Myeong; Ren, Hongwen; Lin, Yi-Hsin; Lee, Seung Hee

    2015-06-29

    Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast~5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality. PMID:26191743

  16. Gel-like elasticity in glass-forming side-chain liquid-crystal polymers

    NASA Astrophysics Data System (ADS)

    Pozo, O.; Collin, D.; Finkelmann, H.; Rogez, D.; Martinoty, P.

    2009-09-01

    We study the complex shear modulus G of two side-chain liquid-crystal polymers (SCLCPs), a methoxy-phenylbenzoate substituted polyacrylate (thereafter called PAOCH3 ), and a cyanobiphenyl substituted polyacrylate supplied by Merck (thereafter called LCP105) using a piezoelectric rheometer. Two methods of filling the cell are used: (a) a capillary method, which can be used only at high temperature because of the low value of the viscosity, and (b) the classical one, thereafter called compression method, which consists in placing the sample between the two slides of the cell and to bring them closer. By filling the cell at high temperature either with the compression or the capillary method, we show that the response of both compounds is liquidlike ( G'˜f2 and G″˜f , where f is the frequency) for temperatures higher than a certain temperature T0 and gel-like (G'˜const,G″˜f) below T0 . This change in behavior from the conventional flow response to a gel-like response, when approaching the glass transition, is observed for nonsliding conditions and for very weak-imposed shear strains. It can be explained by a percolation-type mechanism of preglassy elastic clusters, which correspond to long-range and long-lived density fluctuations that are frozen at the time scale of the experiment. The sample response is therefore the sum of two contributions: one is due to the flow response of the polymer melt and the other to the elastic response of the network formed by the preglassy elastic clusters. By filling the cell below T0 with the compression method, both compounds exhibit a gel-type behavior by gently bringing closer the slides of the cell and an anomalous low-frequency behavior characterized by G'=const and G″=const by increasing the pressure used to bring closer the slides of the cell. A compression-assisted aggregation of the preglassy elastic clusters can explain both the increase in the low-frequency elastic plateau when the sample thickness is decreased

  17. Programmable and adaptive mechanics with liquid crystal polymer networks and elastomers

    NASA Astrophysics Data System (ADS)

    White, Timothy J.; Broer, Dirk J.

    2015-11-01

    Liquid crystals are the basis of a pervasive technology of the modern era. Yet, as the display market becomes commoditized, researchers in industry, government and academia are increasingly examining liquid crystalline materials in a variety of polymeric forms and discovering their fascinating and useful properties. In this Review, we detail the historical development of liquid crystalline polymeric materials, with emphasis on the thermally and photogenerated macroscale mechanical responses -- such as bending, twisting and buckling -- and on local-feature development (primarily related to topographical control). Within this framework, we elucidate the benefits of liquid crystallinity and contrast them with other stimuli-induced mechanical responses reported for other materials. We end with an outlook of existing challenges and near-term application opportunities.

  18. Programmable and adaptive mechanics with liquid crystal polymer networks and elastomers.

    PubMed

    White, Timothy J; Broer, Dirk J

    2015-11-01

    Liquid crystals are the basis of a pervasive technology of the modern era. Yet, as the display market becomes commoditized, researchers in industry, government and academia are increasingly examining liquid crystalline materials in a variety of polymeric forms and discovering their fascinating and useful properties. In this Review, we detail the historical development of liquid crystalline polymeric materials, with emphasis on the thermally and photogenerated macroscale mechanical responses--such as bending, twisting and buckling--and on local-feature development (primarily related to topographical control). Within this framework, we elucidate the benefits of liquid crystallinity and contrast them with other stimuli-induced mechanical responses reported for other materials. We end with an outlook of existing challenges and near-term application opportunities. PMID:26490216

  19. Dynamic, infrared bandpass filters prepared from polymer-stabilized cholesteric liquid crystals.

    PubMed

    Worth, Bradley; Lee, Kyung Min; Tondiglia, Vincent P; Myers, Joshua; Mou, Shin; White, Timothy J

    2016-09-01

    We report on the formulation and electrical control of the position and bandwidth of reflective bandpass filters prepared from cholesteric liquid crystal (CLC) in the infrared (3-5 μm). These filters are prepared from alignment cells employing infrared transparent electrodes and substrates. The optical nature of the electrodes is shown to strongly influence the resulting transmission of the bandpass filters outside of the spectral reflection. PMID:27607292

  20. Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light.

    PubMed

    Hadjichristov, Georgi B; Marinov, Yordan G; Petrov, Alexander G

    2011-06-01

    The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25 μm and droplet size up to 50 μm exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (λ=633 nm), an electrically commanded phase shift as large as π/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light. PMID:21629309

  1. A biosensor of high-density lipoprotein of human serum on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chang, Kai-Han; Chu, Wei-Lin; Tsou, Yu-Shih; Wu, Li-Ching; Li, Chien-Feng

    2013-10-01

    A biosensor for the concentration of high-density lipoprotein (HDL) in human serum on a liquid crystal and polymer composite film (LCPCF) is demonstrated. The sensing mechanism is based on a polar-polar interaction between orientation of LC directors and HDL in human serum. The concentration of polar HDL in human serum affects the orientations of LC directors at the interface between LCPCF and the human serum. In addition, the surface free energy of LCPCF changes with the applied voltage due to the electrically tunable orientations of LC directors anchored among the polymer grains of LCPCF. As a result, the droplet motion of human serum on LCPCF under applied voltages can sense the concentration of HDL in human serum.

  2. Platinum-scatterer-based random lasers from dye-doped polymer-dispersed liquid crystals in capillary tubes.

    PubMed

    Wang, Jianlong; Zhang, Yating; Cao, Mingxuan; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Zhang, Heng; Yao, Jianquan

    2016-07-20

    The resonance characteristics of platinum-scatter-based random lasers from dye-doped polymer-dispersed liquid crystals (DDPDLCs) in capillary tubes were researched for the first time, to the best of our knowledge. After adding platinum nanoparticles (Pt NPs) into the liquid crystal mixtures, the emission spectra of DDPDLCs revealed a lower lasing threshold in comparison with those of DDPDLCs without Pt NPs due to light scattering of liquid crystal droplets and the local field enhancement around Pt NPs. Furthermore, the full width at half-maximum (FWHM) and the lasing threshold were determined by the doping density of the Pt NPs. The threshold was decreased by about half from 17.5  μJ/pulse to 8.7  μJ/pulse on the condition that around 1.0 wt. % was the optimum concentration of Pt NPs doped into the DDPDLCs. The FWHM of the peaks sharply decreased to 0.1 nm. Our work provides an extremely simple method to enhance random lasers from DDPDLCs doped with Pt NPs, and it has potential applications in random fiber lasers or laser displays.

  3. Platinum-scatterer-based random lasers from dye-doped polymer-dispersed liquid crystals in capillary tubes.

    PubMed

    Wang, Jianlong; Zhang, Yating; Cao, Mingxuan; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Zhang, Heng; Yao, Jianquan

    2016-07-20

    The resonance characteristics of platinum-scatter-based random lasers from dye-doped polymer-dispersed liquid crystals (DDPDLCs) in capillary tubes were researched for the first time, to the best of our knowledge. After adding platinum nanoparticles (Pt NPs) into the liquid crystal mixtures, the emission spectra of DDPDLCs revealed a lower lasing threshold in comparison with those of DDPDLCs without Pt NPs due to light scattering of liquid crystal droplets and the local field enhancement around Pt NPs. Furthermore, the full width at half-maximum (FWHM) and the lasing threshold were determined by the doping density of the Pt NPs. The threshold was decreased by about half from 17.5  μJ/pulse to 8.7  μJ/pulse on the condition that around 1.0 wt. % was the optimum concentration of Pt NPs doped into the DDPDLCs. The FWHM of the peaks sharply decreased to 0.1 nm. Our work provides an extremely simple method to enhance random lasers from DDPDLCs doped with Pt NPs, and it has potential applications in random fiber lasers or laser displays. PMID:27463926

  4. Development of system level integration of compact RF components on multilayer liquid crystal polymer (LCP)

    NASA Astrophysics Data System (ADS)

    Chung, David

    The objective of this research is to optimize compactness for reconfigurable wireless communication systems by integrating Radio Frequency (RF) components on a multilayer Liquid Crystal Polymer (LCP) package while minimizing the size and interconnection of each component. To achieve this goal, various RF/microwave components have been integrated on LCP with the design, fabrication, and testing results to explore the feasibility of the designs for RF applications. The first chapter of this research focuses on the characterization of via interconnects for 3D system designs. As a crucial component for achieving compact multilayer designs, various transition designs are explored from DC to 110 GHz. In particular, High Density Interconnects (HDI) are investigated to achieve low loss performance at mm-wave frequencies. An example of accessing the input and output of a LCP packaged device using via interconnects is included. In addition, a heat sink using via technology is presented for active cooling of heat generating embedded devices. Chapters 3, 4, and 5 demonstrate the results of RF Micro-Electro-Mechanical Systems (MEMS) switches integrated on LCP to create compact reconfigurable devices. RF MEMS switches are essential for designing compact multi-functional devices. A pattern reconfigurable antenna with monolithically integrated RF MEMS switches is presented. In addition, a compact 3D phase shifter using RF MEMS switches for a 2 x 2 phased antenna array is also presented in this work. To create a phased antenna array that is more compatible with Integrated Circuits (IC), Lead Zirconate Titanate (PZT) RF MEMS switches are used to make a low voltage phase shifter. The actuation voltage is under 10 V, which is more easily achievable in a integrated system compared to commonly used electrostatic actuated RF MEMS switches that required at least 30 V. In Chapter 6, an expandable, low cost, and conformal multilayer phased antenna array is presented. Starting with a 4 x 8

  5. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  6. Large exponential gain coefficient in polymer assisted asymmetric liquid crystal cells originating from surface effect

    NASA Astrophysics Data System (ADS)

    Fu, Jiayin; Zhang, Jingwen; Xue, Tingyu; Zhao, Hua

    2016-09-01

    As large as 4607 cm-1 gain coefficient in two beam coupling experiment was obtained by introducing PVK:C60 film to ZnSe assisted liquid crystal system. As short as 5.0 ms holographic recording time was reached when probing the grating formation process, showing great potential in real time applications. Systematical two beam coupling and grating probing experiments were performed in studying the mechanism behind the high photorefractive (PR) performance. Unusual energy transfer direction change and gain coefficient fluctuation were observed when the voltage polarity and incidence side were altered in the related two wave coupling experiments.

  7. Effects of anisotropic diffractions on holographic polymer-dispersed liquid-crystal gratings.

    PubMed

    Ogiwara, Akifumi

    2011-02-01

    Volume gratings fabricated by interferometric exposure using composite materials composed of nematic liquid crystals (LC) and LC diacrylate monomers are discussed in the effects of diffraction properties on different grating formations, such as varying LC content ratios, film thicknesses, and the surface conditions composed of alignment layers and rubbing directions. Diffraction properties are experimentally investigated in the viewpoints of anisotropic diffraction and LC orientation. The polarization-azimuth dependence of diffraction efficiencies as functions of the incident polarization states shows the controllability of anisotropic diffractions based on the effects of different surface conditions. PMID:21283252

  8. Holographic binary grating liquid crystal cells fabricated by one-step exposure of photocrosslinkable polymer liquid crystalline alignment substrates to a polarization interference ultraviolet beam.

    PubMed

    Kawai, Kotaro; Sasaki, Tomoyuki; Noda, Kohei; Sakamoto, Moritsugu; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2015-07-01

    Holographic binary grating liquid crystal (LC) cells, in which the optical anisotropy was rectangularly modulated even as the grating was fabricated using holographic exposure, were fabricated by one-step polarization holographic exposure of an empty glass cell, the interior of which was coated with a photocrosslinkable polymer LC (PCLC). The present study is of great significance in that three types of holographic binary grating LC cells containing twisted alignments can be fabricated by simultaneous exposure of two PCLC substrates to the UV interference beams, which are sinusoidally modulated. The polarization conversion properties of the diffracted beams are explained well by theoretical analysis based on Jones calculus. PMID:26193145

  9. The effect of UV intensities and curing time on polymer dispersed liquid crystal (PDLC) display: A detailed analysis study

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, Muhammad; Lee, Jin Woo; Kim, Seo Rok; Jeon, Young Jae

    2016-08-01

    In current study polymer dispersed liquid crystal (PDLC) films whose composition based on nematic liquid crystal (LC) E7 and prepolymeric NOA65 were formed via the photo induced phase separation method, in a wide intensity range of the UV light (I = 0.33-1.8 mW/cm2) and curing duration (t = 120-600 sec). The PDLC characteristics were monitored by surface morphology, electro optical studies, as well as by phase separation process through measuring the FTIR absorption of the composite layers. Increase of curing light intensity accelerates the phase separation and drastically influences the final morphology of LC droplets inside PDLCs. Likewise by widening the curing duration the enhancement in phase separation was observed. Increase of light intensity from 0.89 mW/cm2 and duration t = 120-240 sec resulted into transition from large LC domains of irregular shape (due to aggregation of droplets) to fine mono dispersed LC droplets. This morphology caused increase in optical scattering on zero voltage and high driving voltage. However unexpectedly, this response was not directly related with the curing conditions (intensity and time). These findings extend the potential applications of thiol-ene based PDLCs. [Figure not available: see fulltext.

  10. The effect of UV intensities and curing time on polymer dispersed liquid crystal (PDLC) display: A detailed analysis study

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, Muhammad; Lee, Jin Woo; Kim, Seo Rok; Jeon, Young Jae

    2016-09-01

    In current study polymer dispersed liquid crystal (PDLC) films whose composition based on nematic liquid crystal (LC) E7 and prepolymeric NOA65 were formed via the photo induced phase separation method, in a wide intensity range of the UV light ( I = 0.33-1.8 mW/cm2) and curing duration ( t = 120-600 sec). The PDLC characteristics were monitored by surface morphology, electro optical studies, as well as by phase separation process through measuring the FTIR absorption of the composite layers. Increase of curing light intensity accelerates the phase separation and drastically influences the final morphology of LC droplets inside PDLCs. Likewise by widening the curing duration the enhancement in phase separation was observed. Increase of light intensity from 0.89 mW/cm2 and duration t = 120-240 sec resulted into transition from large LC domains of irregular shape (due to aggregation of droplets) to fine mono dispersed LC droplets. This morphology caused increase in optical scattering on zero voltage and high driving voltage. However unexpectedly, this response was not directly related with the curing conditions (intensity and time). These findings extend the potential applications of thiol-ene based PDLCs.

  11. In vivo silicon-based flexible radio frequency integrated circuits monolithically encapsulated with biocompatible liquid crystal polymers.

    PubMed

    Hwang, Geon-Tae; Im, Donggu; Lee, Sung Eun; Lee, Jooseok; Koo, Min; Park, So Young; Kim, Seungjun; Yang, Kyounghoon; Kim, Sung June; Lee, Kwyro; Lee, Keon Jae

    2013-05-28

    Biointegrated electronics have been investigated for various healthcare applications which can introduce biomedical systems into the human body. Silicon-based semiconductors perform significant roles of nerve stimulation, signal analysis, and wireless communication in implantable electronics. However, the current large-scale integration (LSI) chips have limitations in in vivo devices due to their rigid and bulky properties. This paper describes in vivo ultrathin silicon-based liquid crystal polymer (LCP) monolithically encapsulated flexible radio frequency integrated circuits (RFICs) for medical wireless communication. The mechanical stability of the LCP encapsulation is supported by finite element analysis simulation. In vivo electrical reliability and bioaffinity of the LCP monoencapsulated RFIC devices are confirmed in rats. In vitro accelerated soak tests are performed with Arrhenius method to estimate the lifetime of LCP monoencapsulated RFICs in a live body. The work could provide an approach to flexible LSI in biointegrated electronics such as an artificial retina and wireless body sensor networks.

  12. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Gao, Hong-Yue; Liu, Pan; Zeng, Chao; Yao, Qiu-Xiang; Zheng, Zhiqiang; Liu, Jicheng; Zheng, Huadong; Yu, Ying-Jie; Zeng, Zhen-Xiang; Sun, Tao

    2016-09-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474194, 11004037, and 61101176) and the Natural Science Foundation of Shanghai, China (Grant No. 14ZR1415500).

  13. Electro-Optical Behavior of Polymer Cholesteric Liquid Crystal FLake/Fluid Suspensions in a Microencapsulation Matrix

    SciTech Connect

    Marshall, K.L.; Kimball, E.; McNamara, S.; Kosc, T.Z.; Trajkovska-Petkoska, A.; Jacobs, S.D.

    2004-10-25

    When flakes of polymer cholesteric liquid crystals (PCLC's) are dispersed in a fluid host and subjected to an applied electric field, their bright, polarization-selective reflection color is extinguished as they undergo field-induced rotation. Maxwell-Wagner (interfacial) polarization is the underlying physical mechanism for flake motion and results from the large difference in dielectric properties of the flake and fluid hosts. Flake reorientation times can be as short as 300 ms to 400 ms at exceedingly low driving fields (10 to 100 mVrms/um) and are dependent on flake size and shape, fluid host dielectric constant and viscosity, and drive-field frequency and magnitude. These attributes make this new materials system of special interest in electro-optical and photonics applications, where reflective-mode operation, polarization selectivity, and low power consumption are of critical importance (e.g., reflective displays).

  14. Current trends in studies on reverse-mode polymer dispersed liquid-crystal films — A review

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, M.; Jeon, Y. J.

    2014-07-01

    Reverse-mode polymer dispersed liquid crystals (PDLCs) comprise an important new class of materials for optical device applications. Generally reverse-mode PDLCs are transparent and opaque in the absence and presence of an external field, respectively. Display devices based on reverse-mode PDLC technology are useful for large-area displays; because their fabrication for manufacturing shutters is considered to be easier and faster, they are also employed for automotive technology and smart windows. These devices can be operated at a low voltage, which conserves energy in intelligent-device applications. This work presents a comprehensive review of past research regarding reverse-mode PDLCs and includes the advantageous features, applications, and various fabrication methods of reverse-mode PDLCs and photo-chromic reverse-mode PDLCs. In addition, some new features of this technology that have recently been reported and future investigations by a variety of research groups are presented.

  15. Threshold improvement in uniformly lying helix cholesteric liquid crystal laser using auxiliary π-conjugated polymer active layer

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroyuki; Shiozaki, Yusuke; Inoue, Yo; Takahashi, Masaya; Ogawa, Yasuhiro; Fujii, Akihiko; Ozaki, Masanori

    2013-05-01

    We propose a device structure to lower the lasing threshold of a uniformly lying helix cholesteric liquid crystal (ChLC) laser. We place a π-conjugated polymer active layer beneath the ChLC layer to provide auxiliary gain, and demonstrate an improvement in the lasing threshold by a factor of 2.3. We also perform finite difference time domain calculations coupled with rate equations for a four-level system, and clarify the effect of the additional active layer on both the photonic density of states and the inversion population density. Although the addition of an extra layer lowers the photonic density of states, the gain provided by the auxiliary layer is sufficient to overcome the losses and decrease the lasing threshold. Our concept is useful for obtaining high-performance ChLC lasers.

  16. Sensor for monitoring the vibration of a laser beam based on holographic polymer dispersed liquid crystal films.

    PubMed

    Li, Ming Shian; Wu, Shing Trong; Fuh, Andy Ying-Guey

    2010-12-01

    A continuous multiple exposure diffraction grating (CMEDG) is fabricated holographically on polymer dispersed liquid crystal (PDLC) films using two-beam interference with multiple exposures. The grating is fabricated by exposing a PDLC film to 18 repeated exposure/non-exposure cycles with an angular step of ~10°/10° while it revolves a circle on a rotation stage. The structure of the sample thus formed is analyzed using a scanning electron microscope (SEM) and shows arc-ripples around the center. From the diffraction patterns of the formed grating obtained using a normally incident laser beam, some or all of the 18 recorded arc beams can be reconstructed, as determined by the probing location. Thus, it can be applied for use as a beam-vibration sensor for a laser.

  17. Gas flow-field induced director alignment in polymer dispersed liquid crystal microdroplets deposited on a glass substrate

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on glass substrates by the processes of polymerization and solvent evaporation induced phase separation. The electron and the optical polarization microscopies of the films reveal that PDLC microdroplets formed during the process of phase separation near the top surface of the film remain exposed and respond to shear stress due to air or gas flow on the surface. Optical response of the film to an air flow-induced shear stress input on the free surface has been measured. Director orientation in the droplets changes with the applied shear stress leading to time varying transmitted light intensity. Director dynamics of the droplet for an applied step shear stress has been discussed from free energy considerations. Results on the measurement of light transmission as a function of the gas flow parameter unambiguously demonstrate the potential of these systems for use as boundary layer and gas flow sensors.

  18. Sensor for monitoring the vibration of a laser beam based on holographic polymer dispersed liquid crystal films.

    PubMed

    Li, Ming Shian; Wu, Shing Trong; Fuh, Andy Ying-Guey

    2010-12-01

    A continuous multiple exposure diffraction grating (CMEDG) is fabricated holographically on polymer dispersed liquid crystal (PDLC) films using two-beam interference with multiple exposures. The grating is fabricated by exposing a PDLC film to 18 repeated exposure/non-exposure cycles with an angular step of ~10°/10° while it revolves a circle on a rotation stage. The structure of the sample thus formed is analyzed using a scanning electron microscope (SEM) and shows arc-ripples around the center. From the diffraction patterns of the formed grating obtained using a normally incident laser beam, some or all of the 18 recorded arc beams can be reconstructed, as determined by the probing location. Thus, it can be applied for use as a beam-vibration sensor for a laser. PMID:21164979

  19. Formation of holographic polymer-dispersed liquid crystal memory by angle-multiplexing recording for optically reconfigurable gate arrays.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru

    2015-12-20

    Formation of holographic polymer-dispersed liquid crystal (HPDLC) memory for an optically reconfigurable gate array is discussed for angle-multiplexing recording by controlling the laser interference exposure in LC composites. The successive laser illumination system to record the various configuration contexts at the specified region and angle in HPDLC memory is constructed by using the combination of a half-mirror and a photomask placed on the motorized stages under the control of a personal computer. The effect of laser exposure energy on the formation of holographic memory is investigated by measuring diffraction intensity as a function of exposure energy during the grating formation process and observing the internal grating structure by scanning electron microscopy. The optical reconfiguration in the gate-array VLSI is executed for configuration contexts of OR and NOR operations shown as logical operators that are reconstructed by laser irradiation at different incident angles for a specified region in the HPDLC memory. PMID:26837028

  20. Liquid crystals for functional nanomaterials: Electroclinic artificial muscle polymers, nanorods from achiral bent-core mesogens, and thiophenic photovoltaics

    NASA Astrophysics Data System (ADS)

    Richardson, Jacqueline Mae

    Three different projects are described, in which target molecules are synthesized based on specific functional goals: electromechanical response, bent-core phase formation, and charge transport behavior. The bulk properties of these materials are then characterized with respect to these goals. The first project entails the synthesis and characterization of several variations on W317, a calamitic liquid crystal with a strong electroclinic effect. alpha,o-diene analogues of this molecule were synthesized and reacted via ADMET into a main-chain polymer, with the goal of creating electromechanical actuators. To improve the bulk strength and macroscopic response of the polymers, attempts were made at cross-linking, including co-polymerization with a unit containing pendant cinnamate groups, or by mixing with a compound containing two benzophenone units linked by a tether. An analogue of W317 containing a thiol at one end and an alkene at the other was synthesized and polymerized in-cell by UV light. In the second project, several homologues of W513 were synthesized and characterized. W513 is known to be an extremely rare example of a bent-core molecule that exhibits the B4 phase, yet does not contain a Schiff base. Seven n-alkyl-tailed homologues were synthesized and all of them exhibit the B4 phase, but interestingly, their behavior and stability in other bent-core phases (particularly the B1) varied widely. In addition, two perfluoroether-tailed versions and an alpha-methyl branched alkyl-tailed version were synthesized, none of which exhibited any bent-core phases. The third project involved the synthesis of a library of materials for use as liquid crystal organic photovoltaics. This library consisted of oligothiophenes containing between three and six rings joined at the alpha positions, with two terminal tails consisting of either alkoxymethyl groups or perfluoroetheroxymethyl groups. Investigations are still ongoing regarding charge-transport behavior in these

  1. Erasable thin-film optical diode based on a photoresponsive liquid crystal polymer.

    PubMed

    Zhang, Xinping; Zhang, Jian; Sun, Yujian; Yang, Huai; Yu, Haifeng

    2014-04-01

    We report a thin-film optical diode written into thin films of a liquid-crystalline polymer (LCP), which is based on the photoinduced LC-to-isotropic phase transition of LCPs. The interference pattern between a collimated and a focused UV laser beam is imprinted as chirped volume-phase gratings in photoresponsive LCP films and no further processing steps like development or liftoff are required for the fabrication. The resultant thin-film device not only possesses the fundamental functions of an optical lens for laser beam focusing, but also shows diode effects with the focusing/defocusing function dependent on the direction of light incidence and orientation of the device. Furthermore, this photonic thin-film lens exhibits a spatially tunable spectroscopic response, revealing a unique physics of secondary excitations of resonance modes of the single-layer LCP waveguide grating structures. This reveals the mechanisms for the focusing/defocusing of laser beams by chirped grating structures. Erasability and reconstructibility of the photoresponsive LCPs guarantee rewritability of the thin-film diode lens. PMID:24584886

  2. Liquid Crystals in Tribology

    PubMed Central

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-01-01

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered. PMID:19865534

  3. New theories for smectic and nematic liquid-crystal polymers: Backbone LCPs (liquid crystalline polymers) and their mixtures and side-chain LCPs

    SciTech Connect

    Dowell, F.

    1987-01-01

    A summary of predictions and explanations from statistical-physics theories for both backbone and side-chain liquid crystalline polymers (LCPs) and for mixtures with backbone LCPs are presented. Trends in the thermodynamic and molecular ordering properties have been calculated as a function of pressure, density, temperature, and molecule chemical structures (including degree of polymerization and the following properties of the chemical structures of the repeat units: lengths and shapes, intra-chain rotation energies, dipole moments, site-site polarizabilities and Lennard-Jones potentials, etc.) in nematic and multiple smectic-A LC phases and in the isotropic liquid phase. The theoretical results are found to be in good agreement with existing experimental data. These theories can also be applied to combined LCPs. Since these theories have no ad hoc or arbitrarily adjustable parameters, these theories can be used to design new LCPs and new solvents as well as to predict and explain properties. 27 refs., 4 tabs.

  4. Power generating reflective-type liquid crystal displays using a reflective polariser and a polymer solar cell.

    PubMed

    Ho Huh, Yoon; Park, Byoungchoo

    2015-06-23

    We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD. The PSC consisted of a polymer bulk-heterojunction photovoltaic (PV) layer of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] and [6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PCBM70), and showed a high power conversion efficiency of about 5%. In order to improve the visibility of the Solar-LCD, between the TN-LC and the PV cells we inserted a reflective polariser of a giant birefringent optical (GBO) film. The reflectivity from the Solar-LCD was observed to be considerably increased by more than 13-15% under illumination by visible light. The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19. We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

  5. Power generating reflective-type liquid crystal displays using a reflective polariser and a polymer solar cell

    PubMed Central

    Ho Huh, Yoon; Park, Byoungchoo

    2015-01-01

    We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD. The PSC consisted of a polymer bulk-heterojunction photovoltaic (PV) layer of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] and [6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PCBM70), and showed a high power conversion efficiency of about 5%. In order to improve the visibility of the Solar-LCD, between the TN-LC and the PV cells we inserted a reflective polariser of a giant birefringent optical (GBO) film. The reflectivity from the Solar-LCD was observed to be considerably increased by more than 13–15% under illumination by visible light. The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17–19. We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices. PMID:26101099

  6. Power generating reflective-type liquid crystal displays using a reflective polariser and a polymer solar cell

    NASA Astrophysics Data System (ADS)

    Ho Huh, Yoon; Park, Byoungchoo

    2015-06-01

    We herein report the results of a study of a power generating reflective-type liquid crystal display (LCD), composed of a 90° twisted nematic (TN) LC cell attached to the top of a light-absorbing polymer solar cell (PSC), i.e., a Solar-LCD. The PSC consisted of a polymer bulk-heterojunction photovoltaic (PV) layer of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] and [6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PCBM70), and showed a high power conversion efficiency of about 5%. In order to improve the visibility of the Solar-LCD, between the TN-LC and the PV cells we inserted a reflective polariser of a giant birefringent optical (GBO) film. The reflectivity from the Solar-LCD was observed to be considerably increased by more than 13-15% under illumination by visible light. The Solar-LCD also exhibited a significantly improved contrast ratio of more than 17-19. We believe there is a clear case for using such Solar-LCDs in new power-generating reflective-type displays; taken as a whole these results also demonstrate the possibility of their application in a number of energy-harvesting opto-electrical display devices.

  7. Effects of multi-context information recorded at different regions in holographic polymer-dispersed liquid crystal on optical reconfiguration

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Watanabe, Minoru

    2016-08-01

    A holographic polymer-dispersed liquid crystal (HPDLC) memory to record multi-context information for an optically reconfigurable gate array is formed by constructing a laser illumination system to implement successive laser exposures at different small regions in a glass cell filled with LC composites. The context pattern arrangements for circuit information are designed in a 3 × 3 in.2 photomask by electron beam lithography, and they are recorded as laser interference patterns at nine regions separated in an HPDLC sample by a laser interferometer composed of movable pinhole and photomask plates placed on motorized stages. The multi-context information reconstructed from the different regions in the HPDLC is written to a photodiode array in a gate-array VLSI by switching only the position of laser irradiation using the displacement of the pinhole plate under the control of a personal computer (PC). The effects of multi-context information recorded at different regions in the HPDLC on optical reconfiguration are discussed in terms of the optical system composed of ORGA VLSI and HPDLC memory. The internal structures in the HPDLC memory formed by multi-context recording are investigated by scanning electron microscopy (SEM) observation, and the configurations composed of LC and polymer phases are revealed at various regions in the HPDLC memory.

  8. Fast response liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Wu, Yung-Hsun

    Liquid crystal (LC) has been widely used for displays, spatial light modulators, variable optical attenuators (VOAs) and other tunable photonic devices. The response time of these devices is mainly determined by the employed liquid crystal material. The response time of a LC device depends on the visco-elastic coefficient (gamma1/K11), LC cell gap (d), and applied voltage. Hence, low visco-elastic coefficient LC materials and thinner cell gap are favorable for reducing the response time. However, low visco-elastic coefficient LCs are usually associated with a low birefringence because of shorter molecular conjugation. For display applications, such as LCD TVs, low birefringence (Deltan<0.1) LCs are commonly used. However, for optical communications at 1550 nm, low birefringence requires to a thick cell gap which, in turn, increases the response time. How to obtain fast response for the LC devices is a fundamentally important and technically challenging task. In this dissertation, we investigate several methods to improve liquid crystal response time, for examples, using dual-frequency liquid crystals, polymer stabilized liquid crystals, and sheared polymer network liquid crystals. We discover a new class of material, denoted as sheared polymer network liquid crystal (SPNLC) which exhibits a submillisecond response time. Moreover, this response time is insensitive to the LC cell gap. This is the first LC device exhibiting such an interesting property. Chapters 1 and 2 describe the motivation and background of this dissertation. From chapter 3 to chapter 6, dual-frequency liquid crystals and polymer network methods are demonstrated as examples for the variable optical attenuators. Variable optical attenuator (VOA) is a key component in optical communications. Especially, the sheared PNLC VOA shows the best result; its dynamic range reaches 43 dB while the response time is in the submillisecond range at 1550 nm wavelength, which is 50 times faster than the commercial

  9. Liquid Crystal Optofluidics

    SciTech Connect

    Vasdekis, Andreas E.; Cuennet, J. G.; Psaltis, D.

    2012-10-11

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  10. Hierarchical assemblies of soft matters from polymers and liquid crystals on structured surfaces

    NASA Astrophysics Data System (ADS)

    Honglawan, Apiradee

    Hierarchical, multifunctional materials hold important keys to numerous advanced technologies, including electronics, optics, and medicine. This thesis encompasses generation of hierarchical structures with novel morphologies and functions through self-assembly directed by lithographically fabricated templates. Here, two soft materials, amphiphilic random copolymers of photopolymerized acryloyl chloride (ranPAC) and smectic-A liquid crystal (SmA-LC) molecule, 4'(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-heptadecaflu-orododecyloxy)-biphenyl-4-carboxylic acid ethyl ester, are synthesized as model systems to investigate the governing principles at the topographic surface/interface. The ranPAC can self-organize into nanomicelles with high regularity and stability, typically not possible in random copolymer systems. The morphology can be controlled by the photopolymerization conditions and solvent; the crosslinked shell makes the micelles robust against drying and storage. Using SU-8 micropillar arrays with spatially controlled surface chemistry as templates, we construct hierarchical microporous structures with tunable pore size and symmetry (e.g. square array), and uncover a new evaporative assembly method. By functionalizing the ranPAC nanovesicles with cationic poly(ethyleneimines), we encapsulate the anticancer drug, doxorubicin hydrochloride, and mRNA at a high payload, which are delivered to HEK 293T cells in vitro at a low cytotoxicity level. SmA-LC are characterized by arrangement of molecules into thin layers with the long molecular axis parallel to the layer normal, forming a close-packed hexagonal array of topological defects known as focal conic domains (FCDs) in a thin film. Using a series of SU-8 micropillar arrays with different size, shape, height, and symmetry as topological templates, we investigate the epitaxial and hierarchical assemblies of FCDs; whether the system favors confinement or "pillar edge-pinning" depends on balance of the elastic energy

  11. Ordered structures in proton conducting membranes from supramolecular liquid crystal polymers.

    PubMed

    Every, Hayley A; Mendes, Eduardo; Picken, Stephen J

    2006-11-30

    Highly sulfonated forms of poly(p-phenylene terephthalamide) (PPTA) have been prepared in three different molecular configurations; sulfonated diamine form (S-PPTA), sulfonated terephthalic acid form (S-invert-PPTA), and the bi-sulfonated form (S2-PPTA). All three polymers are water soluble to a certain degree and films were cast from solution for S-PPTA and S-invert-PPTA. S-PPTA films absorb less water than S-invert-PPTA (under controlled humidity conditions) and consequently, the conductivity for this polymer is also slightly lower. Although the conductivities are comparable to Nafion (of the order of 10(-2) to 10(-1) Scm(-1)), proton mobility is more restricted. X-ray diffraction showed that the rigid molecules are aligned in opposite directions for the two polymer films, being homeotropic in S-PPTA films and planar for S-invert-PPTA. SEM analysis demonstrated layering in the same direction as the alignment of the polymer chains. The variation in the polymer alignment is most likely the result of the differences in the solution properties and the film forming process. It is possible, however, that this alignment could be exploited to enhance proton transport and thus these films are of interest for fuel cell membranes. PMID:17125333

  12. Hard-sphere-chain Equations of State for Lyotropic Polymer LiquidCrystals

    SciTech Connect

    Hino, T.; Prausnitz, John M.

    1998-06-01

    Using Parsons-type scaling, the Onsager theory for theisotropic-nematic (I-N) transition of rigid-rod lyotropic polymer liquidcrystals is combined with the equation of state for hard-sphere-chainfluids of Chapman et al. and that of Hu et al. The equation of Hu et al.gives the I-N transition pressure and density in good agreement withcomputer simulation by Wilson and Allen for a semi-flexible hard-spherechain consisting of seven segments. For real semi-flexible polymers, wefollow the Khokhlov-Semenov theory of persistent chains that introduceschain flexibility into the Onsager theory. Using a consistent procedureto regress the equation-of-state parameters, the equations of Chapman etal. and Hu et al. are also compared with the theory of DuPre and Yangthat uses the equation of Lee for hard spherocylinders. These models arecompared with experiment for two binary polymer solutions containingpoly(hexyl isocyanate) and another solution containing polysaccharideschizophyllan. The concentration of polymer at the I-N transition ispredicted as a function of the molecular weight of polymer. All modelsperform similarly and show semi-quantitative agreement withexperiment.

  13. Incorporation of carbon nanotubes into a lyotropic liquid crystal by phase separation in the presence of a hydrophilic polymer.

    PubMed

    Xin, Xia; Li, Hongguang; Wieczorek, Stefan A; Szymborski, Tomasz; Kalwarczyk, Ewelina; Ziebacz, Natalia; Gorecka, Ewa; Pociecha, Damian; Hołyst, Robert

    2010-03-01

    Single-walled carbon nanotubes (SWNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl octaoxyethene monoether (C(12)E(6)) at room temperature through spontaneous phase separation induced by nonionic hydrophilic polymer poly(ethylene glycol) (PEG). The quality of SWNTs/LLC composite was evaluated by polarized microscopy observations and small-angle X-ray scattering (SAXS) measurements. The results obtained clearly indicated that SWNTs have been successfully incorporated into the LLC matrix up to a considerable high content without destroying the LLC matrix, although interesting changes of the LLC matrix were also induced by SWNTs incorporation. By varying the ratio of PEG to C(12)E(6), the type of LLC matrix can be controlled from hexagonal phase to lamellar phase. Temperature was found to have a significant influence on the quality of SWNTs/LLC composite, and tube aggregation can be induced at higher temperature. When SWNTs were changed to multiwalled carbon nanotubes (MWNTs), they became difficult to be incorporated into LLC matrix because of an increase in the average tube diameter.

  14. Photoalignment control: self-focusing effect in hybrid- and homeotropic-aligned dye-doped polymer-stabilized liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, J.; Shishido, A.

    2015-09-01

    Nonlinear optics has drawn much attention for its great potential in applications, such as frequency conversion, multiple-photon absorption, self-focusing, and so on. However, such optical nonlinearities are generally observed at very high light intensities. In this study, we designed hybrid-aligned dye-doped polymer-stabilized liquid crystals (PSLC), in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. In such film, the threshold intensity required to form self-focusing effect was markedly reduced by a factor of 8.5 compared to that in a conventional homeotropic cell, which enabled the generation of the self-focusing effect using a handheld 1-mW laser pointer. In addition, we investigated the structural effect of dye molecules: azo-dye methyl red (MR, photoisomerizable)-doped PSLC was prepared and its NLO response was evaluated. It turned out that such MR-based LC system was not effective for self-focusing effect compared to oligothiophene-doped systems.

  15. Polarization independent Fabry-Pérot filter based on polymer-stabilized blue phase liquid crystals with fast response time.

    PubMed

    Chen, Yan-Han; Wang, Chun-Ta; Yu, Chin-Ping; Lin, Tsung-Hsien

    2011-12-01

    This work demonstrates a polarization-independent electrically tunable Fabry-Pérot (FP) filter that is based on polymer-stabilized blue phase liquid crystals (PSBPLCs). An external vertical electric field can be applied to modulate the effective refractive index of the PSBPLCs along the optical axis. Therefore, the wavelength-tuning property of the FP filter is completely independent of the polarization state of the incident light. The change in the birefringence in PSBPLCs is governed by Kerr effect-induced isotropic-to-anisotropic transition, and so the PSBPLCs based FP filter has a short response time. The measured tunability and free spectral range of the FP filter are 0.092 nm/ V and 16nm in the visible region, and 0.12nm/ V and 97nm in the NIR region, respectively, and the response time is in sub-millisecond range. The fast-responding polarization-independent electrically tunable FP filter has substantial potential for practical applications.

  16. NIR-Vis-UV Light-Responsive Actuator Films of Polymer-Dispersed Liquid Crystal/Graphene Oxide Nanocomposites.

    PubMed

    Cheng, Zhangxiang; Wang, Tianjie; Li, Xiao; Zhang, Yihe; Yu, Haifeng

    2015-12-16

    To take full advantage of sunlight for photomechanical materials, NIR-vis-UV light-responsive actuator films of polymer-dispersed liquid crystal (PDLC)/graphene oxide (GO) nanocomposites were fabricated. The strategy is based on phase transition of LCs from nematic to isotropic phase induced by combination of photochemical and photothermal processes in the PDLC/GO nanocomposites. Upon mechanical stretching of the film, both topological shape change and mesogenic alignment occurred in the separated LC domains, enabling the film to respond to NIR-vis-UV light. The homodispersed GO flakes act as photoabsorbent and nanoscale heat source to transfer NIR or VIS light into thermal energy, heating the film and photothermally inducing phase transition of LC microdomains. By utilizing photochemical phase transition of LCs upon UV-light irradiation, one azobenzene dye was incorporated into the LC domains, endowing the nanocomposite films with UV-responsive property. Moreover, the light-responsive behaviors can be well-controlled by adjusting the elongation ratio upon mechanical treatment. The NIR-vis-UV light-responsive PDLC/GO nanocomposite films exhibit excellent properties of easy fabrication, low-cost, and good film-forming and mechanical features, promising their numerous applications in the field of soft actuators and optomechanical systems driven directly by sunlight.

  17. Bichromatic coherent random lasing from dye-doped polymer stabilized blue phase liquid crystals controlled by pump light polarization

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Wang, Meng; Yang, Mingchao; Shi, Li-Jie; Deng, Luogen; Yang, Huai

    2016-09-01

    In this paper, we investigate the bichromatic coherent random lasing actions from the dye-doped polymer stabilized blue phase liquid crystals. Two groups of lasing peaks, of which the full widith at half maximum is about 0.3 nm, are clearly observed. The shorter- and longer-wavelength modes are associated with the excitation of the single laser dye (DCM) monomers and dimers respectively. The experimental results show that the competition between the two groups of the lasing peaks can be controlled by varying the polarization of the pump light. When the polarization of the pump light is rotated from 0° to 90°, the intensity of the shorter-wavelength lasing peak group reduces while the intensity of the longer-wavelength lasing peak group increases. In addition, a red shift of the longer-wavelength modes is also observed and the physical mechanisms behind the red-shift phenomenon are discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474021 and 51333001), the Key Program for International S&T Cooperation Projects of China (Grant No. 2013DFB50340), the Issues of Priority Development Areas of the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120001130005), and the Key (Key Grant) Project of Chinese Ministry of Education (Grant No. 313002).

  18. Bichromatic coherent random lasing from dye-doped polymer stabilized blue phase liquid crystals controlled by pump light polarization

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Wang, Meng; Yang, Mingchao; Shi, Li-Jie; Deng, Luogen; Yang, Huai

    2016-09-01

    In this paper, we investigate the bichromatic coherent random lasing actions from the dye-doped polymer stabilized blue phase liquid crystals. Two groups of lasing peaks, of which the full widith at half maximum is about 0.3 nm, are clearly observed. The shorter- and longer-wavelength modes are associated with the excitation of the single laser dye (DCM) monomers and dimers respectively. The experimental results show that the competition between the two groups of the lasing peaks can be controlled by varying the polarization of the pump light. When the polarization of the pump light is rotated from 0° to 90°, the intensity of the shorter-wavelength lasing peak group reduces while the intensity of the longer-wavelength lasing peak group increases. In addition, a red shift of the longer-wavelength modes is also observed and the physical mechanisms behind the red-shift phenomenon are discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474021 and 51333001), the Key Program for International S&T Cooperation Projects of China (Grant No. 2013DFB50340), the Issues of Priority Development Areas of the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120001130005), and the Key (Key Grant) Project of Chinese Ministry of Education (Grant No. 313002).

  19. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Gao, Hong-Yue; Liu, Pan; Zeng, Chao; Yao, Qiu-Xiang; Zheng, Zhiqiang; Liu, Jicheng; Zheng, Huadong; Yu, Ying-Jie; Zeng, Zhen-Xiang; Sun, Tao

    2016-09-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474194, 11004037, and 61101176) and the Natural Science Foundation of Shanghai, China (Grant No. 14ZR1415500).

  20. Effects of monomer functionality on performances of scaffolding morphologic transmission gratings recorded in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Pu, Donglin; Shen, Su; Wei, Guojun; Xuan, Li; Chen, Linsen

    2015-09-01

    The effects of monomer functionality on performances of holographic polymer dispersed liquid crystal (HPDLC) transmission gratings are systematically investigated. Acrylate monomers with an average functionality ranging from 2.0 to 5.0 are used to prepare these samples. We find scaffolding morphologic transmission gratings (characterized by a high phase separation degree, a well alignment of LCs and low scattering loss) can be obtained irrespective of the monomer functionality, although the exact optimal curing intensity varies. The temporal evolution of the grating formation is studied and the onset time of the LC phase separation decreases significantly with the increase in average monomer functionality. It is also shown that the gratings prepared from low average functionality monomers require a comparatively low switch-off electric field (~8 V μm-1) whilst suffering from mechanical fragility and long-term instability. Our results not only provide a complete understanding of scaffolding morphologic gratings in terms of the material composition effect, but also provide insight into the formation mechanisms of non-droplet morphologic HPDLC gratings.

  1. Photovoltaic properties and morphology of organic solar cells based on liquid-crystal semiconducting polymer with additive

    SciTech Connect

    Suzuki, Atsushi; Zushi, Masahito; Suzuki, Hisato; Ogahara, Shinichi; Akiyama, Tsuyoshi; Oku, Takeo

    2014-02-20

    Bulk heterojunction organic solar cell based on liquid crystal semiconducting polymers of poly[9,9-dioctylfluorene-co-bithiophene] (F8T2) as p-type semiconductors and fullerenes (C{sub 60}) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron donor and acceptor has been fabricated and characterized for improving photovoltaic and optical properties. The photovoltaic performance including current voltage curves in the dark and illumination of the F8T2/C{sub 60} conventional and inverted bulk heterojunction solar cells were investigated. Relationship between the photovoltaic properties and morphological behavior was focused on tuning for optimization of photo-voltaic performance under annealing condition near glass transition temperature. Additive-effect of diiodooctane (DIO) and poly(3-hexylthiophene-2,5-diyl) (P3HT) on the photovoltaic performance and optical properties was investigated. Mechanism of the photovoltaic properties of the conventional and inverted solar cells will be discussed by the experimental results.

  2. Quantum Hall Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Radzihovsky, Leo

    2003-03-01

    Liquid-crystals, defined as states of matter intermediate in their properties between fully disordered isotropic liquids and fully ordered crystals are ubiquitous in nature. Recent transport measurements on two-dimensional electron systems in moderate magnetic fields suggest the existence of a spontaneously orientationally-ordered, compressible liquid state. I will discuss electronic liquid-crystals interpretation of these experiments, focusing on a recently proposed quantum Hall nematic state that is predicted to exhibit a novel, highly anisotropic q^3 density-director mode and other interesting phenomenology.

  3. Dichroic Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    * Effect of Thickness * Impact of Order Parameter * Impact of the Host * Impact of Polarizer * Colour Applications * Multiplexing * QUARTER WAVE PLATE DICHROIC DISPLAYS * Operational Principle and Display Configuration11-13 * Electro-Optical Performance * DYE-DOPED TN DISPLAYS * Threshold Characteristic, Contrast Ratio and Switching Speed * PHASE CHANGE EFFECT DICHROIC LCDs * Theoretical Background * Threshold Characteristic and Molecular Orientation * MOLECULAR ORIENTATION DURING FIELD-INDUCED PHASE TRANSITION WITH HOMOGENEOUS WALL ALIGNMENT * MOLECULAR ORIENTATION DURING FIELD-INDUCED PHASE TRANSITION WITH HOMEOTROPIC WALL ALIGNMENT * Contrast Ratio, Transmission, Brightness and Switching Speed3,7,10,198-214 * Memory or Reminiscent Contrast * Electro-optical Performance vs. Temperature * Multiplexing Phase Change Dichroic LCDs * DOUBLE CELL DICHROIC LCDs3,9,14-17,232-234 * Double Cell Nematic Dichroic LCD3,8,9,14,15,233 * Double Cell One Pitch Cholesteric LCD16,17 * Double Cell Phase Change Dichroic LCD214,232 * POSITIVE MODE DICHROIC LCDS3,8,9 * Positive Mode Heilmeier Cells3,8,9,43,77,78,235-238 * USING PLEOCHROIC DYES3,8,9,43,235-238 * USING NEGATIVE DICHROIC DYES3,8,9,63,77,78156 * DUAL FREQUENCY ADDRESSED DICHROIC DISPLAYS75,238 * Positive Mode Dichroic LCDs Using λ/4 Plate * Positive Mode Double Cell Dichroic LCD * Positive Mode Dichroic LCDs Using Special Electrode patterns7,8,239-241 * Positive Mode Phase Change Dichroic LCDs3,8,9,230,243-248 * Dichroic LCDs Using an Admixture of Pleochroic and Negative Dichroic Dyes78,118 * SUPERTWIST DICHROIC EFFECT (SDE) DISPLAYS21-23 * FERROELECTRIC DICHROIC LCDs24-27 * Devices Using A Single Polarizer * Devices Using No Polarizer24-27 * POLYMER DISPERSED DICHROIC LCDs28-30,252-259 * DICHROIC POLYMER LIQUID CRYSTAL DISPLAYS * Heilmeier Type Displays * Guest-Host Cell Using an Admixture Of L.C. Polymer and Low Molecular Weight Liquid Crysta As Host * Polymeric Ferroelectric Dichroic LCDs * SMECTIC A DICHROIC LCDs * Laser

  4. Dynamics of a director reorientation and optical response of polymer films filled with a liquid crystal under strong electric field

    NASA Astrophysics Data System (ADS)

    Pasechnik, S. V.; Shmeleva, D. V.; Chopik, A. P.; Vakulenko, A. A.; Zakharov, A. V.

    2016-08-01

    The dynamics of the director reorientation in nematic liquid crystals (NLC) confined by cylindrical cavities of porous polymeric films under strong electric field E with has been investigated theoretically. The main attention was paid to the specific mode of field application characterized by abrupt changes of the applied voltage's polarity. In experiments with porous films filled with a liquid crystal 5CB such mode resulted in appearance of strong peak -like decreasing of an optical transparence of the films. Two mechanisms of such unusual response based on assumption of electrically induced motion of ions and overall motion of a liquid were considered and applied to explain experimental results.

  5. Into the polymer brush regime through the "grafting-to" method: densely polymer-grafted rodlike viruses with an unusual nematic liquid crystal behavior.

    PubMed

    Zan, Tingting; Wu, Fengchi; Pei, Xiaodong; Jia, Shaoyi; Zhang, Ran; Wu, Songhai; Niu, Zhongwei; Zhang, Zhenkun

    2016-01-21

    The current work reports an intriguing discovery of how the force exerted on protein complexes like filamentous viruses by the strong interchain repulsion of polymer brushes can induce subtle changes of the constituent subunits at the molecular scale. Such changes transform into the macroscopic rearrangement of the chiral ordering of the rodlike virus in three dimensions. For this, a straightforward "grafting-to" PEGylation method has been developed to densely graft a filamentous virus with poly(ethylene glycol) (PEG). The grafting density is so high that PEG is in the polymer brush regime, resulting in straight and thick rodlike particles with a thin viral backbone. Scission of the densely PEGylated viruses into fragments was observed due to the steric repulsion of the PEG brush, as facilitated by adsorption onto a mica surface. The high grafting density of PEG endows the virus with an isotropic-nematic (I-N) liquid crystal (LC) phase transition that is independent of the ionic strength and the densely PEGylated viruses enter into the nematic LC phase at much lower virus concentrations. Most importantly, while the intact virus and the one grafted with PEG of low grafting density can form a chiral nematic LC phase, the densely PEGylated viruses only form a pure nematic LC phase. This can be traced back to the secondary to tertiary structural change of the major coat protein of the virus, driven by the steric repulsion of the PEG brush. Quantitative parameters characterising the conformation of the grafted PEG derived from the grafting density or the I-N LC transition are elegantly consistent with the theoretical prediction.

  6. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

  7. Effect of SiO2 nanoparticle doping on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Eunju; Liu, Yang; Hong, Sung-Jei; Han, Jeong In

    2015-03-01

    In this paper, SiO2 nanoparticle doped polymer dispersed liquid crystal (PDLC) lenses were made from a mixture of prepolymer, E7 liquid crystal and SiO2 nanoparticles by the polymerization induced phase separation (PIPS) process for smart electronic glasses with auto-shading and auto-focusing functions. Electro-optical properties of doped and undoped samples including transmittance, driving voltage, contrast ratio and slope of the linear region of the transmittance-voltage were measured, compared and analyzed. Driving voltage of SiO2 nanoparticle doped PDLC lenses moderately improved. But the slope of linear region, response time and contrast ratio deteriorated, especially the latter two. It can be assumed that these doping effects were due to the mechanistic change from liquid-gel separation to liquid-liquid separation by the fast heterogeneous nucleation rate caused by the increased nucleation at the surface of SiO2 nanoparticles. The marked deteriorations of falling response time and contrast ratio were due to well defined liquid crystal molecules in LC droplets, which induced slow and imperfect random rearrangement of LC molecules at the off state.

  8. Micromachining of liquid crystal polymer film with frequency converted diode-pumped Nd:YVO4 laser

    NASA Astrophysics Data System (ADS)

    Li, Mingwei; Hix, Ken; Dosser, Larry R.; Hartke, Kevin; Blackshire, Jim

    2003-07-01

    Liquid crystal polymer (LCP) is a new and innovative material being used as an alternative to polyimide in the flexible circuit industry. LCP has many intrinsic benefits over polyimide including lower moisture absorption and improved dimensional stability. However, LCP is very resistant to chemical milling or etching. As a result, other methods for processing the material are being investigated including laser micromachining. In this paper, three frequency converted diode-pumped solid-state (DPSS) Nd:YVO4 lasers at 355 nm were used to micromachine a LCP film and a copper/LCP laminate. Of them, two are Q-switched lasers operating in the nanosecond regime and the other a mode-locked laser in the picosecond regime. The Q-switched lasers can be operated at pulse repetition rates of 1 to 300 kHz while the mode-locked system is operated at 80 MHz. The micromachining experiments consisted of cutting the 50 μm thick LCP film, cutting the 18 μm thick copper on the film, and drilling micro-vias through both the copper coating and the film substrate. The laser/material interactions and processing speeds were studied and compared. The results show that, compared to polyimide film of the same thickness, LCP film can be more efficiently processed by laser micromachining. In addition, each laser has a unique advantage in processing LCP based flexible circuit materials. The Q-switched lasers are more capable of processing the copper coating while the mode-locked laser can cut LCP film faster with the smallest kerf width.

  9. Biological liquid crystal elastomers.

    PubMed

    Knight, David P; Vollrath, Fritz

    2002-02-28

    Liquid crystal elastomers (LCEs) have recently been described as a new class of matter. Here we review the evidence for the novel conclusion that the fibrillar collagens and the dragline silks of orb web spiders belong to this remarkable class of materials. Unlike conventional rubbers, LCEs are ordered, rather than disordered, at rest. The identification of these biopolymers as LCEs may have a predictive value. It may explain how collagens and spider dragline silks are assembled. It may provide a detailed explanation for their mechanical properties, accounting for the variation between different members of the collagen family and between the draglines in different spider species. It may provide a basis for the design of biomimetic collagen and dragline silk analogues by genetic engineering, peptide- or classical polymer synthesis. Biological LCEs may exhibit a range of exotic properties already identified in other members of this remarkable class of materials. In this paper, the possibility that other transversely banded fibrillar proteins are also LCEs is discussed.

  10. Rheo-Optical Studies on a Polymer Liquid Crystal Under the Influence of Flow or Magnetic Fields.

    NASA Astrophysics Data System (ADS)

    Srinivasarao, Mohan

    1990-01-01

    The response of a lyotropic liquid crystal to an external perturbing field (flow or magnetic field) has been studied. Solutions of rodlike poly(1,4-phenylene -2,6-benzobisthiazole) (PBT) in methane sulfonic acid (MSA) have been used. The study is primarily limited to the anisotropic phase. Two molecular weights were used, both forming a liquid-crystalline phase above 3% by weight of the polymer in solution. Flow birefringence measurements were attempted to characterize flow-induced orientation in the nematic phase. However, a stable, uniform, steady-state flow condition was not reached. The transmitted intensities of polarized light, both with and without an analyzer, fluctuate rapidly, indicating that a stable, uniform flow did not obtain in torsional shear flow. By contrast, a constant stress was measured above 100 units of strain. During the course of this study, we were successful in obtaining monodomain nematic solutions. Monodomains were used to study the response of the material to external fields (flow or magnetic field). Experiments were done in the twist geometry in an effort to obtain the twist elastic constant for the solutions. We found that an instability is created on the application of a magnetic field, producing a phase grating. The instability has been characterized by light microscopy, fluorescence polarization and conoscopy. Theoretical description of this instability is unavailable as yet. We have demonstrated that the instability involves a three -dimensional flow pattern which gives rise to a reorientation of the director in three dimensions. Monodomains were used to study the flow properties of PBT solutions. Microscopic observations were made on textures created during flow. Conoscopy was used to study the director distortion at the onset of shear flows. We have established that alpha_2/ alpha_3 is less than zero, giving rise to unstable flow conditions. Situations with flow parallel and perpendicular to the director were examined. We have

  11. Chem I Supplement: Liquid Crystals--The Chameleon Chemicals.

    ERIC Educational Resources Information Center

    Brown, Glenn H.

    1983-01-01

    Presents information relevant to everyday life so as to stimulate student interest in the properties of the two basic types of liquid crystals: thermotropic and lyotropic. Describes the applications of liquid crystals to electronics, biomedicine, and polymer science and appraises the future of liquid crystal research. (JM)

  12. Magnetically actuated liquid crystals.

    PubMed

    Wang, Mingsheng; He, Le; Zorba, Serkan; Yin, Yadong

    2014-07-01

    Ferrimagnetic inorganic nanorods have been used as building blocks to construct liquid crystals with optical properties that can be instantly and reversibly controlled by manipulating the nanorod orientation using considerably weak external magnetic fields (1 mT). Under an alternating magnetic field, they exhibit an optical switching frequency above 100 Hz, which is comparable to the performance of commercial liquid crystals based on electrical switching. By combining magnetic alignment and lithography processes, it is also possible to create patterns of different polarizations in a thin composite film and control over the transmittance of light in particular areas. Developing such magnetically responsive liquid crystals opens the door toward various applications, which may benefit from the instantaneous and contactless nature of magnetic manipulation.

  13. Electric and Magnetic Field-Assisted Orientational Transitions in the Ensembles of Domains in a Nematic Liquid Crystal on the Polymer Surface

    PubMed Central

    Parshin, Alexander M.; Gunyakov, Vladimir A.; Zyryanov, Victor Y.; Shabanov, Vasily F.

    2014-01-01

    Using electro- and magneto-optical techniques, we investigated orientational transitions in the ensembles of domains in a nematic liquid crystal on the polycarbonate film surface under the conditions of competing surface forces that favor radial and uniform planar alignment of nematic molecules. Having analyzed field dependences of the intensity of light passed through a sample, we established the threshold character of the orientational effects, plotted the calculated intensity versus magnetic coherence length, and compared the latter with the equilibrium length that characterizes the balance of forces on the polymer surface. PMID:25279586

  14. Advancements of vertically aligned liquid crystal displays.

    PubMed

    Kumar, Pankaj; Jaggi, Chinky; Sharma, Vandna; Raina, Kuldeep Kumar

    2016-02-01

    This review describes the recent advancements in the field of the vertical aligned (VA) liquid crystal displays. The process and formation of different vertical alignment modes such as conventional VA, patterned VA, multi-domain VA, and polymer stabilised VA etc are widely discussed. Vertical alignment of liquid crystal due to nano particle dispersion in LC host, bifunctional PR-SAM formed by silane coupling reaction to oxide surfaces, azo dye etc., are also highlighted and discussed. Overall, the article highlights the advances in the research of vertical aligned liquid crystal in terms of their scientific and technological aspects.

  15. Smart electro-optical iris diaphragm based on liquid crystal film coating with photoconductive polymer of poly(N-vinylcarbazole).

    PubMed

    Fuh, Andy Ying-Guey; Chen, Ko Nan; Wu, Shing-Trong

    2016-08-01

    This study develops a light shutter whose transmittance can be tuned electro-optically. The liquid crystal (LC) film applies the photoconductive material of poly(N-vinylcarbazole) (PVK) based on twisted nematic (TN) liquid crystals (LCs). The hole-transport layer of PVK could reduce the built-in electric field of the LC film under the exposure of UV light. The driving voltage is considerably decreased with the aid of UV light exposure. The repeating optical switching is performed under sunlight illumination with an external bias of electric field ∼5  V. Further, it could be operated under a parallel/cross-polarizer to change the light beam/ring as an iris and used to automatically block the UV light to protect an optical integrated system. PMID:27505385

  16. Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

    NASA Astrophysics Data System (ADS)

    Labeeb, A.; Gleeson, H. F.; Hegmann, T.

    2015-12-01

    The smectic C*-alpha (SmCα*) phase is one of the sub-phases of ferroelectric liquid crystals that has drawn much interest due to its electro-optical properties and ultrafast switching. Generally observed above the ferroelectric SmC* phase in temperature, the SmCα* commonly shows only very narrow phase temperature range of a few degree Celsius. To broaden the SmCα* phase, polymer stabilization was investigated for thermal phase stabilization. Two different reactive monomers were tested in three mixtures, and all three broadened the temperature range of the SmCα* phase from 3 °C to 39 °C. The current reversal method was used to determine the phase existence versus temperature. Moreover, the texture and network structure was studied by polarized optical microscopy and scanning electron microscopy, with the latter revealing the confinement of the smectic layer structure within the porous polymer network.

  17. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

    The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.

  18. Morphological instabilities of polymer crystals.

    PubMed

    Grozev, N; Botiz, I; Reiter, G

    2008-09-01

    We present experimental observations at comparatively low supercooling of morphology transitions from dendritic to faceted structures in polymer crystals growing in thin films of a poly-2-vinylpyridine-block-polyethyleneoxid copolymer. Our results are compared with theoretical concepts describing morphological instabilities of single crystals. Although these concepts originally were not developed for polymers, they allow to describe and interpret our experimental results quite well. In particular, the measured temperature dependence of the width W and frequency of dendritic side branches and the radius of curvature p of the growth tips of the crystals follow these concepts. We present preliminary evidence for the influence of polymer attachment kinetics and reorganisation processes behind the growth front. Polymer thin films provide valuable model systems for studying general concepts of crystallisation and allow to distinguish at which point the connectivity of the crystallising units within chain-like molecules starts to play a measurable role.

  19. Bent core liquid crystal elastomers

    SciTech Connect

    Verduzco, R.; DiMasi, E.; Luchette, P.; Ho Hong, S.; Harden, J.; Palffy-Muhoray, P.; Kilbey II, S.M.; Sprunt, S.; Gleeson, G.T. Jakli, A.

    2010-07-28

    Liquid crystal (LC) elastomers with bent-core side-groups incorporate the properties of bent-core liquid crystals in a flexible and self-supporting polymer network. Bent-core liquid crystal elastomers (BCEs) with uniform alignment were prepared by attaching a reactive bent-core LC to poly(hydrogenmethylsiloxane) and crosslinking with a divinyl crosslinker. Phase behavior studies indicate a nematic phase over a wide temperature range that approaches room temperature, and thermoelastic measurements show that these BCEs can reversibly change their length by more than a factor of two upon heating and cooling. Small-angle X-ray scattering studies reveal multiple, broad low-angle peaks consistent with short-range smectic C order of the bent-core side groups. A comparison of these patterns with predictions of a Landau model for short-range smectic C order shows that the length scale for smectic ordering in BCEs is similar to that seen in pure bent-core LCs. The combination of rubber elasticity and smectic ordering of the bent-core side groups suggests that BCEs may be promising materials for sensing, actuating, and other advanced applications.

  20. Tunable liquid crystal photonic devices

    NASA Astrophysics Data System (ADS)

    Fan, Yun-Hsing

    2005-07-01

    Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices. In Chap. 3, we demonstrate a novel electrically tunable-efficiency Fresnel lens which is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. The nanoscale LC devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated tunable Fresnel lens using polymer-network liquid crystal (PNLC) and phase-separated composite film (PSCOF). The operating voltage is below 12 Vrms. The PNLC and PSCOF devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. Using PNLC, we also demonstrated LC blazed grating. The diffraction efficiency of these devices is continuously controlled by the electric field. We also develop a system with continuously tunable focal length. A conventional mechanical zooming system is bulky and power hungry. In Chap. 4, we developed an electrically tunable-focus flat LC spherical lens and microlens array. A huge tunable range from 0.6 m to infinity is achieved by the applied voltage. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative by the applied voltage. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. In

  1. Hierarchical Thin Film Architectures for Enhanced Sensor Performance: Liquid Crystal-Mediated Electrochemical Synthesis of Nanostructured Imprinted Polymer Films for the Selective Recognition of Bupivacaine

    PubMed Central

    Suriyanarayanan, Subramanian; Nawaz, Hazrat; Ndizeye, Natacha; Nicholls, Ian A.

    2014-01-01

    Nanostructured bupivacaine-selective molecularly imprinted 3-aminophenylboronic acid-p-phenylenediamine co-polymer (MIP) films have been prepared on gold-coated quartz (Au/quartz) resonators by electrochemical synthesis under cyclic voltammetric conditions in a liquid crystalline (LC) medium (triton X-100/water). Films prepared in water and in the absence of template were used for control studies. Infrared spectroscopic studies demonstrated comparable chemical compositions for LC and control polymer films. SEM studies revealed that the topologies of the molecularly imprinted polymer films prepared in the LC medium (LC-MIP) exhibit discernible 40 nm thick nano-fiber structures, quite unlike the polymers prepared in the absence of the LC-phase. The sensitivity of the LC-MIP in a quartz crystal microbalance (QCM) sensor platform was 67.6 ± 4.9 Hz/mM under flow injection analysis (FIA) conditions, which was ≈250% higher than for the sensor prepared using the aqueous medium. Detection was possible at 100 nM (30 ng/mL), and discrimination of bupivacaine from closely related structural analogs was readily achieved as reflected in the corresponding stability constants of the MIP-analyte complexes. The facile fabrication and significant enhancement in sensor sensitivity together highlight the potential of this LC-based imprinting strategy for fabrication of polymeric materials with hierarchical architectures, in particular for use in surface-dependent application areas, e.g., biomaterials or sensing. PMID:25587412

  2. Hierarchical thin film architectures for enhanced sensor performance: liquid crystal-mediated electrochemical synthesis of nanostructured imprinted polymer films for the selective recognition of bupivacaine.

    PubMed

    Suriyanarayanan, Subramanian; Nawaz, Hazrat; Ndizeye, Natacha; Nicholls, Ian A

    2014-06-01

    Nanostructured bupivacaine-selective molecularly imprinted 3-aminophenylboronic acid-p-phenylenediamine co-polymer (MIP) films have been prepared on gold-coated quartz (Au/quartz) resonators by electrochemical synthesis under cyclic voltammetric conditions in a liquid crystalline (LC) medium (triton X-100/water). Films prepared in water and in the absence of template were used for control studies. Infrared spectroscopic studies demonstrated comparable chemical compositions for LC and control polymer films. SEM studies revealed that the topologies of the molecularly imprinted polymer films prepared in the LC medium (LC-MIP) exhibit discernible 40 nm thick nano-fiber structures, quite unlike the polymers prepared in the absence of the LC-phase. The sensitivity of the LC-MIP in a quartz crystal microbalance (QCM) sensor platform was 67.6 ± 4.9 Hz/mM under flow injection analysis (FIA) conditions, which was ≈250% higher than for the sensor prepared using the aqueous medium. Detection was possible at 100 nM (30 ng/mL), and discrimination of bupivacaine from closely related structural analogs was readily achieved as reflected in the corresponding stability constants of the MIP-analyte complexes. The facile fabrication and significant enhancement in sensor sensitivity together highlight the potential of this LC-based imprinting strategy for fabrication of polymeric materials with hierarchical architectures, in particular for use in surface-dependent application areas, e.g., biomaterials or sensing. PMID:25587412

  3. Gelled Lyotropic Liquid Crystals.

    PubMed

    Xu, Yang; Laupheimer, Michaela; Preisig, Natalie; Sottmann, Thomas; Schmidt, Claudia; Stubenrauch, Cosima

    2015-08-11

    In our previous work we were able to prove that gelled bicontinuous microemulsions are a novel type of orthogonal self-assembled system. The study at hand aims at complementing our previous work by answering the question of whether gelled lyotropic liquid crystals are also orthogonal self-assembled systems. For this purpose we studied the same system, namely, water-n-decane/12-hydroxyoctadecanoic acid (12-HOA)-n-decyl tetraoxyethylene glycol ether (C10E4). The phase boundaries of the nongelled and the gelled lyotropic liquid crystals were determined visually and with (2)H NMR spectroscopy. Oscillating shear measurements revealed that the absolute values of the storage and loss moduli of the gelled liquid crystalline (LC) phases do not differ very much from those of the binary organogel. While both the phase behavior and the rheological properties of the LC phases support the hypothesis that gelled lyotropic liquid crystals are orthogonal self-assembled systems, freeze-fracture electron microscopy (FFEM) seems to indicate an influence of the gel network on the structure of the Lα phase and vice versa.

  4. Spatio-orientationally organized polymer microstructures obtained on self-assembled pattern-forming states of liquid crystals: Morphology, phase separation, and potential applications

    NASA Astrophysics Data System (ADS)

    Kang, Shin-Woong

    The main objective of the dissertation is to develop and exploit a novel technique for imparting multidimensional spatial and orientational order into polymer networks. This approach is based on the use of pattern-forming states of liquid crystals as templates for the network formation. To demonstrate the feasibility and flexibility of this concept, we describe various pattern-forming states observed from ordinary cholesteric and nematic/cholesteric dual-frequency liquid crystals. We present a variety of polymer microstuctures templated on those pattern-forming states. This clearly demonstrates the feasibility and flexibility of templating both orientational and positional order of host pattern-forming states into polymer network. We investigated possible driving forces behind this templating effect of LC pattern-forming states. These include effects of both spatial variations of UV intensity and gradients in elastic distortion caused by the spatial modulation of director field. The effects of the two mechanisms are separated through a series of experiments, including polarization-selective photopolymerization, FTIR imaging of the monomer distribution prior to UV-exposure and initiation of the photoreaction, the effect of temperature on the templated morphology, and the use of a thermal reactive monomer to remove the effect of possible optical inhomogeneities. The model derives from the concept of director gradient templating, whereby monomer phase separation is driven by a competition between reduction in elastic energy when monomer replaces liquid crystal in more (or less) distorted regions of the molecular director, and a consequent decrease in the entropy of mixing of the two species. Another emphasis of this dissertation is to study the control over the network morphology in the "third" dimension---perpendicular to UV wavefront---by relatively simple means of selecting the wavelength of UV light used in photopolymerization to be inside or outside a carefully

  5. Syntheses and crystal structures of benzene-sulfonate and -carboxylate copper polymers and their application in the oxidation of cyclohexane in ionic liquid under mild conditions.

    PubMed

    Hazra, Susanta; Ribeiro, Ana P C; Guedes da Silva, M Fátima C; Nieto de Castro, Carlos A; Pombeiro, Armando J L

    2016-09-21

    The syntheses, crystal structures and catalytic activities of the polymers derived from 2-(2-pyridylmethyleneamino)benzenesulfonic acid (HL), viz. [CuL(H2tma)]n (1) and [{Cu2L2(H2pma)}·(8H2O)]n (2) [H3tma = benzene-1,3,5-tricarboxylic (trimesic) acid and H4pma = benzene-1,2,4,5-tetracarboxylic (pyromellitic) acid], are presented. Despite the comparable combinations and compositions of ligands (sulfonate and carboxylate) in these two polymers the bridging moiety in 1 is sulfonate while in 2 it is carboxylate. Complexes 1 and 2 act as catalysts in the peroxidative oxidation of cyclohexane under mild conditions using either the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] or acetonitrile as the solvent. The ionic liquid medium leads to increases in the yields and in the turnover numbers, achieved in shorter reaction times in comparison with those when using the conventional acetonitrile solvent. A simple recycling of the catalysts in the ionic liquid medium is achieved without loss of activity and selectivity.

  6. Syntheses and crystal structures of benzene-sulfonate and -carboxylate copper polymers and their application in the oxidation of cyclohexane in ionic liquid under mild conditions.

    PubMed

    Hazra, Susanta; Ribeiro, Ana P C; Guedes da Silva, M Fátima C; Nieto de Castro, Carlos A; Pombeiro, Armando J L

    2016-09-21

    The syntheses, crystal structures and catalytic activities of the polymers derived from 2-(2-pyridylmethyleneamino)benzenesulfonic acid (HL), viz. [CuL(H2tma)]n (1) and [{Cu2L2(H2pma)}·(8H2O)]n (2) [H3tma = benzene-1,3,5-tricarboxylic (trimesic) acid and H4pma = benzene-1,2,4,5-tetracarboxylic (pyromellitic) acid], are presented. Despite the comparable combinations and compositions of ligands (sulfonate and carboxylate) in these two polymers the bridging moiety in 1 is sulfonate while in 2 it is carboxylate. Complexes 1 and 2 act as catalysts in the peroxidative oxidation of cyclohexane under mild conditions using either the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] or acetonitrile as the solvent. The ionic liquid medium leads to increases in the yields and in the turnover numbers, achieved in shorter reaction times in comparison with those when using the conventional acetonitrile solvent. A simple recycling of the catalysts in the ionic liquid medium is achieved without loss of activity and selectivity. PMID:27529408

  7. Liquid crystal orientation control in photonic liquid crystal fibers

    NASA Astrophysics Data System (ADS)

    Chychlowski, M. S.; Nowinowski-Kruszelnicki, E.; Woliński, T. R.

    2011-05-01

    Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and transmitting spectra of the PLCF The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid crystal fiber-based devices.

  8. Phase diagrams of binary mixtures of liquid crystals and rodlike polymers in the presence of an external field.

    PubMed

    Matsuyama, Akihiko; Ueda, Tomomi

    2012-06-14

    We theoretically study phase separations in mixtures of a low molecular-weight-liquid crystalline molecule (LC) and a rigid-rodlike polymer (rod) under an external field, such as magnetic or electric fields. By taking into account two orientational order parameters of the rod and the LC, we define four nematic phases (N(0), N(1), N(2), N(3)) on the temperature-concentration plane. Depending on the sign of the dielectric anisotropy Δε(i) of the rod (i = 1) and LC(i = 2), we examine the phase behavior of rod/LC mixtures in the case of Δε(1) > 0, Δε(2) > 0 (a), Δε(1) < 0, Δε(2) > 0 (b), Δε(1) > 0, Δε(2) < 0 (c), and Δε(1) < 0, Δε(2) < 0 (d). We predict a variety of phase separations induced by an external field. PMID:22713070

  9. Topographic-pattern-induced homeotropic alignment of liquid crystals.

    PubMed

    Yi, Youngwoo; Lombardo, Giuseppe; Ashby, Neil; Barberi, Riccardo; Maclennan, Joseph E; Clark, Noel A

    2009-04-01

    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. PMID:19518244

  10. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

  11. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Stevenson, Paige; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

  12. Liquid crystals for laser applications

    NASA Astrophysics Data System (ADS)

    Jacobs, S. D.; Marshall, K. L.; Schmid, A.

    1992-10-01

    This article highlights some of the advances made in the use of liquid crystals for laser applications from 1982 through 1992. New materials and new effects were discovered, many new devices were developed, and novel applications for well-understood phenomena were conceived. This was quite an eventful time period. Several new books were published on the broad subject of LC's, and the international scientific community organized a society devoted to encouraging further scientific and educational advancement in the field. Attention was focused on LC's in October of 1991 when the Nobel Prize in Physics was awarded to Pierre-Gilles de Gennes for his pioneering work toward understanding order phenomena in LC's and polymers. This article is divided into four sections. The first section discusses new materials, specifically ferroelectric LC's and LC polymers. The former have opened up the realm of submicrosecond response for LC devices, and the latter have significantly reduced the sensitivity of LC optics to temperature. Some new insights into the optical properties of materials are also mentioned. The second section reviews new developments in passive applications for cholesterics and nematics. Included here are the fabrication of cholesteric laser mirrors and apodizers, the use of LC polymers for notch filters and as optical storage media, and some novel nematic retarder concepts such as the distributed polarization rotator.

  13. Dual self-healing abilities of composite gels consisting of polymer-brush-afforded particles and an azobenzene-doped liquid crystal.

    PubMed

    Kawata, Yuki; Yamamoto, Takahiro; Kihara, Hideyuki; Ohno, Kohji

    2015-02-25

    We prepared the composite gels from polymer-brush-afforded silica particles (P-SiPs) and an azobenzene-doped liquid crystal, and investigated their inner structure, dynamic viscoelastic properties, thermo- and photoresponsive properties, and self-healing behaviors. It was found that the composite gels had a sponge-like inner structure formed with P-SiPs and exhibited good elastic property and shape recoverability. The surface dents made on the composite gel could be repaired spontaneously at room temperature. Moreover, the composite gel exhibited a gel-sol transition induced by the trans-cis photoisomerization of the azo dye, and the transition could be used as a mending mechanism for surface cracks. Consequently, we successfully developed a material exhibiting two types of self-healing abilities simultaneously: (1) spontaneous repair of surface dents by means of the excellent elasticity of the composite gel and (2) light-assisted mending of surface cracks by photoinduced gel-sol transition.

  14. Generation of Pretilt Angle for Nematic Liquid Crystal Using the Photodimerization Method on Various New Photo-Crosslinkable Polyimide Based Polymers

    NASA Astrophysics Data System (ADS)

    Hwang, Jeoung-Yeon; Seo, Dae-Shik; Son, Jong-Ho; Suh, Dong Hack

    2001-07-01

    We synthesized the various new photo-crosslinkable polyimide based polymers and generation of pretilt angle for a nematic liquid crystal (NLC) using a photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimatric analysis (TGA) measurement until 450°C. The NLC pretilt angle generated was about 2.5°-3.0° by polarized UV exposure on the photopolymers containing a biphenyl (BP), decyl (De), and cholesteryl(chol), chalcone(Chal) group, respectively. However, low pretilt angle of the NLC was measured by polarized UV exposure on the photopolymers containing the fluorine and chalcone group. The NLC pretilt angle generated is attributed to the biphenyl and alkyl moieties, and the photo-dimerized chalcone group of the photopolymer.

  15. Rugged and drapable cholesteric liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Shiyanovskaya, Irina; Khan, Asad; Green, Seth; Magyar, Greg; Pishnyak, Oleg; Doane, J. W.

    2005-05-01

    We developed a novel technology for the fabrication of reflective cholesteric liquid crystal displays coatable on a single substrate using a layer-by-layer approach. Encapsulated cholesteric liquid crystals serving as an electro-optical layer and transparent conducting polymer films serving as electrodes are coated and printed on a variety of unconventional substrates, including ultra-thin plastic, paper, and textile materials to create conformable displays. The displays are capable of offering excellent electro-optical properties of the bulk cholesteric liquid crystals, including full-color, IR capability, bistability, low power, high brightness and contrast, combined with the ruggedness and pressure insensitivity of the liquid crystal droplets embedded in a polymer matrix. Durability of encapsulated cholesteric liquid crystals and single substrate approach allows for display flexing, folding, rolling and draping during image addressing without any image distortion. Our single substrate approach with natural cell-gap control significantly simplifies the fabrication process of the LCDs especially for large area displays. This paper will discuss the development, status, and merits of this novel display technology.

  16. Intense pulsed light induced crystallization of a liquid-crystalline polymer semiconductor for efficient production of flexible thin-film transistors.

    PubMed

    Yang, Hee Yeon; Park, Han-Wool; Kim, Soo Jin; Hong, Jae-Min; Kim, Tae Whan; Kim, Do Hwan; Lim, Jung Ah

    2016-02-14

    Here we demonstrated the split-second crystallization of a liquid-crystalline conjugated polymer semiconductor induced by irradiation with intense pulsed white light (IPWL) for the efficient improvement of electrical properties of flexible thin film transistors. A few seconds of IPWL irradiation of poly(didodecylquaterthiophene-alt-didodecylbithiazole) (PQTBTz-C12) thin films generated heat energy through the photo-thermal effect, leading to the crystallization of PQTBTz-C12 and formation of nodule-like nanostructures. The IPWL-induced crystallization of PQTBTz-C12 resulted in a threefold improvement in the field-effect mobility of thin film transistors compared to as-prepared devices. The conformational change of the PQTBTz-C12 chains was found to be strongly related to the irradiation fluence. As a proof-of-concept, the IPWL treatment was successfully applied to the PQTBTz-C12 layer in flexible transistors based on plastic substrates. The performance of these flexible devices was significantly improved after only 0.6 s of IPWL treatment, without deformation of the plastic substrate. PMID:26795202

  17. Dynamic Theory of Polydomain Liquid Crystal Elastomers.

    PubMed

    Duzgun, Ayhan; Selinger, Jonathan V

    2015-10-30

    When liquid crystal elastomers are prepared without any alignment, disordered polydomain structures emerge as the materials are cooled into the nematic phase. These polydomain structures are often attributed to quenched disorder in the cross-linked polymer network. As an alternative explanation, we develop a theory for the dynamics of the isotropic-nematic transition in liquid crystal elastomers, and show that the dynamics can induce a polydomain structure with a characteristic length scale, through a mechanism analogous to the Cahn-Hilliard equation for phase separation. PMID:26565497

  18. Dynamic Theory of Polydomain Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Duzgun, Ayhan; Selinger, Jonathan V.

    2015-10-01

    When liquid crystal elastomers are prepared without any alignment, disordered polydomain structures emerge as the materials are cooled into the nematic phase. These polydomain structures are often attributed to quenched disorder in the cross-linked polymer network. As an alternative explanation, we develop a theory for the dynamics of the isotropic-nematic transition in liquid crystal elastomers, and show that the dynamics can induce a polydomain structure with a characteristic length scale, through a mechanism analogous to the Cahn-Hilliard equation for phase separation.

  19. Wetting of cholesteric liquid crystals.

    PubMed

    Silvestre, Nuno M; Figueirinhas Pereira, Maria Carolina; Bernardino, Nelson R; Telo da Gama, Margarida M

    2016-02-01

    We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal.

  20. Crystallization of undercooled liquid fenofibrate.

    PubMed

    Amstad, Esther; Spaepen, Frans; Weitz, David A

    2015-11-28

    Formulation of hydrophobic drugs as amorphous materials is highly advantageous as this increases their solubility in water and therefore their bioavailability. However, many drugs have a high propensity to crystallize during production and storage, limiting the usefulness of amorphous drugs. We study the crystallization of undercooled liquid fenofibrate, a model hydrophobic drug. Nucleation is the rate-limiting step; once seeded with a fenofibrate crystal, the crystal rapidly grows by consuming the undercooled liquid fenofibrate. Crystal growth is limited by the incorporation of molecules into its surface. As nucleation and growth both entail incorporation of molecules into the surface, this process likely also limits the formation of nuclei and thus the crystallization of undercooled liquid fenofibrate, contributing to the good stability of undercooled liquid fenofibrate against crystallization.

  1. Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

    SciTech Connect

    Labeeb, A.; Gleeson, H. F.; Hegmann, T.

    2015-12-07

    The smectic C*-alpha (SmC{sub α}*) phase is one of the sub-phases of ferroelectric liquid crystals that has drawn much interest due to its electro-optical properties and ultrafast switching. Generally observed above the ferroelectric SmC* phase in temperature, the SmC{sub α}* commonly shows only very narrow phase temperature range of a few degree Celsius. To broaden the SmC{sub α}* phase, polymer stabilization was investigated for thermal phase stabilization. Two different reactive monomers were tested in three mixtures, and all three broadened the temperature range of the SmC{sub α}* phase from 3 °C to 39 °C. The current reversal method was used to determine the phase existence versus temperature. Moreover, the texture and network structure was studied by polarized optical microscopy and scanning electron microscopy, with the latter revealing the confinement of the smectic layer structure within the porous polymer network.

  2. Morphological appearances and photo-controllable coloration of dye-doped cholesteric liquid crystal/polymer coaxial microfibers fabricated by coaxial electrospinning technique.

    PubMed

    Lin, Jia-De; Chen, Che-Pei; Chen, Lin-Jer; Chuang, Yu-Chou; Huang, Shuan-Yu; Lee, Chia-Rong

    2016-02-01

    This study systematically investigates the morphological appearance of azo-chiral dye-doped cholesteric liquid crystal (DDCLC)/polymer coaxial microfibers obtained through the coaxial electrospinning technique and examines, for the first time, their photocontrollable reflection characteristics. Experimental results show that the quasi-continuous electrospun microfibers can be successfully fabricated at a high polymer concentration of 17.5 wt% and an optimum ratio of 2 for the feeding rates of sheath to core materials at 25 °C and a high humidity of 50% ± 2% in the spinning chamber. Furthermore, the optical controllability of the reflective features for the electrospun fibers is studied in detail by changing the concentration of the azo-chiral dopant in the core material, the UV irradiation intensity, and the core diameter of the fibers. Relevant mechanisms are addressed to explain the optical-control behaviors of the DDCLC coaxial fibers. Considering the results, optically controllable DDCLC coaxial microfibers present potential applications in UV microsensors and wearable smart textiles or swabs. PMID:26906876

  3. Macroscale Janus polymer single crystal film and its wettability analysis

    NASA Astrophysics Data System (ADS)

    Qi, Hao; Wang, Wenda; Zhou, Tian; Li, Christopher

    2014-03-01

    Liquid-liquid interface between two immiscible solvents is crucial to studying amphiphile and colloidal self-assembly. It can also guide chain folding during the crystallization process. In this presentation, we show that crystallization of dicarboxy end functionalized poly(ɛ-caprolactone) at water/pentyl acetate interface result in millimeter scale, uniform polymer single crystal (PSC) film. Due to the asymmetric nature at the liquid-liquid interface, the PSC film exhibit Janus property - a hydrophobic side and a hydrophilic side, which is confirmed by in-situ nano-condensation experiment using an environmental scanning electron microscope. The thickness of the PSC film changes with different polymer solution concentration, revealing a surface tension dominated crystallization process.

  4. Tunable Meta-Liquid Crystals.

    PubMed

    Liu, Mingkai; Fan, Kebin; Padilla, Willie; Powell, David A; Zhang, Xin; Shadrivov, Ilya V

    2016-02-24

    Meta-liquid crystals, a novel form of tunable 3D metamaterials, are proposed and experimentally demonstrated in the terahertz frequency regime. A morphology change under a bias electric field and a strong modulation of the transmission are observed. In comparison to conventional liquid crystals, there is considerable freedom to prescribe the electromagnetic properties through the judicious design of the meta-atom geometry.

  5. Nanotube networks in liquid crystals

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Lagerwall, Jan Peter F.; Scalia, Giusy

    2016-03-01

    Liquid crystals (LCs) are very attractive hosts for the organization of anisotropic nanoparticles such as carbon nanotubes (CNTs) because of the macroscopic organization resulting in properties of nanoparticles manifest at a macroscopic scale. Different types of LCs have demonstrated the ability to organize nanotubes, showing the generality of the approach, i.e., that the liquid crystallinity per se is the driving factor for the organization. Compared to standard nanotube composites (e.g. with disordered polymer hosts) the introduction of carbon nanotubes into an LC allows not only the transfer of the outstanding CNT properties to the macroscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs. The LC molecular structure plays an important even if ancillary role since it enters in the surface interactions, fulfilling a mediating action between the particle and the bulk of the LC. Isolated nanotubes can be obtained by optimized dispersions at lower concentrations and this process requires the use or development of tailored strategies like using solvents or even another LC for pre-dispersing CNTs. Aggregates or networks can be observed in poor dispersions and at higher nanoparticle concentrations. In those, due to surface interactions, the LC behaviour can be strongly affected with changes in phase sequences or transition temperatures and the effect is expected to be more pronounced as the concentration of nanotubes increases. We present preliminary investigations and observations on nanotube - LC systems based on a smectic LC host.

  6. Nanoparticles in liquid crystals, and liquid crystals in nanoparticles

    NASA Astrophysics Data System (ADS)

    de Pablo, Juan

    2015-03-01

    Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface, for example, can be propagated over relatively long length scales, thereby providing the basis for a wide range of applications that rely on amplification of molecular events into macroscopic observables. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles; through a combination of molecular and continuum models, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second type of system, the structure of a liquid crystal is controlled by confinement in submicron droplets. The morphology of the liquid crystal in a drop depends on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes or nanoparticles at the interface, thereby providing the basis for development of hierarchical assembly of responsive, anisotropic materials. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.

  7. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1987-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into and adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  8. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1989-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into an adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  9. Colloidal cholesteric liquid crystal in spherical confinement.

    PubMed

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S; Lavrentovich, Oleg D; Kumacheva, Eugenia

    2016-01-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545

  10. Colloidal cholesteric liquid crystal in spherical confinement

    PubMed Central

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-01-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545

  11. Colloidal cholesteric liquid crystal in spherical confinement

    NASA Astrophysics Data System (ADS)

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-08-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter.

  12. Dual self-healing abilities of composite gels consisting of polymer-brush-afforded particles and an azobenzene-doped liquid crystal.

    PubMed

    Kawata, Yuki; Yamamoto, Takahiro; Kihara, Hideyuki; Ohno, Kohji

    2015-02-25

    We prepared the composite gels from polymer-brush-afforded silica particles (P-SiPs) and an azobenzene-doped liquid crystal, and investigated their inner structure, dynamic viscoelastic properties, thermo- and photoresponsive properties, and self-healing behaviors. It was found that the composite gels had a sponge-like inner structure formed with P-SiPs and exhibited good elastic property and shape recoverability. The surface dents made on the composite gel could be repaired spontaneously at room temperature. Moreover, the composite gel exhibited a gel-sol transition induced by the trans-cis photoisomerization of the azo dye, and the transition could be used as a mending mechanism for surface cracks. Consequently, we successfully developed a material exhibiting two types of self-healing abilities simultaneously: (1) spontaneous repair of surface dents by means of the excellent elasticity of the composite gel and (2) light-assisted mending of surface cracks by photoinduced gel-sol transition. PMID:25686486

  13. Thermotropic liquid crystals from biomacromolecules

    PubMed Central

    Liu, Kai; Chen, Dong; Marcozzi, Alessio; Zheng, Lifei; Su, Juanjuan; Pesce, Diego; Zajaczkowski, Wojciech; Kolbe, Anke; Pisula, Wojciech; Müllen, Klaus; Clark, Noel A.; Herrmann, Andreas

    2014-01-01

    Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components. PMID:25512508

  14. Adaptive Liquid Crystal Windows

    SciTech Connect

    Taheri, Bahman; Bodnar, Volodymyr

    2011-12-31

    Energy consumption by private and commercial sectors in the U.S. has steadily grown over the last decade. The uncertainty in future availability of imported oil, on which the energy consumption relies strongly, resulted in a dramatic increase in the cost of energy. About 20% of this consumption are used to heat and cool houses and commercial buildings. To reduce dependence on the foreign oil and cut down emission of greenhouse gases, it is necessary to eliminate losses and reduce total energy consumption by buildings. To achieve this goal it is necessary to redefine the role of the conventional windows. At a minimum, windows should stop being a source for energy loss. Ideally, windows should become a source of energy, providing net gain to reduce energy used to heat and cool homes. It is possible to have a net energy gain from a window if its light transmission can be dynamically altered, ideally electronically without the need of operator assistance, providing optimal control of the solar gain that varies with season and climate in the U.S. In addition, the window must not require power from the building for operation. Resolution of this problem is a societal challenge and of national interest and will have a broad global impact. For this purpose, the year-round, allclimate window solution to provide an electronically variable solar heat gain coefficient (SHGC) with a wide dynamic range is needed. AlphaMicron, Inc. (AMI) developed and manufactured 1ft × 1ft prototype panels for the world’s first auto-adjusting Adaptive Liquid Crystal Windows (ALCWs) that can operate from sunlight without the need for external power source and demonstrate an electronically adjustable SHGC. This novel windows are based on AlphaMicron’s patented e-Tint® technology, a guesthost liquid crystal system implemented on flexible, optically clear plastic films. This technology is suitable both for OEM and aftermarket (retro-fitting) lamination to new and existing windows. Low level of

  15. Structure-property evolution during polymer crystallization

    NASA Astrophysics Data System (ADS)

    Arora, Deepak

    The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based

  16. Continuous preparation of polymer coated drug crystals by solid hollow fiber membrane-based cooling crystallization.

    PubMed

    Chen, Dengyue; Singh, Dhananjay; Sirkar, Kamalesh K; Pfeffer, Robert

    2016-02-29

    A facile way to continuously coat drug crystals with a polymer is needed in controlled drug release. Conventional polymer coating methods have disadvantages: high energy consumption, low productivity, batch processing. A novel method for continuous polymer coating of drug crystals based on solid hollow fiber cooling crystallization (SHFCC) is introduced here. The drug acting as the host particle and the polymer for coating are Griseofulvin (GF) and Eudragit RL100, respectively. The polymer's cloud point temperature in its acetone solution was determined by UV spectrophotometry. An acetone solution of the polymer containing the drug in solution as well as undissolved drug crystals in suspension were pumped through the tube side of the SHFCC device; a cold liquid was circulated in the shell side to rapidly cool down the feed solution-suspension in the hollow-fiber lumen. The polymer precipitated from the solution and coated the suspended crystals due to rapid temperature reduction and heterogeneous nucleation; crystals formed from the solution were also coated by the polymer. Characterizations by scanning electron microscopy, thermogravimetric analysis, laser diffraction spectroscopy, X-ray diffraction, Raman spectroscopy, and dissolution tests show that a uniformly coated, free-flowing drug/product can be obtained under appropriate operating conditions without losing the drug's pharmaceutical properties and controlled release characteristics.

  17. Polymers at liquid-liquid interfaces: Photophysics and photoredox chemistry

    SciTech Connect

    Webber, S.E.

    1990-11-01

    Research continued on polymers at liquid-liquid interfaces. This quarter, work concentrated on: preparation of poly(styrene-alt-maleic acid-co-chromophore) polymers; studies of vinylnapthalene-maleic acid polymers as emulsifying agents for water-octane; and assembly of optical fiber reticon-based transient absorption system. 3 refs., 1 fig. (CBS)

  18. Relaxation of Liquid Crystal Alignment Layers

    NASA Astrophysics Data System (ADS)

    Rich, David C.; Sichel, Enid K.; Cebe, Peggy

    1997-03-01

    A new method for investigating thermophysical transitions in liquid crystal alignment layers is discussed. The technique involves curing a set of alignment films at an array of temperatures after the films have been brushed with a cloth, but before liquid crystal cells are constructed from the films. When a thermal transition in the polymer is initiated by a post-brush cure, the aligning ability of the brushed films is destroyed. The technique is demonstrated using polyamide- imide, PMDA-APB polyimide, poly(phenylene ether sulfide) and PVA poly(vinyl alcohol) alignment films. The technique is advantageous for examining brush-aligned surfaces which, due to surface roughness, can not be examined using conventional ellipsometry .

  19. Hydrodynamic theories for mixtures of polymers and rodlike liquid crystalline polymers.

    PubMed

    Forest, M Gregory; Wang, Qi

    2005-10-01

    We develop a hydrodynamic theory for flows of incompressible blends of flexible polymers and rodlike nematic polymers (RNPs) or rodlike nematic liquid crystal polymers (RNLCPs) extending the thermodynamical theory of Muratov and E [J. Chem. Phys. 116, 4723 (2002)] for phase separation kinetics of the blend. We model the flexible polymer molecules in the polymer matrix as Rouse chains and assume the translational diffusion of the molecules is predominantly through the volume fraction of the flexible polymer and the molecules of rodlike nematic liquid crystal polymers. We then (i) derive the translational flux for the rodlike nematic liquid crystal polymers to ensure the incompressibility constraint; (ii) derive the elastic stress tensor, accounting for the contribution from both the rodlike nematic polymer and the flexible polymer matrix, as well as the extra elastic body force due to the nonlocal intermolecular potential for long range molecular interaction; (iii) show that the theory obeys positive entropy production and thereby satisfies the second law of thermodynamics. By applying the gradient expansion technique on the number density function of RNLCPs, we present an approximate, weakly nonlocal theory in differential form in which the intermolecular potential is given by gradients of the number density function of the RNLCP and the volume fraction of the flexible polymer. In the approximate theory, the elastic stress is augmented by an extra stress tensor due to the spatial convection of the macroscopic material point and long range interaction, whose divergence yields the analogous extra elastic body force with respect to the nonlocal intermolecular potential. Finally, we compare the model in steady simple shear with the Doi theory for bulk monodomains of rodlike nematic polymers.

  20. Hydrodynamic theories for mixtures of polymers and rodlike liquid crystalline polymers.

    PubMed

    Forest, M Gregory; Wang, Qi

    2005-10-01

    We develop a hydrodynamic theory for flows of incompressible blends of flexible polymers and rodlike nematic polymers (RNPs) or rodlike nematic liquid crystal polymers (RNLCPs) extending the thermodynamical theory of Muratov and E [J. Chem. Phys. 116, 4723 (2002)] for phase separation kinetics of the blend. We model the flexible polymer molecules in the polymer matrix as Rouse chains and assume the translational diffusion of the molecules is predominantly through the volume fraction of the flexible polymer and the molecules of rodlike nematic liquid crystal polymers. We then (i) derive the translational flux for the rodlike nematic liquid crystal polymers to ensure the incompressibility constraint; (ii) derive the elastic stress tensor, accounting for the contribution from both the rodlike nematic polymer and the flexible polymer matrix, as well as the extra elastic body force due to the nonlocal intermolecular potential for long range molecular interaction; (iii) show that the theory obeys positive entropy production and thereby satisfies the second law of thermodynamics. By applying the gradient expansion technique on the number density function of RNLCPs, we present an approximate, weakly nonlocal theory in differential form in which the intermolecular potential is given by gradients of the number density function of the RNLCP and the volume fraction of the flexible polymer. In the approximate theory, the elastic stress is augmented by an extra stress tensor due to the spatial convection of the macroscopic material point and long range interaction, whose divergence yields the analogous extra elastic body force with respect to the nonlocal intermolecular potential. Finally, we compare the model in steady simple shear with the Doi theory for bulk monodomains of rodlike nematic polymers. PMID:16383413

  1. A liquid crystal adaptive lens

    NASA Technical Reports Server (NTRS)

    Kowel, S. T.; Cleverly, D.

    1981-01-01

    Creation of an electronically controlled liquid crystal lens for use as a focusing mechanism in a multi-element lens system or as an adaptive optical element is analyzed. Varying the index of refraction is shown to be equivalent to the shaping of a solid refracting material. Basic characteristics of liquid crystals, essential for the creation of a lens, are reviewed. The required variation of index of refraction is provided by choosing appropriate electrode voltages. The configuration required for any incoming polarization is given and its theoretical performance in terms of modulation transfer function derived.

  2. Liquid crystal Fresnel lens display

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Qian; Abhishek Kumar, Srivastava; Alwin Tam, Ming-Wai; Zheng, Zhi-Gang; Shen, Dong; Vladimir, Chigrinov G.; Kwok, Hoi-Sing

    2016-09-01

    A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. Project supported by Partner State Key Laboratory on Advanced Displays and Optoelectronics Technologies HKUST, China, the National Natural Science Foundation of China (Grant Nos. 61435008 and 61575063), and the Fundamental Research Funds for the Central Universities, China (Grant No. WM1514036).

  3. Liquid crystal Fresnel lens display

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Qian; Abhishek Kumar, Srivastava; Alwin Tam, Ming-Wai; Zheng, Zhi-Gang; Shen, Dong; Vladimir, Chigrinov G.; Kwok, Hoi-Sing

    2016-09-01

    A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. Project supported by Partner State Key Laboratory on Advanced Displays and Optoelectronics Technologies HKUST, China, the National Natural Science Foundation of China (Grant Nos. 61435008 and 61575063), and the Fundamental Research Funds for the Central Universities, China (Grant No. WM1514036).

  4. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

  5. Gain dynamics in liquid crystal photorefractive hybrids

    NASA Astrophysics Data System (ADS)

    Liebig, C. M.; Tabiryan, N. V.; Basun, S. A.; Ighodalo, I. U.; Reshetnyak, V. Y.; Evans, D. R.

    2014-09-01

    Photorefractive (PR) hybrid liquid crystal (LC) cells have combined the space-charge field generated in either a polymer (using e.g. PVK;C60) with the large birefringence from a LC layer to generate PR grating for beam coupling applications. The efficiency of PR beam coupling in hybrid devices is dependent on the amplitude of the space-charge field, as well as the ability of the LC molecules to align with the corresponding field. In this paper the time dynamics of the formation of the PR gratings are measured in LC hybrid systems and are used to explain the large variation of gain coefficients found in the literature.

  6. Copper sulfate: Liquid or crystals?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two separate experiments were conducted to evaluate copper toxicity to channel catfish and free-swimming Ichthyophthirius multifiliis or Ich (the stage of Ich that can be treated); the compounds we used were CuSO4 crystals and a non-chelated liquid CuSO4 product. In 96 hr tests conducted in aquaria...

  7. Liquid-Crystal Optical Correlator

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang

    1989-01-01

    Optical correlator uses commercially-available liquid-crystal television (LCTV) screen as spatial light modulator. Correlations with this device done at video frame rates, making such operations as bar-code recognition possible at reasonable cost. With further development, such correlator useful in automation, robotic vision, and optical image processing.

  8. Experiments with Cholesteric Liquid Crystals

    ERIC Educational Resources Information Center

    Fergason, James L.

    1970-01-01

    Describes laboratory experiments designed to demonstrate (1) the properties of cholesteric liquid crystals, (2) thermal mapping, (3) thermal diffusivity, (4) adiabatic expansion of rubber, and (5) measurement of radiated energy by a point source. Contains all of the information on materials and apparatus needed to perform the experiments.…

  9. Large-amplitude motion in polymer crystals and mesophases

    SciTech Connect

    Wunderlich, B. |

    1994-12-31

    Large-amplitude motion of macromolecules involves mainly rotation about bonds (conformational motion). In the liquid phases, the large- amplitude motion is coupled with disorder and accounts for the flow and viscoelastic behavior. Perfectly ordered crystals, in contrast, permit only little large-amplitude motion. The mesophases are intermediate in order and mobility. In crystals, large-amplitude motion leads initially to gauche defects and kinks (conformational defects), and ultimately may produce conformationally disordered crystals (conis crystals). Molecular dynamics simulations of crystals with up to 30,000 atoms have been carried out and show the mechanism of defect formation, permit the study of the distribution of defects, and the visualization of hexagonal crystals. Distinction between main-chain liquid-crystalline macromolecules and condis crystals, the two mesophases of polymers, can be done on basis of analysis of phase separation (partial crystallinity), present in condis crystals and not in liquid crystals. Solid state NMR is the tool of choice for detecting mobile and rigid phases. In highly drawn fibers one can find four different states of order and mobility. Besides the (defect) crystalline phase and the isotropic amorphous phase, an intermediate oriented phase and a rigid amorphous phase exists.

  10. Orthoconic liquid crystals--a case study.

    PubMed

    Lagerwall, Sven T

    2014-06-01

    Since the early investigations on liquid crystals it was realized how the confining surfaces often determine the textures and even properties of the material. This influence is particularly complex and important for chiral materials. When we come to chiral smectics the surfaces may have dramatic effects. These are illustrated on the ferroelectric liquid crystals; they then again increase in importance for the antiferroelectric liquid crystals where the most recent example is given by the orthoconic liquid crystals.

  11. Smectic layer instabilities in liquid crystals.

    PubMed

    Dierking, Ingo; Mitov, Michel; Osipov, Mikhail A

    2015-02-01

    Scientists aspire to understand the underlying physics behind the formation of instabilities in soft matter and how to manipulate them for diverse investigations, while engineers aim to design materials that inhibit or impede the nucleation and growth of these instabilities in critical applications. The present paper reviews the field-induced rotational instabilities which may occur in chiral smectic liquid-crystalline layers when subjected to an asymmetric electric field. Such instabilities destroy the so-named bookshelf geometry (in which the smectic layers are normal to the cell surfaces) and have a detrimental effect on all applications of ferroelectric liquid crystals as optical materials. The transformation of the bookshelf geometry into horizontal chevron structures (in which each layer is in a V-shaped structure), and the reorientation dynamics of these chevrons, are discussed in details with respect to the electric field conditions, the material properties and the boundary conditions. Particular attention is given to the polymer-stabilisation of smectic phases as a way to forbid the occurrence of instabilities and the decline of related electro-optical performances. It is also shown which benefit may be gained from layer instabilities to enhance the alignment of the liquid-crystalline geometry in practical devices, such as optical recording by ferroelectric liquid crystals. Finally, the theoretical background of layer instabilities is given and discussed in relation to the experimental data.

  12. Liquid crystal polyester thermosets

    DOEpatents

    Benicewicz, Brian C.; Hoyt, Andrea E.

    1992-01-01

    The present invention provides (1) curable liquid crystalline polyester monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 where R.sup.1 and R.sup.2 are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted naimide, ethynyl, and (C(R.sup.3).sub.2).sub.2 where R.sup.3 is hydrogen with the proviso that the two carbon atoms of (C(R.sup.3).sub.2).sub.2 are bound on the aromatic ring of A.sup.1 or A.sup.3 to adjacent carbon atoms, A.sup.1 and A.sup.3 are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro lower alkyl, e.g., methyl, ethyl, or propyl, alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl, e.g., trifluoromethyl, pentafluoroethyl and the like, A.sup.2 is selected from the group consisting of 1,4-phenylene, 4,4'-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B.sup.1 and B.sup.2 are selected from the group consisting of --C(O)--O-- and --O--C(O)--, (2) thermoset liquid crystalline polyester compositions comprised of heat-cured segments derived from monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 as described above, (3) curable blends of at least two of the polyester monomers and (4) processes of preparing the curable liquid crystalline polyester monomers.

  13. Liquid Crystals: The Phase of the Future.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate; And Others

    1992-01-01

    Liquid crystal displays are currently utilized to convey information via graphic displays. Presents experiments and explanations that employ the concept of liquid crystals to learn concepts related to the various states of matter, electric and magnetic forces, refraction of light, and optics. Discusses applications of liquid crystal technology.…

  14. Macroscopic chirality of a liquid crystal from nonchiral molecules

    SciTech Connect

    Jakli, A.; Nair, G. G.; Lee, C. K.; Sun, R.; Chien, L. C.

    2001-06-01

    The transfer of chirality from nonchiral polymer networks to the racemic B2 phase of nonchiral banana-shaped molecules is demonstrated. This corresponds to the transfer of chirality from an achiral material to another achiral material. There are two levels of chirality transfers. (a) On a microscopic level the presence of a polymer network (chiral or nonchiral) favors a chiral state over a thermodynamically stable racemic state due to the inversion symmetry breaking at the polymer-liquid crystal interfaces. (b) A macroscopically chiral (enantimerically enriched) sample can be produced if the polymer network has a helical structure, and/or contains chemically chiral groups. The chirality transfer can be locally suppressed by exposing the liquid crystal to a strong electric field treatment.

  15. Fullerene solar cells with cholesteric liquid crystal doping

    NASA Astrophysics Data System (ADS)

    Jiang, Lulu; Jiang, Yurong; Zhang, Congcong; Chen, Zezhang; Qin, Ruiping; Ma, Heng

    2016-09-01

    This paper reports the doping effect of cholesteric liquid crystal 3β-Hydroxy-5-cholestene 3-oleate on polymer solar cells composed of the poly 3-hexyl thiophene and the fullerene derivative. With a doping ratio of 0.3 wt%, the device achieves an ideal improvement on the shunt resistor and the fill factor. Compared with the reference cell, the power conversion efficiency of the doped cell is improved 24%. The photoelectric measurement and the active layer characterization indicate that the self-assembly liquid crystal can improve the film crystallization and reduce the membrane defect. Project supported by the National Natural Science Foundation of China (Grant No. 61540016).

  16. Function Spaces for Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Bedford, Stephen

    2016-02-01

    We consider the relationship between three continuum liquid crystal theories: Oseen-Frank, Ericksen and Landau-de Gennes. It is known that the function space is an important part of the mathematical model and by considering various function space choices for the order parameters s, n, and Q, we establish connections between the variational formulations of these theories. We use these results to justify a version of the Oseen-Frank theory using special functions of bounded variation. This proposed model can describe both orientable and non-orientable defects. Finally we study a number of frustrated nematic and cholesteric liquid crystal systems and show that the model predicts the existence of point and surface discontinuities in the director.

  17. Substrate-induced gliding in a nematic liquid crystal layer

    NASA Astrophysics Data System (ADS)

    Mema, E.; Kondic, L.; Cummings, L. J.

    2015-12-01

    We consider the interaction between nematic liquid crystals (NLCs) and polymer substrates. Such substrates can interact with NLCs, exhibiting a phenomenon known as director gliding: the preferred orientation of the NLC molecules at the interface changes on time scales that are slow relative to the elastic relaxation time scale of the NLC. We present two models for gliding, inspired by experiments that investigate the interaction between the NLC and a polymer substrate. These models, though simple, lead to nontrivial results, including loss of bistability under gliding. Perhaps surprisingly, we find that externally imposed switching between the steady states of a bistable system may reverse the effect of gliding, preventing loss of bistability if switching is sufficiently frequent. Our findings may be of relevance to a variety of technological applications involving liquid crystal devices, and particularly to a new generation of flexible liquid crystal displays that implement polymeric substrates.

  18. Cholesteric liquid crystal photonic crystal lasers and photonic devices

    NASA Astrophysics Data System (ADS)

    Zhou, Ying

    This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser

  19. Swimming bacteria in liquid crystal

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Zhou, Shuang; Aranson, Igor; Lavrentovich, Oleg

    2014-03-01

    Dynamics of swimming bacteria can be very complex due to the interaction between the bacteria and the fluid, especially when the suspending fluid is non-Newtonian. Placement of swimming bacteria in lyotropic liquid crystal produces a new class of active materials by combining features of two seemingly incompatible constituents: self-propelled live bacteria and ordered liquid crystals. Here we present fundamentally new phenomena caused by the coupling between direction of bacterial swimming, bacteria-triggered flows and director orientations. Locomotion of bacteria may locally reduce the degree of order in liquid crystal or even trigger nematic-isotropic phase transition. Microscopic flows generated by bacterial flagella disturb director orientation. Emerged birefringence patterns allow direct optical observation and quantitative characterization of flagella dynamics. At high concentration of bacteria we observed the emergence of self-organized periodic texture caused by bacteria swimming. Our work sheds new light on self-organization in hybrid bio-mechanical systems and can lead to valuable biomedical applications. Was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under the Contract No. DE AC02-06CH11357.

  20. Thermally switchable flexible liquid crystal devices in prepolymer-doped cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Fuh, A. Y.-G.; Li, J.-H.; Cheng, K.-T.

    2010-10-01

    This work describes an approach for fabricating thermally switchable flexible liquid crystal devices in prepolymer-doped cholesteric liquid crystals (CLCs). The roughness of the UV-cured polymer film eliminates the stability of planar CLCs, allowing the textures in the UV-cured regions to be changed from planar to focal conic. Impurities associated with doping with prepolymers cause the clearing temperature of LCs in the UV-cured regions to differ from that in the uncured regions as the prepolymers are polymerized. Therefore, the textures in these two regions can be switched by controlling the temperature. Thermally switchable flexible LC devices, such as optically addressed smart cards, light valves, and others, can be realized using this approach.

  1. Polymer-cholesteric liquid-crystalline composites with a broad light reflection band

    NASA Astrophysics Data System (ADS)

    Mitov, Michel

    2016-05-01

    Cholesteric liquid crystals selectively reflect the light. The reflection bandgap is typically limited to 100 nm in the visible spectrum and, at the best, 50% of the unpolarized incident light is reflected. Solutions are found in biopolymers and polymer-liquid crystal composite materials to go beyond these limits.

  2. Novel liquid-crystal alignment method using polarized laser light (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Sun, Shao-Tang; Gibbons, Wayne M.; Shannon, Paul J.

    1992-10-01

    The control of liquid crystal alignment is of critical importance to the electro-optic performance of a liquid crystal display. Recently a new alignment method was discovered. Instead of the conventional buffing technique, polarized light is employed to treat the polymer alignment layer on the substrate of the display cell for the control of liquid crystal orientation. This non-contact method of aligning liquid crystals offers unique possibilities for display cell repair or reconfiguration after cell assembly. In addition, novel liquid crystal phase devices can be realized for use in optical processing.

  3. Tracking transient temperatures with liquid crystals

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Facemire, B. R.

    1975-01-01

    The theoretical basis of the use of the liquid crystal technique to obtain transient thermal data is discussed. Results of calibrations of liquid crystal temperature sensors are given. The effects of crystal aging, lighting effects, observer bias, etc., on accuracy are discussed. The sensitivity of liquid crystal tapes as sensors of dynamic temperature changes is quite high. The accuracy of the technique is determined primarily by the type of calibration apparatus used.

  4. Spontaneous Crystallization in Athermal Polymer Packings

    PubMed Central

    Karayiannis, Nikos Ch.; Foteinopoulou, Katerina; Laso, Manuel

    2013-01-01

    We review recent results from extensive simulations of the crystallization of athermal polymer packings. It is shown that above a certain packing density, and for sufficiently long simulations, all random assemblies of freely-jointed chains of tangent hard spheres of uniform size show a spontaneous transition into a crystalline phase. These polymer crystals adopt predominantly random hexagonal close packed morphologies. An analysis of the local environment around monomers based on the shape and size of the Voronoi polyhedra clearly shows that Voronoi cells become more spherical and more symmetric as the system transits to the ordered state. The change in the local environment leads to an increase in the monomer translational contribution to the entropy of the system, which acts as the driving force for the phase transition. A comparison of the crystallization of hard-sphere polymers and monomers highlights similarities and differences resulting from the constraints imposed by chain connectivity. PMID:23263666

  5. Crystallization analysis for fiber/polymer composites

    NASA Astrophysics Data System (ADS)

    Raimo, Maria

    2016-05-01

    The peculiar nucleation behavior of low thermal conductivity polymer matrixes and the particular morphologies around fibers found in several composites, invalidate some assumptions invoked in the general description of the solidification kinetics of polycrystalline substances. The model of solidification universally adopted for polycrystalline substances, originally developed for metals, needs to be adapted also to account for large differences between polymers and fibers in thermoplastic composites. The extension of the classical phase transitions theory to fiber/polymer composites, in view of their specific thermal properties, allows to achieve reliable information on crystallization behavior and microstructure inside composites.

  6. Protein crystallization facilitated by molecularly imprinted polymers

    PubMed Central

    Saridakis, Emmanuel; Khurshid, Sahir; Govada, Lata; Phan, Quan; Hawkins, Daniel; Crichlow, Gregg V.; Lolis, Elias; Reddy, Subrayal M.; Chayen, Naomi E.

    2011-01-01

    We present a previously undescribed initiative and its application, namely the design of molecularly imprinted polymers (MIPs) for producing protein crystals that are essential for determining high-resolution 3D structures of proteins. MIPs, also referred to as “smart materials,” are made to contain cavities capable of rebinding protein; thus the fingerprint of the protein created on the polymer allows it to serve as an ideal template for crystal formation. We have shown that six different MIPs induced crystallization of nine proteins, yielding crystals in conditions that do not give crystals otherwise. The incorporation of MIPs in screening experiments gave rise to crystalline hits in 8–10% of the trials for three target proteins. These hits would have been missed using other known nucleants. MIPs also facilitated the formation of large single crystals at metastable conditions for seven proteins. Moreover, the presence of MIPs has led to faster formation of crystals in all cases where crystals would appear eventually and to major improvement in diffraction in some cases. The MIPs were effective for their cognate proteins and also for other proteins, with size compatibility being a likely criterion for efficacy. Atomic force microscopy (AFM) measurements demonstrated specific affinity between the MIP cavities and a protein-functionalized AFM tip, corroborating our hypothesis that due to the recognition of proteins by the cavities, MIPs can act as nucleation-inducing substrates (nucleants) by harnessing the proteins themselves as templates. PMID:21690356

  7. Perspectives in active liquid crystals.

    PubMed

    Majumdar, Apala; Cristina, Marchetti M; Virga, Epifanio G

    2014-11-28

    Active soft matter is a young, growing field, with potential applications to a wide variety of systems. This Theme Issue explores this emerging new field by highlighting active liquid crystals. The collected contributions bridge theory to experiment, mathematical theories of passive and active nematics, spontaneous flows to defect dynamics, microscopic to continuum levels of description, spontaneous activity to biological activation. While the perspectives offered here only span a small part of this rapidly evolving field, we trust that they might provide the interested reader with a taste for this new class of non-equilibrium systems and their rich behaviour.

  8. Computer simulations of liquid crystals

    NASA Astrophysics Data System (ADS)

    Smondyrev, Alexander M.

    Liquid crystal physics is an exciting interdisciplinary field of research with important practical applications. Their complexity and the presence of strong translational and orientational fluctuations require a computational approach, especially in the studies of nonequlibrium phenomena. In this dissertation we present the results of computer simulation studies of liquid crystals using the molecular dynamics technique. We employed the Gay-Berne phenomenological model of liquid crystals to describe the interaction between the molecules. Both equilibrium and non-equilibrium phenomena were studied. In the first case we studied the flow properties of the liquid crystal system in equilibrium as well as the dynamics of the director. We measured the viscosities of the Gay-Berne model in the nematic and isotropic phases. The temperature-dependence of the rotational and shear viscosities, including the nonmonotonic behavior of one shear viscosity, are in good agreement with experimental data. The bulk viscosities are significantly larger than the shear viscosities, again in agreement with experiment. The director motion was found to be ballistic at short times and diffusive at longer times. The second class of problems we focused on is the properties of the system which was rapidly quenched to very low temperatures from the nematic phase. We find a glass transition to a metastable phase with nematic order and frozen translational and orientational degrees of freedom. For fast quench rates the local structure is nematic-like, while for slower quench rates smectic order is present as well. Finally, we considered a system in the isotropic phase which is then cooled to temperatures below the isotropic-nematic transition temperature. We expect topological defects to play a central role in the subsequent equilibration of the system. To identify and study these defects we require a simulation of a system with several thousand particles. We present the results of large

  9. Perspectives in active liquid crystals

    PubMed Central

    Majumdar, Apala; Cristina, Marchetti M.; Virga, Epifanio G.

    2014-01-01

    Active soft matter is a young, growing field, with potential applications to a wide variety of systems. This Theme Issue explores this emerging new field by highlighting active liquid crystals. The collected contributions bridge theory to experiment, mathematical theories of passive and active nematics, spontaneous flows to defect dynamics, microscopic to continuum levels of description, spontaneous activity to biological activation. While the perspectives offered here only span a small part of this rapidly evolving field, we trust that they might provide the interested reader with a taste for this new class of non-equilibrium systems and their rich behaviour. PMID:25332386

  10. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

    The process of simultaneous optical visualization and quantitative measurement of aerodynamic boundary layer parameters requires new concepts, materials and utilization methods. Measurement of shear stress in terms of the transmitted or the reflected light intensity from an aligned ferroelectric liquid crystal (FLC) thin (approx. 1 micron) film deposited on a glass substrate has been the first step in this direction. In this paper, recent progress in utilization of FLC thin films for skin friction measurement and for studying the state of the boundary layer in a wind tunnel environment is reviewed. The switching characteristics of FLCs have been used to measure pressure from the newly devised system of partially exposed polymer dispersed ferroelectric liquid crystals (PEPDFLCs). In this configuration, a PEPDFLC thin film (approx. 10-25 microns) is sandwiched between two transparent conducting electrodes, one a rigid surface and the other a flexible sheet such as polyvinylidene fluoride or mylar. The switching characteristics of the film are a function of the pressure applied to the flexible transparent electrode and a predetermined bias voltage across the two electrodes. The results, considering the dielectrics of composite media, are discussed.

  11. Modeling of Crystallizing Polymer Melts in Electrospinning

    SciTech Connect

    Zhmayev, Eduard; Joo, Yong Lak

    2008-07-07

    In electrospinning, applied electric field elongates a charged fluid jet to produce nanofibers. While most polymer melts result in highly-aligned amorphous structures, some fast-crystallizing polymers such as Nylon can produce semi-crystalline fibers, and by controlling this crystallinity the mechanical properties of electrospun fibers can be tailored. Short inflight residence times, high extensional forces, and radially-uniform stress distributions in electrospinning result in the dominance of flow induced crystallization (FIC) and a nearly 1D microstructure. We present our FIC model based on Kolmogoroff's equation, Hoffman-Lauritzen theory, and key modifications from molecular scale insights to account for flow effects. The model behavior is compared to the conventional Ziabicki FIC model using Nylon-6,6 as the model polymer.

  12. 3D interconnected ionic nano-channels formed in polymer films: self-organization and polymerization of thermotropic bicontinuous cubic liquid crystals.

    PubMed

    Ichikawa, Takahiro; Yoshio, Masafumi; Hamasaki, Atsushi; Kagimoto, Junko; Ohno, Hiroyuki; Kato, Takashi

    2011-02-23

    Thermotropic bicontinuous cubic (Cub(bi)) liquid-crystalline (LC) compounds based on a polymerizable ammonium moiety complexed with a lithium salt have been designed to obtain lithium ion-conductive all solid polymeric films having 3D interconnected ionic channels. The monomer shows a Cub(bi) phase from -5 to 19 °C on heating. The complexes retain the ability to form the Cub(bi) LC phase. They also form hexagonal columnar (Col(h)) LC phases at temperatures higher than those of the Cub(bi) phases. The complex of the monomer and LiBF(4) at the molar ratio of 4:1 exhibits the Cub(bi) and Col(h) phases between -6 to 19 °C and 19 to 56 °C, respectively, on heating. The Cub(bi) LC structure formed by the complex has been successfully preserved by in situ photopolymerization through UV irradiation in the presence of a photoinitiator. The resultant nanostructured film is optically transparent and free-standing. The X-ray analysis of the film confirms the preservation of the self-assembled nanostructure. The polymer film with the Cub(bi) LC nanostructure exhibits higher ionic conductivities than the polymer films obtained by photopolymerization of the complex in the Col(h) and isotropic phases. It is found that the 3D interconnected ionic channels derived from the Cub(bi) phase function as efficient ion-conductive pathways.

  13. Stretchable liquid-crystal blue-phase gels.

    PubMed

    Castles, F; Morris, S M; Hung, J M C; Qasim, M M; Wright, A D; Nosheen, S; Choi, S S; Outram, B I; Elston, S J; Burgess, C; Hill, L; Wilkinson, T D; Coles, H J

    2014-08-01

    Liquid-crystalline polymers are materials of considerable scientific interest and technological value. An important subset of these materials exhibit rubber-like elasticity, combining the optical properties of liquid crystals with the mechanical properties of rubber. Moreover, they exhibit behaviour not seen in either type of material independently, and many of their properties depend crucially on the particular mesophase employed. Such stretchable liquid-crystalline polymers have previously been demonstrated in the nematic, chiral-nematic, and smectic mesophases. Here, we report the fabrication of a stretchable gel of blue phase I, which forms a self-assembled, three-dimensional photonic crystal that remains electro-optically switchable under a moderate applied voltage, and whose optical properties can be manipulated by an applied strain. We also find that, unlike its undistorted counterpart, a mechanically deformed blue phase exhibits a Pockels electro-optic effect, which sets out new theoretical challenges and possibilities for low-voltage electro-optic devices.

  14. Cooperative liquid-crystal alignment generated by overlaid topography

    NASA Astrophysics Data System (ADS)

    Yi, Youngwoo; Maclennan, Joseph E.; Clark, Noel A.

    2011-05-01

    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.

  15. Cooperative liquid-crystal alignment generated by overlaid topography.

    PubMed

    Yi, Youngwoo; Maclennan, Joseph E; Clark, Noel A

    2011-05-01

    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. PMID:21728557

  16. Observation of large nematic domains of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Shinde, Abhijeet; Wang, Xuezhen; Cheng, Zhengdong

    2015-03-01

    Discotic liquid crystals are commonly found in nature in the form of clay, nacre. They are technologically important in applications such as conductive polymers, semiconductors and photovoltaics. Size and its distribution play an important role in their self-assemblies. Here we observed large nematic domains of discotic liquid crystals grown on a time scale of months. The development of such domains is observed to be faster for nanodisks that relatively smaller in size. The orientation of nanodisks is affected by gravity and inter-particle interactions which are yet to be fully understood.

  17. Nanoscopic Manipulation and Imaging of Liquid Crystals

    SciTech Connect

    Rosenblatt, Charles S.

    2014-02-04

    This is the final project report. The project’s goals centered on nanoscopic imaging and control of liquid crystals and surfaces. We developed and refined techniques to control liquid crystal orientation at surfaces with resolution as small as 25 nm, we developed an optical imaging technique that we call Optical Nanotomography that allows us to obtain images inside liquid crystal films with resolution of 60 x 60 x 1 nm, and we opened new thrust areas related to chirality and to liquid crystal/colloid composites.

  18. All-polymer photonic crystal slab sensor.

    PubMed

    Hermannsson, Pétur G; Sørensen, Kristian T; Vannahme, Christoph; Smith, Cameron L C; Klein, Jan J; Russew, Maria-Melanie; Grützner, Gabi; Kristensen, Anders

    2015-06-29

    An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications. PMID:26191664

  19. Reflective Direct-View Displays Using a Dye-Doped Dual-Frequency Liquid Crystal Gel

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Ren, Hongwen; Gauza, Sebastian; Wu, Yung-Hsun; Liang, Xiao; Wu, Shin-Tson

    2005-12-01

    A high-contrast, fast-response, and polarizer-free reflective display using a dye-doped dual-frequency liquid crystal gel is demonstrated. The high contrast ratio originates from the combination of light scattering from the microdomain polymer gel and absorption from the black dyes. The fast response is due to the frequency modulation of the dual-frequency liquid crystal.

  20. How Does Phase Separation Affect Crystallization Kinetics in a Polymer Blend?

    NASA Astrophysics Data System (ADS)

    Wang, Howard; Müller, A. J.; Shimizu, K.; Wang, Z. G.; Han, C. C.; Hsiao, B. S.

    2003-03-01

    Polymer blends can exhibit both liquid-liquid phase separation (LLPS) and crystallization. The effect of LLPS on crystallization kinetics has been investigated in a blend of statistical ethylene/hexane (PEH) and ethylene/butene (PEB) copolymers, where PEH is the predominantly crystallizable component. The composition dependence of the primary crystallization kinetics shows a minimum near the LLPS boundary, resembling a critical slowing down behavior. The kinetics of secondary crystallization, however, shows a minimum near the critical composition of LLPS. Those behaviors are discussed in terms of thermodynamic and circumstantial metastability in polymers. During the primary crystallization, density fluctuations in phase separating melts may effectively lower the free energy barrier for nucleation; during the secondary crystallization, coexisting LLPS domains and crystal superstructures interfere with each other and change the course of their development.

  1. Liquid-Crystal Point-Diffraction Interferometer

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.

    1996-01-01

    Liquid-crystal point-diffraction interferometer (LCPDI) invented to combine flexible control of liquid-crystal phase-shifts with robustness of point-diffraction interferometers. Produces interferograms indicative of shapes of wavefronts of laser beams having passed through or reflected from objects of interest. Interferograms combined in computers to produce phase maps describing wavefronts.

  2. Demonstrations with a Liquid Crystal Shutter

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2012-01-01

    The experiments presented show the response of a liquid crystal shutter to applied electric voltages and the delay of the operations. Both properties are important for liquid crystal displays of computers and television sets. Two characteristics of the shutter are determined: (i) the optical transmittance versus applied voltage of various…

  3. Liquid Crystals in Education--The Basics

    ERIC Educational Resources Information Center

    Cepic, Mojca

    2012-01-01

    The introduction of teaching about liquid crystals is discussed from several points of view: the rationale why to teach them, the basics about liquid crystals or what the teacher should teach about them, the fundamental pre-knowledge of students required, the set of experiments accompanying the teaching and the brief report on the already…

  4. Study of local stress, morphology, and liquid-crystal alignment on buffed polyimide surfaces

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hirotsugu; Logan, J. A.; Yoon, Do Y.

    1996-05-01

    The magnitude of local stress applied to a polymer surface in the buffing process, which is a critical method to uniformly align liquid crystals for displays, has been evaluated from the polarizing optical microscopic investigation of nematic liquid crystals in contact with polyimide surfaces which were suitably buffed in order to visualize the individual tracks of the buffing rayon fibers. The estimated magnitude of local stress is most likely to be far greater than the yield stress of the polymer film, thereby causing permanent molecular orientation along the buffing direction. The surfaces of poly(amic acid) and cured polyimide films, subjected to different buffing and cure profiles, have been examined by atomic force microscopy. The ability of these buffed polymer surfaces to align nematic and chiral smectic C (ferroelectric) liquid crystals were also investigated. These studies show that the presence of microgrooves on buffed polymer surfaces is not necessary for alignment of liquid crystals. The contribution of polymer molecules from the buffing fibers, deposited and oriented on the polyimide surfaces during buffing, can also be ruled out. Rather, it is concluded that the liquid-crystal alignment is mainly caused by the anisotropic interactions between liquid-crystal molecules and the polymer segments oriented through plastic deformation, with little contribution from frictional heating. For the alignment of smectics, both the degree of order and mechanical properties of polyimide films are found to be important factors.

  5. Observation and Analysis of Polymer Crystal Structures at the Stem Level. Implications Regarding Polymer Crystallization Processes.

    NASA Astrophysics Data System (ADS)

    Lotz, Bernard

    2003-03-01

    The building element of chain folded polymer crystals is the individual stem that spans the lamellar thickness. For chiral but racemic helical polymers such as polyolefins (e.g. isotactic and syndiotactic polypropylene and poly(1-butene)), stems can be right- or left-handed helices. These polymers can exist in various crystal polymorphs that are either "racemic" or "chiral" (made of both, or of only one helical hand). Upon crystallization, each stem has a conformational "choice", but must adapt to the crystal structure and, once crystallized, is characterized by a "conformational tag" (right or left hand). Various means exist to determine or observe helical hands in polyolefin lamellae: Atomic Force Microscopy on epitaxially crystallized samples, or, for the alpha phase of isotactic polypropylene, analysis of its specific lamellar branching. These observations and analyses indicate that the helical hand of stems is tightly determined by the substrate or growth face topography, i.e. indicate that the depositing stem probes and adapts to the surface structure prior to successful attachment. This "post-mortem" analysis of the crystal structure and stem chirality emphasizes the "sequential" nature of the growth process (successive attachment of individual stems). It is in line with early views on polymer crystallization. It is at variance with recently introduced models or scenarios that assume either some pre-ordering of the polymer melt as a result of spinodal decomposition and/or accretion of polymer chains in pseudo-crystalline bundles followed by (solid state) reorganization of the bundles to generate fully grown lamellae.

  6. Chemical and biological sensing using liquid crystals

    PubMed Central

    Carlton, Rebecca J.; Hunter, Jacob T.; Miller, Daniel S.; Abbasi, Reza; Mushenheim, Peter C.; Tan, Lie Na; Abbott, Nicholas L.

    2014-01-01

    The liquid crystalline state of matter arises from orientation-dependent, non-covalent interaction between molecules within condensed phases. Because the balance of intermolecular forces that underlies formation of liquid crystals is delicate, this state of matter can, in general, be easily perturbed by external stimuli (such as an electric field in a display). In this review, we present an overview of recent efforts that have focused on exploiting the responsiveness of liquid crystals as the basis of chemical and biological sensors. In this application of liquid crystals, the challenge is to design liquid crystalline systems that undergo changes in organization when perturbed by targeted chemical and biological species of interest. The approaches described below revolve around the design of interfaces that selectively bind targeted species, thus leading to surface-driven changes in the organization of the liquid crystals. Because liquid crystals possess anisotropic optical and dielectric properties, a range of different methods can be used to read out the changes in organization of liquid crystals that are caused by targeted chemical and biological species. This review focuses on principles for liquid crystal-based sensors that provide an optical output. PMID:24795857

  7. Liquid crystal applications in photonics

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir G.

    2009-02-01

    Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. We have already successfully fabricated certain prototypes of the optical switches based on various electrooptic modes in ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. We have already used the photoaligning materials to align LC mixtures in small cavities, such as the holes and tubes of photonic crystals, having size of 1 μm and less and obtained excellent LC orientation inside the tubes by photoalignment. The prototypes of new LC efficient Photonics devices, such as optically rewritable LC waveguides and voltage controllable diffraction gratings are envisaged. The polarization controllers, polarization rotators, variable optical attenuators and other passive LC optical elements for fiber communication networks are under way.

  8. Nonequilibrium molecular dynamics of liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, S. S.; Cummings, P. T.; Evans, D. J.

    1994-11-01

    During the last 15 years, noneyuilibrium molecular dynamics (NEMD) has been successfully applied to study transport phenomena in fluids that are isotropic at equilibrium. A natural extension is therefore to study liquid crystals, which are anisotropic al equilibrium. The lower symmetry of these systems means that the linear transport coefficients are considerably more complicated than in an isotropic system. Part of the reason for this is that there are crosscouplings between tensors of different rank and parity. Such couplings arc symmetry-forbidden in isotropic phases. In this paper. we review some of fundamental theoretical results we have derived concerning the rheology of liquid crystals. report NEMD simulations of thermal conductivity and shear viscosity of liquid crystals, and present NEMD simulations of shear cessation phenomena. All of the NEMD results are presented for a model liquid crystal fluid which is a modification of the Gay-Borne fluid. The results obtained are in qualitative agreement with experimental measurements on liquid crystal systems.

  9. Liquid crystal device and method thereof

    DOEpatents

    Shiyanovskii, Sergij V; Gu, Mingxia; Lavrentovich, Oleg D

    2012-10-23

    The invention provides a liquid crystal device and method thereof. Subsequent to applying a first electrical voltage on a liquid crystal to induce a reorientation of the liquid crystal, a second electrical voltage with proper polarity is applied on the liquid crystal to assist the relaxation of the reorientation that was induced by the first electrical voltage. The "switch-off" phase of the liquid crystal can therefore be accelerated or temporally shortened, and the device can exhibit better performance such as fast response to on/off signals. The invention can be widely used LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device, among others.

  10. Influence of Polymers on the Crystal Growth Rate of Felodipine: Correlating Adsorbed Polymer Surface Coverage to Solution Crystal Growth Inhibition.

    PubMed

    Schram, Caitlin J; Taylor, Lynne S; Beaudoin, Stephen P

    2015-10-20

    The bioavailability of orally administered drugs that exhibit poor aqueous solubility can be enhanced with the use of supersaturating dosage forms. Stabilization of these forms by preventing or inhibiting crystallization in solution is an important area of study. Polymers can be used to stabilize supersaturated systems; however, the properties that impact their effectiveness as crystal growth rate inhibitors are not yet fully understood. In this study, the impact of various polymers on the crystal growth rate of felodipine and the conformation of these polymers adsorbed to crystalline felodipine was investigated in order to gain a mechanistic understanding of crystal growth inhibition. It was determined that polymer hydrophobicity impacted polymer adsorption as well as adsorbed polymer conformation. Polymer conformation impacts its surface coverage, which was shown to directly correlate to the polymer's effectiveness as a growth rate inhibitor. By modeling this correlation, it is possible to predict polymer effectiveness given the surface coverage of the polymer.

  11. Liquid-crystal materials find a new order in biomedical applications

    NASA Astrophysics Data System (ADS)

    Woltman, Scott J.; Jay, Gregory D.; Crawford, Gregory P.

    2007-12-01

    With the maturation of the information display field, liquid-crystal materials research is undergoing a modern-day renaissance. Devices and configurations based on liquid-crystal materials are being developed for spectroscopy, imaging and microscopy, leading to new techniques for optically probing biological systems. Biosensors fabricated with liquid-crystal materials can allow label-free observations of biological phenomena. Liquid-crystal polymers are starting to be used in biomimicking colour-producing structures, lenses and muscle-like actuators. New areas of application in the realms of biology and medicine are stimulating innovation in basic and applied research into these materials.

  12. Tunable scattering from liquid crystal devices using carbon nanotubes network electrodes

    NASA Astrophysics Data System (ADS)

    Khan, Ammar A.; Dabera, G. Dinesha M. R.; Butt, Haider; Qasim, Malik M.; Amaratunga, Gehan A. J.; Silva, S. Ravi P.; Wilkinson, Timothy D.

    2014-11-01

    Liquid crystals are of technological interest as they allow for optical effects which can be electrically controlled. In this paper we present an electro-optical device consisting of nematic liquid crystals addressed by an electrode structure consisting of thin films of polymer wrapped single walled carbon nanotubes (nanohybrids). Thin films of nanohybrids display excellent optical transmission and electrical conduction properties. Due to the randomly organised nanohybrids these composite films produce interesting director profile arrangements within the liquid crystal layers. As a result, enhanced scattering of laser and white light was observed from these liquid crystal cells which bend themselves as electrically controllable optical diffusers and beam shapers.

  13. Domain structures in nematic liquid crystals on a polycarbonate surface.

    PubMed

    Parshin, Alexander M; Gunyakov, Vladimir A; Zyryanov, Victor Y; Shabanov, Vasily F

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface. PMID:23965955

  14. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    PubMed Central

    Parshin, Alexander M.; Gunyakov, Vladimir A.; Zyryanov, Victor Y.; Shabanov, Vasily F.

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface. PMID:23965955

  15. Domain structures in nematic liquid crystals on a polycarbonate surface.

    PubMed

    Parshin, Alexander M; Gunyakov, Vladimir A; Zyryanov, Victor Y; Shabanov, Vasily F

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  16. Bistable liquid crystal device fabricated via microscale liquid crystal alignment

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Toyoshima, Wataru; Nose, Toshiaki

    2016-10-01

    Bistable liquid crystal (LC) molecular orientation properties in micropatterned LC cells were investigated experimentally and theoretically. When an LC cell was heated to the phase-transition temperature and then cooled, an LC orientation with ±π/2-twist domains (±π/2-twist mode) was obtained. Furthermore, a different LC orientation with ±π-twist domains (±π-twist mode) was observed when a 10-V potential was applied across a sample LC cell. Both orientation states were stably retained over a long period. Herein, cross-sectional LC orientation models in the ±π/2- and ±π-twist modes are proposed to explain the generation and behavior of two different disclination lines. The total energies within one period in the ±π/2- and ±π-twist modes (F±π/2 and F±π, respectively) were estimated theoretically. These energies were found to depend on the LC layer thickness and to cross over at a certain thickness; this indicates that F±π is equal to F±π/2 at this equilibrium thickness. The best temporal stability is likely attained at this equilibrium thickness. We demonstrated a bistable color-switching device by combining a full-wave plate and crossed polarizers. When these optical components were configured properly, stable bistable switching between two colors was achieved.

  17. Polymer-induced phase separation and crystallization in immunoglobulin G solutions.

    PubMed

    Li, Jianguo; Rajagopalan, Raj; Jiang, Jianwen

    2008-05-28

    We study the effects of the size of polymer additives and ionic strength on the phase behavior of a nonglobular protein-immunoglobulin G (IgG)-by using a simple four-site model to mimic the shape of IgG. The interaction potential between the protein molecules consists of a Derjaguin-Landau-Verwey-Overbeek-type colloidal potential and an Asakura-Oosawa depletion potential arising from the addition of polymer. Liquid-liquid equilibria and fluid-solid equilibria are calculated by using the Gibbs ensemble Monte Carlo technique and the Gibbs-Duhem integration (GDI) method, respectively. Absolute Helmholtz energy is also calculated to get an initial coexisting point as required by GDI. The results reveal a nonmonotonic dependence of the critical polymer concentration rho(PEG) (*) (i.e., the minimum polymer concentration needed to induce liquid-liquid phase separation) on the polymer-to-protein size ratio q (equivalently, the range of the polymer-induced depletion interaction potential). We have developed a simple equation for estimating the minimum amount of polymer needed to induce the liquid-liquid phase separation and show that rho(PEG) (*) approximately [q(1+q)(3)]. The results also show that the liquid-liquid phase separation is metastable for low-molecular weight polymers (q=0.2) but stable at large molecular weights (q=1.0), thereby indicating that small sizes of polymer are required for protein crystallization. The simulation results provide practical guidelines for the selection of polymer size and ionic strength for protein phase separation and crystallization.

  18. Fast-switching flexoelectric cholesteric liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Kim, Sang Hwa; Shi, Lei; Chien, Liang-Chy

    2006-05-01

    Fast-switching flexoelectric cholesteric liquid crystal displays that can be operated in two modes: amplitude (flexoelectric effect, in-plane-switching) and phase (dielectric coupling, out-of-plane switching) have been developed. The device comprises of a small amount of polymer network localized at the substrate surfaces and short-pitch cholesteric liquid crystal whose helical axis laid in the direction parallel to the substrates. The polymer network stabilizes the helical axis in the plane parallel to the substrates at zero voltage. The response times for amplitude and phase switching of a polymer-stabilized cholesteric display with 2 microns cell gap are 200 μs at 3.5 V/μm and 3 ms at 12.5 V/μm, respectively. Using a dual-frequency switchable nematic liquid crystal, we are able to improve the contrast of the amplitude switching by obtaining a larger deviation angle of helical axis with a high voltage and in the same time, suppressing the helix unwinding.

  19. Defects and order in liquid crystal phases

    NASA Astrophysics Data System (ADS)

    Jain, Shilpa

    This thesis investigates the partial destruction of ordering in liquid crystalline systems due to the influence of defects and thermal fluctuations. The systems under consideration are hexagonal columnar crystals with crystalline order perpendicular to the columns, and two-dimensional smectics with order perpendicular to the layers. We first study the possibility of reentrant melting of a hexagonal columnar crystal of flexible charged polymers at high enough densities. The Lindemann criterion is employed in determining the melting point. Lattice fluctuations are calculated in the Debye model, and an analogy with the Abrikosov vortex lattice in superconductors is exploited in estimating both the elastic constants of the hexagonal lattice, and the appropriate Lindemann constant. We also discuss the unusual functional integral describing the statistical mechanics of a single polymer in an Einstein cage model using the path-integral formulation. A crossover as a function of an external field along the column axis is discussed as well. Next, we study defects in a columnar crystal in the form of vacancy/interstitial loops or strings of vacancies and interstitials bounded by column "heads" and "tails". These defect strings are oriented by the columnar lattice and can change size and shape by movement of the ends and forming kinks along the length. Hence an analysis in terms of directed living polymers is appropriate to study their size and shape distribution, volume fraction, etc. If the entropy of transverse fluctuations overcomes the string line tension in the crystalline phase, a string proliferation transition occurs, leading to a "supersolid" phase with infinitely long vacancy or interstitial strings. We estimate the wandering entropy and examine the behaviour in the transition regime. We also calculate numerically the line tension of various species of vacancies and interstitials in a triangular lattice for power-law potentials as well as for a modified Bessel

  20. Two distinct crystallization processes in supercooled liquid.

    PubMed

    Tane, Masakazu; Kimizuka, Hajime; Ichitsubo, Tetsu

    2016-05-21

    Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport. PMID:27208956

  1. Two distinct crystallization processes in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Tane, Masakazu; Kimizuka, Hajime; Ichitsubo, Tetsu

    2016-05-01

    Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport.

  2. Liquid Crystal Research Shows Deformation By Drying

    NASA Technical Reports Server (NTRS)

    2003-01-01

    These images, from David Weitz's liquid crystal research, show ordered uniform sized droplets (upper left) before they are dried from their solution. After the droplets are dried (upper right), they are viewed with crossed polarizers that show the deformation caused by drying, a process that orients the bipolar structure of the liquid crystal within the droplets. When an electric field is applied to the dried droplets (lower left), and then increased (lower right), the liquid crystal within the droplets switches its alignment, thereby reducing the amount of light that can be scattered by the droplets when a beam is shone through them.

  3. Multicomponent Thermodynamics of Strain-Induced Polymer Crystallization.

    PubMed

    Zha, Liyun; Wu, Yixian; Hu, Wenbing

    2016-07-14

    We developed a linear combination of two Flory's melting-point theories, one for stretched and the other for solution polymers, to predict the melting point of stretched solution polymers. The dependences of the melting strains on varying temperatures, polymer volume fractions, and solvent qualities were verified by the onset strains of crystallization in our dynamic Monte Carlo simulations of stretched solution polymers under a constant strain rate. In addition, owing to phase separation before crystallization in a poor solvent, calibration of polymer concentration to the polymer-rich phase appears necessary for the verification. Our results set up a preliminary thermodynamic background for the investigation of the multicomponent effect on strain-induced crystallization of polymers in rubbers and gels as well as on shear-induced crystallization of polymers in solutions and blends. PMID:27337066

  4. Tactoids of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo

    The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.

  5. Hierarchical Organization in Liquid Crystal-in-Liquid Crystal Emulsions

    PubMed Central

    Mushenheim, Peter C.

    2014-01-01

    We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4′-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field director of the DSCG phase. We determine that this coupling of orientations does not result from either anisometric LC droplet shape or interfacial ionic phenomena but rather is consistent with the influence of van der Waals interactions that arise from the anisotropic polarizabilities of nematic 5CB (Δn = + 0.18) and DSCG (Δn = − 0.02) phases. We also find that it is possible to rotate and uniformly align the nematic droplets by using a weak magnetic field (B ∼ 0.3 T). An analysis of the dynamics of relaxation of the orientations of the 5CB droplets following removal of the magnetic field reveals the DSCG and 5CB droplets to be coupled by energies of ∼104kT, consistent with a simple theoretical estimate of the influence of anisotropic van der Waals interactions. We also observed the nematic 5CB droplets to form dimers and larger assemblies mediated by the elasticity of the nematic DSCG. Overall, these results reveal that LC-in-LC emulsions define a new class of hierarchically ordered soft matter in which both thermotropic and lyotropic LCs are coupled in their ordering. PMID:25278032

  6. Nanoimprinted polymer photonic crystal dye lasers

    NASA Astrophysics Data System (ADS)

    Christiansen, Mads B.; Smith, Cameron L. C.; Buss, Thomas; Xiao, Sanshui; Mortensen, Niels A.; Kristensen, Anders

    2010-05-01

    Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of photodefinable Ormocore hybrid polymer, doped with the laser dye Pyrromethene 597. A compact frequency doubled Nd:YAG laser (352 nm, 5 ns pulses) is used to pump the lasers from above the chip. The laser devices are 450 nm thick slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The 2-dimensional rectangular lattice is described by two orthogonal unit vectors of length a and b, defining the ΓP and ΓX directions. The frequency of the laser can be tuned via the lattice constant a (187 nm - 215 nm) while pump light is resonantly coupled into the laser from an angle (θ) depending on the lattice constant b (355 nm). The lasers are fabricated in parallel on a 10 cm diameter wafer by combined nanoimprint and photolithography (CNP). CNP relies on a UV transparent quartz nanoimprint stamp with an integrated metal shadow mask. In the CNP process the photonic crystal is formed by mechanical deformation (imprinting) while the larger features are defined by UV exposure through the combined mask/mold.

  7. Rapid leak detection with liquid crystals

    NASA Technical Reports Server (NTRS)

    Heisman, R. M.; Iceland, W. F.; Ruppe, E. P.

    1978-01-01

    Small leaks in vacuum lines are detected by applying liquid-crystal coating, warming suspected area, and observing color change due to differential cooling by leak jet. Technique is used on inside or outside walls of vacuum-jacketed lines.

  8. Liquid crystal television spatial light modulators

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

  9. Liquid crystal on subwavelength metal gratings

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-01

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  10. Slow light in liquid crystal media

    NASA Astrophysics Data System (ADS)

    Bortolozzo, Umberto; Wei, Dong; Huignard, Jean-Pierre; Residori, Stefania

    2014-10-01

    Liquid crystal media are characterized by large and tunable dispersive properties and hence allow achievement of large group delays. At the same time, liquid crystals provide large areas and are easily reconfigurable and highly sensitive devices; they are, therefore, well adapted for interferometric applications. Two different ways of achieving slow light in liquid crystals are presented. The first method consists of exploiting photoisomerization-induced transparency in dye-doped chiral liquid crystals, and the second method makes use of two-wave mixing optical resonance in pure nematics. In both mechanisms, two beams are sent to the medium, where they create a grating, either of absorption or of refractive index. Both physical mechanisms are elucidated in the context of slow light, then, as examples of sensing applications, Doppler shift measurements and adaptive holography are presented.

  11. Thermal Conductivity and Liquid Crystal Thermometers.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1993-01-01

    Describes using stock liquid crystal postcards as inexpensive classroom thermometers. Also suggests using these postcards as a good visual temperature indicator for classroom demonstrations such as temperature gradients. One such activity is provided. (MVL)

  12. Liquid crystal on subwavelength metal gratings

    SciTech Connect

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-14

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  13. Disassembly and characterization of liquid crystal screens.

    PubMed

    Juchneski, Nichele C F; Scherer, Janine; Grochau, Inês H; Veit, Hugo M

    2013-06-01

    The technology used in the manufacturing of televisions and monitors has been changing in recent years. Monitors with liquid crystal displays (LCD) emerged in the market with the aim of replacing cathode ray tube monitors. As a result, the disposal of this type of product, which is already very high, will increase. Thus, without accurate knowledge of the components and materials present in an LCD monitor, the recycling of materials, such as mercury, thermoplastic polymers, glasses, metals and precious metals amongst others, is not only performed, but allows contamination of soil, water and air with the liberation of toxic compounds present in this type of waste when disposed of improperly. Therefore, the objective of this study was to disassemble and characterize the materials in this type of waste, identify the composition, amount and form to enable, in further work, the development of recycling routes. After various tests and analyses, it was observed that an LCD display can be recycled, provided that precautions are taken. Levels of lead, fluoride and copper are above those permitted by the Brazilian law, characterizing this residue as having a high pollution potential. The materials present in printed circuit boards (base and precious metals)-thermoplastics, such as polyethylene terephthalate, acrylic, acrylonitrile butadiene styrene and polycarbonate and metals, such as steel and aluminum, and a layer of indium (in the internal face of the glass)-are components that make a point in terms of their potential for recycling.

  14. Liquid crystal polyester-carbon fiber composites

    NASA Technical Reports Server (NTRS)

    Chung, T. S.

    1984-01-01

    Liquid crystal polymers (LCP) have been developed as a thermoplastic matrix for high performance composites. A successful melt impregnation method has been developed which results in the production of continuous carbon fiber (CF) reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP/CF composites are comparable to those of epoxy/CF composites. The LCP/CF composites have better impact resistance than the latter, although epoxy/CF composites possess superior compression and shear strength. The LCP/CF composites have good property retention until 200 F (67 % of room temperature value). Above 200 F, mechanical properties decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber as adequate toughness of the LCP matrix. Low mechanical property retention at high temperatures may be attributable to the low beta-transition temperature (around 80 C) of the LCP matrix material.

  15. Molecular Models of Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Rajshekhar

    Liquid crystal elastomers combine the elastic properties of conventional rubbers with the optical properties of liquid crystals. This dual nature gives rise to unusual physical properties, including the stress induced transition from a polydomain state, consisting of multiple nematic regions with independent orientations, to a monodomain state consisting of a single nematic region with a uniform director. We propose several molecular-scale coarse-grained models of liquid crystal elastomers with varying degrees of resolution. The models employ the Gay-Berne soft potential, and exhibit the chain connectivity of a diamond network. Simulation results show that these models are able to capture the polydomain state exhibited by liquid crystal elastomers in the absence of any external stress. When subjected to uniaxial stress, our models exhibit a polydomain to monodomain transition. We explain that the polydomain state occurs through the aggregation of liquid crystal molecules assisted by crosslinking sites, and conclude that the transition mechanism to the monodomain state is based on the reorientation of nematic domains along the direction of applied stress. Our modeling efforts are primarily focused on three models. The first two models consider the effects of rigid and flexible crosslinkers in liquid crystal elastomers with a diamond topology for chain connectivity. The third model deviates from the diamond network topology and adopts a random network topology.

  16. Biosensing using smectic and cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Popov, Piotr; Mann, Elizabeth; Jakli, Antal

    2015-03-01

    Liquid-crystal-based biosensors utilize liquid crystal alignment's high sensitivity to the presence of lipids and proteins self-assembled at the liquid crystal/aqueous solution interface. The optical response of the bulk liquid crystal to the interface offers inexpensive, easy optical detection of such biologically relevant molecules. Present technique uses nematic liquid crystal phase state that typically has a planar-to-homeotropic response only. Here we show that smectic and cholesteric phase states of liquid crystals can be used as new sensing modes that can provide additional information or improve the characteristics of a potential biosensor device. Smectic-A phase extends the detection range both toward the lower and higher concentration. Cholesteric phase (nematic with a chiral dopant) may be sensitive to the chirality of biological surface-active molecules such as phospholipids. Additionally, the ``finger-print'' texture of a cholesteric phase may show the differences between biomolecule homologues, thus providing a promising way of distinguishing between subtle differences of hydrocarbon chain or head-group size and structure.

  17. Semiconductor liquid crystal composition and methods for making the same

    DOEpatents

    Alivisatos, A. Paul; Li, Liang-shi

    2005-04-26

    Semiconductor liquid crystal compositions and methods for making such compositions are disclosed. One embodiment of the invention is directed to a liquid crystal composition including a solvent and semiconductor particles in the solvent. The solvent and the semiconductor particles are in an effective amount in the liquid crystal composition to form a liquid crystal phase.

  18. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  19. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  20. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  1. Electro-osmosis in nematic liquid crystals.

    PubMed

    Tovkach, O M; Calderer, M Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  2. Electro-osmosis in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Tovkach, O. M.; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J.

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  3. Electro-osmosis in nematic liquid crystals.

    PubMed

    Tovkach, O M; Calderer, M Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities. PMID:27575193

  4. Liquid nitrogen dewar for protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Gaseous Nitrogen Dewar apparatus developed by Dr. Alex McPherson of the University of California, Irvine for use aboard Mir and the International Space Station allows large quantities of protein samples to be crystallized in orbit. The specimens are contained either in plastic tubing (heat-sealed at each end). Biological samples are prepared with a precipitating agent in either a batch or liquid-liquid diffusion configuration. The samples are then flash-frozen in liquid nitrogen before crystallization can start. On orbit, the Dewar is placed in a quiet area of the station and the nitrogen slowly boils off (it is taken up by the environmental control system), allowing the proteins to thaw to begin crystallization. The Dewar is returned to Earth after one to four months on orbit, depending on Shuttle flight opportunities. The tubes then are analyzed for crystal presence and quality

  5. Tetrahedral Order in Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Pleiner, Harald; Brand, Helmut R.

    2016-10-01

    We review the impact of tetrahedral order on the macroscopic dynamics of bent-core liquid crystals. We discuss tetrahedral order comparing with other types of orientational order, like nematic, polar nematic, polar smectic, and active polar order. In particular, we present hydrodynamic equations for phases, where only tetrahedral order exists or tetrahedral order is combined with nematic order. Among the latter, we discriminate between three cases, where the nematic director (a) orients along a fourfold, (b) along a threefold symmetry axis of the tetrahedral structure, or (c) is homogeneously uncorrelated with the tetrahedron. For the optically isotropic T d phase, which only has tetrahedral order, we focus on the coupling of flow with, e.g., temperature gradients and on the specific orientation behavior in external electric fields. For the transition to the nematic phase, electric fields lead to a temperature shift that is linear in the field strength. Electric fields induce nematic order, again linear in the field strength. If strong enough, electric fields can change the tetrahedral structure and symmetry leading to a polar phase. We briefly deal with the T phase that arises when tetrahedral order occurs in a system of chiral molecules. To case (a), defined above, belong (i) the non-polar, achiral, optically uniaxial D2d phase with ambidextrous helicity (due to a linear gradient free energy contribution) and with orientational frustration in external fields, (ii) the non-polar tetragonal S4 phase, (iii) the non-polar, orthorhombic D2 phase that is structurally chiral featuring ambidextrous chirality, (iv) the polar orthorhombic C2v phase, and (v) the polar, structurally chiral, monoclinic C2 phase. Case (b) results in a trigonal C3v phase that behaves like a biaxial polar nematic phase. An example for case (c) is a splay bend phase, where the ground state is inhomogeneous due to a linear gradient free energy contribution. Finally, we discuss some experiments

  6. Key Developments in Ionic Liquid Crystals.

    PubMed

    Alvarez Fernandez, Alexandra; Kouwer, Paul H J

    2016-05-16

    Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material?

  7. Key Developments in Ionic Liquid Crystals

    PubMed Central

    Alvarez Fernandez, Alexandra; Kouwer, Paul H. J.

    2016-01-01

    Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material? PMID:27196890

  8. Molecular Dynamics Simulations of Spinodal-Assisted Polymer Crystallization

    SciTech Connect

    Gee, R H; Lacevic, N M; Fried, L

    2005-07-08

    Large scale molecular dynamics simulations of bulk melts of polar (poly(vinylidene fluoride) (pVDF)) polymers are utilized to study chain conformation and ordering prior to crystallization under cooling. While the late stages of polymer crystallization have been studied in great detail, recent theoretical and experimental evidence indicates that there are important phenomena occurring in the early stages of polymer crystallization that are not understood to the same degree. When the polymer melt is quenched from a temperature above the melting temperature to the crystallization temperature, crystallization does not occur instantaneously. This initial interval without crystalline order is characterized as an induction period. It has been thought of as a nucleation period in the classical theories of polymer crystallization, but recent experiments, computer simulations, and theoretical work suggest that the initial period in polymer crystallization is assisted by a spinodal decomposition type mechanism. In this study we have achieved physically realistic length scales to study early stages of polymer ordering, and show that spinodal-assisted ordering prior to crystallization is operative in polar polymers suggesting general applicability of this process.

  9. Nanoscale control of polymer crystallization by nanoimprint lithography.

    PubMed

    Hu, Zhijun; Baralia, Gabriel; Bayot, Vincent; Gohy, Jean-François; Jonas, Alain M

    2005-09-01

    Polymer crystallization is notoriously difficult to control. Here, we demonstrate that the orientation of polymer crystals can be fully controlled at the nanoscale by using nanoimprint lithography (NIL) with molds bearing nanotrenches to shape thin films of poly(vinylidene fluoride). This unprecedented control is due to the thermomechanical history experienced by the polymer during embossing, to the shift of the nucleation mechanism from heterogeneous to homogeneous in confined regions of the mold, and to the constraining of the fast growth axis along the direction of the trenches. NIL thus appears as an ideal tool to realize smart polymer surfaces where crystal ordering can be tuned locally.

  10. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  11. Polymer-mediated growth of crystals and mesocrystals.

    PubMed

    Cölfen, Helmut

    2013-01-01

    Polymers are important additives for the control of mineralization reactions in both biological and bioinspired mineralization. The reason is that they allow for a number of interactions with the growing crystals and even amorphous minerals. These can substantially influence the way the mineral grows on several levels. Already in the prenucleation phase, polymers can control the formation of prenucleation clusters and subsequently the nucleation event. Also, polymers can control whether the further crystallization follows a classical or nonclassical particle-mediated growth path. In this chapter, the main ways in which polymers can be used to control a crystallization reaction will be highlighted. In addition, polymers that are useful for this purpose and the experimental conditions suitable for directing a crystallization reaction into the desired direction through the use of polymers will be described.

  12. Cloning polymer single crystals through self-seeding

    NASA Astrophysics Data System (ADS)

    Xu, Jianjun; Ma, Yu; Hu, Wenbing; Rehahn, Matthias; Reiter, Günter

    2009-04-01

    In general, when a crystal is molten, all molecules forget about their mutual correlations and long-range order is lost. Thus, a regrown crystal does not inherit any features from an initially present crystal. Such is true for materials exhibiting a well-defined melting point. However, polymer crystallites have a wide range of melting temperatures, enabling paradoxical phenomena such as the coexistence of melting and crystallization. Here, we report a self-seeding technique that enables the generation of arrays of orientation-correlated polymer crystals of uniform size and shape (`clones') with their orientation inherited from an initial single crystal. Moreover, the number density and locations of these cloned crystals can to some extent be predetermined through the thermal history of the starting crystal. We attribute this unique behaviour of polymers to the coexistence of variable fold lengths in metastable crystalline lamellae, typical for ordering of complex chain-like molecules.

  13. Versatile alignment layer method for new types of liquid crystal photonic devices

    SciTech Connect

    Finnemeyer, V.; Bryant, D.; Lu, L.; Bos, P.; Reich, R.; Clark, H.; Berry, S.; Bozler, C.; Yaroshchuk, O.

    2015-07-21

    Liquid crystal photonic devices are becoming increasingly popular. These devices often present a challenge when it comes to creating a robust alignment layer in pre-assembled cells. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photo-definable alignment layer. However, previous research on such alignment layers has shown that they have limited stability, particularly against subsequent light exposure. As such, we further describe a method of utilizing a pre-polymer, infused into the microcavity along with the liquid crystal, to provide photostability. We demonstrate that the polymer layer, formed under ultraviolet irradiation of liquid crystal cells, has been effectively localized to a thin region near the substrate surface and provides a significant improvement in the photostability of the liquid crystal alignment. This versatile alignment layer method, capable of being utilized in devices from the described microcavities to displays, offers significant promise for new photonics applications.

  14. Development and design of multilayer antennas based on liquid crystals

    NASA Astrophysics Data System (ADS)

    Missaoui, S.; Kaddour, M.; Gharbi, A.

    2010-11-01

    In this paper we present a conception and design of microwave circuit based on liquid crystal. The conception will be made of a manner to have a device that functions with a dual frequency and dual polarization. The goal of the dual frequency and dual polarization is to provide a multi-dimensional picture of meteorological phenomena to get more complete data of survey climatic long term and also for the use precipitation of the pictures in the radars. The whole system required in the broadcasts of space as in satellite imaging systems. The liquid crystal polymer has unique features: electric, mechanical, chemical; its extremely flexible nature and the capacity to be laminated with a low cost and a lightweight, to return an appropriate substrate for the big applications of the multilayer antennas.

  15. Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

    2006-08-01

    A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

  16. Hybrid Alignment Induced by Asymmetric Photopolymerization of Liquid Crystal-Reactive Mesogen Composition between Two Plastic Substrates

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Sun; Lee, Ji-Hoon

    2011-05-01

    A hybrid aligned liquid crystal layer was prepared between plastic substrates by the asymmetric photopolymerization of the reactive mesogen. The planar alignment of liquid crystal molecules was induced on the top substrate facing the UV light by the predominant photopolymerization at this substrate, whereas a homeotropic orientation was induced on the bottom substrate. The extinction ratio of the hybrid aligned samples vs the polymer concentration and the thickness of the liquid crystal layer was examined.

  17. Charge transfer reactions in nematic liquid crystals

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R. |; Galili, T.; Levanon, H.

    1998-07-01

    Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4{prime}-(n-pentyl)-4-cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. The authors show that excited state charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains. They also show that charge recombination is adiabatic and is controlled by the comparatively slow collective reorientation of the liquid crystal microdomains relative to the orientation of PNI{sup +}-PI{sup {minus}}. They also report the results of time resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.

  18. Liquid crystal thermography in boiling heat transfer

    SciTech Connect

    Klausner, J.F.; Mei, R.; Chen, W.C.

    1995-12-31

    The utilization of liquid crystal thermography to study heterogeneous boiling phenomena has gained popularity in recent years. In order not to disturb the nucleation process, which occurs in the microstructure of the heating surface, the crystals are applied to the backside of a thin heater. This work critically examines the ability of liquid crystal thermography to quantitatively capture the thermal field on the boiling surface. The thermal field identified experimentally through liquid crystal thermography is compared against that computed in the vicinity of a growing vapor bubble using a simulation which considers the simultaneous heat transfer between three phases: the solid heater, the liquid microlayer, and the growing vapor bubble. The temperature history beneath a growing vapor bubble elucidates the high frequency response required to capture the transient thermal fields commonly encountered in boiling experiments. Examination of the governing equations and numerical results reveal that due to the heater thermal inertia, the temperature variation on the bottom of the heater is significantly different than that on the boiling surface. In addition, the crystals themselves have a finite spatial resolution and frequency response which filter out much of the microscale phenomenon associated with boiling heat transfer. Analysis of existing pool and flow boiling liquid crystal thermographs indicate that the typical spacial resolution is on the order of 0.25 mm and the response time is on the order of 5 ms which are insufficient to resolve the fine spacial and temporal details of the heating surface thermal field. Thus the data obtained from liquid crystal thermography applied to boiling heat transfer must be cautiously interpreted.

  19. Room Temperature Single-Photon Source: Single-Dye Molecule Fluorescence in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; McNamara, A.J.; Boyd, R.W.; Stroud, C.R.Jr.

    2003-12-31

    OAK-(B204)We report on new approaches toward an implementation of an efficient, room temperature, deterministically polarized, single-photon source (SPS) on demand-a key hardware element for quantum information and quantum communication. Operation of a room temperature SPS is demonstrated via photon antibunching in the fluorescence from single terrylene-dye molecules embedded in a cholesteric liquid crystal host. Using oxygen-depleted liquid crystal hosts, dye-bleaching was avoided over the course of more than 1 h of continuous 532-nm excitation. Liquid crystal hosts (including liquid crystal oligomers/polymers) permit further increase of the efficiency of the source: (1) by aligning the dye molecules along a direction preferable for the maximum excitation efficiency; (2) by tuning a one-dimensional (1-D) photonic-band-gap microcavity of planar-aligned cholesteric (chiral nematic) liquid crystal layer to the dye fluorescence band.

  20. Stabilizing blue phase liquid crystals with linearly polarized UV light

    NASA Astrophysics Data System (ADS)

    Xu, Daming; Yuan, Jiamin; Schadt, Martin; Yan, Jing; Wu, Shin-Tson

    2015-03-01

    Polymer-stabilized blue-phase liquid crystal (PS-BPLC) has become an increasingly important technology trend for information display and photonic applications. BPLC exhibits several attractive features, such as reasonably wide temperature range, submillisecond gray-to-gray response time, no need for alignment layer, optically isotropic voltageoff state, and large cell gap tolerance when an in-plane switching (IPS) cell is employed. However, some bottlenecks such as high operation voltage, relatively low transmittance, and noticeable hysteresis and prolonged response time at high field region for IPS mode, still remain to be overcome before widespread application of BPLC can be realized. To reduce operation voltage, both new BPLC materials and new device structures have been investigated. In this paper, we demonstrate the stabilization a photopolymer-embedded blue phase liquid crystal precursor using a linearly polarized UV light for first time. When the UV polarization axis is perpendicular to the stripe electrodes of an IPS cell, anisotropic polymer networks are formed through the linear photo-polymerization process and the electrostriction effect is suppressed. As a result, the measured hysteresis is dramatically reduced from 6.95% to 0.36% and the response time shortened by ~2X compared to unpolarized UV exposure. To induce larger anisotropy in polymer networks for mitigating the electrostriction effect, high-intensity linearly polarized UV exposure is preferred. It is foreseeable this method will guide future BPLC device and material development as well as manufacturing process. The dawn of BPLCD is near.

  1. A Finsler Geometry Modeling of the Liquid Crystal Elastomer

    NASA Astrophysics Data System (ADS)

    Koibuchi, Hiroshi; Shobukhov, Andrey

    2015-09-01

    Liquid crystal elastomer (LCE) is a rubbery material composed of polymer chains and liquid crystals (LC). LCE is well known to undergo a shape transformation from the isotropic to the anisotropic phase. This shape transformation is caused by the nematic transition of the LC included in the LCE. However, the mechanism of this transformation is unknown because the interaction of LC with the bulk polymers is too complex. In this presentation, we extend the two-dimensional Finsler geometry model for membranes to a three-dimensional model for LCE. The Finsler geometry model for LCE is a coarse grained one: the Guassian bond potential S1 is obtained by extending the one for membranes, which is originally obtained by a simple extension of the Guassian bond potential for the linear chain polymer model. The continuous Hamiltonian, which contains S1 and the curvature energy S2, is discretized using a three-dimensional rigid sphere composed of tetrahedrons. We study the shape transformation as a phase transition between the isotropic and anisotropic phases and report the results of the transition order, obtained by the Monte Carlo simulations.

  2. A phase-field-crystal model for liquid crystals.

    PubMed

    Löwen, Hartmut

    2010-09-15

    On the basis of static and dynamical density functional theory, a phase-field-crystal model is derived which involves both the translational density and the orientational degree of ordering as well as a local director field. The model exhibits stable isotropic, nematic, smectic A, columnar, plastic-crystalline and orientationally ordered crystalline phases. As far as the dynamics is concerned, the translational density is a conserved order parameter while the orientational ordering is non-conserved. The derived phase-field-crystal model can serve for use in efficient numerical investigations of various nonequilibrium situations in liquid crystals.

  3. Diastereomeric liquid crystal domains at the mesoscale.

    PubMed

    Chen, Dong; Tuchband, Michael R; Horanyi, Balazs; Korblova, Eva; Walba, David M; Glaser, Matthew A; Maclennan, Joseph E; Clark, Noel A

    2015-08-07

    In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

  4. Diastereomeric liquid crystal domains at the mesoscale

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Tuchband, Michael R.; Horanyi, Balazs; Korblova, Eva; Walba, David M.; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.

    2015-08-01

    In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

  5. Defects in liquid crystal nematic shells

    NASA Astrophysics Data System (ADS)

    Fernandez-Nieves, A.; Utada, A. S.; Vitelli, V.; Link, D. R.; Nelson, D. R.; Weitz, D. A.

    2006-03-01

    We generate water/liquid crystal (LC)/water double emulsions via recent micro-capillary fluidic devices [A. S. Utada, et.al. Science 308, 537 (2005)]. The resultant objects are stabilized against coalescence by using surfactants or adequate polymers; these also fix the boundary conditions for the director field n. We use 4-pentyl-4-cyanobiphenyl (5CB) and impose tangential boundary conditions at both water/LC interfaces by having polyvinyl alcohol (PVA) dispersed in the inner and outer water phases. We confirm recent predictions [D. R. Nelson, NanoLetters 2, 1125 (2002)] and find that four strength s=+1/2 defects are present; this is in contrast to the two s=+1 defect bipolar configuration observed for bulk spheres [A. Fernandez-Nieves, et.al. Phys. Rev. Lett. 92, 105503 (2004)]. However, these defects do not lie in the vertices of a tetrahedron but are pushed towards each other until certain equilibration distance is reached. In addition to the four defect shells, we observe shells with two s=+1 defects and even with three defects, a s=+1 and two s=+1/2. We argue these configurations arise from nematic bulk distortions that become important as the shell thickness increases. Finally, by adding a different surfactant, sodium dodecyl sulphate (SDS), to the outer phase, we can change the director boundary conditions at the outermost interface from parallel to homeotropic, to induce coalescing of the two pair of defects in the four defect shell configuration to yield two defect bipolar shells.

  6. Orientation of nematic liquid crystal in open glass microstructures

    NASA Astrophysics Data System (ADS)

    Azarinia, H.; Beeckman, J.; Neyts, K.; Schacht, E.; Gironès, J.; James, R.; Fernandez, F. A.

    2009-09-01

    Liquid crystal materials can have bulk reorientation due to surface interaction and are therefore of interest for biosensing applications. We present a setup, with holes etched in a substrate, filled with liquid crystal and covered by a sample fluid. The influence of the depth of the microcavities and the type of liquid on the liquid crystal orientation is investigated by experiments and simulations.

  7. Surfaces and chirality in liquid crystals

    NASA Astrophysics Data System (ADS)

    Kang, Daeseung

    1999-10-01

    The effects of surfaces and chirality in liquid crystals were studied in this thesis. Four different experiments were presented to investigate the different aspects of their role in liquid crystal physics. A liquid crystal cell treated for homeotropic alignment with different surfactants at the two surfaces was subjected to an electric field E in the plane of the cell. The longitudinal polarization at the surface couples with the external field, and in consequence exerts a torque on molecules. The differential optical retardation deltaalpha due to a slight deformation was found to be linear in field over a frequency range 10 < o < 105 Hz, where d(deltaalpha)/dE is proportional to o -1. As a different aspect of the surface, the phenomenon of a chiral liquid crystal in highly restricted geometry was also investigated, where the random surface dominates the bulk. The optical rotatory power of the chiral liquid crystal in the porous medium was drastically altered from that of the bulk liquid crystal. The observed behavior may be attributed to a combination of surface interactions and finite size effects, which are discussed in terms of an infrared cutoff in the orientational pair correlation function. Chirality manifests itself not only as an optical activity in nematics, but more strikingly in forms of ferroelectric and antiferroelectric phases in smectics. The anticlinic interlayer coupling coefficient U between smectic layers was evaluated for a pitch-compensated antiferroelectric liquid crystal by optical observation of the optic mode response to an in-plane electric field. The result is in good agreement with Us estimated from the threshold field for the onset of solitary waves, and provides a strong support for the switching model based on the free energy. Finally, a new trimer liquid crystal based on a terminal-lateral-lateral-terminal connection was investigated. Magnetically induced Freedericksz measurements were performed to extract the elastic constants of

  8. Topology and bistability in liquid crystal devices

    SciTech Connect

    Majumdar, A.; Newton, C. J. P.; Robbins, J. M.; Zyskin, M.

    2007-05-15

    We study nematic liquid crystal configurations in a prototype bistable device--the post aligned bistable nematic (PABN) cell. Working within the Oseen-Frank continuum model, we describe the liquid crystal configuration by a unit-vector field n, in a model version of the PABN cell. First, we identify four distinct topologies in this geometry. We explicitly construct trial configurations with these topologies which are used as initial conditions for a numerical solver, based on the finite-element method. The morphologies and energetics of the corresponding numerical solutions qualitatively agree with experimental observations and suggest a topological mechanism for bistability in the PABN cell geometry.

  9. How different is water crystallization from polymer crystallization under confinement?

    NASA Astrophysics Data System (ADS)

    Floudas, George; Suzuki, Yasuhito; Duran, Hatice; Steinhart, Martin; Butt, Hans-Juergen

    2015-03-01

    The freezing mechanism of water under confinement can be fundamentally different from the bulk. Despite fundamental importance, the lack of well-defined confining media precluded a systematic investigation. Herein we employ self-ordered nanoporous aluminum oxide (AAO) which contains arrays of discrete, parallel and cylindrical nanopores with uniform pore length and diameter to study the effect of confinement on water crystallization. By varying different parameters such as pore size, temperature and cooling rate, the respective conditions under which the hexagonal form (Ih) and the less common form of cubic ice (Ic) could be studied. We found a transition from heterogeneous nucleation of Ih to homogeneous nucleation of predominantly Ic with decreasing pore diameter. Furthermore, the monotropic Ic --> Ih transition commonly observed upon heating is suppressed inside pores having diameters <= 35 nm. These findings lead to the phase diagram of water under confinement. It contains a predominant cubic form, a form known to exist only in the upper atmosphere.There are many similarities between the freezing of water and the crystallization of polymers under confinement.

  10. Optical solitons in liquid crystals

    SciTech Connect

    Yung, Y.S.; Lam, L.; Los Alamos National Lab., NM )

    1989-01-01

    In this paper, we will discuss theoretically the possible existence of optical solitons in the isotropic liquid and in the nematic phase. For the same compound, when heated, the nematic phase will go through a first order transition at temperature T{sub c} to the isotropic liquid phase. As temperature increases from below T{sub c}, the orientation order parameter, Q, decreases, drops to zero abruptly at T{sub c} and remains zero for T > T{sub c}. 10 refs., 1 fig.

  11. Atomistic Simulation of Polymer Crystallization at Realistic Length Scales

    SciTech Connect

    Gee, R H; Fried, L E

    2005-01-28

    Understanding the dynamics of polymer crystallization during the induction period prior to crystal growth is a key goal in polymer physics. Here we present the first study of primary crystallization of polymer melts via molecular dynamics simulations at physically realistic (about 46 nm) length scales. Our results show that the crystallization mechanism involves a spinodal decomposition microphase separation caused by an increase in the average length of rigid trans segments along the polymer backbone during the induction period. Further, the characteristic length of the growing dense domains during the induction period is longer than predicted by classical nucleation theory. These results indicate a new 'coexistence period' in the crystallization, where nucleation and growth mechanisms coexist with a phase separation mechanism. Our results provide an atomistic verification of the fringed micelle model.

  12. Single Molecule Studies on Dynamics in Liquid Crystals

    PubMed Central

    Täuber, Daniela; von Borczyskowski, Christian

    2013-01-01

    Single molecule (SM) methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC). Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC. PMID:24077123

  13. Deposition of calcium carbonate films by a polymer-induced liquid-precursor (PILP) process

    NASA Astrophysics Data System (ADS)

    Gower, Laurie B.; Odom, Damian J.

    2000-03-01

    A polypeptide additive has been used to transform the solution crystallization of calcium carbonate to a solidification process of a liquid-phase mineral precursor. In situ observations reveal that polyaspartate induces liquid-liquid phase separation of droplets of a mineral precursor. The droplets deposit on the substrate and coalesce to form a coating, which then solidifies into calcitic tablets and films. Transition bars form during the amorphous to crystalline transition, leading to sectorization of calcite tablets, and the defect textures and crystal morphologies are atypical of solution grown crystals. The formation of nonequilibrium crystal morphologies using an acidic polypeptide may have implications in the field of biomineralization, and the environmentally friendly aspects of this polymer-induced liquid-precursor (PILP) process may offer new techniques for aqueous-based processing of ceramic films, coatings, and particulates.

  14. Switchable tackiness and wettability of a liquid crystalline polymer

    PubMed

    de Crevoisier G; Fabre; Corpart; Leibler

    1999-08-20

    The spreading velocity of liquids on the surface of a liquid crystalline polymer can be tremendously affected by a slight temperature change. Indeed, a bulk transition between a highly ordered smectic and an isotropic phase induces a sharp change from a rigid to a soft behavior, with consequent effects on the tack properties of the liquid crystalline polymer and on the dewetting dynamics of a liquid on its surface. PMID:10455047

  15. Switchable tackiness and wettability of a liquid crystalline polymer

    PubMed

    de Crevoisier G; Fabre; Corpart; Leibler

    1999-08-20

    The spreading velocity of liquids on the surface of a liquid crystalline polymer can be tremendously affected by a slight temperature change. Indeed, a bulk transition between a highly ordered smectic and an isotropic phase induces a sharp change from a rigid to a soft behavior, with consequent effects on the tack properties of the liquid crystalline polymer and on the dewetting dynamics of a liquid on its surface.

  16. Liquid Crystalline Polymers and Networks -- orientation, molecular shape change, mechanics

    NASA Astrophysics Data System (ADS)

    Warner, Mark

    2008-03-01

    In a prescient paper of 1969, Pierre-Gilles de Gennes envisaged both liquid crystal polymers and elastomers. 10 years later, these systems were realised. After 25 years, monodomain elastomers were prepared and displayed phenomena he had predicted: rods incorporated into polymers induce liquid crystallinity in polymer melts and elastomers; orientational order causes shape changes in the back bones of such polymers; mechanical ramifications follow in networks, e.g. spontaneous elongations and contractions on changing order. The latter are proposed as the basis of micro-actuation and artificial muscles, both heat and light-driven. In 1969, de Gennes already described ideal networks heated through the nematic-isotropic transition losing all their order by mechanical relaxation. It is not obvious, but is true in theory and largely in experiment, even in highly non-ideal networks. He also envisaged that a cholesteric network, where there is a topological memory of chirality imprinted by crosslinking chains in a twisted state. Chirality cannot relax away on entering the isotropic phase, even in systems without molecular chirality (for instance those crosslinked in the presence of chiral solvent that is subsequently exchanged away). His chiral elastomers have found application as mechanically-tuneable, rubber lasers. De Gennes also constructed the first continuum elastic theories of nematic elastomers (1982), though distortions are generally very large. His elasticity has informed non-linear elasticity that works even at large amplitudes. I shall describe de Gennes' many contributions, and the current state of a field that has since yielded still more remarkable phenomena.

  17. Molecular dynamics of biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, Sten

    1996-01-01

    We devise a constraint algorithm that makes the angular velocity of the director of a liquid crystal a constant of motion. When the angular velocity is set equal to zero, a director based coordinate system becomes an inertial frame. This is a great advantage because most thermodynamic properties and time correlation functions of a liquid crystal are best expressed relative to a director based coordinate system. One also prevents the director reorientation from interfering with the tails of the time correlation functions. When the angular velocity is forced to be zero the constraints do not do any work on the system. This makes it possible to prove that ensemble averages of phase functions and time correlation functions are unaffected by the director constraint torques. The constraint algorithm also facilitates generalization of nonequilibrium molecular dynamics algorithms to liquid crystal phases. In order to test the algorithm numerically we have simulated a biaxial nematic phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)]. The director constraint algorithm works very well. We have calculated the velocity autocorrelation functions and the self diffusion coefficients. In a biaxial nematic liquid crystal there are three independent components of the self-diffusion tensor. They have been found to be finite and different thus proving that we really simulate a liquid rather than a solid and that the symmetry is biaxial. Simulation of biaxial liquid crystals requires fairly large systems. We have therefore developed an algorithm that we run on a parallel computer instead of an ordinary work station.

  18. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  19. Liquid-Crystal Thermal-Control Panels

    NASA Technical Reports Server (NTRS)

    Dehaye, R. F.; Edge, T. M.; Feltner, W. R.

    1987-01-01

    Radiative temperature regulators have no moving parts. Conceptual temperature-regulating system proposed for spacecraft useful in automatic or remotely controlled regulation of solar heating in buildings, provided cost reduced sufficiently. System consists of liquid-crystal panels made to absorb or reflect sunlight.

  20. Infrared diagnosis using liquid crystal detectors

    NASA Technical Reports Server (NTRS)

    Hugenschmidt, M.; Vollrath, K.

    1986-01-01

    The possible uses of pulsed carbon dioxide lasers for analysis of plasmas and flows need appropriate infrared image converters. Emphasis was placed on liquid crystal detectors and their operational modes. Performance characterstics and selection criteria, such as high sensitivity, short reaction time, and high spatial resolution are discussed.

  1. Helmet-Mounted Liquid-Crystal Display

    NASA Technical Reports Server (NTRS)

    Smith, Steve; Plough, Alan; Clarke, Robert; Mclean, William; Fournier, Joseph; Marmolejo, Jose A.

    1991-01-01

    Helmet-mounted binocular display provides text and images for almost any wearer; does not require fitting for most users. Accommodates users from smallest interpupillary distance to largest. Two liquid-crystal display units mounted in helmet. Images generated seen from any position head can assume inside helmet. Eyes directed to position for best viewing.

  2. Inexpensive Electrooptic Experiments on Liquid Crystal Displays.

    ERIC Educational Resources Information Center

    Ciferno, Thomas M.; And Others

    1995-01-01

    Describes the construction and use of an electrooptic apparatus that can be incorporated into the classroom to test liquid crystal displays (LCDs) and introduce students to experiments of an applied physics nature with very practical implications. Presents experiments that give students hands-on experience with technologies of current interest to…

  3. Sub-wavelength phononic crystal liquid sensor

    NASA Astrophysics Data System (ADS)

    Ke, Manzhu; Zubtsov, Mikhail; Lucklum, Ralf

    2011-07-01

    We introduce an acoustic liquid sensor based on phononic crystals consisting of steel plate with an array of holes filled with liquid. We both theoretically and experimentally demonstrate sensor properties considering the mechanism of the extraordinary acoustic transmission as underlying phenomenon. The frequency of this resonant transmission peak is shown to rely on the speed of sound of the liquid, and the resonant frequency can be used as a measure of speed of sound and related properties, like concentration of a component in the liquid mixture. The finite-difference time domain method has been applied for sensor design. Ultrasonic transmission experiments are performed. Good consistency of the resonant frequency shift has been found between theoretical results and experiments. The proposed scheme offers a platform for an acoustic liquid sensor.

  4. Polarization-modulated smectic liquid crystal phases.

    PubMed

    Coleman, D A; Fernsler, J; Chattham, N; Nakata, M; Takanishi, Y; Körblova, E; Link, D R; Shao, R-F; Jang, W G; Maclennan, J E; Mondainn-Monval, O; Boyer, C; Weissflog, W; Pelzl, G; Chien, L-C; Zasadzinski, J; Watanabe, J; Walba, D M; Takezoe, H; Clark, N A

    2003-08-29

    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.

  5. Liquid-crystalline polymer holograms for high-density optical storage and photomechanical analysis

    NASA Astrophysics Data System (ADS)

    Shishido, A.; Akamatsu, N.

    2012-10-01

    We report linear and crosslinked azobenzene containing liquid-crystalline polymers which can be applied to high-density optical storage and photomechanical analysis. We introduced a molecular design concept of multicomponent systems composed of photoresponse, refactive-index change amplification, and transparency units. Taking advantage of characteristics of liquid crystals (optical anisotropy and cooperative motion), polarization holograms were recorded, which enabled us higher-density holographic storage. On the other hand, crosslinked liquid-crystalline azobenzene polymer films were fabricated to investigate the photomechanical behavior. We have found that a large change in Young's modulus is induced by several mol%-cis form production. Furthermore, a unique bending behavior, which cannot be explained by the conventional bending mechanism, was observed in the crosslinked liquid-crystalline polymer films with azobenzene in the side chain.

  6. Electric heating effects in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Yin, Y.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2006-07-01

    Electric heating effects in the nematic liquid crystal change the liquid crystal physical properties and dynamics. We propose a model to quantitatively describe the heating effects caused by dielectric dispersion and ionic conductivity in the nematic liquid crystals upon the application of an ac electric field. The temperature increase of the liquid crystal cell is related to the properties of the liquid crystal such as the imaginary part of the dielectric permittivity, thermal properties of the bounding plates, and the surrounding medium as well as frequency and amplitude of the electric field. To study the temperature dynamics experimentally, we use a small thermocouple inserted directly into the nematic bulk; we assure that the thermocouple does not alter the thermal behavior of the system by comparing the results to those obtained by a noncontact birefringent probing technique recently proposed by Wen and Wu [Appl. Phys. Lett. 86, 231104 (2005)]. We determine how the temperature dynamics and the stationary value of the temperature increase depend on the parameters of the materials and the applied field. We used different surrounding media, from extremely good heat conductors such as aluminum cooling device to extremely poor conductor, Styrofoam; these two provide two limiting cases as compared to typical conditions of nematic cell exploitation in a laboratory or in commercial devices. The experiments confirm the theoretical predictions, namely, that the temperature rise is controlled not only by the heat transfer coefficient of the surrounding medium (as in the previous model) but also by the thickness and the thermal conductivity coefficient of the bounding plates enclosing the nematic layer. The temperature increase strongly depends on the director orientation and can change nonmonotonously with the frequency of the applied field.

  7. Density Fluctuations in Crystallizing Polymers: Fact or Fiction?

    NASA Astrophysics Data System (ADS)

    Baert, Jimmy; Van Puyvelde, Peter

    2008-07-01

    The fact that, in polymer crystallization, nucleation might be accompanied by large scale density fluctuations has been investigated for the flow-induced crystallization of isotactic poly-1-butene (PB-1). Small Angle Light Scattering (SALS) was applied to measure density and orientation fluctuations, whereas complementary results were obtained from optical microscopy. The observations seem to indicate that the detected density fluctuations result from the presence of weakly anisotropic structures, rather than being an indication of densification before the onset of crystallization. In addition, the present work provides a critical review of polymer crystallization studies using SALS.

  8. Bulk and dispersed aqueous phase behavior of phytantriol: effect of vitamin E acetate and F127 polymer on liquid crystal nanostructure.

    PubMed

    Dong, Yao-Da; Larson, Ian; Hanley, Tracey; Boyd, Ben J

    2006-11-01

    Phytantriol (3,7,11,15-tetramethylhexadecane-1,2,3-triol, PHYT) is a cosmetic ingredient that exhibits similar lyotropic phase behavior to monoolein (GMO), forming bicontinuous cubic liquid crystalline structures (Q(II)) at low temperatures and reversed hexagonal phase (H(II)) at higher temperatures in excess water. Despite these similarities, phytantriol has received little attention in the scientific community. In this study, the thermal phase behavior of the binary PHYT-water and ternary PHYT-vitamin E acetate (VitEA)-water systems have been studied and compared with the behavior of the dispersed cubosomes and hexosomes formed with the aid of a stabilizer (Pluronic F127). The phase behavior and nanostructure were studied using crossed polarized light microscopy (CPLM), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS) techniques. The presence of lipophilic VitEA in the PHYT-water system suppressed the temperature of the Q(II)-to-H(II)-to-L2 transitions, indicating that lipophilic compounds, in relatively small amounts, may have a significant impact on the phase behavior. Increasing the F127 concentration in the phytantriol-based cubosome system did not induce the Q(II)(Pn3m) to Q(II)(Im3m) transition known for the GMO-water system. This indicates a different mode of interaction between F127 and the lipid domains of phytantriol-water systems. Taken together, these results indicate that phytantriol may not only provide an alternative lipid for preparation of liquid crystalline systems in excess water but may also provide access to properties not available when using GMO.

  9. Metal-ion-ligand interactions in thermotropic liquid crystals

    NASA Astrophysics Data System (ADS)

    Diehl, P.; Wasser, H. R.; Gowda, G. A. Nagana; Suryaprakash, N.; Khetrapal, C. L.

    1989-07-01

    The interactions of lithium perchlorate with ligands such as dimethyl sulphoxide, acetonitrile, pyridine and the Schiff base liquid crystals are investigated. The experiments open a new field for the study of metal-ion-ligand interactions in thermotropic liquid crystals.

  10. Polymer crystallization in thin films: morphology and physical properties

    NASA Astrophysics Data System (ADS)

    Kelly, Giovanni; Albert, Julie

    Polymer crystallization has been studied both computationally and experimentally for decades, elucidating many of the mysteries surrounding crystallization kinetics and thermodynamics. However, many unanswered questions remain pertaining to the relationships between crystallization phenomena and material properties needed for specific applications that range from drug delivery and tissue engineering to optical devices and mechanically robust membranes. One of the especially interesting facets of polymer crystallization is the behavior observed when these long chain molecules are spatially confined in thin and ultrathin films. Confined geometry leads to chain configurations, and therefore thermal, mechanical, and optical properties, sometimes far removed from reported bulk values. This project aims to study the phenomena exhibited by linear semi-crystalline polymers in thin films as well as the way in which blending with homopolymers, block copolymers, and novel polymer chain architectures affect morphology, biodegradation, optical, thermal, and mechanical properties.

  11. Liquid Crystals: Graphene Oxide Liquid Crystals: Discovery, Evolution and Applications (Adv. Mater. 16/2016).

    PubMed

    Narayan, Rekha; Kim, Ji Eun; Kim, Ju Young; Lee, Kyung Eun; Kim, Sang Ouk

    2016-04-01

    Graphene-oxide liquid crystals (GOLCs) have recently been discovered as a novel 2D material with remarkable properties. On page 3045, S. O. Kim and co-workers review the discovery of different GOLC mesophases and recent progress on fundamental studies and applications. The image displays the nematic schlieren texture (in the background) formed by flowing domains of graphene-oxide liquid crystals and their potential applications in energy storage, optoelectronics and wet-spun fibers.

  12. A functionally separated nanoimprinting material tailored for homeotropic liquid crystal alignment.

    PubMed

    Gwag, Jin Seog; Oh-E, Masahito; Kim, Kwang-Ryul; Cho, Sung-Hak; Yoneya, Makoto; Yokoyama, Hiroshi; Satou, Hiroyuki; Itami, Setsuo

    2008-10-01

    In order to homeotropically align liquid crystals (LCs) at the nanosized surface grooves processed by nanoimprint lithography technology (NIL), we propose to design a hybrid-type homeotropic polymer material consisting of two distinct moieties with largely different thermo-mechanical properties and surface activity. Surface contact angle measurements and sum-frequency vibrational spectroscopy allow us to conclude that the polymer film is a functionally separated composite suitable for the homeotropic LC alignment processed by NIL. As one of the potential applications using the hybrid-type homeotropic polymer, we demonstrate that the nanoimprinted grooves at the polymer surface can achieve a zenithal nematic LC bistability.

  13. A functionally separated nanoimprinting material tailored for homeotropic liquid crystal alignment.

    PubMed

    Gwag, Jin Seog; Oh-E, Masahito; Kim, Kwang-Ryul; Cho, Sung-Hak; Yoneya, Makoto; Yokoyama, Hiroshi; Satou, Hiroyuki; Itami, Setsuo

    2008-10-01

    In order to homeotropically align liquid crystals (LCs) at the nanosized surface grooves processed by nanoimprint lithography technology (NIL), we propose to design a hybrid-type homeotropic polymer material consisting of two distinct moieties with largely different thermo-mechanical properties and surface activity. Surface contact angle measurements and sum-frequency vibrational spectroscopy allow us to conclude that the polymer film is a functionally separated composite suitable for the homeotropic LC alignment processed by NIL. As one of the potential applications using the hybrid-type homeotropic polymer, we demonstrate that the nanoimprinted grooves at the polymer surface can achieve a zenithal nematic LC bistability. PMID:21832590

  14. Molecular-dynamics simulation of crystallization in helical polymers.

    PubMed

    Yamamoto, Takashi; Sawada, Kaoru

    2005-12-15

    The molecular mechanism of crystallization in helical polymers is a fascinating but very difficult subject of research. We here report our recent efforts toward better understanding of the crystallization in helical polymers by use of molecular-dynamics simulation. With straightforward approaches to the problem being quite difficult, we adopt a different strategy of categorizing the helical polymers into two distinct types: one type is a simple bare helix which is essentially made of backbone atomic groups only and has smoother molecular contours, and the other is a more general helix having large side groups that would considerably hamper molecular motion and crystallization. Both types of helical polymers are here constructed by use of the united atom model, but they show quite distinct crystallization behavior; the crystallization of the former-type polymer is rather fast, while that of the latter-type polymer is extremely slow. We find that the bare helix, when rapidly cooled in free three-dimensional space, freezes into partially ordered state with limited intramolecular and intermolecular orders, and that remarkable improvement of order and growth of an ordered chain-folded crystallite occurs by very long-time annealing of the partially ordered state around the apparent freezing temperature. We also study crystallization of the bare helix upon a growth surface; the crystallization in this case proceeds much faster through highly cooperative process of the intermolecular and the intramolecular degrees of freedom. On the other hand, crystallization of the realistic model of isotactic polypropylene (iPP) having pendant methylene groups is found to be extremely sluggish. By restricting the spatial dimension of the system thereby fully disentangling the chain, we observe that the molecule of iPP crystallizes very quickly onto the crystal substrate made of the same iPP chain. Quite remarkable is that the molecule of iPP strictly recognizes the helical sense of the

  15. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  16. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to indicate the location of a vein by revealing variations in the surface temperature of...

  17. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  18. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  19. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  20. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to indicate the location of a vein by revealing variations in the surface temperature of...

  1. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  2. Numerical investigation of viscoelastic flow induced crystallization in polymer processing

    NASA Astrophysics Data System (ADS)

    Mu, Yue; Zhao, Guoqun; Wu, Xianghong; Dong, Guiwei

    2013-05-01

    The investigation of viscoelastic flow induced crystallization is of great engineering significance in polymer processing like extrusion, injection and blow molding. In the study, the behavior of viscoelastic flow induced crystallization of semi-crystalline polymers is investigated by using finite element-finite difference method. The Schneider's approach is introduced to describe the evolution of crystallization kinetic process. The numerical model of three-dimensional flow induced crystallization of polymer melts obeying Phan-Thien and Tanner constitutive model is established. A penalty method is introduced to solve the nonlinear governing equations with a decoupled algorithm. The effect of flow state on the crystallization behavior is investigated. The crystalline distribution within the flow channel is obtained based on the proposed mathematical model and numerical method.

  3. Liquid crystal assemblies in biologically inspired systems

    PubMed Central

    Safinya, Cyrus R.; Deek, Joanna; Beck, Roy; Jones, Jayna B.; Leal, Cecilia; Ewert, Kai K.; Li, Youli

    2013-01-01

    In this paper, which is part of a collection in honor of Noel Clark's remarkable career on liquid crystal and soft matter research, we present examples of biologically inspired systems, which form liquid crystal (LC) phases with their LC nature impacting biological function in cells or being important in biomedical applications. One area focuses on understanding network and bundle formation of cytoskeletal polyampholytes (filamentous-actin, microtubules, and neurofilaments). Here, we describe studies on neurofilaments (NFs), the intermediate filaments of neurons, which form open network nematic liquid crystal hydrogels in axons. Synchrotron small-angle-x-ray scattering studies of NF-protein dilution experiments and NF hydrogels subjected to osmotic stress show that neurofilament networks are stabilized by competing long-range repulsion and attractions mediated by the neurofilament's polyampholytic sidearms. The attractions are present both at very large interfilament spacings, in the weak sidearm-interpenetrating regime, and at smaller interfilament spacings, in the strong sidearm-interpenetrating regime. A second series of experiments will describe the structure and properties of cationic liposomes (CLs) complexed with nucleic acids (NAs). CL-NA complexes form liquid crystalline phases, which interact in a structure-dependent manner with cellular membranes enabling the design of complexes for efficient delivery of nucleic acid (DNA, RNA) in therapeutic applications. PMID:24558293

  4. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  5. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2011-09-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  6. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2012-03-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  7. Tetrahedral Order in Banana Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Radzihovsky, Leo

    2005-03-01

    Bent-core liquid crystal molecules can exhibit phases that require a third-rank symmetric-traceless tensor order parameter, as well as a vector order parameter and the usual second-rank nematic order parameter. The combination gives rise to a rich variety of spatially homogeneous phases ranging from the well-known nematic to novel tetrahedratic and chiral liquids. I discuss experimental signatures of these phases and phase transitions between them.[0.3cm] L. Radzihovsky and T.C. Lubensky, Europhys. Lett.54, 206 (2001); Phys. Rev.E 66, 031704 (2002).

  8. A Physical Chemistry Experiment in Polymer Crystallization Kinetics

    ERIC Educational Resources Information Center

    Singfield, Kathy L.; Chisholm, Roderick A.; King, Thomas L.

    2012-01-01

    A laboratory experiment currently used in an undergraduate physical chemistry lab to investigate the rates of crystallization of a polymer is described. Specifically, the radial growth rates of typical disc-shaped crystals, called spherulites, growing between microscope glass slides are measured and the data are treated according to polymer…

  9. Nanoparticle interfacial assembly in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Rahimi, Mohammad; Roberts, Tyler; Armas-Perez, Julio; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Controlled assembly of nanoparticles at liquid crystal interfaces could lead to easily manufacturable building blocks for assembly of materials with tunable mechanical, optical, and electronic properties. Past work has examined nanoparticle assembly at planar liquid crystal interfaces. In this work we show that nanoparticle assembly on curved interfaces is drastically different, and arises for conditions under which assembly is too weak to occur on planar interfaces. We also demonstrate that LC-mediated nanoparticle interactions are strong, are remarkably sensitive to surface anchoring, and lead to hexagonal arrangements that do not arise in bulk systems. All these elements form the basis for a highly tunable, predictable, and versatile platform for hierarchical materials assembly. National Science Foundation through the UW MRSEC.

  10. Reflective liquid crystal hybrid beam-steerer.

    PubMed

    Willekens, Oliver; Jia, Xiaoning; Vervaeke, Michael; Shang, Xiaobing; Baghdasaryan, Tigran; Thienpont, Hugo; De Smet, Herbert; Neyts, Kristiaan; Beeckman, Jeroen

    2016-09-19

    We report on efficient optical beam-steering using a hot-embossed reflective blazed grating in combination with liquid crystal. A numerical simulation of the electrical switching characteristics of the liquid crystal is performed and the results are used in an FDTD optical simulator to analyze the beam deflection. The corresponding experiment on the realized device is performed and is found to be in good agreement. Beam deflection angles of 4.4° upon perpendicular incidence are found with low applied voltages of 3.4 V. By tilting the device with respect to the incoming optical beam it can be electronically switched such that the beam undergoes either total internal reflection or reflection with a tunable angle. PMID:27661892

  11. Axial polarizers based on dichroic liquid crystals

    NASA Astrophysics Data System (ADS)

    Nersisyan, Sarik; Tabiryan, Nelson; Steeves, Diane M.; Kimball, Brian R.

    2010-08-01

    Polarizers capable of producing linearly polarized beams with axial (radial and azimuthal) symmetry have been fabricated with the aid of a dichroic liquid crystal. Photoalignment was achieved using a printing technique to reduce the UV exposure time required for production of axially aligning substrates from 1 h, typical for direct writing techniques, to 10 min. The polarizing features of axial polarizers and their pairs are characterized and their differences outlined. We demonstrate that the transmission switching contrast of an axial polarizer/analyzer pair, comprised of an electrically controlled liquid crystal cell, is comparable to conventional systems with linear polarizers. The opportunities for using axial polarizers for polarization imaging, sensor protection, and nonlinear optics are discussed. Particularly, we show that the technology could reduce the fluence of a laser beam on an optical sensor without affecting imaging.

  12. Phototunable reflection notches of cholesteric liquid crystals

    SciTech Connect

    Hrozhyk, Uladzimir A.; Serak, Svetlana V.; Tabiryan, Nelson V.; Bunning, Timothy J.

    2008-09-15

    The reflection notch of cholesteric liquid crystals (CLCs) formed from highly photosenstive azobenzene nematic liquid crystals doped with light-insensitive, large helical twisting power chiral dopants is shown to be widely phototunable by green laser beams. The nonlinear transmission properties of these materials were studied. We have shown that the relative shift in Bragg wavelength is independent of the chiral dopant concentration and develop a predictive theory of such behavior. The theory describes the dynamics of phototuning as well. Reflection shifts greater than 150 nm were driven with low power, cw of 532 nm in these photosensitive CLCs, previously attainable only through UV pre-exposure. A nonlinear feedback mechanism was demonstrated for CLCs of left, right, and both handedness upon laser-induced blueshifting of the reflection notch from a red wavelength using a green cw laser.

  13. Dye-doped cholesteric-liquid-crystal room-temperature single-photon source

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; Supranowitz, C.M.; Lippa, N.; McNamara, A.J.; Boyd, R.W.; Stroud, Jr., C.R.

    2004-06-15

    Fluorescence antibunching from single terrylene molecules embedded in a cholesteric-liquid-crystal host is used to demonstrate operation of a room-temperature single-photon source. One-dimensional (1-D) photonic-band-gap microcavities in planar-aligned cholesteric liquid crystals with band gaps from visible to near-infrared spectral regions are fabricated. Liquid-crystal hosts (including liquid crystal oligomers and polymers) increase the source efficiency, firstly, by aligning the dye molecules along the direction preferable for maximum excitation efficiency (deterministic molecular alignment provides deterministically polarized output photons), secondly, by tuning the 1-D photonic-band-gap microcavity to the dye fluorescence band and thirdly, by protecting the dye molecules from quenchers, such as oxygen.

  14. Evidence for localized surface plasmon polaritons in a liquid crystal containing gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal; Singh, Ankit; Sharma, Suresh

    2012-02-01

    We report an observation of the localized surface plasmon polaritons (SPPs) in a nematic liquid crystal containing 14 nm diameter gold nanoparticles (Au NPs). We observe attenuated total reflection (ATR) of p-polarized laser beam incident upon a high-index prism/liquid-crystal-Au-NPs/glass structure used in the Kretschmann configuration.^1 Unlike the ubiquitous ATR configuration, in which the prism base is coated with a noble metal thin film, our experimental set up does not utilize any such coating. The ATR observed at a specific incident angle and only for p-polarized laser reflects the excitation of localized SPPs at NP/liquid-crystal interface. We discuss possible SPPs related effects, which can significantly change the electro-optical properties of polymer-dispersed liquid crystals.^2

  15. Molecular-scale soft imprint lithography for alignment layers in liquid crystal devices.

    PubMed

    Lin, Rongsheng; Rogers, John A

    2007-06-01

    We describe molecular-scale soft nanoimprint lithographic replication of rubbed polyimide substrates to form alignment layers for liquid crystal devices. Systematic studies of the surface relief morphology of the polyimide and molded structures in three different polymers illustrate good lithographic fidelity down to relief heights of several nanometers, and with some capabilities at the level of approximately 1 nm. Collective results of experiments with several polymer formulations for molds and molded materials and process conditions indicate that this molecular-scale fidelity in replication can be used to produce surfaces that will effectively align liquid crystal molecules. Good electro-optical responses from liquid crystal light modulators that are formed in this manner suggest utility for fundamental studies and potential practical application.

  16. Graphene-based liquid crystal device.

    PubMed

    Blake, Peter; Brimicombe, Paul D; Nair, Rahul R; Booth, Tim J; Jiang, Da; Schedin, Fred; Ponomarenko, Leonid A; Morozov, Sergey V; Gleeson, Helen F; Hill, Ernie W; Geim, Andre K; Novoselov, Kostya S

    2008-06-01

    Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

  17. Liquid crystal phase shifters for space applications

    NASA Astrophysics Data System (ADS)

    Woehrle, Christopher D.

    Space communication satellites have historically relied heavily on high gain gimbal dish antennas for performing communications. Reflector dish antennas lack flexibility in anti-jamming capabilities, and they tend to have a high risk associated to them given the need for mechanical mechanisms to beam steer. In recent years, a great amount of investment has been made into phased array antenna technologies. Phased arrays offer increased signal flexibility at reduced financial cost and in system risk. The problem with traditional phased arrays is the significant program cost and overall complexity added to the satellite by integrating antenna elements that require many dedicated components to properly perform adaptive beam steering. Several unique methods have been proposed to address the issues that plague traditional phase shifters slated for space applications. Proposed approaches range from complex mechanical switches (MEMS) and ferroelectric devices to more robust molecular changes. Nematic liquid crystals offer adaptive beam steering capabilities that traditional phased arrays have; however, with the added benefit of reduced system cost, complexity, and increased resilience to space environmental factors. The objective of the work presented is to investigate the feasibility of using nematic liquid crystals as a means of phase shifting individual phased array elements slated for space applications. Significant attention is paid to the survivability and performance of liquid crystal and associated materials in the space environment. Performance regarding thermal extremes and interactions with charged particles are the primary factors addressed.

  18. Orientational transitions in antiferromagnetic liquid crystals

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Petrov, D. A.

    2016-09-01

    The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, impurity ferroparticles with the magnetic moments directed parallel and antiparallel to the director are equiprobably distributed in it. It is established that under the action of a magnetic field the ferronematic undergoes orientational transitions compensated (antiferromagnetic) phase-non-uniform phase-saturation (ferrimagnetic) phase. The analytical expressions for threshold fields of the transitions as functions of material parameters are obtained. It is shown that with increasing magnetic impurity segregation parameter, the threshold fields of the transitions significantly decrease. The bifurcation diagram of the ferronematic orientational phases is built in terms of the energy of anchoring of magnetic particles with the liquid-crystal matrix and magnetic field. It is established that the Freedericksz transition is the second-order phase transition, while the transition to the saturation state can be second- or first-order. In the latter case, the suspension exhibits orientational bistability. The orientational and magnetooptical properties of the ferronematic in different applied magnetic fields are studied.

  19. Optical modeling of liquid crystal biosensors

    NASA Astrophysics Data System (ADS)

    Hwang, Dae Kun; Rey, Alejandro D.

    2006-11-01

    Optical simulations of a liquid crystal biosensor device are performed using an integrated optical/textural model based on the equations of nematodynamics and two optical methods: the Berreman optical matrix method [J. Opt. Soc. Am. 62, 502 (1972)] and the discretization of the Maxwell equations based on the finite difference time domain (FDTD) method. Testing the two optical methods with liquid crystal films of different degrees of orientational heterogeneities demonstrates that only the FDTD method is suitable to model this device. Basic substrate-induced texturing process due to protein adsorption gives rise to an orientation correlation function that is nearly linear with the transmitted light intensity, providing a basis to calibrate the device. The sensitivity of transmitted light to film thickness, protein surface coverage, and wavelength is established. A crossover incident light wavelength close to λco≈500nm is found, such that when λ >λco thinner films are more sensitive to the amount of protein surface coverage, while for λ <λco the reverse holds. In addition it is found that for all wavelengths the sensitivity increases with the amount of protein coverage. The integrated device model based on FDTD optical simulations in conjunction with the Landau-de Gennes nematodynamics model provides a rational basis for further progress in liquid crystal biosensor devices.

  20. Microscale locomotion in a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Krieger, Madison S.; Spagnolie, Saverio E.; Powers, Thomas

    Microorganisms often encounter anisotropy, for example in mucus and biofilms. We study how anisotropy and elasticity of the ambient fluid affects the speed of a swimming microorganism with a prescribed stroke. Motivated by recent experiments on swimming bacteria in anisotropic environments, we extend a classical model for swimming microorganisms, the Taylor swimming sheet, actuated either by transverse or longitudinal traveling waves in a three-dimensional nematic liquid crystal without twist. We calculate the swimming speed and entrained volumetric flux as a function of the swimmer's stroke properties as well as the elastic and rheological properties of the liquid crystal. The behavior is quantitatively and qualitatively well-approximated by a hexatic liquid crystal except in the cases of small Ericksen number and in a nematic fluid with tumbling parameter near the transition to a flow-aligning nematic, where anisotropic effects dominate. We also propose a novel method of swimming or pumping in a nematic fluid by passing a traveling wave of director oscillation along a rigid wall.

  1. Silylene-diethynyl-arylene polymers having liquid crystalline properties

    DOEpatents

    Barton, T.J.; Yiwei Ding.

    1993-09-07

    The present invention provides linear organosilicon polymers including diethynyl-(substituted)arylene units, and a process for their preparation. These novel polymers possess useful properties including electrical conductivity, liquid crystallinity, and/or photoluminescence. These polymers possess good solubility in organic solvents. A preferred example is produced according to the following reaction scheme. ##STR1## These polymers can be solvent-cast to yield excellent films and can also be pulled into fibers from concentrated solutions. All possess substantial crystallinity as revealed by DSC analysis and observation through a polarizing microscope, and possess liquid crystalline properties.

  2. Three-dimensional vector recording in polarization sensitive liquid crystal composites by using axisymmetrically polarized beam.

    PubMed

    Sakamoto, Moritsugu; Sasaki, Tomoyuki; Noda, Kohei; Tien, Tran Minh; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2016-02-01

    Three-dimensional anisotropic structures were fabricated by a recording axisymmetrically polarized beam in azobenzene (azo)-dye doped liquid crystal polymer composites. Polarization and wavefront modulation properties of fabricated anisotropic structures are investigated by experimentally and theoretically analyzing the diffraction properties. Photo-induced anisotropic structures would be utilized to generate singular light waves, such as optical and polarization vortices.

  3. High-efficiency and fast-response tunable phase grating using a blue phase liquid crystal.

    PubMed

    Yan, Jin; Li, Yan; Wu, Shin-Tson

    2011-04-15

    We demonstrate a tunable phase grating using a polymer-stabilized blue phase liquid crystal. Because of the electric-field-induced rectangularlike phase profile, a high diffraction efficiency of 40% is achieved. Moreover, this device shows submillisecond response time. The proposed tunable phase grating holds great potential for photonics and display applications. PMID:21499371

  4. Structures of cyano-biphenyl liquid crystals

    NASA Technical Reports Server (NTRS)

    Chu, Yuan-Chao; Tsang, Tung; Rahimzadeh, E.; Yin, L.

    1989-01-01

    The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

  5. Graphene liquid crystal retarded percolation for new high-k materials

    PubMed Central

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-01-01

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed. PMID:26567720

  6. Graphene liquid crystal retarded percolation for new high-k materials

    NASA Astrophysics Data System (ADS)

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-11-01

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed.

  7. Graphene liquid crystal retarded percolation for new high-k materials.

    PubMed

    Yuan, Jinkai; Luna, Alan; Neri, Wilfrid; Zakri, Cécile; Schilling, Tanja; Colin, Annie; Poulin, Philippe

    2015-11-16

    Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed.

  8. Monte Carlo simulations of single crystals from polymer solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Muthukumar, M.

    2007-06-01

    A novel "anisotropic aggregation" model is proposed to simulate nucleation and growth of polymer single crystals as functions of temperature and polymer concentration in dilute solutions. Prefolded chains in a dilute solution are assumed to aggregate at a seed nucleus with an anisotropic interaction by a reversible adsorption/desorption mechanism, with temperature, concentration, and seed size being the control variables. The Monte Carlo results of this model resolve the long-standing dilemma regarding the kinetic and thermal roughenings, by producing a rough-flat-rough transition in the crystal morphology with increasing temperature. It is found that the crystal growth rate varies nonlinearly with temperature and concentration without any marked transitions among any regimes of polymer crystallization kinetics. The induction time increases with decreasing the seed nucleus size, increasing temperature, or decreasing concentration. The apparent critical nucleus size is found to increase exponentially with increasing temperature or decreasing concentration, leading to a critical nucleus diagram composed in the temperature-concentration plane with three regions of different nucleation barriers: no growth, nucleation and growth, and spontaneous growth. Melting temperatures as functions of the crystal size, heating rate, and concentration are also reported. The present model, falling in the same category of small molecular crystallization with anisotropic interactions, captures most of the phenomenology of polymer crystallization in dilute solutions.

  9. Formation of Liquid Crystal Elastomer Microparticles

    NASA Astrophysics Data System (ADS)

    Kim, Chanjoong; Yan, Huan; Mukherjee, Souptik; Luchette, Paul; Palffy-Muhoray, Peter

    2011-03-01

    Liquid crystal elastomer (LCE) combines the properties of rubber elasticity and anisotropic properties of liquid crystalline materials. In particular, LCE has a potential to exhibit interesting properties like electric polarization, ferroelectricity and piezo-electricity. Thin films, fibers and even balloons of LCE using techniques such as spin coating, electro-spinning and in cells have been reported by many groups before. Using microfluidics technique followed by photo-polymerization, we produce uniform spherical LCE microspheres with diameter of 20 - 85 μm . Compression of the LCE microspheres generates a characteristic director configuration. The elastomers may also reveal interesting magnetic and electrical properties due to the intrinsically anisotropic nature of liquid crystalline materials.

  10. Protein crystallization on liquid surfaces: Forced versus natural crystallization

    NASA Astrophysics Data System (ADS)

    Hirsa, A.

    2005-11-01

    Two-dimensional crystallization of proteins has recently been reported where streptavidin protein dissolved in the bulk liquid anchors to binding sites on a biotinylated lipid monolayer initially spread on the liquid surface. Thermodynamic aspects investigated include the effects of subphase buffer and pH, dilution of bulk protein and monolayer. Here, we investigate three possible avenues where flow can influence protein crystallization: i) change the initial state of monolayer, ii) advect dissolved protein to the interface, iii) apply direct hydrodynamic force on the crystals at the interface. The flow system consists of a stationary open cylinder driven by constant rotation of the floor, in the axisymmetric flow regime with inertia. Direct imaging of the interface illuminated by forward scattering of a laser was utilized to avoid labeling proteins for conventional fluorescence microscopy. These images provide greater detail than Brewster angle microscopy. Scientific motivation is to use flow to probe protein structure, and the application is to make designer protein thin-films, e.g. for biosensors.

  11. Fast response dual frequency liquid crystal materials

    NASA Astrophysics Data System (ADS)

    Song, Qiong

    Dual frequency liquid crystal (DFLC) exhibits a positive dielectric anisotropy at low frequencies and negative dielectric anisotropy at high frequencies. The frequency where dielectric anisotropy is zero is called crossover frequency. DFLC can achieve fast rise time and fast decay time with the assistance of applied voltage. However, one drawback of DFLC is that it has dielectric heating effect when driven at a high frequency. Thus, the first part of this dissertation is to develop low crossover frequency DFLC materials. The dielectric relaxation and physical properties of some single- and double-ester compounds were investigated. Experimental results indicate that the double-ester compound exhibits a ˜3X lower dielectric relaxation frequencies and larger dielectric anisotropy than the single ester, but its viscosity is also higher. More generally, ten groups of dual frequency liquid crystals were compared in terms of dielectric relaxation frequency and dielectric anisotropy. The dielectric relaxation theory was discussed at last. To realize fast response time, high birefringence and low viscosity LC are required. From these two aspects, firstly four new high birefringence laterally difluoro phenyl tolane liquid crystals with a negative dielectric anisotropy were studied. These materials are used to enhance the birefringence of DFLC. They have a fairly small heat fusion enthalpy (˜3000 cal/mol) which improves their solubility in a host. We dope 10 wt% of each compound into a commercial negative mixture N1 and measured their birefringence, viscoelastic constant and figure of merit. Birefringence varies very little among homologues while viscoelastic constant increases as alkyl chain length increases. Secondly, we studied the effects of six diluters for lowering the viscosity while stabilizing the vertical alignment (VA) of the laterally difluoro terphenyl host mixture at elevated temperatures. The pros and cons of each diluter are analyzed. These lateral difluoro

  12. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-01-01

    The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal

  13. Two-dimensional photonic crystals from semiconductor material with polymer filled holes

    NASA Astrophysics Data System (ADS)

    van der Heijden, Rob; Kjellander, Charlotte; Carlström, Carl-Fredrik; Snijders, Juri; van der Heijden, Rob W.; Bastiaansen, Kees; Broer, Dick; Karouta, Fouad; Nötzel, Richard; van der Drift, Emile; Salemink, Huub W. M.

    2006-04-01

    Polymer filling of the air holes of indiumphosphide based two-dimensional photonic crystals is reported. The filling is performed by infiltration with a liquid monomer and solidification of the infill in situ by thermal polymerization. Complete hole filling is obtained with infiltration under ambient pressure. This conclusion is based both on cross-sectional scanning electron microscope inspection of the filled samples as well as on optical transmission measurements.

  14. Solvent-free Liquid Crystals and Liquids from DNA.

    PubMed

    Liu, Kai; Shuai, Min; Chen, Dong; Tuchband, Michael; Gerasimov, Jennifer Y; Su, Juanjuan; Liu, Qing; Zajaczkowski, Wojciech; Pisula, Wojciech; Müllen, Klaus; Clark, Noel A; Herrmann, Andreas

    2015-03-23

    As DNA exhibits persistent structures with dimensions that exceed the range of their intermolecular forces, solid-state DNA undergoes thermal degradation at elevated temperatures. Therefore, the realization of solvent-free DNA fluids, including liquid crystals and liquids, still remains a significant challenge. To address this intriguing issue, we demonstrate that combining DNA with suitable cationic surfactants, followed by dehydration, can be a simple generic scheme for producing these solvent-free DNA fluid systems. In the anhydrous smectic liquid crystalline phase, DNA sublayers are intercalated between aliphatic hydrocarbon sublayers. The lengths of the DNA and surfactant are found to be extremely important in tuning the physical properties of the fluids. Stable liquid-crystalline and liquid phases are obtained in the -20 °C to 200 °C temperature range without thermal degradation of the DNA. Thus, a new type of DNA-based soft biomaterial has been achieved, which will promote the study and application of DNA in a much broader context.

  15. Invited review liquid crystal models of biological materials and silk spinning.

    PubMed

    Rey, Alejandro D; Herrera-Valencia, Edtson E

    2012-06-01

    A review of thermodynamic, materials science, and rheological liquid crystal models is presented and applied to a wide range of biological liquid crystals, including helicoidal plywoods, biopolymer solutions, and in vivo liquid crystals. The distinguishing characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is established. Biological polymer processing based on liquid crystalline precursors includes viscoelastic flow to form and shape fibers. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from optical textures and rheometers. It is shown that viscoelastic modeling the silk spinning process using liquid crystal theories sheds light on textural transitions in the duct of spiders and silk worms as well as on tactoidal drops and interfacial structures. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is another tool to develop the science and biomimetic applications of mesogenic biological soft matter.

  16. Invited review liquid crystal models of biological materials and silk spinning.

    PubMed

    Rey, Alejandro D; Herrera-Valencia, Edtson E

    2012-06-01

    A review of thermodynamic, materials science, and rheological liquid crystal models is presented and applied to a wide range of biological liquid crystals, including helicoidal plywoods, biopolymer solutions, and in vivo liquid crystals. The distinguishing characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is established. Biological polymer processing based on liquid crystalline precursors includes viscoelastic flow to form and shape fibers. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from optical textures and rheometers. It is shown that viscoelastic modeling the silk spinning process using liquid crystal theories sheds light on textural transitions in the duct of spiders and silk worms as well as on tactoidal drops and interfacial structures. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is another tool to develop the science and biomimetic applications of mesogenic biological soft matter. PMID:21994072

  17. Liquid crystal-ZnO nanoparticle photovoltaics: Role of nanoparticles in ordering the liquid crystal

    SciTech Connect

    Martinez-Miranda, L. J.; Traister, Kaitlin M.; Melendez-Rodriguez, Iriselies; Salamanca-Riba, Lourdes

    2010-11-29

    We investigate the role that order plays in the transfer of charges in the ZnO nano-particle-octylcyanobiphenyl (8CB) liquid crystal system, considered for photovoltaic applications. We have changed the concentration of ZnO nanoparticles in 8CB from 1.18 to 40 wt %. Our results show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles, up to a concentration of 30 wt %. In addition, the current generated by the system increases by three orders of magnitude.

  18. Liquid crystal nanocomposites produced by mixtures of hydrogen bonded achiral liquid crystals and functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Katranchev, B.; Petrov, M.; Keskinova, E.; Naradikian, H.; Rafailov, P. M.; Dettlaff-Weglikowska, U.; Spassov, T.

    2014-12-01

    The liquid crystalline (LC) nature of alkyloxybenzoic acids is preserved after adding of any mesogenic or non-mesogenic compound through hydrogen bonding. However, this noncovalent interaction provokes a sizable effect on the physical properties as, e. g. melting point and mesomorphic states. In the present work we investigate nanocomposites, prepared by mixture of the eighth homologue of p-n-alkyloxybenzoic acids (8OBA) with single-walled carbon nanotubes (SWCNT) with the purpose to modify the optical properties of the liquid crystal. We exercise optical control on the LC system by inserting SWCNT specially functionalized by carboxylic groups. Since the liquid crystalline state combines order and mobility at the molecular (nanoscale) level, molecular modification can lead to different macroscopical nanocomposite symmetry. The thermal properties of the functionalized nanocomposite are confirmed by DSC analyses. The mechanism of the interaction between surface-treated nanoparticles (functionalized nanotubes) and the liquid crystal 8OBA bent- dimer molecules is briefly discussed.

  19. Perdeuterated liquid crystals for near infrared applications

    NASA Astrophysics Data System (ADS)

    Kula, P.; Bennis, N.; Marć, P.; Harmata, P.; Gacioch, K.; Morawiak, P.; Jaroszewicz, L. R.

    2016-10-01

    For majority of Liquid Crystalline compounds the absorption occurs at two spectral regions: ultraviolet UV (due to electronic excitations) and infrared IR (caused by molecular vibrations). Both cause the absorption which deteriorates electro-optical modulation abilities of LC. In the MWIR and LWIR regions, there are many fundamental molecular vibration bands. The most intense are the ones with high anharmonicity, which in the case of LCs corresponds to the Csbnd H bonds, especially present in the aliphatic chains. In the NIR region, overtone molecular vibration bands derived from IR region begin to appear. In the case of Csbnd H bond system, the first overtones are present at 1.6-1.7 μm. To reduce NIR absorptions, perdeuterated Liquid crystal has been proposed. In this paper, we report the physical and optical properties of liquid crystals based on polarimetry measurements method. We also provide a polar decomposition of experimentally measured Mueller matrix in order to determine polarization properties of the device such as depolarization and diattenuation which cannot be obtained from absorption spectra.

  20. Magnetically recyclable polymer single crystal supported silver nanocatalyst.

    PubMed

    Shi, Lili; Liu, Mei; Liu, Limei; Gao, Wenlong; Su, Miaoda; Ge, Ya; Zhang, Hui; Dong, Bin

    2014-11-11

    We report the immobilization of unprotected silver nanoparticle on the carboxylic acid abundant polymer single crystal surface with controllable size through photogenerated chemical reduction reaction. The resulting silver nanoparticle decorated polymer single crystal not only shows higher catalytic activity as compared to its counterpart bearing surface ligand but also exhibits size-dependent catalytic activity with the smallest size (∼1.5 nm) being the most active. By further introducing iron oxide nanoparticles onto its surface, the resulting catalyst system can be magnetically recycled for up to five times with little loss in catalytic activity. These, together with the high loading originated from the high surface area to volume ratio for a polymer single crystal, make current catalyst system attractive for many industrial important catalytic applications.

  1. Liquid crystal devices for photonics applications

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir G.

    2007-11-01

    Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. Application of nematic and ferroelectric LC for high speed communication systems, producing elements that are extremely fast, stable, durable, of low loss, operable over a wide temperature range, and that require small operating voltages and extremely low power consumption. The known LC applications in fiber optics enable to produce switches, filters, attenuators, equalizers, polarization controllers, phase emulators and other fiber optical components. Good robustness due to the absence of moving parts and compatibility with VLSI technology, excellent parameters in a large photonic wavelength range, whereas the complexity of the design and the cost of the device are equivalent to regular passive matrix LC displays makes LC fiber optical devices very attractive for mass production. We have already successfully fabricated certain prototypes of the optical switches based on ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. We used the powerful software to optimize the LC modulation characteristics. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. The prototypes of new LC efficient Photonics devices are envisaged. Controllable

  2. Observation of nematic/smectic liquid crystal configurations in a prolate spheroidal confinement

    NASA Astrophysics Data System (ADS)

    Jeong, Joonwoo; Kim, Mahn Won

    2011-03-01

    Polymer-dispersed liquid crystal (PDLC) is a composite of dispersed LC droplets in a polymer matrix. The electro-optic properties of PDLCs, such as reorientation field strength and response time, are strongly related to the director configuration. Various factors including the intrinsic properties of LC/polymer and the size/shape of droplets affect the liquid crystal configuration. A balance between the bulk elastic energy and the surface anchoring energy determines the configuration. To study systematically the effect of size/shape of droplets on the configuration, we have prepared thin PDLC films with 4-Cyano-4'-pentylbiphenyl (5CB)/ 4-Cyano-4'-octylbiphenyl (8CB) and Polydimethylsiloxane (PDMS) elastomer. Using polarized optical microscopy, we have observed the change in the director configuration of LC droplets as a function of the aspect ratio up to 6 by stretching the film unidirectionally. We have also observed the effect of surface anchoring on the configuration.

  3. Biomedical spectroscopy in clinical applications and implications of liquid crystal filter technologies

    NASA Astrophysics Data System (ADS)

    McMurdy, John W.

    This dissertation discusses two related clinical applications of visible regime diffuse reflectance spectroscopy as well as two new configurations of liquid crystal microspectrometer suitable in these applications. Total hemoglobin concentration can be determined, and thus anemia diagnosed, using diffuse reflectance signals from the inner lining of the eyelid, the palpebral conjunctiva. Alternative technologies for anemia detection are explored, a theoretical model for light diffusion through the conjunctiva is presented, and predictive models are established relating spectral signatures to hemoglobin concentration. Two separate clinical trials were conducted showing accuracy of hemoglobin determination with respect to invasive determination of 5% and 8% of mean hemoglobin concentration, respectively. Local hemoglobin concentration can also be determined in vivo at individual vessels using a single fiber which is directly applicable in endoscopic and laparoscopic surgery. Clinical trials showed signal differentiation of different hemoglobin levels in laparoscopic cases when pressing the single fiber against an individual vessel, and donor/recipient differentiation in fetal endoscopy cases of twin to twin transfusion syndrome. Liquid crystal technologies can be used to create integrated chip-scale microspectrometers. In one configuration, analog tunable ferroelectric liquid crystals are applied to create a tunable filter spectrometer with resolution from 15-30 nm. In a second configuration, stressed liquid crystal polymer composites are used to create large phase modulators, subsequently applied as single panel Fourier transform spectrometers. Proof of concept studies show a 100 microm stressed liquid crystal polymer in double pass mode is capable of 60 nm resolving power.

  4. New triazolium based ionic liquid crystals

    SciTech Connect

    Stappert, Kathrin; Unal, Derya; Mallick, Bert; Mudring, Anja-Verena

    2014-01-01

    A set of novel 1,2,3-triazolium based ionic liquid crystals was synthesized and their mesomorphic behaviour studied by DSC (differential scanning calorimetry), POM (polarizing optical microscopy) and SAXS (small angle X-ray scattering). Beside the variation of the chain length (C10, C12 and C14) at the 1,2,3-triazolium cation also the anion has been varied (Br-, I-, I3-, BF4-, SbF6-, N(CN)2-, Tf2N-) to study the influence of ion size, symmetry and H-bonding capability on the mesophase formation. Interestingly, for the 1,3-didodecyl-1,2,3-triazolium cation two totally different conformations were found in the crystal structure of the bromide (U-shaped) and the triiodide (rod shaped).

  5. High birefringence liquid crystals for photonic applications

    NASA Astrophysics Data System (ADS)

    Gauza, S.; Wen, C. H.; Wu, S. T.; Dabrowski, R.; Hsu, C. S.; Catanescu, C. O.; Chien, L. C.

    2005-09-01

    High birefringence liquid crystals (LCs) play an important role for laser beam steering, tunable-focus lens, reflective display, cholesteric LC laser, infrared dynamic scene projector, and telecom variable optical attenuator applications. We have developed some high birefringence compounds and eutectic mixtures with birefringence in the 0.4-0.7 range. For some photonic devices where response time is critical, we have also developed high birefringence dual-frequency LC mixtures. The cross-over frequency is around 5-10 kHz. Using such a dual-frequency LC mixture, sub-millisecond response time is achieved.

  6. Thermal diode made by nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Melo, Djair; Fernandes, Ivna; Moraes, Fernando; Fumeron, Sébastien; Pereira, Erms

    2016-09-01

    This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed.

  7. Stochastic rotation dynamics for nematic liquid crystals

    SciTech Connect

    Lee, Kuang-Wu Mazza, Marco G.

    2015-04-28

    We introduce a new mesoscopic model for nematic liquid crystals (LCs). We extend the particle-based stochastic rotation dynamics method, which reproduces the Navier-Stokes equation, to anisotropic fluids by including a simplified Ericksen-Leslie formulation of nematodynamics. We verify the applicability of this hybrid model by studying the equilibrium isotropic-nematic phase transition and nonequilibrium problems, such as the dynamics of topological defects and the rheology of sheared LCs. Our simulation results show that this hybrid model captures many essential aspects of LC physics at the mesoscopic scale, while preserving microscopic thermal fluctuations.

  8. Probing and controlling liquid crystal helical nanofilaments.

    PubMed

    Zhu, Chenhui; Wang, Cheng; Young, Anthony; Liu, Feng; Gunkel, Ilja; Chen, Dong; Walba, David; Maclennan, Joseph; Clark, Noel; Hexemer, Alexander

    2015-05-13

    We report the first in situ measurement of the helical pitch of the helical nanofilament B4 phase of bent-core liquid crystals using linearly polarized, resonant soft X-ray scattering at the carbon K-edge. A strong, anisotropic scattering peak corresponding to the half-pitch of the twisted smectic layer structure was observed. The equilibrium helical half-pitch of NOBOW is found to be 120 nm, essentially independent of temperature. However, the helical pitch can be tuned by mixing guest organic molecules with the bent-core host, followed by thermal annealing.

  9. Liquid Crystal Television For Optical Correlation

    NASA Astrophysics Data System (ADS)

    Perng, Wen-Sheng; Cheng, Yih-Shyang; Chang, Ming-Wen

    1987-08-01

    In this paper, we present a newly developed hybrid multi-channel real-time pattern recognition system. Two modified commercial liquid crystal televisions are applied as a real-time incoherent to coherent image transducer and a device to produce converging wavelets with different focal positions. Taking advantages of the cross-grating nature of the LCTV screen, a multi-channel correlator becomes possible. This hybrid system has both the high processing speed of an optical system and the flexibility of an electronic system.

  10. Liquid crystal-based hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Brodzeli, Zourab; Silvestri, Leonardo; Michie, Andrew; Chigrinov, Vladimir G.; Guo, Qi; Pozhidaev, Eugene P.; Kiselev, Alexei D.; Ladouceur, Francois

    2012-09-01

    We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications (e.g. military, counter terrorist, and customs authorities in protecting ports and harbors), offshore production facilities or coastal approaches as well as various marine applications. In this paper, we propose a new approach to underwater sonar systems using the voltage-controlled liquid crystals and simple multiplexing method. The proposed method permits measurement of sound under water at multiple points along an optical fiber using the low cost components and standard single mode fiber, without complex interferometric measurement techniques, electronics or demodulation software.

  11. Laser damage resistant nematic liquid crystal cell

    NASA Astrophysics Data System (ADS)

    Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

    2013-08-01

    There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

  12. Wide Angle Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xing-Hua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John J.; Miranda, Felix A.; McManamon, Paul F.

    2004-01-01

    Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

  13. Holographically generated twisted nematic liquid crystal gratings

    SciTech Connect

    Choi, Hyunhee; Wu, J.W.; Chang, Hye Jeong; Park, Byoungchoo

    2006-01-09

    A reflection holographic method is introduced to fabricate an electro-optically tunable twisted nematic (TN) liquid crystal (LC) grating, forgoing the geometrical drawing. The photoisomerization process occurring on the LC alignment layers of an LC cell in the reflection holographic configuration gives a control over the twist angle, and the grating spacing is determined by the slant angle of reflection holographic configuration. The resulting diffraction grating is in a structure of a reverse TN LC, permitting a polarization-independent diffraction efficiency. The electro-optic tunability of the diffraction efficiency is also demonstrated.

  14. One-dimensional photonic crystals containing memory-enabling liquid-crystal defect layers

    NASA Astrophysics Data System (ADS)

    Wu, Po-Chang; Lee, Wei

    2013-09-01

    Incorporating liquid crystal (LC) as a defect layer in a photonic crystal (PC) leads to the electrically tunable optical spectrum in defect modes within the photonic band gap. While the LC defect layer has bi- or multi-stable states, the profile of defect modes in each stable state can be preserved permanently without applied voltage, indicating a feature of low power consumption for photonic applications. In this paper, we report on our recent development of optical and spectral properties of multilayer PC structures containing various types of memory-enabling LC (ME-LC), including a bistable chiral-tilted homeotropic nematic (BHN), a bistable chiral-splay nematic (BCSN), a bistable dual-frequency cholesteric LC (DFCLC), a tristable polymer-stabilized cholesteric texture (PSCT), and a tristable smectic-A liquid crystal as a defect layer. The defect modes of the PC/ME-LC cell can be switched to not only the voltage-sustained states but the memory states. As a result, PC/ME-LC cells reveal several features such as the wavelength tunability, transmission tunability and optical bistability or tristability of defect modes that are of potential for realizing tunable and memorable optical devices such as low-power-consumption multichannel filters, light shutters or electrically controllable intensity modulators with green concept.

  15. Synthesis of fluoro substituted quaterphenyl liquid crystals

    NASA Astrophysics Data System (ADS)

    Sasnouski, G.; Lapanik, V.; Bezborodov, V.; Dabrowski, R.; Dziaduszek, J.

    2014-08-01

    The improved approaches for the preparation of four ring quaterphenyl liquid crystalline compounds possessing fluoro substituted moieties have been developed. The key stage for the most synthetic schemes was the preparation of 3,6-diarylsubstituted cyclohex-2-en-1-ones via condensation of the corresponding aromatic Mannich salts with the fluoro substituted methyl benzyl ketone in the presence of base. The chlorination of these cyclohexenones with phosphorous pentachloride or methylation with methylmagnesium iodide followed oxidative aromatization allows the synthesis of final four ring fluoro substituted quaterphenyl liquid crystal (LC) compounds. Another approach provides for the condensation synthesis of bromo substituted intermediate terphenyls. They have been undergoing catalytic cross-coupling with the corresponding fluoro substituted phenyl boronic acid giving a wide range of quaterphenyl LC derivatives.

  16. Tuning Fluidic Resistance via Liquid Crystal Microfluidics

    PubMed Central

    Sengupta, Anupam

    2013-01-01

    Flow of molecularly ordered fluids, like liquid crystals, is inherently coupled with the average local orientation of the molecules, or the director. The anisotropic coupling—typically absent in isotropic fluids—bestows unique functionalities to the flowing matrix. In this work, we harness this anisotropy to pattern different pathways to tunable fluidic resistance within microfluidic devices. We use a nematic liquid crystalline material flowing in microchannels to demonstrate passive and active modulation of the flow resistance. While appropriate surface anchoring conditions—which imprint distinct fluidic resistances within microchannels under similar hydrodynamic parameters—act as passive cues, an external field, e.g., temperature, is used to actively modulate the flow resistance in the microfluidic device. We apply this simple concept to fabricate basic fluidic circuits, which can be hierarchically extended to create complex resistance networks, without any additional design or morphological patterning of the microchannels. PMID:24256819

  17. Localized soft elasticity in liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Ware, Taylor H.; Biggins, John S.; Shick, Andreas F.; Warner, Mark; White, Timothy J.

    2016-02-01

    Synthetic approaches to prepare designer materials that localize deformation, by combining rigidity and compliance in a single material, have been widely sought. Bottom-up approaches, such as the self-organization of liquid crystals, offer potential advantages over top-down patterning methods such as photolithographic control of crosslink density, relating to the ease of preparation and fidelity of resolution. Here, we report on the directed self-assembly of materials with spatial and hierarchical variation in mechanical anisotropy. The highly nonlinear mechanical properties of the liquid crystalline elastomers examined here enables strain to be locally reduced >15-fold without introducing compositional variation or other heterogeneities. Each domain (>=0.01 mm2) exhibits anisotropic nonlinear response to load based on the alignment of the molecular orientation with the loading axis. Accordingly, we design monoliths that localize deformation in uniaxial and biaxial tension, shear, bending and crack propagation, and subsequently demonstrate substrates for globally deformable yet locally stiff electronics.

  18. UV sensors based on liquid crystals mixtures

    NASA Astrophysics Data System (ADS)

    Chanishvili, Andro; Petriashvili, Gia; Chilaya, Guram; Barberi, Riccardo; De Santo, Maria P.; Matranga, Mario A.; Ciuchi, F.

    2006-04-01

    The Erythemal Response Spectrum is a scientific expression that describes the sensitivity of the skin to the ultraviolet radiation. The skin sensitivity strongly depends on the UV wavelength: a long exposition to UV radiation causes erythema once a threshold dose has been exceeded. In the past years several devices have been developed in order to monitor the UV exposure, most of them are based on inorganic materials that are able to mimic the human skin behaviour under UV radiation. We present a new device based on liquid crystals technology. The sensor is based on a liquid crystalline mixture that absorbs photons at UV wavelength and emits them at a longer one. This system presents several innovative features: the absorption range of the mixture can be varied to be sensitive to different wavelengths, the luminescence intensity can be tuned, the system can be implemented on flexible devices.

  19. Fast Electromechanical Response in Liquid Crystal Elastomer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Verduzco, Rafael; Agrawal, Aditya; Jacot, Jeff; Adetiba, Tomi

    2014-03-01

    Liquid crystal elastomers (LCEs) combine the elasticity of polymer networks with the fluidity and responsiveness of liquid crystals. LCEs can respond to a variety of external stimuli - heat, light, electric and magnetic fields - with large and reversible shape-changes. However, the response can be slow and/or require large external fields. Here, we present our recent work with LCE bilayers and LCE composite materials that demonstrates LCEs can respond quickly and with 3-D shape changes. Nematic LCE bilayers are prepared by depositing a PS film on top of a nematic LCE, and the bilayers exhibit reversible wrinkling, folding, and curling with temperature. The shape change of LCE bilayers is quantitatively predicted using finite-element modeling. Next, we show that a fast response to an electric field is achieved in nematic LCE composites. While typical nematic LCEs are relatively unresponsive to electric fields, LCE composites with 2 wt % carbon black can reversibly contract and expand in response to a 40 V electric field. The response time (0.1 - 10 Hz) and amplitude of shape change (1 - 20 %) depends on the external field and carbon black content. These composites may be useful for biomedical applications, such as substrates for dynamic cell culture and biocompatible scaffolds for heart tissue regeneration. Neonatal rat ventricular myocytes remain viable on LCE-carbon black bilayer substrates, and aligned myocyte cell sheets were successfully grown on LCE-composite bilayers.

  20. Molecular reorientation of a nematic liquid crystal by thermal expansion

    PubMed Central

    Kim, Young-Ki; Senyuk, Bohdan; Lavrentovich, Oleg D.

    2012-01-01

    A unique feature of nematic liquid crystals is orientational order of molecules that can be controlled by electromagnetic fields, surface modifications and pressure gradients. Here we demonstrate a new effect in which the orientation of nematic liquid crystal molecules is altered by thermal expansion. Thermal expansion (or contraction) causes the nematic liquid crystal to flow; the flow imposes a realigning torque on the nematic liquid crystal molecules and the optic axis. The optical and mechanical responses activated by a simple temperature change can be used in sensing, photonics, microfluidic, optofluidic and lab-on-a-chip applications as they do not require externally imposed gradients of temperature, pressure, surface realignment, nor electromagnetic fields. The effect has important ramifications for the current search of the biaxial nematic phase as the optical features of thermally induced structural changes in the uniaxial nematic liquid crystal mimic the features expected of the biaxial nematic liquid crystal. PMID:23072803