WorldWideScience

Sample records for polymer liquid crystal

  1. Investigation of Polymer Liquid Crystals

    Science.gov (United States)

    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.

  2. Strong dielectric liquid crystal polymer (Part 3)

    Energy Technology Data Exchange (ETDEWEB)

    Kurata, Hideaki; Shibasaki, Akira

    1988-11-01

    Influence of change of molecular parameters on liquid crystal condition is studied to get the correlation between molecular structure of liquid crystal and phase structure or visco-elastic properties. Eight kinds of biphenyl type liquid crystals with polyacrilate main chain and triphenyl type liquid crystals were used as samples. Followings were found by a ploarizing microscope and X-ray diffraction: Phases are transferred from isotropic phase S/sub A/ phase S/sup *//sub C/ phase S/sub 1/ phase to solid on temperature desending sequence. Degree of polymerization changes only these transfer point but spacer length affects not only transfer points and layer distance but also liquid crystal structure itself. Visco-elasticity of isotropic phase shows Newtonian viscosity and is affected by the main chain length. Macroscopic and microscopic structures influence on viscoelasticity in S/sub A/ phase and S/sup *//sub C/ phase. Two rapid rises of viscoelasticity are found in low molecular weight liquid crystal when S/sub A/ transfer and S/sub A/ to S/sup *//sub C/ transfer occur by temperature desending from the isotropic phase. Viscoelastic behavior is contributed by the properties of domain itself and interaction between domains, and the interaction is changed by polymerization. 6 references, 13 figures, 1 table.

  3. Simulation of nuclear magnetic resonance spectra of liquid crystals, polymers liquid crystals and conventional polymers

    International Nuclear Information System (INIS)

    Gerard, H.

    1993-01-01

    The aim of this study is the simulation and the exploitation of NMR spectra of nematic liquid crystals and of polymers. The NMR forms of lines are analysed owing to two complementary models. The first (single conformation model) describes the purely molecular contribution (geometry and internal movements in the molecule), the second the contribution of collective movements (visco elastic modes). Recallings on the NMR method and the orientational order notion within the nematic phase, are given in the first part, where these two models are also described. In a second part these models are applied to data relative to nematic molecules of weak molecular mass and to nematic polymers. This application allows to obtain informations on the structure and the internal movements of the molecule, the orientational order prevailing within the phase and the visco-elastic properties of the studied material. At last it is demonstrated that extension of these models to NMR data of polymers which don't present nematic phase in pure phase allows to obtain similar informations if we consider that their amorphous phase presents locally a nematic order. 136 refs., 46 figs., 4 tabs

  4. Thin aligned organic polymer films for liquid crystal devices

    International Nuclear Information System (INIS)

    Foster, Kathryn Ellen

    1997-01-01

    This project was designed to investigate the possibility of producing alignment layers for liquid crystal devices by cross-linking thin films containing anisotropic polymer bound chromophores via irradiation with polarised ultraviolet light. Photocross-linkable polymers find use in microelectronics, liquid crystal displays, printing and UV curable lacquers and inks; so there is an increasing incentive for the development of new varieties of photopolymers in general. The synthesis and characterisation of two new photopolymers that are suitable as potential alignment layers for liquid crystal devices are reported in this thesis. The first polymer contains the anthracene chromophore attached via a spacer unit to a methacrylate backbone and the second used a similarly attached aryl azide group. Copolymers of the new monomers with methyl methacrylate were investigated to establish reactivity ratios in order to understand composition drift during polymerisation. (author)

  5. Neutron scattering studies of molecular conformations in liquid crystal polymers

    Science.gov (United States)

    Noirez, L.; Moussa, F.; Cotton, J. P.; Keller, P.; Pépy, G.

    1991-03-01

    A comblike liquid crystal polymer (LPC) is a polymer on which mesogenic molecules have been grafted. It exhibits a succession of liquid crystal phases. Usually the equilibrium conformation of an ordinary polymeric chain corresponds to a maximum entropy, i.e., to an isotropic spherical coil. How does the backbone of a LCP behave in the nematic and smectic field? Small-angle neutron scattering may answer this question. Such measurements are presented here on four different polymers as a function of temperature. An anisotropy of the backbone conformation is found in all these studied compounds, much more pronounced in the smectic phase than in the nematic phase: the backbone spreads more or less perpendicularly to its hanging cores. A comparison with existing theories and a discussion of these results is outlined.

  6. Study of memory effects in polymer dispersed liquid crystal films

    International Nuclear Information System (INIS)

    Han, Jinwoo

    2006-01-01

    In this work, we have studied the memory effects in polymer dispersed liquid crystal films. We found that optical responses, such as the memory effects, of the films depended strongly on the morphology. For example, memory effects were observed for films with polymer ball morphologies; however, only weak hysteresis effects were observed for films with droplet morphologies. In particular, a stronger memory effect was observed for films with more complicated polymer ball structures. Coincidentally, T TE , the temperature at which the memory state is thermally erased, was generally higher for the films exhibiting a stronger memory effect. In addition, studies of the temporal evolution of the films show that the memory effects become stronger after films have been kept on the shelf for a period of time. This change is likely to be associated with a modification of surface anchoring properties at the LC-polymer interface.

  7. Morphological studies of polymer dispersed liquid crystal materials

    International Nuclear Information System (INIS)

    Han, Jin-Woo

    2006-01-01

    In this work, we have studied the morphologies of polymer dispersed liquid crystals (PDLCs) based on E7/NOA61. Scanning electron microscope studies show that the PDLC morphology is strongly affected by the LC concentration and the cure temperature. A typical PDLC morphology with isolated LC droplets dispersed in a polymer matrix is only observed at low LC compositions and at low cure temperatures. Increasing either the LC composition or the cure temperature results in a polymer ball morphology, in which LCs exist in irregularly shaped voids in the polymer network structure. It is shown that the transition between these two morphologies can be qualitatively explained using a pseudo-binary phase diagram.

  8. Application of Thin Films of Conjugated Polymers in Novel LED's and Liquid Crystal 'Light Valves'

    National Research Council Canada - National Science Library

    MacDiarmid, A

    1997-01-01

    .... Flexible, completely organic polymer dispersed liquid crystal light valves have been fabricated from transparent plastic substrates on which a conducting film of polypyrrole has been deposited...

  9. Time-dependent deformation of polymer network in polymer-stabilized cholesteric liquid crystals (Conference Presentation)

    Science.gov (United States)

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

    2017-02-01

    Recently, we reported direct current (DC) field controllable electro-optic (EO) responses of negative dielectric anisotropy polymer stabilized cholesteric liquid crystals (PSCLCs). A potential mechanism is: Ions in the liquid crystal mixtures are trapped in/on the polymer network during the fast photopolymerization process, and the movement of ions by the application of the DC field distorts polymer network toward the negative electrode, inducing pitch variation through the cell thickness, i.e., pitch compression on the negative electrode side and pitch expansion on positive electrode side. As the DC voltage is directly applied to a target voltage, charged polymer network is deformed and the reflection band is tuned. Interestingly, the polymer network deforms further (red shift of reflection band) with time when constantly applied DC voltage, illustrating DC field induced time dependent deformation of polymer network (creep-like behavior). This time dependent reflection band changes in PSCLCs are investigated by varying the several factors, such as type and concentration of photoinitiators, liquid crystal monomer content, and curing condition (UV intensity and curing time). In addition, simple linear viscoelastic spring-dashpot models, such as 2-parameter Kelvin and 3-parameter linear models, are used to investigate the time-dependent viscoelastic behaviors of polymer networks in PSCLC.

  10. Polymer Stabilization of Liquid-Crystal Blue Phase II toward Photonic Crystals.

    Science.gov (United States)

    Jo, Seong-Yong; Jeon, Sung-Wook; Kim, Byeong-Cheon; Bae, Jae-Hyun; Araoka, Fumito; Choi, Suk-Won

    2017-03-15

    The temperature ranges where a pure simple-cubic blue phase (BPII) emerges are quite narrow compared to the body-centered-cubic BP (BPI) such that the polymer stabilization of BPII is much more difficult. Hence, a polymer-stabilized BPII possessing a wide temperature range has been scarcely reported. Here, we fabricate a polymer-stabilized BPII over a temperature range of 50 °C including room temperature. The fabricated polymer-stabilized BPII is confirmed via polarized optical microscopy, Bragg reflection, and Kossel diagram observations. Furthermore, we demonstrate reflective BP liquid-crystal devices utilizing the reflectance-voltage performance as a potential application of the polymer-stabilized BPII. Our work demonstrates the possibility of practical application of the polymer-stabilized BPII to photonic crystals.

  11. Blue Shifting Tuning of the Selective Reflection of Polymer Stabilized Cholesteric Liquid Crystals (Postprint)

    Science.gov (United States)

    2017-08-08

    crystal (MLC-2079, Merck). The polymer stabi- lizing network was formed within the samples by photoinitiated polymerization with 50–700 mW cm2 of 365...AFRL-RX-WP-JA-2017-0347 BLUE-SHIFTING TUNING OF THE SELECTIVE REFLECTION OF POLYMER STABILIZED CHOLESTERIC LIQUID CRYSTALS (POSTPRINT...BLUE-SHIFTING TUNING OF THE SELECTIVE REFLECTION OF POLYMER STABILIZED CHOLESTERIC LIQUID CRYSTALS (POSTPRINT) 5a. CONTRACT NUMBER FA8650-16-F

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

    Energy Technology Data Exchange (ETDEWEB)

    Ouskova, Elena; Sio, Luciano De, E-mail: luciano@beamco.com; Vergara, Rafael; Tabiryan, Nelson [Beam Engineering for Advanced Measurements Company, Winter Park, Florida 32789 (United States); White, Timothy J.; Bunning, Timothy J. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433-7707 (United States)

    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.

  13. Surface dynamics and mechanics in liquid crystal polymer coatings

    Science.gov (United States)

    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.

  14. Polymer dispersed liquid crystals. Pt.1 Concept, Preparation and Materials

    International Nuclear Information System (INIS)

    Hakemi, H. A.; Santangelo, M.

    1998-01-01

    It is more than a decade since Polymer Dispersed Liquid Crystal (PDLC) film technology became the subject of a world-wide scientific and industrial research and development for commercial applications as large-area reflective displays and electrooptical windows, for privacy, security and light transmission control. In view of current interest and intensive fundamental and industrial research on PDLC, the authors attempt to provide a review of the state-of-art of this technology, from concept to its industrial production, in a series of articles. In the present introductory part, the authors discuss the basic concept, the principle of operation, the materials and the preparation techniques of a PDLC device by phase separation method [it

  15. Optical bistability and limiting in polymer dispersed liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yshino, K.; Tagawa, A.; Sadohara, Y.; Ozaki, M. (Osaka University, Osaka (Japan). Faculty of Engineering); Munezawa, T. (Ajinomoto Co. Inc., Tokyo (Japan)); Nomura, Y. (Takiron Co. Ltd., Osaka (Japan))

    1991-04-15

    The linear electro-optical effect of polymer dispersed liquid crystal (PDLC) and the nonlinear optical response of electrically feedbacked PDLC were studied. Electro-optical limiting and bistability were observed in PDLCs with negative and positive feedback, respectively. In the PDLC film with positive feedback gain, an optical hysteresis loop shifted toward a high intensity region with decreasing magnitude of the feedback gain. The switching between high and low transmission states in an optical bistable region was realized by controlling incident light, and the on-off switching by superimposing light pulse on incident light for an extremely short period (several hundreds {mu}s). As the light pulse was strong, the minimum pulse width required for switching was as short as 500 {mu}s or less. The on-off switching was also realized by shutting out the incident light for a period equivalent to the pulse width. Slower response times of the PDLC film required longer minimum pulse widths. 12 refs., 11 figs.

  16. Dichroic dye-dependent studies in guest-host polymer-dispersed liquid crystal films

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Praveen, E-mail: pmalik100@yahoo.co [Department of Physics, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar 144011, Punjab (India); Raina, K.K. [Liquid Crystal Group, Materials Research Laboratory, School of Physics and Materials Science, Thapar University, Patiala 147004, Punjab (India)

    2010-01-01

    Guest-host polymer-dispersed liquid crystal (GHPDLC) films were prepared using a nematic liquid crystal, photo-curable polymer and dichroic dye (anthraquinone blue) by polymerization-induced phase separation (PIPS) technique. Non-ionic dichroic dye (1%, 2% and 4% wt./wt. ratio) was taken as guest in PDLC host. Polarizing microscopy shows that in the absence of electric field, liquid crystal (LC) droplets in polymer matrix mainly exhibit bipolar configuration, however, relatively at higher field, maltese-type crosses were observed. Our results show that approx1% dye-doped PDLC film shows better transmission and faster response times over pure polymer-dispersed nematic liquid crystal (PDNLC) and higher concentrated (2% and 4%) GHPDLC films.

  17. Carbon/Liquid Crystal Polymer Prepreg for Cryogenic and High-Temp Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — KaZaK Composites proposes to develop a pultrusion process to produce carbon fiber / liquid crystal polymer (LCP) prepreg, a first for this category of materials and...

  18. Dichroic dye-dependent studies in guest-host polymer-dispersed liquid crystal films

    International Nuclear Information System (INIS)

    Malik, Praveen; Raina, K.K.

    2010-01-01

    Guest-host polymer-dispersed liquid crystal (GHPDLC) films were prepared using a nematic liquid crystal, photo-curable polymer and dichroic dye (anthraquinone blue) by polymerization-induced phase separation (PIPS) technique. Non-ionic dichroic dye (1%, 2% and 4% wt./wt. ratio) was taken as guest in PDLC host. Polarizing microscopy shows that in the absence of electric field, liquid crystal (LC) droplets in polymer matrix mainly exhibit bipolar configuration, however, relatively at higher field, maltese-type crosses were observed. Our results show that ∼1% dye-doped PDLC film shows better transmission and faster response times over pure polymer-dispersed nematic liquid crystal (PDNLC) and higher concentrated (2% and 4%) GHPDLC films.

  19. Les polymères auto-renforcés à cristaux liquides Self-Reinforcing Liquid-Crystal Polymers

    Directory of Open Access Journals (Sweden)

    Dorbon M.

    2006-11-01

    Full Text Available Les polymères auto-renforcés à cristaux liquides (PARCL sont des matériaux dont les molécules, des polymères organiques, sont susceptibles de s'auto-orienter les unes par rapport aux autres. Cette propriété leur confère des caractéristiques mécaniques proches de celles des acier: pour des poids plus faibles sans qu'il soit nécessaire d'avoir recours à des fibres renforçantes. Il existe deux types de PARCL: ceux pouvant s'orienter en solution, qualifiés de lyotropiques, et ceux pouvant s'orienter à l'état fondu, appelés thermotropiques. Des fibres en poly (p-phénylène térephtalamide PPT, PARCL de type lyotropique, sont disponibles commercialement et connaissent déjà de nombreuses applications. Les PARCL thermotropiques n'existent pas encore sur le marché mais sont porteurs de nombreux espoirs car ils sont susceptibles d'être moulés et donc de prendre les formes les plus diverses, ce qui n'est pas le cas de ceux de type lyotropique. Self-reinforcing liquid-crystal polymers are materials in which the molecules, i. e. organic polymers, are capable of orienting themselves in relation to one another. This property gives them mechanical characteristics close to those of steels yet of much less weight without having to use reinforcing fibers. There are two types of self-reinforcing liquid-crystal polymers: (i those capable of orienting themselves in solution, called Iyotropic, and (ii those capable of orienting themselves in a molten state, called thermotropic. Poly (p-phenylene terephthalamide fibers, self-reinforcing liquid-crystal polymers of the Iyotropic type, are commercially available and have already found numerous applications. Thermotropic self-reinforcing liquid-crystal polymers are not yet on the market but seem to be very promising because they are capable of being molded and hence of taking on a wide variety of shapes, which is not the case of those of the lyotropic type.

  20. Theory of liquid crystal elastomers and polymer networks : Connection between neoclassical theory and differential geometry.

    Science.gov (United States)

    Nguyen, Thanh-Son; Selinger, Jonathan V

    2017-09-01

    In liquid crystal elastomers and polymer networks, the orientational order of liquid crystals is coupled with elastic distortions of crosslinked polymers. Previous theoretical research has described these materials through two different approaches: a neoclassical theory based on the liquid crystal director and the deformation gradient tensor, and a geometric elasticity theory based on the difference between the actual metric tensor and a reference metric. Here, we connect those two approaches using a formalism based on differential geometry. Through this connection, we determine how both the director and the geometry respond to a change of temperature.

  1. Chemistry of Discotic Liquid Crystals From Monomers to Polymers

    CERN Document Server

    Kumar, Sandeep

    2010-01-01

    Compiling the scattered literature into a single seminal work, this book describes the basic design principles, synthesis, and mesomorphic properties of discotic liquid crystals. Of fundamental importance as models for the study of energy and charge migration in self-organized systems, discotic liquid crystals find functional application as one-dimensional conductors, photoconductors, light emitting diodes, photovoltaic solar cells, field-effect transistors, and gas sensors. This book highlights the scientific concepts behind the hierarchical self-assembly of these disc-shaped molecules alongs

  2. Thermal tunability of photonic bandgaps in liquid crystal infiltrated microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wei, Lei; Alkeskjold, Thomas Tanggaard

    2009-01-01

    We demonstrate the photonic bandgap effect and the thermal tunability of bandgaps in microstructured polymer optical fibers infiltrated with liquid crystal. Two liquid crystals with opposite sign of the temperature gradient of the ordinary refractive index (E7 and MDA-00- 1444) are used to demons......We demonstrate the photonic bandgap effect and the thermal tunability of bandgaps in microstructured polymer optical fibers infiltrated with liquid crystal. Two liquid crystals with opposite sign of the temperature gradient of the ordinary refractive index (E7 and MDA-00- 1444) are used...... to demonstrate that both signs of the thermal tunability of the bandgaps are possible. The useful bandgaps are ultimately bounded to the visible range by the transparency window of the polymer....

  3. Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

    International Nuclear Information System (INIS)

    Cho, Woosum; Lee, Jae Wook; Gal, Yeong-Soon; Kim, Mi-Ra; Jin, Sung Ho

    2014-01-01

    Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I 2 ), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J sc , 10.75 mA cm −2 ) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm −2 irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte

  4. Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Woosum [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of); Lee, Jae Wook, E-mail: jlee@donga.ac.kr [Department of Chemistry, Dong-A University, Busan 604-714 (Korea, Republic of); Gal, Yeong-Soon [Polymer Chemistry Lab, College of General Education, Kyungil University, Hayang 712-701 (Korea, Republic of); Kim, Mi-Ra, E-mail: mrkim2@pusan.ac.kr [Department of Polymer Science and Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Jin, Sung Ho, E-mail: shjin@pusan.ac.kr [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of)

    2014-02-14

    Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I{sub 2}), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J{sub sc}, 10.75 mA cm{sup −2}) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm{sup −2} irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte.

  5. Surface dynamics and mechanics in liquid crystal polymer coatings

    NARCIS (Netherlands)

    Liu, D.; Broer, D.J.; Chien, L.-C.; Coles, H.J.; Kikuchi, H.; Smalyukh, I.I.

    2015-01-01

    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

  6. Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends

    Directory of Open Access Journals (Sweden)

    Ilze ELKSNITE

    2011-07-01

    Full Text Available Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-polyester modifier on the properties of polyethylene is investigated. Various compositions of laboratory synthesized hydroxybenzoic acid /polyethylene terephtalate copolymer containing polyethylene composites have been manufactured by thermoplastic blending. It has been observed that 1 modulus of elasticity, yield strength and ultimate strength increase with raising the content of liquid crystalline modifier; 2 void content in the investigated polyethylene/liquid crystal copolymer composites is not greater that 1 %; 3 addition of liquid crystalline co-polyester modifier improves arrangement of PE crystalline phase.http://dx.doi.org/10.5755/j01.ms.17.2.483

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

    Science.gov (United States)

    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

  8. Infiltration liquid crystal in microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wei, Lei; Bang, Ole

    2009-01-01

    7 is then infiltrated into about 6 cm of the length of mPOF by using capillary forces with the duration of 45 minutes. The transmission spectrum is measured by an optical spectrum analyzer with 1 nm resolution, and normalized to that of the unfilled fiber as shown by the solid line. The difference......POF is butt-coupled to a conventional single mode fiber (SMF) with the broadband light from a supercontinuum source. It is clear to see the colour of the guided modes is red, since some wavelengths are attenuated by the material loss of PMMA in visible region. A positive dielectric anisotropy liquid crystal E...

  9. Polarization and switching properties of holographic polymer-dispersed liquid-crystal gratings. I. Theoretical model

    Science.gov (United States)

    Sutherland, Richard L.

    2002-12-01

    Polarization properties and electro-optical switching behavior of holographic polymer-dispersed liquid-crystal (HPDLC) reflection and transmission gratings are studied. A theoretical model is developed that combines anisotropic coupled-wave theory with an elongated liquid-crystal-droplet switching model and includes the effects of a statistical orientational distribution of droplet-symmetry axes. Angle- and polarization-dependent switching behaviors of HPDLC gratings are elucidated, and the effects on dynamic range are described. A new type of electro-optical switching not seen in ordinary polymer-dispersed liquid crystals, to the best of the author's knowledge, is presented and given a physical interpretation. The model provides valuable insight to the physics of these gratings and can be applied to the design of HPDLC holographic optical elements.

  10. Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction

    Science.gov (United States)

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

    2014-03-01

    The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

  11. Monotonicity of a Key Function Arised in Studies of Nematic Liquid Crystal Polymers

    Directory of Open Access Journals (Sweden)

    Hongyun Wang

    2007-01-01

    Full Text Available We revisit a key function arised in studies of nematic liquid crystal polymers. Previously, it was conjectured that the function is strictly decreasing and the conjecture was numerically confirmed. Here we prove the conjecture analytically. More specifically, we write the derivative of the function into two parts and prove that each part is strictly negative.

  12. Liquid crystal polymers: evidence of hairpin defects in nematic main chains, comparison with side chain polymers

    Science.gov (United States)

    Li, M. H.; Brûlet, A.; Keller, P.; Cotton, J. P.

    1996-09-01

    This article describes the conformation of two species of liquid crystalline polymers as revealed by small angle neutron scattering. The results obtained with side chain polymers are recalled. The procedure used to analyze the scattering data of main chains in the nematic phase is reported in this paper. It permits a demonstration of the existence of hairpins. Comparison of both polymer species shows that in the isotropic phase, the two polymers adopt a random coil conformation. In the nematic phase, the conformations are very different; the side chains behave as a melt of penetrable random coils whereas the main chains behave as a nematic phase of non penetrable cylinders.

  13. Dynamic Time Multiplexing Fabrication of Holographic Polymer Dispersed Liquid Crystals for Increased Wavelength Sensitivity

    Science.gov (United States)

    Fontecchio, Adam K. (Inventor); Rai, Kashma (Inventor)

    2017-01-01

    Described herein is a new holographic polymer dispersed liquid crystal (HPDLC) medium with broadband reflective properties, and a new technique for fabrication of broadband HPDLC mediums. The new technique involves dynamic variation of the holography setup during HPDLC formation, enabling the broadening of the HPDLC medium's wavelength response. Dynamic variation of the holography setup may include the rotation and/or translation of one or more motorized stages, allowing for time and spatial, or angular, multiplexing through variation of the incident angles of one or more laser beams on a pre-polymer mixture during manufacture. An HPDLC medium manufactured using these techniques exhibits improved optical response by reflecting a broadband spectrum of wavelengths. A new broadband holographic polymer dispersed liquid crystal thin film polymeric mirror stack with electrically-switchable beam steering capability is disclosed. XXXX Described herein is a new holographic polymer dispersed liquid crystal (HPDLC) medium with broadband reflective properties, and a new technique for fabrication of broadband 10 HPDLC mediums. The new technique involves dynamic variation of the holography setup during HPDLC formation, enabling the broadening of the HPDLC medium's wavelength response. Dynamic variation of the holography setup may include the rotation and/or translation of one or more 15 motorized stages, allowing for time and spatial, or angular, multiplexing through variation of the incident angles of one or more laser beams on a pre-polymer mixture during manufacture. An HPDLC medium manufactured using these techniques exhibits improved optical response by reflecting 20 a broadband spectrum of wavelengths. A new broadband holographic polymer dispersed liquid crystal thin film polymeric mirror stack with electrically switchable beam steering capability is disclosed.

  14. New method for preparing a liquid crystal polymer that exhibits linearly polarized white fluorescence

    International Nuclear Information System (INIS)

    Zheng Shijun; Kun, Wang; Kobayashi, Takaomi

    2011-01-01

    With the aim of developing a single-chain white-light-emitting polymer, liquid crystal (LC) polymers with a shish-kebab-type moiety on their cross-conjugated (p-phenylene)s-poly(p-phenylenevinylene)s main chain were synthesized by Gilch polymerization. They were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarizing optical microscopy (POM). 1 H-NMR indicated that the polymers had a shish-kebab structure, which strongly suppressed the formation of structural defects in the polymers. DSC revealed that the polymers had thermotropic LC properties, indicating that the LC polymers were enantiotropic. XRD showed that the polymers had a mesophase, which implies that they were in a smectic LC phase. A polymer with 'kebabs' of 2,5-bis(4'-alkoxyphenyl)benzene was combined with an aligned polyimide film with orientated microgrooves. The polymer main chain was aligned due to the orientation of the 'kebabs' of the uniform cross-conjugated structure. It lay between the kebabs and the 'shish' of the polymer main chains. The aligned polymer main chain emitted yellow light while and the oriented LC side chains emitted blue light emission. These two emissions resulted in linearly polarized white fluorescence.

  15. Memory effect of polymer dispersed liquid crystal by hybridization with nanoclay

    Directory of Open Access Journals (Sweden)

    2010-01-01

    Full Text Available The electro-optical performances of polymer dispersed liquid crystal (PDLC were investigated in the presence of organically modified clays. With the addition and increasing amount of modified clay, driving voltage and memory effect, viz. transparent state of the film after the electricity is off simultaneously increased due most likely to the increased viscosity. Among the two types of modifier, 4-(4-aminophenyl benzonitrile having greater chemical affinity with LC than hexylamine, gave finer dispersion of clay in liquid crystal, greater viscosity, larger driving voltage and response time, and greater memory effect.

  16. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingxue

    2013-02-26

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T{sub 1}) and rotating frame (T{sub 1{rho}}) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of {sup 1}H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T{sub 1} and T{sub 1{rho}} relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T{sub 1{rho}} in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  17. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    International Nuclear Information System (INIS)

    Tang, Mingxue

    2013-01-01

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T 1 ) and rotating frame (T 1ρ ) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of 1 H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T 1 and T 1ρ relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T 1ρ in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  18. A new polymer electrolyte based on a discotic liquid crystal triblock copolymer

    International Nuclear Information System (INIS)

    Stoeva, Zlatka; Lu, Zhibao; Ingram, Malcolm D.; Imrie, Corrie T.

    2013-01-01

    A discotic liquid crystal triblock copolymer consisting of a central main chain triphenylene-based liquid crystal block capped at both ends by blocks of poly(ethylene oxide) (PEO) (M W = 2000 g mol −1 ) has been doped with lithium perchlorate in an EO:Li 6:1 ratio. The polymer electrolyte exhibits a phase separated morphology consisting of a columnar hexagonal liquid crystal phase and PEO-rich regions. The polymer electrolyte forms self-supporting, solid-like films. The ionic conductivity on initial heating of the sample is very low below ca. 60 °C but increases rapidly above this temperature. This is attributed to the melting of crystalline PEO-rich regions. Crystallisation is suppressed on cooling, and subsequent heating cycles exhibit higher conductivities but still less than those measured for the corresponding lithium perchlorate complex in poly(ethylene glycol) (M W = 2000 g mol −1 ). Instead the triblock copolymer mimics the behaviour of high molecular weight poly(ethylene oxide) (M W = 300,000 g mol −1 ). This is attributed, in part, to the anchoring of the short PEG chains to the liquid crystal block which prevents their diffusion through the sample. Temperature and pressure variations in ion mobility indicate that the ion transport mechanism in the new material is closely related to that in the conventional PEO-based electrolyte, opening up the possibility of engineering enhanced conductivities in future

  19. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Science.gov (United States)

    Torres, Juan C.; Vergaz, Ricardo; Barrios, David; Sánchez-Pena, José Manuel; Viñuales, Ana; Grande, Hans Jürgen; Cabañero, Germán

    2014-01-01

    A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed. PMID:28788632

  20. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Directory of Open Access Journals (Sweden)

    Juan C. Torres

    2014-05-01

    Full Text Available A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed.

  1. Electrically switchable holographic liquid crystal/polymer Fresnel lens using a Michelson interferometer.

    Science.gov (United States)

    Jashnsaz, Hossein; Mohajerani, Ezeddin; Nemati, Hossein; Razavi, Seyed Hossein; Alidokht, Isa Ahmad

    2011-06-10

    A holographic technique for fabricating an electrically switchable liquid crystal/polymer composite Fresnel lens is reported. A Michelson interferometer is used to produce the required Fresnel pattern, by placing a convex lens into one path of the interferometer. Simplicity of the method and the possibility of fabricating different focal length lenses in a single arrangement are advantages of the method. The performance of the fabricated lens was demonstrated and its electro-optical properties were investigated for its primary focal length.

  2. Conformation of comb liquid crystal polymers by neutron small angle scattering

    International Nuclear Information System (INIS)

    Noirez, L.; Pepy, G.

    1988-01-01

    A review is made of the direct information obtained by small angle neutron scattering about the anisotropy of the components parallel and perpendicular to the orienting magnetic field of the radius of gyration of comb like liquid crystal polymers. The behaviour of the conformation versus temperature is reported for several samples. Until now all samples show an oblate conformation in the smectic phase and probably the whole range of the nematic phase. The results are compared with the available theoretical predictions

  3. Abnormal viscoelastic behavior of side-chain liquid-crystal polymers

    Science.gov (United States)

    Gallani, J. L.; Hilliou, L.; Martinoty, P.; Keller, P.

    1994-03-01

    We show that, contrary to what is commonly believed, the isotropic phase of side-chain liquid-crystal polymers has viscoelastic properties which are totally different from those of ordinary flexible melt polymers. The results can be explained by the existence of a transient network created by the dynamic association of mesogenic groups belonging to different chains. The extremely high sensitivity of the compound to the state of the surfaces with which it is in contact offers us an unexpected method of studying surface states.

  4. Aligned silane-treated MWCNT/liquid crystal polymer films

    International Nuclear Information System (INIS)

    Cervini, Raoul; Simon, George P; Ginic-Markovic, Milena; Matisons, Janis G; Huynh, Chi; Hawkins, Stephen

    2008-01-01

    We report on a method to preferentially align multiwall carbon nanotubes (MWCNTs) in a liquid crystalline matrix to form stable composite thin films. The liquid crystalline monomeric chains can be crosslinked to form acrylate bridges, thereby retaining the nanotube alignment. Further post-treatment by ozone etching of the composite films leads to an increase in bulk conductivity, leading to higher emission currents when examined under conducting scanning probe microscopy. The described methodology may facilitate device manufacture where electron emission from nanosized tips is important in the creation of new display devices

  5. Thermotropic Ionic Liquid Crystals

    Science.gov (United States)

    Axenov, Kirill V.; Laschat, Sabine

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed. PMID:28879986

  6. Thermotropic Ionic Liquid Crystals.

    Science.gov (United States)

    Axenov, Kirill V; Laschat, Sabine

    2011-01-14

    The last five years' achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  7. Thermotropic Ionic Liquid Crystals

    OpenAIRE

    Axenov, Kirill V.; Laschat, Sabine

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  8. Multiplexing storage using angular variation in a transmission holographic polymer dispersed liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Hee; Jung, Yeon-Gil, E-mail: jungyg@changwon.ac.kr

    2015-12-01

    Simultaneous angular multiplexing of transmission gratings in a holographic polymer dispersed liquid crystal (HPDLC) film as a function of resin and film compositions, irradiation intensity, and cell thickness has been studied by exposing the material to three coherent laser beams. It was found that the diffraction efficiency monotonically increases with irradiation intensity and cell gap, whereas a maximum of 43% is obtained at specific compositions of trimethylolpropane triacrylate (TMPTA)/N-vinylpyrrolidone (NVP) = 8/1 and polymer/LC = 65/35. The multiplexed gratings have been captured using SEM imaging and the reconstructed images using a charge-coupled device camera, showing successful reconstructed images of gratings. - Highlights: • Multiplex images were well recorded using simultaneous angular method. • The periodic structures of the LC and polymer regions were well prepared. • The angular selectivity was variable nevertheless fabrication by three beams. • The images were successfully reconstructed in gratings of same spot.

  9. Multiplexing storage using angular variation in a transmission holographic polymer dispersed liquid crystal

    International Nuclear Information System (INIS)

    Kim, Eun-Hee; Jung, Yeon-Gil

    2015-01-01

    Simultaneous angular multiplexing of transmission gratings in a holographic polymer dispersed liquid crystal (HPDLC) film as a function of resin and film compositions, irradiation intensity, and cell thickness has been studied by exposing the material to three coherent laser beams. It was found that the diffraction efficiency monotonically increases with irradiation intensity and cell gap, whereas a maximum of 43% is obtained at specific compositions of trimethylolpropane triacrylate (TMPTA)/N-vinylpyrrolidone (NVP) = 8/1 and polymer/LC = 65/35. The multiplexed gratings have been captured using SEM imaging and the reconstructed images using a charge-coupled device camera, showing successful reconstructed images of gratings. - Highlights: • Multiplex images were well recorded using simultaneous angular method. • The periodic structures of the LC and polymer regions were well prepared. • The angular selectivity was variable nevertheless fabrication by three beams. • The images were successfully reconstructed in gratings of same spot.

  10. Photo polymerization-induced vertical phase separation and homeotropic alignment in liquid crystal and polymer mixtures

    International Nuclear Information System (INIS)

    Kang, Hyo; Joo, Sangwoo; Kang, Daeseung

    2012-01-01

    We presented a novel method for the homeotropic alignment of LC by using the irradiation of UV light on the LC/NOA65 mixture cell, in which the photo-initiated-polymerization-induced phase separation lowers the surface energy. When the amount of polymer content is sufficiently small, the gravel and network patterns were formed at the substrates via the vertical phase separation. We found that surface roughness plays an important role in the formation of the homeotropic alignment of LC. We also observed the alignment transition of the cells by varying the mixing ratio of LC/NOA65 or the UV radiation time. Furthermore, the present proposed method has great potential for application in display devices. For decades, studies on the alignment of liquid crystal (LC) molecules have been of significant interest due to their immediate applications for display devices and the intriguing physiochemical properties they exhibit at the surface of mixtures. Usually, homeotropic (or vertical) alignment, in which the long axes of the LC molecules are oriented in a direction perpendicular to the surface, is achieved by using surfactants such as lecithin, silanes or polyimide. Recently homeotropic alignment of liquid crystal molecules was achieved by irradiating photosensitive polymers, by doping nanoparticles into LC, by utilizing nano/micro patterns, or by incorporating self-assembled monolayers (SAMs). However, a clear understanding about the alignment mechanism is still elusive. In this paper, we report a novel method for homeotropic alignment of LC by utilizing the phase separation of LC/polymer mixtures

  11. Liquid Crystal Polymer (LCP) based antenna for flexible system on package (SoP) applications

    KAUST Repository

    Marnat, Loic; Shamim, Atif

    2012-01-01

    The design, fabrication and measurement of a bowtie antenna on a flexible Liquid Crystal Polymer (LCP) substrate is reported in this paper. The antenna is fed by a balun transition which helps improve the gain up to 5.1 dB. The antenna performance is analyzed for both planar and curved substrates. The comparison between simulation and measurements shows a good agreement. This structure can either be used to sense the bending of the substrate or use the bending to tilt the beam. © 2012 IEEE.

  12. High transmittance optical films based on quantum dot doped nanoscale polymer dispersed liquid crystals

    Science.gov (United States)

    Gandhi, Sahil Sandesh; Chien, Liang-Chy

    2016-04-01

    We propose a simple way to fabricate highly transparent nanoscale polymer dispersed liquid crystal (nano-PDLC) films between glass substrates and investigate their incident angle dependent optical transmittance properties with both collimated and Lambertian intensity distribution light sources. We also demonstrate that doping nano-PDLC films with 0.1% InP/ZnS core/shell quantum dots (QD) results in a higher optical transmittance. This work lays the foundation for such nanostructured composites to potentially serve as roll-to-roll coatable light extraction or brightness enhancement films in emissive display applications, superior to complex nanocorrugation techniques proposed in the past.

  13. Liquid Crystal Polymer (LCP) based antenna for flexible system on package (SoP) applications

    KAUST Repository

    Marnat, Loic

    2012-06-01

    The design, fabrication and measurement of a bowtie antenna on a flexible Liquid Crystal Polymer (LCP) substrate is reported in this paper. The antenna is fed by a balun transition which helps improve the gain up to 5.1 dB. The antenna performance is analyzed for both planar and curved substrates. The comparison between simulation and measurements shows a good agreement. This structure can either be used to sense the bending of the substrate or use the bending to tilt the beam. © 2012 IEEE.

  14. Electro-optical characteristics of a liquid crystal lens with polymer network

    International Nuclear Information System (INIS)

    Bielyikh, S.P.; Subota, S.L.; Reshetnyak, V.Y.; Galstian, T.

    2010-01-01

    We study a tunable-focus lens in which the key element is a gradient-polymer-stabilized liquid crystal (G-PSLC) structure. In this paper, we further develop the theoretical model, that describes the dependence of the G-PSLC lens' focal length on the applied voltage and presents a theoretical study of lens aberrations. According to Fermat's principle, we minimize the optical path of a test light beam and calculate the angles of a ray exiting from the cell. Using these results, the lateral and longitudinal aberrations are estimated. The obtained results can be used to optimize the G-PSLC lenses.

  15. Preparation and characterization of high performance Schiff-base liquid crystal diepoxide polymer

    International Nuclear Information System (INIS)

    Liu Huan; Fu Zien; Xu Kai; Cai Hualun; Liu Xin; Chen Mingcai

    2012-01-01

    Graphical abstract: The specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer were proposed first by us. From the point of view of structure-properties relationship, it can be considered that owing to the presence of the Schiff-base group, the high performance liquid crystal diepoxide polymer displayed improved thermal stability. Highlights: ► In this work, we first proposed that specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer. ► As one aim of this study, the thermal and thermal-oxidative stabilities of the thermosets were studied by TGA under nitrogen and under air. ► The second aim of this study was to further understand the thermal degradation mechanism. ► For thermal degradation mechanism of this polymer under nitrogen, TG-IR was used to investigate volatile components, and SEM/EDS was used to explore morphologies and chemical components of the residual char. ► From the point of view of structure-properties relationship, it can be considered that owing to the presence of the Schiff-base group, the high performance liquid crystal diepoxide polymer displayed the improved thermal stability. - Abstract: A novel Schiff-base liquid crystal diepoxide polymer was prepared via a thermal copolymerization of a Schiff-base epoxy monomer (PBMBA) with a diamine co-monomer (MDA). We first proposed that specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer (PBMBA/MDA). Thermal degradation behavior of the polymer was characterized using thermogravimetric analysis (TGA) under nitrogen and under air, respectively. Thermogravimetric data obtained from TGA under nitrogen and under air reveal that PBMBA/MDA exhibits higher thermal stability compared with bisphenol-A type epoxy polymer (DGEBA/MDA) and other mesogene-containing epoxy polymer. It is worth pointing out that the outstanding residual

  16. Transflective multiplexing of holographic polymer dispersed liquid crystal using Si additives

    Directory of Open Access Journals (Sweden)

    2011-01-01

    Full Text Available Morphology, grating formation dynamics and electro-optical performance of transflective multiplexing with holographic polymer dispersed liquid crystal (HPDLC were investigated in the presence of silica nanoparticles (Aerosil R812 (RS and modified Aerosil 200 (MS and silicon monomer (vinyltrimethoxy silane (VTMS by using three coherent laser beams. The addition of Si additive significantly augmented the diffraction efficiencies of transmission and reflection gratings due to the enhanced phase separation with large LC channels. The film was driven only with Si additives which are enriched at the polymer-LC interfaces. As the additive content increased, driving voltage decreased to a minimum of 30 V at 2.0 wt% VTMS. It was found that the interface modification and large droplet size are crucial to operate the film. Among the three types of Si additive, VTMS showed the highest electro-optical performance due to its low viscosity and high reactivity.

  17. A high throughput liquid crystal light shutter for unpolarized light using polymer polarization gratings

    Science.gov (United States)

    Komanduri, Ravi K.; Lawler, Kris F.; Escuti, Michael J.

    2011-05-01

    We report on a broadband, diffractive, light shutter with the ability to modulate unpolarized light. This polarizer-free approach employs a conventional liquid crystal (LC) switch, combined with broadband Polarization Gratings (PGs) formed with polymer LC materials. The thin-film PGs act as diffractive polarizing beam-splitters, while the LC switch operates on both orthogonal polarization states simultaneously. As an initial experimental proof-of- concept for unpolarized light with +/-7° aperture, we utilize a commercial twisted-nematic LC switch and our own polymer PGs to achieve a peak transmittance of 80% and peak contrast ratio of 230:1. We characterize the optoelectronic performance, discuss the limitations, and evaluate its use in potential nonmechanical shutter applications (imaging and non-imaging).

  18. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films

    OpenAIRE

    Yujian Sun; Cuihong Zhang; Le Zhou; Hua Fang; Jianhua Huang; Haipeng Ma; Yi Zhang; Jie Yang; Lan-Ying Zhang; Ping Song; Yanzi Gao; Jiumei Xiao; Fasheng Li; Kexuan Li

    2016-01-01

    Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found...

  19. Radhard optical patchcords and packaging for satellites using liquid crystal polymers

    Science.gov (United States)

    O'Riorden, S.; Mahapatra, A.

    2017-11-01

    There are many advantages to employing fiber optics for high capacity satellite communication. However, optical cables can be susceptible to high radiation, temperature extremes and vacuum environment. Any hardware used in these systems must be rugged, durable and immune to the detrimental effects of the aforementioned conditions. Standard COTS optical fiber will darken when exposed to high levels of radiation limiting the effectiveness of the communications system. Of particular concern to satellites in GEO are energetic electrons, bursts of heavy particles due to solar storms which can cause total dose and single event effects (SEE). Conventional fiber optic cables have several issues performing in high radiation environments. Linden has patented and developed a novel cable using an extruded layer of Liquid Crystal Polymer (LCP) applied to commercially available fiber. Total dose effects are minimized by shielding with Liquid Crystal Polymer jacketing. It is a simple, inexpensive way to increase the radiation shielding and mechanical performance of cables in satellites while concomitantly providing hermeticity and thus increased fatigue factor for optical glass. • LCPs exposed to 5000 Mrad dose of gamma rays retain in excess of 90% of their mechanical properties. • LCPs exposed to 1 Mrad radiation dose with energetic protons retain almost 100% of their mechanical strength. Tensile modulus increases with exposure to the radiation. • Weight for weight the proton absorbing power of LCP is 25% better than that of aluminum. We will present experimental data on radhard optical patchcords.

  20. Fabrication of flexible polymer dispersed liquid crystal films using conducting polymer thin films as the driving electrodes

    International Nuclear Information System (INIS)

    Kim, Yang-Bae; Park, Sucheol; Hong, Jin-Who

    2009-01-01

    Conducting polymers exhibit good mechanical and interfacial compatibility with plastic substrates. We prepared an optimized coating formulation based on poly(3,4-ethylenedioxythiophene) (PEDOT) and 3-(trimethoxysilyl)propyl acrylate and fabricated a transparent electrode on poly(ethylene terephthalate) (PET) substrate. The surface resistances and transmittance of the prepared thin films were 500-600 Ω/□ and 87% at 500 nm, respectively. To evaluate the performance of the conducting polymer electrode, we fabricated a five-layer flexible polymer-dispersed liquid crystal (PDLC) device as a PET-PEDOT-PDLC-PEDOT-PET flexible film. The prepared PDLC device exhibited a low driving voltage (15 VAC), high contrast ratio (60:1), and high transmittance in the ON state (60%), characteristics that are comparable with those of conventional PDLC film based on indium tin oxide electrodes. The fabrication of conducting polymer thin films as the driving electrodes in this study showed that such films can be used as a substitute for an indium tin oxide electrode, which further enhances the flexibility of PDLC film

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tartan, Chloe C., E-mail: chloe.tartan@eng.ox.ac.uk, E-mail: steve.elston@eng.ox.ac.uk; Salter, Patrick S.; Booth, Martin J.; Morris, Stephen M.; Elston, Steve J., E-mail: chloe.tartan@eng.ox.ac.uk, E-mail: steve.elston@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom)

    2016-05-14

    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.

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

    Science.gov (United States)

    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.

  4. Thermotropic Ionic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Sabine Laschat

    2011-01-01

    Full Text Available The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  5. Effects of gold nanoparticles on the electro-optical properties of a polymer dispersed liquid crystal

    Science.gov (United States)

    Hinojosa, A.; Shive, C.; Sharma, Suresh

    2010-03-01

    We have studied the electro-optical properties of a polymer-dispersed liquid crystal (PDLC) as functions of relative concentrations of gold nanoparticles. PDLC samples were synthesized between indium-tin-oxide (ITO) coated glass slides, separated by SiO2 spacers, by using liquid crystal E44, a monofunctional acrylic oligomer (CN135), and a tetrafunctional crosslinker (SR295). A UV photoinitiator (SR1124) was used to facilitate the curing of the monomer exposed to UV radiation from a Hg spectral lamp. A He-Ne laser was used to measure optical transmission through the PDLC as a function of applied ac electric field (1 kHz). The PDLC without gold nanoparticles shows the expected behavior; transmission through the PDLC increases from a minimum (opaque) to a maximum (transparent) with increasing electric field. The electro-optical behavior of the PDLC is altered significantly (e. g., relatively low switching field) upon addition of relatively low concentrations of gold nanoparticles into the starting PDLC syrup. We present electro-optical data as functions of gold nanoparticle concentration and discuss possible mechanism to understand our results.

  6. Polarization-Independent Electrically Tunable Holographic Polymer Dispersed Liquid Crystals Grating Doped with Chiral Molecules

    Directory of Open Access Journals (Sweden)

    Hui LI

    2017-08-01

    Full Text Available This study proposes a holographic grating made of polymer dispersed liquid crystal (PDLC, with a small amount of chiral molecules doped into PDLC material. The major advantage of this grating is that it is independent of light polarization. This characteristic was verified by applying the interference beam intensity of a He-Cd laser at 150 mW/cm2, with an incidence angle between the two interference beams of 24°, for an irradiation curing duration of 120 s. The observed periodic structure of the grating is consistent with the theoretical value. As chiral molecules are doped, nematic-LC experiences a phase-change in the grating. However, the electro-optical features are only slightly affected. This proposed grating has greatly potential in 3D imaging because of its polarization-independent feature.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16312

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  9. Advances in nonlinear polymers and inorganic crystals, liquid crystals, and laser media

    International Nuclear Information System (INIS)

    Musikant, S.

    1987-01-01

    These proceedings collect papers on laser materials. Topics include: solid state lasers, fracture mechanics in laser materials, optical second harmonic generation, nonlinear optics, molecular crystals, crystal-phase transformation, and materials for laser fusion reactors

  10. Electro-optic and thermo-optic and properties of phase separated polymer dispersed liquid crystal films

    Czech Academy of Sciences Publication Activity Database

    Malik, P.; Bubnov, Alexej M.; Raina, K.K.

    2008-01-01

    Roč. 494, č. 12 (2008), s. 242-251 ISSN 1542-1406 Institutional research plan: CEZ:AV0Z10100520 Keywords : polymer dispersed liquid crystals * electro-optics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.537, year: 2008

  11. Liquid crystalline order in polymers

    CERN Document Server

    Blumstein, Alexandre

    1978-01-01

    Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    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%. (paper)

  13. Enhanced Deformation of Azobenzene-Modified Liquid Crystal Polymers under Dual Wavelength Exposure: A Photophysical Model

    Science.gov (United States)

    Liu, Ling; Onck, Patrick R.

    2017-08-01

    Azobenzene-embedded liquid crystal polymers can undergo mechanical deformation in response to ultraviolet (UV) light. The natural rodlike trans state azobenzene absorbs UV light and isomerizes to a bentlike cis state, which disturbs the order of the polymer network, leading to an anisotropic deformation. The current consensus is that the magnitude of the photoinduced deformation is related to the statistical building up of molecules in the cis state. However, a recent experimental study [Liu and Broer, Nat. Commun. 6 8334 (2015)., 10.1038/ncomms9334] shows that a drastic (fourfold) increase of the photoinduced deformation can be generated by exposing the samples simultaneously to 365 nm (UV) and 455 nm (visible) light. To elucidate the physical mechanism that drives this increase, we develop a two-light attenuation model and an optomechanical constitutive relation that not only accounts for the statistical accumulation of cis azobenzenes, but also for the dynamic trans-cis-trans oscillatory isomerization process. Our experimentally calibrated model predicts that the optimal single-wavelength exposure is 395 nm light, a pronounced shift towards the visible spectrum. In addition, we identify a range of optimal combinations of two-wavelength lights that generate a favorable response for a given amount of injected energy. Our model provides mechanistic insight into the different (multi)wavelength exposures used in experiments and, at the same time, opens new avenues towards enhanced, multiwavelength optomechanical behavior.

  14. Small-angle light scattering symmetry breaking in polymer-dispersed liquid crystal films with inhomogeneous electrically controlled interface anchoring

    Energy Technology Data Exchange (ETDEWEB)

    Loiko, V. A., E-mail: loiko@ifanbel.bas-net.by; Konkolovich, A. V. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus); Zyryanov, V. Ya. [Russian Academy of Sciences, Kirensky Institute of Physics, Federal Research Center “Krasnoyarsk Scientific Center,” Siberian Branch (Russian Federation); Miskevich, A. A. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus)

    2017-03-15

    We have described the method of analyzing and reporting on the results of calculation of the small-angle structure of radiation scattered by a polymer-dispersed liquid crystal film with electrically controlled interfacial anchoring. The method is based on the interference approximation of the wave scattering theory and the hard disk model. Scattering from an individual liquid crystal droplet has been described using the anomalous diffraction approximation extended to the case of droplets with uniform and nonuniform interface anchoring at the droplet–polymer boundary. The director field structure in an individual droplet is determined from the solution of the problem of minimizing the volume density of the free energy. The electrooptical effect of symmetry breaking in the angular distribution of scattered radiation has been analyzed. This effect means that the intensities of radiation scattered within angles +θ{sub s} and–θ{sub s} relative to the direction of illumination in the scattering plane can be different. The effect is of the interference origin and is associated with asymmetry of the phase shift of the wavefront of an incident wave from individual parts of the droplet, which appears due to asymmetry of the director field structure in the droplet, caused by nonuniform anchoring of liquid crystal molecules with the polymer on its surface. This effect is analyzed in the case of normal illumination of the film depending on the interfacial anchoring at the liquid crystal–polymer interface, the orientation of the optical axes of droplets, their concentration, sizes, anisometry, and polydispersity.

  15. Dynamic roughness and power dissipation of polymer films actuated with liquid crystal polymer inclusions

    International Nuclear Information System (INIS)

    Gutiérrez, J M; Barbero, E J; Cairns, D R; Mucino, V H; Mayugo, J A

    2012-01-01

    Analytical and numerical tools for the analysis and design of actuated polymer films (APFs) are developed and described in this paper. Computational micromechanical models are set up and correlated in order to calculate the deformation and power requirement to actuate an APF taking into account hyperelastic and viscous effects. A method is developed to correlate material parameters in the viscous branch of the Bergström–Boyce model to available experimental data. The effects of various geometric and material parameters are elucidated by a parametric study including coherent versus non-coherent actuators, excitation frequency and magnitude, modulus of elasticity of the actuator and the top film, and actuator volume fraction. (paper)

  16. A liquid crystal polymer membrane MEMS sensor for flow rate and flow direction sensing applications

    International Nuclear Information System (INIS)

    Kottapalli, A G P; Tan, C W; Olfatnia, M; Miao, J M; Barbastathis, G; Triantafyllou, M

    2011-01-01

    The paper reports the design, fabrication and experimental results of a liquid crystal polymer (LCP) membrane-based pressure sensor for flow rate and flow direction sensing applications. Elaborate experimental testing results demonstrating the sensors' performance as an airflow sensor have been illustrated and validated with theory. MEMS sensors using LCP as a membrane structural material show higher sensitivity and reliability over silicon counterparts. The developed device is highly robust for harsh environment applications such as atmospheric wind flow monitoring and underwater flow sensing. A simple, low-cost and repeatable fabrication scheme has been developed employing low temperatures. The main features of the sensor developed in this work are a LCP membrane with integrated thin film gold piezoresistors deposited on it. The sensor developed demonstrates a good sensitivity of 3.695 mV (ms −1 ) −1 , large operating range (0.1 to >10 ms −1 ) and good accuracy in measuring airflow with an average error of only 3.6% full-scale in comparison with theory. Various feasible applications of the developed sensor have been demonstrated with experimental results. The sensor was tested for two other applications—in clinical diagnosis for breath rate, breath velocity monitoring, and in underwater applications for object detection by sensing near-field spatial flow pressure

  17. Electrically Tunable Binary-Phase Fresnel Lens Based on Polymer Dispersed Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Hui LI

    2017-08-01

    Full Text Available This is a proposal for a Fresnel lens with an electrically tunable binary-phase made of polymer dispersed liquid crystal (PDLC, which has relatively fast response time and low applied voltage. Simple fabrication is the major advantage of the proposed method. In this study, NOA65 and E7 were utilized with weight ratios of 60 wt.%: 40 wt.%. There was also the utilization of a relatively low intensity UV-light, 0.53 mW/cm2. The duration time of exposure was about 30 hours. The performance improvement of the Fresnel lens resulted from the infiltration of large LC droplet into the PDLC film. The phenomenon of black cross strip patterns could be explained with the use of the electro-hydrodynamics theory. The diffraction efficiency of the proposed lens was from 31.1 % to 41 % with the changes of externally applied voltage. This work presents an effective approach to get relatively complete phase separation in PDLC. The proposed method also provides great potential in developing high performance Fresnel lens.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16317

  18. Flexible, ferroelectric nanoparticle doped polymer dispersed liquid crystal devices for lower switching voltage and nanoenergy generation

    Science.gov (United States)

    Nimmy John, V.; Varanakkottu, Subramanyan Namboodiri; Varghese, Soney

    2018-06-01

    Flexible polymer dispersed liquid crystal (F-PDLC) devices were fabricated using transparent conducting ITO/PET film. Polymerization induced phase separation (PIPS) method was used for pure and ferroelectric BaTiO3 (BTO) and ZnO doped PDLC devices. The distribution of nanoparticles in the PDLC and the formation of micro cavities were studied using field emission scanning electron microscopy (FESEM). It was observed that the addition of ferroelectric BTO nanoparticles has reduced the threshold voltage (Vth) and saturation voltage (Vsat) of FNP-PDLC by 85% and 41% respectively due to the spontaneous polarization of ferroelectric nanoparticles. The ferroelectric properties of BTO and ZnO in the fabricated devices were investigated using dynamic contact electrostatic force microscopy (DC EFM). Flexing the device can generate a potential due to the piezo-tribo electric effect of the ferroelectric nanomaterial doped in the PDLC matrix, which could be utilized as an energy generating system. The switching voltage after multiple flexing was also studied and found to be in par with non-flexing situations.

  19. The Relationship between the Monomer Chain Length and the Electro-Optical Properties of Polymer Dispersed Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Liu J.

    2016-03-01

    Full Text Available Five polymers dispersed liquid crystalline (LC films were fabricated using photo-polymerizable monomers with different lengths of carbon chains. These LC films have shown different electro-optical (EO properties. Through their SEM pictures, the relationship between the linear electro-optical effect and the mesh size of the polymer network was explored. With the increase of number of photo-polymerizable monomers, the mesh size of the polymer network would become larger. So the liquid crystal molecules would be easily oriented in the electric field and therefore, the threshold voltage and saturation voltage would decrease. The open state response times were also reduced and the off state response times would be extended. The DFT simulations have shown principal role of the ground state dipole moments in the observed electro-optical efficiency.

  20. Micro-Holograms in a Methyl Red-Doped Polymer-Dispersed Liquid Crystal (E48:PVP

    Directory of Open Access Journals (Sweden)

    N. P. Hermosa II

    2003-06-01

    Full Text Available Feasibility of a holographic point-by-point storage in a methyl red-doped Polymer-Dispersed LiquidCrystal (PDLC is determined. Micro-holograms (gratings are recorded next to each other. Smallestgrating diameter obtained is 69.9 mm, with minimum grating distance of 80 mm. Recording of adjacentgrating reduces the diffraction efficiency of existing grating by 17% (average.

  1. Dual electrically and thermally responsive broadband reflectors based on polymer network stabilized chiral nematic liquid crystals: the role of crosslink density

    NARCIS (Netherlands)

    Khandelwal, H.; Timmermans, G.H.; Debije, M.G.; Schenning, A.P.H.J.

    2016-01-01

    A broadband reflector based on a polymer stabilized chiral nematic liquid crystal has been fabricated. The reflection bandwidth can be manually controlled by an electric field and autonomously by temperature.

  2. Modeling liquid crystal polymeric devices

    Science.gov (United States)

    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.

  3. Nanotube liquid crystal elastomers: photomechanical response and flexible energy conversion of layered polymer composites

    International Nuclear Information System (INIS)

    Fan, Xiaoming; King, Benjamin C; Loomis, James; Panchapakesan, Balaji; Campo, Eva M; Hegseth, John; Cohn, Robert W; Terentjev, Eugene

    2014-01-01

    Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using a simple vacuum filtration technique of fabricating nanotube LC films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LC arrangement is preserved, here we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. On excitation by NIR photons, with application of small or large pre-strains, significant expansion or contraction of the sample occurs, respectively, that is continuously reversible and three orders of magnitude larger than in pristine polymer. Schlieren textures were noted in these LC composites confirming long range macroscopic nematic order of nanotubes within the composites. Order parameters of LC films ranged from S optical  = 0.51–0.58 from dichroic measurements. Film concentrations, elastic modulus and photomechanical stress were all seen to be related to the nematic order parameter. For the same nanotube concentration, the photomechanical stress was almost three times larger for the self-assembled LC nanotube actuator compared to actuator based on randomly oriented carbon nanotubes. Investigation into the kinetics of photomechanical actuation showed variation in stretching exponent β with pre-strains, concentration and orientation of nanotubes. Maximum photomechanical stress of ∼0.5 MPa W −1 and energy conversion of ∼0.0045% was achieved for these layered composites. The combination of properties, namely, optical anisotropy, reversible mechanical response to NIR excitation and flexible energy conversion all in one system accompanied with low cost makes nanotube LC elastomers important for soft photochromic actuation, energy conversion and photo-origami applications. (paper)

  4. Broadband reflection of polymer-stabilized chiral nematic liquid crystals induced by a chiral azobenzene compound.

    Science.gov (United States)

    Chen, Xingwu; Wang, Ling; Chen, Yinjie; Li, Chenyue; Hou, Guoyan; Liu, Xin; Zhang, Xiaoguang; He, Wanli; Yang, Huai

    2014-01-21

    A chiral nematic liquid crystal-photopolymerizable monomer-chiral azobenzene compound composite was prepared and then polymerized under UV irradiation. The reflection wavelength of the composite can be extended to cover the 1000-2400 nm range and also be adjusted to the visible light region by controlling the concentration of chiral compounds.

  5. Liquid crystals in tribology.

    Science.gov (United States)

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

    2009-09-18

    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.

  6. Liquid Crystals in Decorative and Visual Arts

    Science.gov (United States)

    Makow, David

    The following sections are included: * INTRODUCTION * PIGMENT AND STRUCTURAL COLOURS AND THEIR RELEVANCE TO LIQUID CRYSTALS * LIQUID CRYSTAL MATERIALS AND TECHNIQUES FOR DECORATIVE AND VISUAL ARTS * Free cholesteric liquid crystals (FCLC's) * Encapsulated liquid crystals (ECLC's) * Nonsteroid Chiral nematics * Polymers with liquid crystalline properties (PLCs) * COLOUR PROPERTIES OF CHOLESTERIC LIQUID CRYSTALS (CLC's) * Molecular structure and the mechanism of colour production * Dependence of perceived colours on the angle of illumination and viewing * Dependence of perceived colours on temperature * Additive colour properties * Methods of doubling the peak reflectance of cholesteric liquid crystals * Colour gamut * Colours of superimposed and pigmented coatings * Colours in transmission * ACKNOWLEDGEMENTS * REFERENCES

  7. Self-Assembled Polymeric Ionic Liquid-Functionalized Cellulose Nano-crystals: Constructing 3D Ion-conducting Channels Within Ionic Liquid-based Composite Polymer Electrolytes.

    Science.gov (United States)

    Shi, Qing Xuan; Xia, Qing; Xiang, Xiao; Ye, Yun Sheng; Peng, Hai Yan; Xue, Zhi Gang; Xie, Xiao Lin; Mai, Yiu-Wing

    2017-09-04

    Composite polymeric and ionic liquid (IL) electrolytes are some of the most promising electrolyte systems for safer battery technology. Although much effort has been directed towards enhancing the transport properties of polymer electrolytes (PEs) through nanoscopic modification by incorporating nano-fillers, it is still difficult to construct ideal ion conducting networks. Here, a novel class of three-dimensional self-assembled polymeric ionic liquid (PIL)-functionalized cellulose nano-crystals (CNC) confining ILs in surface-grafted PIL polymer chains, able to form colloidal crystal polymer electrolytes (CCPE), is reported. The high-strength CNC nano-fibers, decorated with PIL polymer chains, can spontaneously form three-dimensional interpenetrating nano-network scaffolds capable of supporting electrolytes with continuously connected ion conducting networks with IL being concentrated in conducting domains. These new CCPE have exceptional ionic conductivities, low activation energies (close to bulk IL electrolyte with dissolved Li salt), high Li + transport numbers, low interface resistances and improved interface compatibilities. Furthermore, the CCPE displays good electrochemical properties and a good battery performance. This approach offers a route to leak-free, non-flammable and high ionic conductivity solid-state PE in energy conversion devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

    Science.gov (United States)

    Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

    2018-03-01

    In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

  9. Pressure sensor using liquid crystals

    Science.gov (United States)

    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.

  10. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films.

    Science.gov (United States)

    Sun, Yujian; Zhang, Cuihong; Zhou, Le; Fang, Hua; Huang, Jianhua; Ma, Haipeng; Zhang, Yi; Yang, Jie; Zhang, Lan-Ying; Song, Ping; Gao, Yanzi; Xiao, Jiumei; Li, Fasheng; Li, Kexuan

    2016-12-30

    Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

  11. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films

    Directory of Open Access Journals (Sweden)

    Yujian Sun

    2016-12-01

    Full Text Available Polymer-dispersed liquid crystal (PDLC films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

  12. Synthesis of electro-optically active polymer composite of poly[2,2'-bis(3,4-ethylenedioxythiophene-alt-fluorene]/hydroxypropyl cellulose showing liquid crystal structure

    Directory of Open Access Journals (Sweden)

    N. Eguchi

    2017-10-01

    Full Text Available Electrochemical preparation of a composite consisting of poly[2,2′-bis(3,4-ethylenedioxythiophene-alt-fluorene] and hydroxypropyl cellulose (PEFE/HPC was carried out. We conducted electrochemical polymerization of poly[2,2′-bis(3,4-ethylenedioxythiophene-alt-fluorene] (EFE as a monomer in a lyotropic liquid crystal of HPC. We used an organic solvent instead of water for lyotropic liquid crystal medium to expand the possibility of the range of monomers, although water is usually employed as a solvent for HPC for showing liquid crystallinity. Here, we employed N,N-dimethylformamide (DMF as a solvent for HPC. Electrochemical polymerization in the polymer liquid crystal was carried out to obtain a polymer film with liquid crystal order. The polymer film thus prepared exhibited optical activity. Fourier transfer infrared (FT-IR absorption spectroscopy reveals that the film is a composite consisting of HPC and polymer. The composite PEFE/HPC thus prepared in HPC/DMF system showed electrochromism.

  13. Theoretical predictions for side-chain liquid-crystal polymers and comparison to experiment

    International Nuclear Information System (INIS)

    Dowell, F.

    1988-01-01

    This paper presents results from a new unique microscopic molecular theory for side-chain liquid-crystalline polymers (LCPs) in the nematic (N) and multiple smectic-A (SA) LC phases and the isotropic (I) liquid phase. There are no ad hoc or arbitrarily adjustable parameters in this theory. The agreement between the theoretical and experimental values for various properties (including transition temperatures and quadratic characteristic radii) is very good (relative deviations between 0% and less than 6.2%). The theoretical results also show--for the first time--that the N and I phases for these LCPs involve the packing of plate-like sections of backbones and side chains and that the local bilayer SA phase involves packing of side-chains within a plate-like section. This type of packing is predicted to be typical for side-chain LCPs. This theory can predict--for the first time--whether the side chains of a molecule pack on the same or alternating opposite sides of the backbone and whether side chains on different molecules interdigitate (overlap) with each other. 13 refs., 1 fig., 4 tabs

  14. SANS study of deformation and relaxation of a comb-like liquid crystal polymer in the nematic phase

    Science.gov (United States)

    Brûlet, A.; Boué, F.; Keller, P.; Davidson, P.; Strazielle, C.; Cotton, J. P.

    1994-06-01

    A comb-like liquid crystal polymer is stretched and quenched after a certain time in the nematic phase. The conformation of the deformed chain is determined using small angle neutron scattering (SANS) as a function of the temperature of stretching, the stretching ratio and the duration of the relaxation. The scattering data are well fitted to junction affine and phantom network models. Some data are even well fitted by a totally affine model that we call “ pseudo affine ” because the only parameter, the stretching ratio, is found to be well below the macroscopic stretching ratio. The latter result, never encountered with amorphous polymers, is attributed to the cooperative effects of the nematic phase. We also note that the form factors of the chain in the underformed sample remain similar in the isotropic, nematic and glassy state ; they correspond to a Gaussian chain. The same samples were studied by wide angle X-ray scattering. On one hand, the orientation of the mesogenic groups is found to be parallel or perpendicular to the stretching direction depending on the stretching temperature. This result is discussed as a function of the presence of smectic fluctuations. On the other hand, longer relaxations at constant elongation ratio do not lead to a disorganization of the mesogenic group orientation whereas the polymer chains are partly relaxed.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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. (special topic)

  16. Liquid Crystals in Tribology

    Directory of Open Access Journals (Sweden)

    María-Dolores Bermúdez

    2009-09-01

    Full Text Available 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.

  17. Progress in liquid crystal displays by new developments in functional polymers

    NARCIS (Netherlands)

    Broer, D.J.; Haaren, van J.A.M.M.; Bastiaansen, C.W.M.

    2001-01-01

    A review. Functional polymers have become essential in the functioning and performance of many products for information and communication technologies. Special polymers were constructed with an accurate control over their morphol. to a size down to the wavelength of light. These polymers improve

  18. Fabrication of micro- and nanometre-scale polymer structures in liquid crystal devices for next generation photonics applications

    Science.gov (United States)

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

    2016-09-01

    Direct Laser Writing (DLW) by two-photon photopolymerization (TPP) enables the fabrication of micron-scale polymeric structures in soft matter systems. The technique has implications in a broad range of optics and photonics; in particular fast-switching liquid crystal (LC) modes for the development of next generation display technologies. In this paper, we report two different methodologies using our TPP-based fabrication technique. Two explicit examples are provided of voltage-dependent LC director profiles that are inherently unstable, but which appear to be promising candidates for fast-switching photonics applications. In the first instance, 1 μm-thick periodic walls of polymer network are written into a planar aligned (parallel rubbed) nematic pi-cell device containing a nematic LC-monomer mixture. The structures are fabricated when the device is electrically driven into a fast-switching nematic LC state and aberrations induced by the device substrates are corrected for by virtue of the adaptive optics elements included within the DLW setup. Optical polarizing microscopy images taken post-fabrication reveal that polymer walls oriented perpendicular to the rubbing direction promote the stability of the so-called optically compensated bend mode upon removal of the externally applied field. In the second case, polymer walls are written in a nematic LC-optically adhesive glue mixture. A polymer- LCs-polymer-slices or `POLICRYPS' template is formed by immersing the device in acetone post-fabrication to remove any remaining non-crosslinked material. Injecting the resultant series of polymer microchannels ( 1 μm-thick) with a short-pitch, chiral nematic LC mixture leads to the spontaneous alignment of a fast-switching chiral nematic mode, where the helical axis lies parallel to the glass substrates. Optimal contrast between the bright and dark states of the uniform lying helix alignment is achieved when the structures are spaced at the order of the device thickness

  19. Effect of carbon derivatives in sulfonated poly(etherimide)-liquid crystal polymer composite for methanol vapor sensing

    Science.gov (United States)

    Bag, Souvik; Rathi, Keerti; Pal, Kaushik

    2017-05-01

    A class of highly sensitive chemiresistive sensors is developed for methanol (MeOH) vapor detection in ambient atmosphere by introducing conductive nanofillers like carbon black, multi-wall carbon nanotubes, and reduced graphene oxide into sulfonated poly(etherimide) (PEI)/liquid crystal polymer (LCP) composite (sPEI-LCP). Polar composites are prepared by a sulfonation process for instantaneous enhancement in adsorption capability of the sensing films to the target analyte (MeOH). Sensing properties exhibit that polymer composite-based fabricated sensors are efficient for the detection of different concentration of methanol vapor from 300-1200 parts-per-million (ppm) at room temperature. The incorporation of nanofiller induces the dramatic change in sensing behavior of base composite film (sPEI-LCP). Thus, less mass fraction of nanofillers (i.e. 2 wt%) influences the nonlinear sensing behavior for the entire range of methanol vapor. The simple method and low fabrication cost of the prepared sensor are compelling reasons that methanol vapor sensor is suitable for environmental monitoring.

  20. New theories for smectic and nematic liquid-crystal polymers: Backbone LCPs [liquid crystalline polymers] and their mixtures and side-chain LCPs

    International Nuclear Information System (INIS)

    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

  1. All-organic polymer-dispersed liquid crystal light-valves integrated with electroactive anthraquinone-2-sulfonate-doped polypyrrole thin films as driving electrodes

    International Nuclear Information System (INIS)

    Wang, Pen-Cheng; Yu, Jing-Yu; Li, Kuan-Hsun

    2011-01-01

    Highlights: → Fabrication of flexible semi-transparent all-polymer electrodes under ambient conditions without using a CVD system. → Characterization of the above electrodes based on anthraquinone-2-sulfonate-doped polypyrrole thin films. → Demonstration of all-organic liquid crystal light-valves with polypyrrole thin films as the driving electrodes. - Abstract: All-organic PDLC (polymer-dispersed liquid crystal) light-valves using all-polymer conductive substrates containing thin films of polypyrrole doped with anthraquinone-2-sulfonate (AQSA - ) as the driving electrodes were fabricated in this study. The all-polymer conductive substrates were prepared under ambient conditions by in situ depositing polypyrrole thin films on blank flexible poly(ethylene terephthalate), or PET, substrates from aqueous media in which oxidative polymerization of pyrrole was taking place. The obtained flexible all-polymer conductive substrates were semi-transparent with cohesive coatings of AQSA - doped polypyrrole thin films (thickness ∼55 nm). The all-polymer flexible conductive substrates had sheet resistivity ∼40 kΩ □ -1 and T% transparency against air ∼78% at 600 nm. The light-valves fabricated using the above all-polymer conductive substrates showed ∼50% transparency against air at 600 nm when 4 V μm -1 electric field was applied.

  2. Dichroic Liquid Crystal Displays

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  4. P-V-T properties of a polymer liquid crystal subjected to pre-drawing at several temperatures

    International Nuclear Information System (INIS)

    Broza, Georg; Castano, Victor M.; Martinez-Barrera, Gonzalo; Menard, Kevin P.; Simoes, Carla

    2005-01-01

    We have studied the copolymer of poly(ethylene terephthalate) (PET) with 0.6mole fraction of p-hydroxybenzoic acid (PHB). It is a longitudinal polymer liquid crystal (PLC). A number of otherwise identical samples were subjected to drawing to achieve in turn 20%, 40%, 60%, 80% and 100% increase in length. The drawing was performed isothermally at 60, 100 and 140 deg. C. Pressure-volume-temperature (P-V-T) results have been obtained for pressures up to 200Jcm -3 and temperatures up to 150 deg. C or so. Parameters of the Hartmann equation of state have been evaluated. Drawing first results in an increase in specific (and also free) volume, then in a decrease caused by increased orientation of the PLC, and finally in an apparent increase caused by the appearance of voids. The tensile modulus E has been determined for all pre-drawn samples. It reflects the volumetric changes a rebours: the initial increase in specific volume results in lower E values, orientation in E increase, and void formation in a second decrease

  5. Influence of the strength of the smectic order on the backbone anisotropy of side-chain liquid crystal polymers as revealed by SANS

    Science.gov (United States)

    Noirez, L.; Keller, P.; Cotton, J. P.

    1992-06-01

    It is proposed that the strength of the smectic order determines the backbone anisotropy of side-chain liquid crystal polymers. Here this strength increases with the length of the alkyl terminal group of the mesogens. Two liquid crystal polymethacrylates differing only by the mesogenic tails —OCH3 and —OC4H9 are considered. The backbone anisotropy of these polymers is measured by small angle neutron scattering (SANS) whereas the smectic order is evaluated from the intensity of the 001 Bragg peak. Il est proposé que la qualité de l'ordre smectique détermine l'anisotropie du squelette de polymères mésomorphes en peigne confinés dans les lamelles. Ici l'ordre smectique est augmenté en allongeant le groupe alkyl terminal des mésogènes. Nous étudions deux polyméthacrylates cristal liquide qui ne différent que par leurs groupes terminaux : —OCH3 et —OC4H9. L'anisotropie du squellete est mesurée par diffusion de neutrons aux petits angles tandis que l'ordre smectique est évalué à l'aide de l'intensité du pic de Bragg 001.

  6. Photo-orientation at liquid crystal–polymer interfaces

    Indian Academy of Sciences (India)

    affected by the phase of the liquid crystal covering the polymer. Photo-orientation is significantly more efficient when the liquid crystal is in the isotropic phase than when it exhibits orientational order. The observations are interpreted by assuming that in the smectic and nematic phases the liquid crystal stabilises to a large ...

  7. Liquid Crystal Colloids

    Science.gov (United States)

    Smalyukh, Ivan I.

    2018-03-01

    Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientific and technological potential.

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

    Science.gov (United States)

    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)

  9. Optical Power Limiting Liquid Crystal Composites

    Science.gov (United States)

    1994-11-10

    materials. In addition to the nonlinear studies, a separate subproject involving linear properties 0 of polymer dispersed liquid crystals in the infrared ...The horizontal axis represents on-axis laser intensity Io, defined as Io = 2P/( ww2 ), where P is the power and u0 is the beam waist. As can be seen in...I * 9 IR Shutter 1 Included in our original contract was a separate project to evaluate the use of liquid crystal composites in infrared shattering

  10. Homogeneous crystal nucleation in polymers.

    Science.gov (United States)

    Schick, C; Androsch, R; Schmelzer, J W P

    2017-11-15

    The pathway of crystal nucleation significantly influences the structure and properties of semi-crystalline polymers. Crystal nucleation is normally heterogeneous at low supercooling, and homogeneous at high supercooling, of the polymer melt. Homogeneous nucleation in bulk polymers has been, so far, hardly accessible experimentally, and was even doubted to occur at all. This topical review summarizes experimental findings on homogeneous crystal nucleation in polymers. Recently developed fast scanning calorimetry, with cooling and heating rates up to 10 6 K s -1 , allows for detailed investigations of nucleation near and even below the glass transition temperature, including analysis of nuclei stability. As for other materials, the maximum homogeneous nucleation rate for polymers is located close to the glass transition temperature. In the experiments discussed here, it is shown that polymer nucleation is homogeneous at such temperatures. Homogeneous nucleation in polymers is discussed in the framework of the classical nucleation theory. The majority of our observations are consistent with the theory. The discrepancies may guide further research, particularly experiments to progress theoretical development. Progress in the understanding of homogeneous nucleation is much needed, since most of the modelling approaches dealing with polymer crystallization exclusively consider homogeneous nucleation. This is also the basis for advancing theoretical approaches to the much more complex phenomena governing heterogeneous nucleation.

  11. Liquid crystal display

    International Nuclear Information System (INIS)

    Takami, K.

    1981-01-01

    An improved liquid crystal display device is described which can display letters, numerals and other necessary patterns in the night time using a minimized amount of radioactive material. To achieve this a self-luminous light source is placed in a limited region corresponding to a specific display area. (U.K.)

  12. Thermoelectricity in liquid crystals

    Science.gov (United States)

    Mohd Said, Suhana; Nordin, Abdul Rahman; Abdullah, Norbani; Balamurugan, S.

    2015-09-01

    The thermoelectric effect, also known as the Seebeck effect, describes the conversion of a temperature gradient into electricity. A Figure of Merit (ZT) is used to describe the thermoelectric ability of a material. It is directly dependent on its Seebeck coefficient and electrical conductivity, and inversely dependent on its thermal conductivity. There is usually a compromise between these parameters, which limit the performance of thermoelectric materials. The current achievement for ZT~2.2 falls short of the expected threshold of ZT=3 to allow its viability in commercial applications. In recent times, advances in organic thermoelectrics been significant, improving by over 3 orders of magnitude over a period of about 10 years. Liquid crystals are newly investigated as candidate thermoelectric materials, given their low thermal conductivity, inherent ordering, and in some cases, reasonable electrical conductivity. In this work the thermoelectric behaviour of a discotic liquid crystal, is discussed. The DLC was filled into cells coated with a charge injector, and an alignment of the columnar axis perpendicular to the substrate was allowed to form. This thermoelectric behavior can be correlated to the order-disorder transition. A reasonable thermoelectric power in the liquid crystal temperature regime was noted. In summary, thermoelectric liquid crystals may have the potential to be utilised in flexible devices, as a standalone power source.

  13. Interest of neutron scattering for the investigation of liquid-crystalline polymers

    International Nuclear Information System (INIS)

    Noirez, L.

    1994-01-01

    Small-angle Neutron scattering is the unique method which allows the determination of polymer conformation in the bulk state. This method has been applied to several kinds of liquid crystalline polymers. Results concerning side-chain liquid-crystal polymer, main-chain liquid-crystal polymer and combined liquid-crystal polymers, are reported. It is shown that the polymer conformation is largely dependent on the insertion site of the liquid crystal molecule and of the structure of the meso-phase. (author). 11 refs

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    The smectic C*-alpha (SmC 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 α * commonly shows only very narrow phase temperature range of a few degree Celsius. To broaden the SmC 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 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

  15. On possible contribution of standing wave like spacer dynamics in polymer liquid crystals to quasi-elastic cold neutron scattering spectra

    International Nuclear Information System (INIS)

    Jecl, R.; Cvikl, B.

    1998-01-01

    The quasi-elastic cold neutron incoherent scattering law, QNS, for the assumed case of transversal standing wave type of motion of the linear chain a spacer-of the polyacrylate polymer liquid crystal, based upon the random walk of the particle between two perfectly potential barriers, is derived. The spacer protons are taken to vibrate (within the stationary plane) transversely to the line joining the oxygen atoms in a way where they are all simultaneously displaced in the same direction with amplitudes of the standing wave fundamental mode of the vibration excited. The calculated relevant incoherent scattering law is found to be a non-distinct function of the scattering vector Q, in the sense that the postulated dynamical effect of the spacer protons causes the peak value of the calculated incoherent scattering law, S(Q,ω), to remain constant throughout the experimentally accessible range of the scattering vector Q. It appears that, when the experimental resolution broadening effects is taken into account, the contribution of the postulated dynamical behavior to the measured QNS spectra might be small, particularly so, if dome additional motion of the scatters is present, and consequently the standing wave like spacer dynamics in polymer liquid crystals will be very difficult to be identified uniquely in the quasielastic neutron scattering experiments.(author)

  16. Preparation and thermo-optical characteristics of a smart polymer-stabilized liquid crystal thin film based on smectic A–chiral nematic phase transition

    International Nuclear Information System (INIS)

    Sun, Jian; Wang, Huihui; Cao, Hui; Ding, Hangjun; Yang, Zhou; Yang, Huai; Wang, Ling; Xie, Hui; Luo, Xueyao; Xiao, Jiumei

    2014-01-01

    A smart polymer stabilized liquid crystal (PSLC) thin film with temperature-controllable light transmittance was prepared based on a smectic-A (SmA)–chiral nematic (N*) phase transition, and then the effect of the composition and the preparation condition of the PSLC film on its thermo-optical (T-O) characteristics has been investigated in detail. Within the temperature range of the SmA phase, the PSLC shows a strong opaque state due to the focal conic alignment of liquid crystal (LC) molecules, while the film exhibits a transparent state result from the parallel alignment of N* phase LC molecules at a higher temperature. Importantly, the PSLC films with different temperature of phase transition and contrast ratio can be prepared by changing the composition of photo-polymerizable monomer/LC/chiral dopant. According to the competition between the polymerization of the curable monomers and the diffusion of LC molecules, the ultraviolet (UV) curing surrounding temperature and the intensity of UV irradiation play a critical role in tuning the size of the polymer network meshes, which in turn influence the contrast ratio and the switching speed of the film. Our observations are expected to pave the way for preparing smart PSLC thin films for applications in areas of smart windows, thermo-detectors and other information recording devices. (paper)

  17. Liquid crystal dimers

    CERN Document Server

    Kumar Pal, Santanu

    2017-01-01

    This book covers in-depth discussion of design principles, synthesis and thermal behavior of all types of liquid crystal (LC) dimers. The text presents recent advances in the field of LC dimers consisting of different mesogenic units such as calamitic, discotic and bent-core molecules. It starts with a chapter on the introduction of liquid crystal dimers, including their odd-even behavior, basic classification of dimers and common mesophases in dimers. The text shows how the molecular architectures are being used to develop new materials to study a range of interesting phenomena such as the biaxial nematic phase containing rod-like and disc-like mesogenic units. Finally, the text presents perspectives related to technological relevance of these dimers such as dopants in LC display mixtures exhibiting faster relaxation time, strong flexoelectric coupling and others to effect control over the properties of these materials.

  18. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  19. High Resolution Displays Using NCAP Liquid Crystals

    Science.gov (United States)

    Macknick, A. Brian; Jones, Phil; White, Larry

    1989-07-01

    Nematic curvilinear aligned phase (NCAP) liquid crystals have been found useful for high information content video displays. NCAP materials are liquid crystals which have been encapsulated in a polymer matrix and which have a light transmission which is variable with applied electric fields. Because NCAP materials do not require polarizers, their on-state transmission is substantially better than twisted nematic cells. All dimensional tolerances are locked in during the encapsulation process and hence there are no critical sealing or spacing issues. By controlling the polymer/liquid crystal morphology, switching speeds of NCAP materials have been significantly improved over twisted nematic systems. Recent work has combined active matrix addressing with NCAP materials. Active matrices, such as thin film transistors, have given displays of high resolution. The paper will discuss the advantages of NCAP materials specifically designed for operation at video rates on transistor arrays; applications for both backlit and projection displays will be discussed.

  20. Polymer and Polymer Gel of Liquid Crystalline Semiconductors

    Institute of Scientific and Technical Information of China (English)

    Teppei Shimakawa; Naoki Yoshimoto; Jun-ichi Hanna

    2004-01-01

    It prepared a polymer and polymer gel of a liquid crystalline (LC) semiconductor having a 2-phenylnaphthalene moiety and studied their charge carrier transport properties by the time-of-flight technique. It is found that polyacrylate having the mesogenic core moiety of 2-phenylnaphtalene (PNP-acrylate) exhibited a comparable mobility of 10-4cm2/Vs in smectic A phase to those in smectic A (SmA) phase of small molecular liquid crystals with the same core moiety, e.g., 6-(4'-octylphenyl)- 2-dodecyloxynaphthalene (8-PNP-O12), and an enhanced mobility up to 10-3cm2/Vs in the LC-glassy phase at room temperature, when mixed with a small amount of 8-PNP-O12. On the other hand, the polymer gel consisting of 20 wt %-hexamethylenediacrylate (HDA)-based cross-linked polymer and 8-PNP-O12 exhibited no degraded mobility when cross-linked at the mesophase. These results indicate that the polymer and polymer composite of liquid crystalline semiconductors provide us with an easy way to realize a quality organic semiconductor thin film for the immediate device applications.

  1. Polymer liquids fracture like solids

    DEFF Research Database (Denmark)

    Huang, Qian; Hassager, Ole

    2017-01-01

    While fracture in brittle solids has been studied for centuries until today, there are few studies on fracture in polymer liquids. Recent developments in experimental techniques, especially the combination of controlled filament stretching rheometry and high speed imaging, have opened new windows...... into the detailed study of fracture processes for polymer liquids. High speed imaging shows that polymer liquids fracture like solids with initiation and propagation of an edge fracture. However, remarkable features such as highly reproducible critical stress, independent appearance of multiple fractures...

  2. Liquid Crystal Airborne Display

    Science.gov (United States)

    1977-08-01

    Cum.nings, J. P., et al., Properties and Limitations oe Liquid Crystals for Aircraft Displays, Honeywell Corporate Researc ."I Center, Final Report HR-72...basic module could be used to build displays for both the commercial and military! 157- marhecs, and so would establi sh a broad and sizable market ... market for the display becomes a reality; therein lies, f TABLE 16 THE COURSE OF FUTURE DISPLAY DEVELOPMENT Today 1976-77 1980 1985 Display Size 2" 1 3.2

  3. Nanoporous polymer liquid core waveguides

    DEFF Research Database (Denmark)

    Gopalakrishnan, Nimi; Christiansen, Mads Brøkner; Ndoni, Sokol

    2010-01-01

    We demonstrate liquid core waveguides defined by UV to enable selective water infiltration in nanoporous polymers, creating an effective refractive index shift Δn=0.13. The mode confinement and propagation loss in these waveguides are presented.......We demonstrate liquid core waveguides defined by UV to enable selective water infiltration in nanoporous polymers, creating an effective refractive index shift Δn=0.13. The mode confinement and propagation loss in these waveguides are presented....

  4. Formation of radial aligned and uniform nematic liquid crystal droplets via drop-on-demand inkjet printing into a partially-wet polymer layer

    Science.gov (United States)

    Parry, Ellis; Kim, Dong-Jin; Castrejón-Pita, Alfonso A.; Elston, Steve J.; Morris, Stephen M.

    2018-06-01

    This paper investigates the drop-on-demand inkjet printing of a nematic liquid crystal (LC) onto a variety of substrates. Achieving both a well-defined droplet boundary and uniformity of the LC director in printed droplets can be challenging when traditional alignment surfaces are employed. Despite the increasing popularity of inkjet printing LCs, the mechanisms that are involved during the deposition process such as drop impact, wetting and spreading have received very little attention, in the way of experiments, as viable routes for promoting alignment of the resultant LC droplets. In this work, radial alignment of the director and uniformity of the droplet boundary are achieved in combination via the use of a partially-wet polymer substrate, which makes use of the forces and flow generated during droplet impact and subsequent wetting process. Our findings could have important consequences for future LC inkjet applications, including the development of smart inks, printable sensors and lasers.

  5. Physical Properties of Liquid Crystals

    CERN Document Server

    Gray, George W; Spiess, Hans W

    1999-01-01

    This handbook is a unique compendium of knowledge on all aspects of the physics of liquid crystals. In over 500 pages it provides detailed information on the physical properties of liquid crystals as well as the recent theories and results on phase transitions, defects and textures of different types of liquid crystals. An in-depth understanding of the physical fundamentals is a prerequisite for everyone working in the field of liquid crystal research. With this book the experts as well as graduate students entering the field get all the information they need.

  6. Wetting of cholesteric liquid crystals.

    Science.gov (United States)

    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.

  7. NATO Advanced Research Workshop on Computational Methods for Polymers and Liquid Crystalline Polymers

    CERN Document Server

    Pasini, Paolo; Žumer, Slobodan; Computer Simulations of Liquid Crystals and Polymers

    2005-01-01

    Liquid crystals, polymers and polymer liquid crystals are soft condensed matter systems of major technological and scientific interest. An understanding of the macroscopic properties of these complex systems and of their many and interesting peculiarities at the molecular level can nowadays only be attained using computer simulations and statistical mechanical theories. Both in the Liquid Crystal and Polymer fields a considerable amount of simulation work has been done in the last few years with various classes of models at different special resolutions, ranging from atomistic to molecular and coarse-grained lattice models. Each of the two fields has developed its own set of tools and specialized procedures and the book aims to provide a state of the art review of the computer simulation studies of polymers and liquid crystals. This is of great importance in view of a potential cross-fertilization between these connected areas which is particularly apparent for a number of experimental systems like, e.g. poly...

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

    Science.gov (United States)

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

    2016-02-08

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Labeeb, A. [Liquid Crystal Institute, Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (United States); Microwave Physics and Dielectrics, National Research Center, Dokki 12622 (Egypt); Gleeson, H. F. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Hegmann, T., E-mail: thegmann@kent.edu [Liquid Crystal Institute, Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (United States)

    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.

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

    Science.gov (United States)

    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.

  11. Nanoparticles Doped, Photorefractive Liquid Crystals

    National Research Council Canada - National Science Library

    Kaczmarek, Malgosia

    2005-01-01

    ...: The main objectives of this exploratory, short project will concern the study of the quality of liquid crystal cells with diluted suspensions of ferroelectric nanoparticles and their photorefractive properties...

  12. Adaptive Liquid Crystal Windows

    Energy Technology Data Exchange (ETDEWEB)

    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

  13. Computer simulation of liquid crystals

    International Nuclear Information System (INIS)

    McBride, C.

    1999-01-01

    Molecular dynamics simulation performed on modern computer workstations provides a powerful tool for the investigation of the static and dynamic characteristics of liquid crystal phases. In this thesis molecular dynamics computer simulations have been performed for two model systems. Simulations of 4,4'-di-n-pentyl-bibicyclo[2.2.2]octane demonstrate the growth of a structurally ordered phase directly from an isotropic fluid. This is the first time that this has been achieved for an atomistic model. The results demonstrate a strong coupling between orientational ordering and molecular shape, but indicate that the coupling between molecular conformational changes and molecular reorientation is relatively weak. Simulations have also been performed for a hybrid Gay-Berne/Lennard-Jones model resulting in thermodynamically stable nematic and smectic phases. Frank elastic constants have been calculated for the nematic phase formed by the hybrid model through analysis of the fluctuations of the nematic director, giving results comparable with those found experimentally. Work presented in this thesis also describes the parameterization of the torsional potential of a fragment of a dimethyl siloxane polymer chain, disiloxane diol (HOMe 2 Si) 2 O, using ab initio quantum mechanical calculations. (author)

  14. Nanoimprinted polymer photonic crystal dye lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Smith, Cameron; Buss, Thomas

    2010-01-01

    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...

  15. Artificial muscles based on liquid crystal elastomers.

    Science.gov (United States)

    Li, Min-Hui; Keller, Patrick

    2006-10-15

    This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35-45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block.Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.

  16. Fundamentals of liquid crystal devices

    CERN Document Server

    Yang, Deng-Ke

    2014-01-01

    Revised throughout to cover the latest developments in the fast moving area of display technology, this 2nd edition of Fundamentals of Liquid Crystal Devices, will continue to be a valuable resource for those wishing to understand the operation of liquid crystal displays. Significant updates include new material on display components, 3D LCDs and blue-phase displays which is one of the most promising new technologies within the field of displays and it is expected that this new LC-technology will reduce the response time and the number of optical components of LC-modules. Prof. Yang is a pion

  17. Liquid Crystals for Nondestructive Evaluation

    Science.gov (United States)

    1978-09-01

    polarizers (e.g., where p is the distance of alignment or pitch, X is the Nicol, Rochon, and Wollaston prisms ) are based upon peak wavelength of scattered...RANGE OF so 45" 45 - EVENT SEVENT T(°C) TEMPERATUJRE TC)4"TEMPERATURE 40RANGE OF T(°) 0-RANGE OF 40LIQUID ’ ൫" CRYSTAL S 36 3S. 30 0 IS 90 180 - I...Temperatures TI > T2 > - > TS defects was possible using the liquid crystal. are the Average TemperatursI Thes Resptivegi. Kapfer , Burns, Salvo, and Doyle

  18. Ionic Liquid Crystals: Versatile Materials.

    Science.gov (United States)

    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.

  19. Bicontinuous liquid crystals

    CERN Document Server

    Lynch, Mathew L

    2005-01-01

    PrefaceIntroduction AcknowledgmentsBicontinuous Cubic Liquid Crystalline Materials: A Historical Perspective and Modern Assessment; Kr̄e LarssonIntermediate Phases; Michael C. Holmes and Marc S. LeaverCubic Phases and Human Skin: Theory and Practice; Steven Hoath and Lars NorlňThe Relationship between Bicontinuous Inverted Cubic Phases and Membrane Fusion; D.P. SiegelAspects of the Differential Geometry and Topology of Bicontinuous Liquid-Crystalline Phases; Robert W. CorkeryNovel L3 Phases and Their Macroscopic Properties; R. Beck and H. HoffmannBicontinuous Cubic Phases of Lipids with Entra

  20. Computer modeling of liquid crystals

    International Nuclear Information System (INIS)

    Al-Barwani, M.S.

    1999-01-01

    In this thesis, we investigate several aspects of the behaviour of liquid crystal molecules near interfaces using computer simulation. We briefly discuss experiment, theoretical and computer simulation studies of some of the liquid crystal interfaces. We then describe three essentially independent research topics. The first of these concerns extensive simulations of a liquid crystal formed by long flexible molecules. We examined the bulk behaviour of the model and its structure. Studies of a film of smectic liquid crystal surrounded by vapour were also carried out. Extensive simulations were also done for a long-molecule/short-molecule mixture, studies were then carried out to investigate the liquid-vapour interface of the mixture. Next, we report the results of large scale simulations of soft-spherocylinders of two different lengths. We examined the bulk coexistence of the nematic and isotropic phases of the model. Once the bulk coexistence behaviour was known, properties of the nematic-isotropic interface were investigated. This was done by fitting order parameter and density profiles to appropriate mathematical functions and calculating the biaxial order parameter. We briefly discuss the ordering at the interfaces and make attempts to calculate the surface tension. Finally, in our third project, we study the effects of different surface topographies on creating bistable nematic liquid crystal devices. This was carried out using a model based on the discretisation of the free energy on a lattice. We use simulation to find the lowest energy states and investigate if they are degenerate in energy. We also test our model by studying the Frederiks transition and comparing with analytical and other simulation results. (author)

  1. Thermotropic liquid crystals recent advances

    CERN Document Server

    Ramamoorthy, Ayyalusamy

    2007-01-01

    This book covers developments in the field of thermotropic liquid crystals and their functional importance. It also presents advances related to different sub-areas pertinent to this interdisciplinary area of research. This text brings together research from synthetic scientists and spectroscopists and attempts to bridge the gaps between these areas. New physical techniques that are powerful in characterizing these materials are discussed.

  2. Polymer Dispersed Liquid Crystal Displays

    Science.gov (United States)

    Doane, J. William

    The following sections are included: * INTRODUCTION AND HISTORICAL DEVELOPMENT * PDLC MATERIALS PREPARATION * Polymerization induced phase separation (PIPS) * Thermally induced phase separation (TIPS) * Solvent induced phase separation (SIPS) * Encapsulation (NCAP) * RESPONSE VOLTAGE * Dielectric and resistive effects * Radial configuration * Bipolar configuration * Other director configurations * RESPONSE TIME * DISPLAY CONTRAST * Light scattering and index matching * Incorporation of dyes * Contrast measurements * PDLC DISPLAY DEVICES AND INNOVATIONS * Reflective direct view displays * Large-scale, flexible displays * Switchable windows * Projection displays * High definition spatial light modulator * Haze-free PDLC shutters: wide angle view displays * ENVIRONMENTAL STABILITY * ACKNOWLEDGEMENTS * REFERENCES

  3. Macroscopic chirality of a liquid crystal from nonchiral molecules

    International Nuclear Information System (INIS)

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

    2001-01-01

    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

  4. Molecular dynamics of liquid crystals

    Science.gov (United States)

    Sarman, Sten

    1997-02-01

    We derive Green-Kubo relations for the viscosities of a nematic liquid crystal. The derivation is based on the application of a Gaussian constraint algorithm that makes the director angular velocity of a liquid crystal a constant of motion. Setting this velocity equal to zero means that a director-based coordinate system becomes an inertial frame and that the constraint torques do not do any work on the system. The system consequently remains in equilibrium. However, one generates a different equilibrium ensemble. The great advantage of this ensemble is that the Green-Kubo relations for the viscosities become linear combinations of time correlation function integrals, whereas they are complicated rational functions in the conventional canonical ensemble. This facilitates the numerical evaluation of the viscosities by molecular dynamics simulations.

  5. Electro-optics of novel polymer-liquid crystalline composites

    International Nuclear Information System (INIS)

    Ibragimov, T.D.; Bayramov, G.M.; Imamaliyev, A.R.; Bayramov, G.M.

    2014-01-01

    The polymer network liquid crystals based on the liquid crystals H37 and 5CB with PMVP and PEG have been developed. Mesogene substance HOBA is served for stabilization of obtaining composites. Kinetics of network formation is investigated by methods of polarization microscopy and integrated small-angle scattering. It is shown that gel-like states of the composite H-37+PMVP+HOBA and 5CB+PEG+HOBA are formed at polymer concentration above 7 percent and 9 percent, correspondingly. The basic electro-optic parameters of the obtained composites are determined at room temperature. Experimental results are explained by phase separation of the system, diminution of a working area of electro-optical effects and influence of areas with high polymer concentration on areas with their low concentration

  6. Liquid crystals in biotribology synovial joint treatment

    CERN Document Server

    Ermakov, Sergey; Eismont, Oleg; Nikolaev, Vladimir

    2016-01-01

    This book summarizes the theoretical and experimental studies confirming the concept of the liquid-crystalline nature of boundary lubrication in synovial joints. It is shown that cholesteric liquid crystals in the synovial liquid play a significant role in the mechanism of intra-articular friction reduction. The results of structural, rheological and tribological research of the creation of artificial synovial liquids - containing cholesteric liquid crystals in natural synovial liquids - are described. These liquid crystals reproduce the lubrication properties of natural synovia and provide a high chondroprotective efficiency. They were tested in osteoarthritis models and in clinical practice.

  7. Twinning of Polymer Crystals Suppressed by Entropy

    Directory of Open Access Journals (Sweden)

    Nikos Ch. Karayiannis

    2014-09-01

    Full Text Available We propose an entropic argument as partial explanation of the observed scarcity of twinned structures in crystalline samples of synthetic organic polymeric materials. Polymeric molecules possess a much larger number of conformational degrees of freedom than low molecular weight substances. The preferred conformations of polymer chains in the bulk of a single crystal are often incompatible with the conformations imposed by the symmetry of a growth twin, both at the composition surfaces and in the twin axis. We calculate the differences in conformational entropy between chains in single crystals and chains in twinned crystals, and find that the reduction in chain conformational entropy in the twin is sufficient to make the single crystal the stable thermodynamic phase. The formation of cyclic twins in molecular dynamics simulations of chains of hard spheres must thus be attributed to kinetic factors. In more realistic polymers this entropic contribution to the free energy can be canceled or dominated by nonbonded and torsional energetics.

  8. Poly-Phenylene-Quinonediimine as a possible conducting liquid crystal

    Science.gov (United States)

    Hall, H. K.

    1986-06-01

    The synthesis of stable electrically conducting, fabricable polymers of known structure represents an important goal of current polymer science. It seems to us that conductive, processable, and stable materials of defined structure should not be beyond the reach of the modern synthetic polymer chemist. Our approach has been to utilize a wide variety of polycondensation reactions to see whether they are useful for the synthesis of potentially conducting, stable, processable polymers. Polycondensation routes are preferred because they will lead to polymers of rational, known structure. Standard techniques of polymer chemistry such as copolymerization, use of unsymmetrical monomers, and introduction of softening substituents can be used to enhance processability. Further, the extended para structures preferred for conductivity may also lead to liquid crystal behavior, another potential tool for fabrication.

  9. Large Three-Dimensional Photonic Crystals Based on Monocrystalline Liquid Crystal Blue Phases (Postprint)

    Science.gov (United States)

    2017-09-28

    a pair of glass slides with plastic spacers to determine the cell gap: 100 and 300 μm for the polymer-free BPLCs and 12 μm for the polymer-stabilized...Nissan) and rubbed with cloth to induce uniform planar alignment. Measurements. Reflection and transmission spectra were taken using a spectro- meter...thermal recycles . Opt. Mater. Express 2, 1149–1155 (2012). 34. Onusseit, H. & Stegemeyer, H. Liquid single crystals of cholesteric blue phases. Z

  10. Electrically controlled liquid crystal fiber

    Science.gov (United States)

    Corella-Madueño, A.; Reyes, J. Adrián

    2006-08-01

    We consider a cylindrical fiber whose core is a liquid crystal (LC) subject to the action of a low frequency field applied parallel to the axis of the cylinder and having initially the escaped configuration. We find the distorted textures of the nematic inside the cylinder by assuming arbitrary anchoring boundary conditions. In the optical limit we calculate the ray trajectories followed by a low intensity beam along the fiber parametrized by a low frequency electric field. Finally, we calculate exactly the spatial dependence of the transverse magnetic modes distribution in the guide, on the electric field, by using a numerical scheme. We summarize our paper and discuss our results.

  11. All-polymer photonic crystal slab sensor

    DEFF Research Database (Denmark)

    Hermannsson, Pétur Gordon; Sørensen, Kristian Tølbøl; Vannahme, Christoph

    2015-01-01

    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 4.5x10-6 RIU when measured...

  12. Nanoscopic Manipulation and Imaging of Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rosenblatt, Charles S. [Case Western Reserve Univ., Cleveland, OH (United States)

    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.

  13. Tuning crystallization pathways through sequence engineering of biomimetic polymers

    Science.gov (United States)

    Ma, Xiang; Zhang, Shuai; Jiao, Fang; Newcomb, Christina J.; Zhang, Yuliang; Prakash, Arushi; Liao, Zhihao; Baer, Marcel D.; Mundy, Christopher J.; Pfaendtner, James; Noy, Aleksandr; Chen, Chun-Long; de Yoreo, James J.

    2017-07-01

    Two-step nucleation pathways in which disordered, amorphous, or dense liquid states precede the appearance of crystalline phases have been reported for a wide range of materials, but the dynamics of such pathways are poorly understood. Moreover, whether these pathways are general features of crystallizing systems or a consequence of system-specific structural details that select for direct versus two-step processes is unknown. Using atomic force microscopy to directly observe crystallization of sequence-defined polymers, we show that crystallization pathways are indeed sequence dependent. When a short hydrophobic region is added to a sequence that directly forms crystalline particles, crystallization instead follows a two-step pathway that begins with the creation of disordered clusters of 10-20 molecules and is characterized by highly non-linear crystallization kinetics in which clusters transform into ordered structures that then enter the growth phase. The results shed new light on non-classical crystallization mechanisms and have implications for the design of self-assembling polymer systems.

  14. Tuning crystallization pathways through sequence engineering of biomimetic polymers

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiang; Zhang, Shuai; Jiao, Fang; Newcomb, Christina J.; Zhang, Yuliang; Prakash, Arushi; Liao, Zhihao; Baer, Marcel D.; Mundy, Christopher J.; Pfaendtner, James; Noy, Aleksandr; Chen, Chun-Long; De Yoreo, James J.

    2017-04-17

    Two-step nucleation pathways in which disordered, amorphous, or dense liquid states precede appearance of crystalline phases have been reported for a wide range of materials, but the dynamics of such pathways are poorly understood. Moreover, whether these pathways are general features of crystallizing systems or a consequence of system-specific structural details that select for direct vs two-step processes is unknown. Using atomic force microscopy to directly observe crystallization of sequence-defined polymers, we show that crystallization pathways are indeed sequence dependent. When a short hydrophobic region is added to a sequence that directly forms crystalline particles, crystallization instead follows a two-step pathway that begins with creation of disordered clusters of 10-20 molecules and is characterized by highly non-linear crystallization kinetics in which clusters transform into ordered structures that then enter the growth phase. The results shed new light on non-classical crystallization mechanisms and have implications for design of self-assembling polymer systems.

  15. Chiral-nematic liquid crystals as one dimensional photonic materials in optical sensors

    NARCIS (Netherlands)

    Mulder, D.J.; Schenning, A.P.H.J.; Bastiaansen, C.W.M.

    2014-01-01

    Current developments in the field of thermotropic chiral-nematic liquid crystals as sensors are discussed. These one dimensional photonic materials are based on low molecular weight liquid crystals and chiral-nematic polymeric networks. For both low molecular weight LCs and polymer networks,

  16. Crystal structure and thin film morphology of BBL ladder polymer

    Energy Technology Data Exchange (ETDEWEB)

    Song, H H [Department of Macromolecular Science, Han Nam University, Taejon (Korea, Republic of); Fratini, A V [Department of Chemistry, University of Dayton, Dayton, OH (United States); Chabinyc, M [Department of Chemistry, University of Dayton, Dayton, OH (United States); Price, G E [University of Dayton Research, Dayton, OH (United States); Agrawal, A K [Systran Corporation, Dayton, OH (United States); Wang, C S [University of Dayton Research, Dayton, OH (United States); Burkette, J [University of Dayton Research, Dayton, OH (United States); Dudis, D S [Materials Directorate, Wright Laboratory, Wright-Patterson Air Force Base, OH (United States); Arnold, F E [Materials Directorate, Wright Laboratory, Wright-Patterson Air Force Base, OH (United States)

    1995-03-01

    Crystal structure and morphology of poly[7-oxo-7H-benz(d,e)imidazo(4`,5`:5,6)-benzimidazo(2,1-a)isoquinoline-3,4:10,11-tetrayl-10-carbonyl] (BBL) ladder-like polymer were studied. The polymer forms a two-dimensional lattice of nematic liquid crystalline structure. An orthorhombic unit cell with cell parameters of a=7.87 b=3.37 c=11.97A was determined from the fiber diffraction pattern. In thin films, the rigid chains spontaneously form a layered structure across the film thickness, but in a very unusual manner, i.e. the very large molecular plane is standing perpendicularly to the film surface plane. The results are identical to our recent results of poly(p-phenylene benzobisthiazole) (PBT) film [7]. The polymer, however, lost its anisotropic order upon extrusion into a film and resulted in a fiber-like structure. (orig.)

  17. Biaxiality of chiral liquid crystals

    International Nuclear Information System (INIS)

    Longa, L.; Trebin, H.R.; Fink, W.

    1993-10-01

    Using extended deGennes-Ginzburg-Landau free energy expansion in terms of the anisotropic part of the dielectric tensor field Q αβ (χ) a connection between the phase biaxiality and the stability of various chiral liquid crystalline phases is studied. In particular the cholesteric phase, the cubic Blue Phases and the phases characterized by an icosahedral space group symmetry are analysed in detail. Also a general question concerning the applicability of the mean-field approximation in describing the chiral phases is addressed. By an extensive study of the model over a wide range of the parameters a new class of phenomena, not present in the original deGennes-Ginzburg-Landau model, has been found. These include: a) re-entrant phase transitions between the cholesteric and the cubic blue phases and b) the existence of distinct phases of the same symmetry but of different biaxialities. The phase biaxiality serves here as an extra scalar order parameter. Furthermore, it has been shown that due to the presence of the competing bulk terms in the free energy, the stable phases may acquire a large degree of biaxiality, also in liquid crystalline materials composed of effectively uniaxial molecules. A study of icosahedral space group symmetries gives a partial answer to the question as to whether an icosahedral quasicrystalline liquid could be stabilized in liquid crystals. Although, in general, the stability of icosahedral structures could be enhanced by the extra terms in the free energy no absolutely stable icosahedral phase has been found. (author). 16 refs, 3 figs, 1 tab

  18. Angular selectivity asymmetry of holograms recorded in near infrared sensitive liquid crystal photopolymerizable materials

    Science.gov (United States)

    Harbour, Steven; Galstian, Tigran; Akopyan, Rafik; Galstyan, Artur

    2004-08-01

    We have experimentally observed and theoretically explained the angular selectivity asymmetry in polymer dispersed liquid crystal holograms. Experiments are conducted in compounds with near infrared sensitivity. The coupled-wave theory is used to describe the diffraction properties of obtained anisotropic holographic gratings. Furthermore, the comparison of theory and experiments provides information about the optical axis direction that is defined by the average molecular orientation of the liquid crystal in the polymer matrix.

  19. Nonlinear and quantum optics with liquid crystals

    International Nuclear Information System (INIS)

    Lukishova, Svetlana G

    2014-01-01

    Thermotropic liquid crystals' usual application is display technology. This paper describes experiments on light interaction with pure and doped liquid crystals under for these materials unconventional incident light powers: (1) under high-power laser irradiation, and (2) at the single-photon level. In (1), I will outline several nonlinear optical effects under high-power, nanosecond laser irradiation which should be taken into account in the design of lasers with liquid crystal components and in fabrication of optical power limiters based on liquid crystals: (1.1) athermal helical pitch dilation and unwinding of cholesteric mirrors (both in free space and inside laser resonators); (1.2) some pitfalls in measurements of refractive nonlinearity using z-scan technique under two-photon or linear absorption of liquids; (1.3) the first observation of thermal lens effects in liquid crystals under several-nanosecond, low-pulse-repetition rate (2-10 Hz) laser irradiation in the presence of two-photon absorption; (1.4) feedback-free kaleidoscope of patterns (hexagons, stripes, etc.) in dye-doped liquid crystals. In (2), at the single-photon level, it will be shown that with a proper selection of liquid crystals and a single-emitter dopant spectral range, liquid crystal structures can be used to control emitted single photons (both polarization and count rate). The application of the latter research is absolutely secure quantum communication with polarization coding of information. In particular, in (2.1), definite handedness, circular polarized cholesteric microcavity resonance in quantum dot fluorescence is reported. In (2.2), definite linear polarization of single (antibunched) photons from single-dye-molecules in planar-aligned nematic host is discussed. In (2.3), some results on photon antibunching from NV-color center in nanodiamond in liquid crystal host and circularly polarized fluorescence of definite handedness from nanocrystals doped with trivalent ions of

  20. Demonstrations with a Liquid Crystal Shutter

    Science.gov (United States)

    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…

  1. Flow induced/ refined solution crystallization of a semiconducting polymer

    Science.gov (United States)

    Nguyen, Ngoc A.

    Organic photovoltaics, a new generation of solar cells, has gained scientific and economic interests due to the ability of solution-processing and potentially low-cost power production. Though, the low power conversion efficiency of organic/ plastic solar cells is one of the most pertinent challenges that has appealed to research communities from many different fields including materials science and engineering, electrical engineering, chemical engineering, physics and chemistry. This thesis focuses on investigating and controlling the morphology of a semi-conducting, semi-crystalline polymer formed under shear-flow. Molecular structures and processing techniques are critical factors that significantly affect the morphology formation in the plastic solar cells, thus influencing device performance. In this study, flow-induced solution crystallization of poly (3-hexylthiophene) (P3HT) in a poor solvent, 2-ethylnapthalene (2-EN) was utilized to make a paint-like, structural liquid. The polymer crystals observed in this structured paint are micrometers long, nanometers in cross section and have a structure similar to that formed under quiescent conditions. There is pi-pi stacking order along the fibril axis, while polymer chain folding occurs along the fibril width and the order of the side-chain stacking is along fibril height. It was revealed that shear-flow not only induces P3HT crystallization from solution, but also refines and perfects the P3HT crystals. Thus, a general strategy to refine the semiconducting polymer crystals from solution under shear-flow has been developed and employed by simply tuning the processing (shearing) conditions with respect to the dissolution temperature of P3HT in 2-EN. The experimental results demonstrated that shear removes defects and allows more perfect crystals to be formed. There is no glass transition temperature observed in the crystals formed using the flow-induced crystallization indicating a significantly different

  2. Key Developments in Ionic Liquid Crystals

    OpenAIRE

    Fernandez, A.A.; Kouwer, P.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...

  3. Liquid crystals for organic transistors (Conference Presentation)

    Science.gov (United States)

    Hanna, Jun-ichi; Iino, Hiroaki

    2016-09-01

    Liquid crystals are a new type of organic semiconductors exhibiting molecular orientation in self-organizing manner, and have high potential for device applications. In fact, various device applications have been proposed so far, including photosensors, solar cells, light emitting diodes, field effect transistors, and so on.. However, device performance in those fabricated with liquid crystals is less than those of devices fabricated with conventional materials in spite of unique features of liquid crystals. Here we discuss how we can utilize the liquid crystallinity in organic transistors and how we can overcome conventional non-liquid crystalline organic transistor materials. Then, we demonstrate high performance organic transistors fabricated with a smectic E liquid crystal of Ph-BTBT-10, which show high mobility of over 10cm2/Vs and high thermal durability of over 200oC in OFETs fabricated with its spin-coated polycrystalline thin films.

  4. A Review on Polymer Crystallization Theories

    Directory of Open Access Journals (Sweden)

    Michael C. Zhang

    2016-12-01

    Full Text Available It is the aim of this article to review the major theories of polymer crystallization since up to now we still have not completely comprehended the underlying mechanism in a unified framework. A lack of paradigm is an indicator of immaturity of the field itself; thus, the fundamental issue of polymer crystallization remains unsolved. This paper provides an understanding of the basic hypothesis, as well as relevant physical implications and consequences of each theory without too much bias. We try to present the essential aspects of the major theories, and intuitive physical arguments over rigorously mathematical calculations are highlighted. In addition, a detailed comparison of various theories will be made in a logical and self-contained fashion. Our personal view of the existing theories is presented as well, aiming to inspire further open discussions. We expect that new theories based on the framework of kinetics with direct consideration of long-range multi-body correlation will help solve the remaining problems in the field of polymer crystallization.

  5. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available 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.

  6. Small-angle neutron scattering technique in liquid crystal studies

    International Nuclear Information System (INIS)

    Shahidan Radiman

    2005-01-01

    The following topics discussed: general principles of SAS (Small-angle Neutron Scattering), liquid crystals, nanoparticle templating on liquid crystals, examples of SAS results, prospects of this studies

  7. Lyotropic Liquid Crystal Phases from Anisotropic Nanomaterials

    Directory of Open Access Journals (Sweden)

    Ingo Dierking

    2017-10-01

    Full Text Available Liquid crystals are an integral part of a mature display technology, also establishing themselves in other applications, such as spatial light modulators, telecommunication technology, photonics, or sensors, just to name a few of the non-display applications. In recent years, there has been an increasing trend to add various nanomaterials to liquid crystals, which is motivated by several aspects of materials development. (i addition of nanomaterials can change and thus tune the properties of the liquid crystal; (ii novel functionalities can be added to the liquid crystal; and (iii the self-organization of the liquid crystalline state can be exploited to template ordered structures or to transfer order onto dispersed nanomaterials. Much of the research effort has been concentrated on thermotropic systems, which change order as a function of temperature. Here we review the other side of the medal, the formation and properties of ordered, anisotropic fluid phases, liquid crystals, by addition of shape-anisotropic nanomaterials to isotropic liquids. Several classes of materials will be discussed, inorganic and mineral liquid crystals, viruses, nanotubes and nanorods, as well as graphene oxide.

  8. Nanoparticles in discotic liquid crystals

    Science.gov (United States)

    Kumar, Sandeep

    The self-assembly of disc-shaped molecules creates discotic liquid crystals (DLCs). These nanomaterials of the sizes ranging from 2-6 nm are emerging as a new class of organic semiconducting materials. The unique geometry of columnar mesophases formed by discotic molecules is of great importance to study the one-dimensional charge and energy migration in organized systems. A number of applications of DLCs, such as, one-dimensional conductor, photoconductor, photovoltaic solar cells, light emitting diodes and gas sensors have been reported. The conductivity along the columns in columnar mesophases has been observed to be several orders of magnitude greater than in perpendicular direction and, therefore, DLCs are described as molecular wires. On the other hand, the fields of nanostructured materials, such as gold nanoparticles, quantum dots, carbon nanotubes and graphene, have received tremendous development in the past decade due to their technological and fundamental interest. Recently the hybridization of DLCs with various metallic and semiconducting nanoparticles has been realized to alter and improve their properties. These nanocomposites are not only of basic science interest but also lead to novel materials for many device applications. This article provides an overview on the development in the field of newly immersed discotic nanoscience. After a brief introduction of DLCs, the article will cover the inclusion of various zero-, one- and two-dimensional nanoparticles in DLCs. Finally, an outlook into the future of this newly emerging intriguing field of discotic nanoscience research will be provided.

  9. NMR spectroscopy using liquid crystal solvents

    CERN Document Server

    Emsley, JW

    2013-01-01

    NMR Spectroscopy using Liquid Crystal Solvents covers the importance of using a liquid crystal solvent in NMR to derive nuclear dipolar spin-spin coupling constants. This book is composed of ten chapters, and begins with a brief description of the features and benefits of liquid crystal in NMR spectroscopic analysis. The succeeding chapters deal with the mode of operation of nuclear spin Hamiltonian for partially oriented molecules and the analysis of NMR spectra of partially oriented molecules, as well as the determination of rigid molecule structure. These topics are followed by discussions

  10. Liquid crystalline biopolymers: A new arena for liquid crystal research

    International Nuclear Information System (INIS)

    Rizvi, Tasneem Zahra

    2001-07-01

    This paper gives a brief introduction to liquid crystals on the basis of biopolymers and reviews literature on liquid crystalline behaviour of biopolymers both in vitro and in vivo in relation to their implications in the fields of biology, medicine and material science. Knowledge in the field of biological liquid crystals is crucial for understanding complex phenomena at supramolecular level which will give information about processes involved in biological organization and function. The understanding of the interaction of theses crystals with electric, magnetic, optical and thermal fields will uncover mechanisms of near quantum-energy detection capabilities of biosystems

  11. Molecular dynamics simulations of liquid crystals at interfaces

    International Nuclear Information System (INIS)

    Shield, Mark

    2002-01-01

    Molecular dynamics simulations of an atomistic model of 4-n-octyl-4'-cyanobiphenyl (8CB) were performed for thin films of 8CB on solid substrates (a pseudopotential representation of the molecular topography of the (100) crystal surface of polyethylene (PE), a highly ordered atomistic model of a pseudo-crystalline PE surface and an atomistic model of a partially orientated film of PE), free standing thin films of 8CB and 8CB droplets in a hexagonal pit. The systems showed strong homeotropic anchoring at the free volume interface and planar anchoring at the solid interface whose strength was dependent upon the surface present. The free volume interface also demonstrated weak signs of smectic wetting of the bulk. Simulations of thin free standing films of liquid crystals showed the ordered nature of the liquid crystals at the two free volume interfaces can be adopted by the region of liquid crystal molecules between the homeotropic layer at each interface only if there is a certain number of liquid crystal molecules present. The perpendicular anchoring imposed by the free volume interface and the solid interface for the thin films on the solid substrates resulted in some evidence for the liquid crystal director undergoing a continual rotation at low temperatures and a definite discontinuous change at higher temperatures. The liquid crystal alignment imparted by these substrates was found to depend upon the topography of the surface and not the direction of the polymer chains in the substrate. The liquid crystal was found to order via an epitaxy-like mechanism. The perpendicular anchoring results in a drop in the order - disorder transition temperature for the molecules in the region between the homeotropic layer at the free volume interface and the planar layers at the solid interface. An increase in the size of this region does not alter the transition temperature. The shape of the liquid crystal molecules is dependent upon the degree of order and thus the nematic

  12. Characterising laser beams with liquid crystal displays

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2016-09-01

    Full Text Available the intensity, phase, wavefront, Poynting vector, and orbital angular momentum density of unknown optical fields. This measurement technique makes use of a single spatial light modulator (liquid crystal display), a Fourier transforming lens and detector (CCD...

  13. Liquid crystal television spatial light modulators

    Science.gov (United States)

    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.

  14. Thermal Conductivity and Liquid Crystal Thermometers.

    Science.gov (United States)

    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)

  15. Liquid crystal interfaces: Experiments, simulations and biosensors

    Science.gov (United States)

    Popov, Piotr

    Interfacial phenomena are ubiquitous and extremely important in various aspects of biological and industrial processes. For example, many liquid crystal applications start by alignment with a surface. The underlying mechanisms of the molecular organization of liquid crystals at an interface are still under intensive study and continue to be important to the display industry in order to develop better and/or new display technology. My dissertation research has been devoted to studying how complex liquid crystals can be guided to organize at an interface, and to using my findings to develop practical applications. Specifically, I have been working on developing biosensors using liquid-crystal/surfactant/lipid/protein interactions as well as the alignment of low-symmetry liquid crystals for potential new display and optomechanical applications. The biotechnology industry needs better ways of sensing biomaterials and identifying various nanoscale events at biological interfaces and in aqueous solutions. Sensors in which the recognition material is a liquid crystal naturally connects the existing knowledge and experience of the display and biotechnology industries together with surface and soft matter sciences. This dissertation thus mainly focuses on the delicate phenomena that happen at liquid interfaces. In the introduction, I start by defining the interface and discuss its structure and the relevant interfacial forces. I then introduce the general characteristics of biosensors and, in particular, describe the design of biosensors that employ liquid crystal/aqueous solution interfaces. I further describe the basic properties of liquid crystal materials that are relevant for liquid crystal-based biosensing applications. In CHAPTER 2, I describe the simulation methods and experimental techniques used in this dissertation. In CHAPTER 3 and CHAPTER 4, I present my computer simulation work. CHAPTER 3 presents insight of how liquid crystal molecules are aligned by

  16. Liquid crystal boojum-colloids

    International Nuclear Information System (INIS)

    Tasinkevych, M; Silvestre, N M; Telo da Gama, M M

    2012-01-01

    Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

  17. Liquid crystals of carbon nanotubes and graphene.

    Science.gov (United States)

    Zakri, Cécile; Blanc, Christophe; Grelet, Eric; Zamora-Ledezma, Camilo; Puech, Nicolas; Anglaret, Eric; Poulin, Philippe

    2013-04-13

    Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneously aligned nanotubes or graphene particles. Nevertheless, achieving high orientational order parameter and large monodomains remains a challenge. In addition, our restricted knowledge of the structure of the currently available materials is a limitation for fundamental studies and future applications. This paper presents recent methodologies that have been developed to achieve large monodomains of nematic liquid crystals. These allow quantification and increase of their order parameters. Nematic ordering provides an efficient way to prepare conductive films that exhibit anisotropic properties. In particular, it is shown how the electrical conductivity anisotropy increases with the order parameter of the nematic liquid crystal. The order parameter can be tuned by controlling the length and entanglement of the nanotubes. In the second part of the paper, recent results on graphene liquid crystals are reported. The possibility to obtain water-based liquid crystals stabilized by surfactant molecules is demonstrated. Structural and thermodynamic characterizations provide indirect but statistical information on the dimensions of the graphene flakes. From a general point of view, this work presents experimental approaches to optimize the use of nanocarbons as liquid crystals and provides new methodologies for the still challenging characterization of such materials.

  18. Liquid crystal polyester-carbon fiber composites

    Science.gov (United States)

    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.

  19. Applications of ionic liquids in polymer science and technology

    CERN Document Server

    2015-01-01

    This book summarizes the latest knowledge in the science and technology of ionic liquids and polymers in different areas. Ionic liquids (IL) are actively being investigated in polymer science and technology for a number of different applications. In the first part of the book the authors present the particular properties of ionic liquids as speciality solvents. The state-of-the art in the use of ionic liquids in polymer synthesis and modification reactions including polymer recycling is outlined. The second part focuses on the use of ionic liquids as speciality additives such as plasticizers or antistatic agents.  The third part examines the use of ionic liquids in the design of functional polymers (usually called polymeric ionic liquids (PIL) or poly(ionic liquids)). Many important applications in diverse scientific and industrial areas rely on these polymers, like polymer electrolytes in electrochemical devices, building blocks in materials science, nanocomposites, gas membranes, innovative anion sensitive...

  20. Liquid nitrogen dewar for protein crystal growth

    Science.gov (United States)

    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

  1. Key Developments in Ionic Liquid Crystals.

    Science.gov (United States)

    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?

  2. Key Developments in Ionic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Alexandra Alvarez Fernandez

    2016-05-01

    Full Text Available 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?

  3. Ionic Liquids in Polymer Design: From Energy to Health

    Science.gov (United States)

    2016-10-19

    of Papers published in non peer- reviewed journals: Final Report: Ionic Liquids in Polymer Design: From Energy to Health Report Title ACS Symposium...SECURITY CLASSIFICATION OF: ACS Symposium: Ionic Liquids in Polymer Design: From Energy to Health at Fall 2015 ACS Meeting in Boston, MA The...combination of ionic liquids and polymers has emerged as an active field of exploration in polymer science, where new materials have be realized for

  4. Crystallization of Polymers Investigated by Temperature-Modulated DSC

    OpenAIRE

    Maria Cristina Righetti

    2017-01-01

    The aim of this review is to summarize studies conducted by temperature-modulated differential scanning calorimetry (TMDSC) on polymer crystallization. This technique can provide several advantages for the analysis of polymers with respect to conventional differential scanning calorimetry. Crystallizations conducted by TMDSC in different experimental conditions are analysed and discussed, in order to illustrate the type of information that can be deduced. Isothermal and non-isothermal crystal...

  5. Characterising laser beams with liquid crystal displays

    Science.gov (United States)

    Dudley, Angela; Naidoo, Darryl; Forbes, Andrew

    2016-02-01

    We show how one can determine the various properties of light, from the modal content of laser beams to decoding the information stored in optical fields carrying orbital angular momentum, by performing a modal decomposition. Although the modal decomposition of light has been known for a long time, applied mostly to pattern recognition, we illustrate how this technique can be implemented with the use of liquid-crystal displays. We show experimentally how liquid crystal displays can be used to infer the intensity, phase, wavefront, Poynting vector, and orbital angular momentum density of unknown optical fields. This measurement technique makes use of a single spatial light modulator (liquid crystal display), a Fourier transforming lens and detector (CCD or photo-diode). Such a diagnostic tool is extremely relevant to the real-time analysis of solid-state and fibre laser systems as well as mode division multiplexing as an emerging technology in optical communication.

  6. Liquid Crystal photonic Bandgap Fiber Devices

    DEFF Research Database (Denmark)

    Wei, Lei

    In this Ph.D. thesis, an experimental investigation of liquid crystal photonic bandgap (LCPBG) fiber devices and applications is presented. Photonic crystal fibers (PCFs) consist of a cladding microstructure with periodic index variations and a core defined by a defect of the structure. The prese......In this Ph.D. thesis, an experimental investigation of liquid crystal photonic bandgap (LCPBG) fiber devices and applications is presented. Photonic crystal fibers (PCFs) consist of a cladding microstructure with periodic index variations and a core defined by a defect of the structure...... of each LCPBG fiber. Finally, the applications for LCPBG fiber devices based on the on-chip platform design have been demonstrated in realizing microwave true-time delay and creating an electrically tunable fiber laser. Referatet mailes...

  7. NMR studies of macroscopic and microscopic properties of liquid crystals

    International Nuclear Information System (INIS)

    Hughes, J.R.

    1998-03-01

    The work presented is concerned with studies of orientational order in liquid crystals and the behaviour of certain mesophases. The experimental technique used in common with all the work is deuterium NMR spectroscopy. Much of the work involves studies of the orientational order of deuteriated solute molecules dissolved in liquid crystal solvents. Chapter 1 gives an introduction to liquid crystals followed by a quantitative description of orientational order. Deuterium NMR in liquid crystals is described and an outline of the molecular field theory behind the orientational order of a rigid, biaxial solute in a uniaxial mesophase is given. In Chapter 2 a novel type of mesophase induction is studied using NMR, where a solute induces up to two extra phases in a discotic mesogen depending on its concentration. The purpose of this work is to try to gain an understanding into the mechanism of the phase induction involved. Chapter 3 is concerned primarily with the macroscopic behaviour of the nematic phase formed by a semi-rigid main-chain polymer in solution. Of particular interest is the study of the reorientation of the monodomain, once the director has been rotated with respect to the magnetic field of the NMR spectrometer. A mesogen which has been claimed to exhibit a biaxial nematic phase is studied in Chapter 4, in order to determine the symmetry of the phase using NMR. Finally, Chapter 5 deals with the differing behaviour of a liquid crystal monomer and its dimer dissolved in common nematic solvents in order to determine whether this agrees with molecular field theory. (author)

  8. Liquid crystal parameter analysis for tunable photonic bandgap fiber devices

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Wei, Lei

    2010-01-01

    We investigate the tunability of splay-aligned liquid crystals for the use in solid core photonic crystal fibers. Finite element simulations are used to obtain the alignment of the liquid crystals subject to an external electric field. By means of the liquid crystal director field the optical...

  9. Alignment structures in ferroelectric liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Islam, N.U

    1998-07-01

    Although for many years liquid crystals were of purely scientific interest, they have now become ubiquitous in everyday life. The use of the nematic liquid crystal phase in flat panel display applications has been the main factor in this popularity. However, with the advent of the SuperTwist Nematic (STN) device, the limits to which this phase could be exploited for display applications was perhaps reached. With the discovery by Clark et al. of the Surface Stabilised Ferroelectric Liquid Crystal (SSFLC) configuration, the possibility arose of using chiral smectic liquid crystals to create large area, passively addressed, fast switching, flat panel displays. Unfortunately, the structures that form within smectic liquid crystals, and the dynamics of the switching within these, are still not fully understood. In this thesis we address the former of these, making a detailed the study of the structures that form within tilted smectic liquid crystal devices. We present here the first complete theoretical and experimental study of various different ferroelectric liquid crystal materials, where we employed theoretical models based on a simple set of assumptions to understand the behaviour of a set of increasingly complex experimental systems. We started with the simplest of these, Freely Suspended Smectic Films (FSSFs) and then worked with progressively more realistic systems in the form of homeotropically, and later, homogeneously aligned liquid crystal cells. The equilibrium structures that form get particularly complex in the last case, taking the form of tilted and chevron layering structures. In each of these cases, the predictions of the modelling are compared with our experimental results. Further, we present here the first model of the chevron cusp that seeks to include the effects of biaxiality in the S{sub C} phase. We also present a model that seeks to analyse the stability of the chevron layering structure and its relationship with tilted layers. This includes

  10. Alignment structures in ferroelectric liquid crystals

    International Nuclear Information System (INIS)

    Islam, N.U.

    1998-01-01

    Although for many years liquid crystals were of purely scientific interest, they have now become ubiquitous in everyday life. The use of the nematic liquid crystal phase in flat panel display applications has been the main factor in this popularity. However, with the advent of the SuperTwist Nematic (STN) device, the limits to which this phase could be exploited for display applications was perhaps reached. With the discovery by Clark et al. of the Surface Stabilised Ferroelectric Liquid Crystal (SSFLC) configuration, the possibility arose of using chiral smectic liquid crystals to create large area, passively addressed, fast switching, flat panel displays. Unfortunately, the structures that form within smectic liquid crystals, and the dynamics of the switching within these, are still not fully understood. In this thesis we address the former of these, making a detailed the study of the structures that form within tilted smectic liquid crystal devices. We present here the first complete theoretical and experimental study of various different ferroelectric liquid crystal materials, where we employed theoretical models based on a simple set of assumptions to understand the behaviour of a set of increasingly complex experimental systems. We started with the simplest of these, Freely Suspended Smectic Films (FSSFs) and then worked with progressively more realistic systems in the form of homeotropically, and later, homogeneously aligned liquid crystal cells. The equilibrium structures that form get particularly complex in the last case, taking the form of tilted and chevron layering structures. In each of these cases, the predictions of the modelling are compared with our experimental results. Further, we present here the first model of the chevron cusp that seeks to include the effects of biaxiality in the S C phase. We also present a model that seeks to analyse the stability of the chevron layering structure and its relationship with tilted layers. This includes an

  11. Morphological control and polarization switching in polymer ...

    Indian Academy of Sciences (India)

    Liquid crystals dispersed in polymer systems constitute novel class of optical materials. The precise ... Polymer dispersed liquid crystals; nematic liquid crystal; ferroelectric liquid crystal; viscosity; drop- ... threshold voltage and the switching speed of the resulting ... crystal droplet size distribution and uniformity can be.

  12. Crystal and molecular simulation of high-performance polymers.

    Science.gov (United States)

    Colquhoun, H M; Williams, D J

    2000-03-01

    Single-crystal X-ray analyses of oligomeric models for high-performance aromatic polymers, interfaced to computer-based molecular modeling and diffraction simulation, have enabled the determination of a range of previously unknown polymer crystal structures from X-ray powder data. Materials which have been successfully analyzed using this approach include aromatic polyesters, polyetherketones, polythioetherketones, polyphenylenes, and polycarboranes. Pure macrocyclic homologues of noncrystalline polyethersulfones afford high-quality single crystals-even at very large ring sizes-and have provided the first examples of a "protein crystallographic" approach to the structures of conventionally amorphous synthetic polymers.

  13. Cross-Linked Liquid Crystalline Systems From Rigid Polymer Networks to Elastomers

    CERN Document Server

    Broer, Dirk

    2011-01-01

    With rapidly expanding interest in liquid crystalline polymers and elastomers among the liquid crystal community, researchers are currently exploring the wide range of possible application areas for these unique materials, including optical elements on displays, tunable lasers, strain gauges, micro-structures, and artificial muscles. Written by respected scientists from academia and industry around the world, who are not only active in the field but also well-known in more traditional areas of research, "Cross-Linked Liquid Crystalline Systems: From Rigid Polymer Networks to Elastomers&qu

  14. A theory of the nematic liquid crystals

    International Nuclear Information System (INIS)

    Hazoume, R.P.

    1980-09-01

    A theory of the nematic phase of liquid crystals is presented, taking explicit account of the geometry of the molecule. The three broad peaks of the neutron scattering structure factor are explained. Expressions of the order parameters (average value of Psub(2L)) are given and they can be extracted by comparison with scattering experiments. (author)

  15. Viscoelastic modes in chiral liquid crystals

    Indian Academy of Sciences (India)

    amit@fs.rri.local.net (Amit Kumar Agarwal)

    our studies on the viscoelastic modes of some chiral liquid crystals using dynamic light scattering. We discuss viscoelastic ... In the vicinity of the direct beam for a sample aligned in the Bragg mode and. 297 ... experimental investigations on these modes. Duke and Du ..... scattering volume is not true in practice. In an actual ...

  16. Nonlinear dynamical phenomena in liquid crystals

    International Nuclear Information System (INIS)

    Wang, X.Y.; Sun, Z.M.

    1988-09-01

    Because of the existence of the orientational order and anisotropy in liquid crystals, strong nonlinear phenomena and singular behaviors, such as solitary wave, transient periodic structure, chaos, fractal and viscous fingering, can be excited by a very small disturbance. These phenomena and behaviors are in connection with physics, biology and mathematics. 12 refs, 6 figs

  17. Nuclear magnetic resonance of liquid crystals

    National Research Council Canada - National Science Library

    Dong, Ronald Y

    1997-01-01

    ... operator in the small-step rotational diffusion model, while appendix D contains a list of liquid crystal abbreviations used in the book. A portion of this revision is carried out while the author is on leave at the University of Pisa. The author wishes to thank Professor C.A. Veracini for his kind hospitality and many authors for their preprints....

  18. Characteristics of bulk liquid undercooling and crystallization ...

    Indian Academy of Sciences (India)

    Characteristics of bulk liquid undercooling and crystallization behaviors ... cooling rate is fixed, the change of undercooling depends on the melt processing tem- ... solidification and a deep knowledge of undercooling of ... evolution, to obtain the information for the nucleation and ..... When cooling rate is fixed, the change.

  19. Supramolecular Liquid Crystal Displays Construction and Applications

    OpenAIRE

    Hoogboom, J.T.V.

    2004-01-01

    This thesis describes chemical methodologies, which can be ued to construct alignment layers for liquid crystal display purposes in a non-clean room environment, by making use of supramolecular chemistry. These techniques are subsequently used to attain control over LCD-properties, both pre- and post-LCD construction. In addition, the thesis describes the application of LCD technology in biosensors.

  20. Lasing in liquid crystal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)], E-mail: palto@online.ru

    2006-09-15

    A lasing condition is formulated in matrix form for optically anisotropic thin films. Lasing behavior of liquid-crystal slabs is analyzed. In particular, it is shown that if the spatial extent of a liquid crystal slab is much larger than its thickness, then laser emission is feasible not only along the normal to the slab, but also in the entire angular sector. The generated laser light can be observed experimentally as a spot or as concentric rings on a screen. The lowest lasing threshold corresponds to in-plane sliding modes leaking into the substrate. The feedback required for lasing is provided by reflection from the interfaces, rather than edges, of the liquid-crystal slab operating as a planar Fabry-Perot cavity. For cholesteric liquid crystals, it is shown that energy loss to the sliding modes leaking into the substrates and escaping through their edges is a key factor that limits the efficiency of band-edge emission along the normal to the slab.

  1. Some problems of the statistical theory of polymeric lyotropic liquid crystals

    International Nuclear Information System (INIS)

    Grosberg, A.Yu.; Khokhlov, A.R.

    1980-06-01

    In this article we consider some topics of the statistical physics of liquid-crystalline phase in the solutions of stiff chain macromolecules. Among these topics are: the problem of the phase diagram for the liquid-crystalline transition in the solutions of completely stiff macromolecules (rigid rods); conditions of formation of the liquid-crystalline phase in the solutions of semiflexible macromolecules; possibility of the intramolecular liquid-crystalline ordering in semiflexible macromolecules; structure of intramolecular liquid crystals and dependence of the properties of the liquid-crystalline phase on the microstructure of the polymer chain. (author)

  2. Recent advances in IR liquid crystal spatial light modulators

    Science.gov (United States)

    Peng, Fenglin; Twieg, Robert J.; Wu, Shin-Tson

    2015-09-01

    Liquid crystal (LC) is an amazing class of electro-optic media; its applications span from visible to infrared, millimeter wave, and terahertz regions. In the visible and short-wavelength infrared (SWIR) regions, most LCs are highly transparent. However, to extend the electro-optic application of LCs into 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. In the MWIR and LWIR regions, several fundamental molecular vibration bands and overtones exist, which contribute to high absorption loss. The absorbed light turns to heat and then alters the birefringence locally, which in turns causes spatially non-uniform phase modulation. To suppress the optical loss, several approaches have been investigated: (1) Employing thin cell gap by choosing a high birefringence LC mixture; (2) Shifting the absorption bands outside the spectral region of interest by deuteration, fluorination, or chlorination; (3) Reducing the overtone absorption by using a short alkyl chain. In this paper, we report some recently developed chlorinated LC compounds and mixtures with low absorption loss in the SWIR and MWIR regions. To achieve fast response time, we demonstrated a polymer network liquid crystal with 2π phase change at MWIR and response time less than 5 ms. Approaches to extend such a liquid crystal spatial light modulator to long-wavelength infrared will be discussed.

  3. Thermo-, photo-, and mechano-responsive liquid crystal networks enable tunable photonic crystals.

    Science.gov (United States)

    Akamatsu, N; Hisano, K; Tatsumi, R; Aizawa, M; Barrett, C J; Shishido, A

    2017-10-25

    Tunable photonic crystals exhibiting optical properties that respond reversibly to external stimuli have been developed using liquid crystal networks (LCNs) and liquid crystal elastomers (LCEs). These tunable photonic crystals possess an inverse opal structure and are photo-responsive, but circumvent the usual requirement to contain dye molecules in the structure that often limit their applicability and cause optical degradation. Herein, we report tunable photonic crystal films that reversibly tune the reflection peak wavelength under thermo-, photo- and mechano-stimuli, through bilayering a stimuli-responsive LCN including azobenzene units with a colourless inverse opal film composed of non-responsive, flexible durable polymers. By mechanically deforming the azobenzene containing LCN via various stimuli, the reflection peak wavelength from the bilayered film assembly could be shifted on demand. We confirm that the reflection peak shift occurs due to the deformation of the stimuli-responsive layer propagating towards and into the inverse opal layer to change its shape in response, and this shift behaviour is repeatable without optical degradation.

  4. Thin liquid films dewetting and polymer flow

    CERN Document Server

    Blossey, Ralf

    2012-01-01

    This book is a treatise on the thermodynamic and dynamic properties of thin liquid films at solid surfaces and, in particular, their rupture instabilities. For the quantitative study of these phenomena, polymer thin films haven proven to be an invaluable experimental model system.   What is it that makes thin film instabilities special and interesting, warranting a whole book? There are several answers to this. Firstly, thin polymeric films have an important range of applications, and with the increase in the number of technologies available to produce and to study them, this range is likely to expand. An understanding of their instabilities is therefore of practical relevance for the design of such films.   Secondly, thin liquid films are an interdisciplinary research topic. Interdisciplinary research is surely not an end to itself, but in this case it leads to a fairly heterogeneous community of theoretical and experimental physicists, engineers, physical chemists, mathematicians and others working on the...

  5. Current progress and technical challenges of flexible liquid crystal displays

    Science.gov (United States)

    Fujikake, Hideo; Sato, Hiroto

    2009-02-01

    We focused on several technical approaches to flexible liquid crystal (LC) display in this report. We have been developing flexible displays using plastic film substrates based on polymer-dispersed LC technology with molecular alignment control. In our representative devices, molecular-aligned polymer walls keep plastic-substrate gap constant without LC alignment disorder, and aligned polymer networks create monostable switching of fast-response ferroelectric LC (FLC) for grayscale capability. In the fabrication process, a high-viscosity FLC/monomer solution was printed, sandwiched and pressed between plastic substrates. Then the polymer walls and networks were sequentially formed based on photo-polymerization-induced phase separation in the nematic phase by two exposure processes of patterned and uniform ultraviolet light. The two flexible backlight films of direct illumination and light-guide methods using small three-primary-color light-emitting diodes were fabricated to obtain high-visibility display images. The fabricated flexible FLC panels were driven by external transistor arrays, internal organic thin film transistor (TFT) arrays, and poly-Si TFT arrays. We achieved full-color moving-image displays using the flexible FLC panel and the flexible backlight film based on field-sequential-color driving technique. Otherwise, for backlight-free flexible LC displays, flexible reflective devices of twisted guest-host nematic LC and cholesteric LC were discussed with molecular-aligned polymer walls. Singlesubstrate device structure and fabrication method using self-standing polymer-stabilized nematic LC film and polymer ceiling layer were also proposed for obtaining LC devices with excellent flexibility.

  6. Enhancement of polymer dye lasers by multifunctional photonic crystal lattice

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Xiao, Sanshui; Mortensen, Asger

    2009-01-01

    The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser.......The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser....

  7. Application of liquid crystals in thermal nondestructive evaluation

    International Nuclear Information System (INIS)

    Panakal, J.P.; Mukherjee, S.; Ghosh, J.K.

    1983-01-01

    In recent years, thermal nondestructive evaluation using Cholestric liquid crystals have found wide applications in industry. Thermography using Cholesteric liquid crystals can be used for detection of nonbonds in metallic composites, hot spots in electronic circuits and preliminary examination of welded pressure vessels. This paper presents the results of experiments on thermography of components using encapsulated liquid crystals. (author)

  8. Piezoelectricity of a ferroelectric liquid crystal with a glass transition.

    Science.gov (United States)

    Jákli, A; Tóth-Katona, T; Scharf, T; Schadt, M; Saupe, A

    2002-07-01

    Pressure-electric (hydrostatic piezoelectric) measurements are reported on bookshelf textures of a ferroelectric smectic-C (Sm C*) liquid crystal with a glass transition. The continuous variation of a partially fluid state to the solid glass enables one to trace how the piezoelectric effect depends on the consistency of the material. It was observed that in the Sm C* samples with poled glass the piezoelectric constants are comparable to conventional piezoelectric crystals and poled piezoelectric polymers. This implies their application possibilities. The magnitude of the piezoelectric constant in the glassy state depends very much on the poling conditions. The studies indicate that there are two counteracting effects, which cancel each other out in the Sm C* phase near the glass transition. Our analysis indicates that the pressure-induced director tilt change has a dominating effect both in the fluid and the glassy Sm C* states.

  9. TSD current investigations in pristine and 100 MeV Ni-ion irradiated PET/0.3 PHB polymer liquid crystal

    International Nuclear Information System (INIS)

    Quamara, J.K.; Singh, Nafa; Prabhavathi, T.; Sridharbabu, Y.

    2002-01-01

    The dielectric relaxations investigations have been carried out in pristine as well as 100 MeV 58 Ni ion irradiated (PELLETRON facility, Nuclear Science Center, New Delhi) PET/0.3 PHB PLC samples. Thermally stimulated depolarization current technique (TSDC) has been employed for this purpose. The plc samples were polarized at 180 deg C under the influence of various polarizing fields following the usual method. Three current maxima are observed around 35deg, 120deg and 155degC which are ascribed as β', β and α transitions. These transitions are mainly due to the fast reacting dipoles of PHB regions, dipolar character due to carbonyl groups in PET rich phase and to the cold crystallization of PET. The results confirm the biphasic nature of this plc. The high energy irradiation influences both β and α transitions. Increase in fluence shifts the β peak as well as α peak towards higher temperature. This confirms that high energy irradiation has not only affected the carbonyl groups but has created new phases. (author)

  10. Reflective and transflective liquid crystal displays

    Science.gov (United States)

    Zhou, Fushan

    Recently transflective liquid crystal displays (LCD) received a lot of attention. A transflective display has a transmissive mode and a reflective mode. It combines the high contrast, high brightness of the transmissive mode with energy-saving of reflective mode and has good performance in various illumination conditions. However, state-of-the-art transflective displays have problems such as different electro-optical properties, difficulty in compatibility and optimization of both modes, low efficiency of light utilization, and complexity in structure. This dissertation focuses on finding new designs of transflective displays that address those problems. One way to do this is to study film compensation of LCD. We first studied film compensation of bistable twisted nematic (BTN) LCD. Starting form the reduced (3x3) Mueller matrices, we derived and simplified the conditions that film compensated BTN can be optimized. Based on these relations, electro-optical properties of some particular configurations, and designs of transflective BTN with high brightness and contrast were given. To confirm and get a better understanding of the results, we use the Poincare sphere to analyze film compensated BTN. The key to this approach is the existence of "fixed points". Compared with the matrix approach, this approach is more simple, elegant, and efficient. We then generalized the Poincare sphere approach to a universal approach of LCD. We applied the universal approach to film compensation of ECB and IPS, and the design of achromatic birefringent filters. We also give two more new designs of transflective displays. In the first design, a dichroic mirror is used to split the visible spectrum into two parts used in transmissive and reflective modes, respectively. Both modes can be optimized. It has a simple structure and good light utilization. A design for a full-color transflective display with good performance is also given. In the second design, each pixel is divided into two

  11. The sweet world of liquid crystals : The synthesis of non-amphiphilic carbohydrate-derived liquid crystals

    NARCIS (Netherlands)

    Smits, E

    1998-01-01

    The research in carbohydrate-derived liquid crystals was initiated by a review article by Jeffrey in 1986. This is rather late if one considers that the research on liquid crystals underwent a revival already in the 1960s after the discovery of the liquid crystal display (LCD). Carbohydrates were

  12. Smart lighting using a liquid crystal modulator

    Science.gov (United States)

    Baril, Alexandre; Thibault, Simon; Galstian, Tigran

    2017-08-01

    Now that LEDs have massively invaded the illumination market, a clear trend has emerged for more efficient and targeted lighting. The project described here is at the leading edge of the trend and aims at developing an evaluation board to test smart lighting applications. This is made possible thanks to a new liquid crystal light modulator recently developed for broadening LED light beams. The modulator is controlled by electrical signals and is characterized by a linear working zone. This feature allows the implementation of a closed loop control with a sensor feedback. This project shows that the use of computer vision is a promising opportunity for cheap closed loop control. The developed evaluation board integrates the liquid crystal modulator, a webcam, a LED light source and all the required electronics to implement a closed loop control with a computer vision algorithm.

  13. Thermal diode made by nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Djair, E-mail: djfmelo@gmail.com [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Fernandes, Ivna [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Moraes, Fernando [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa, PB (Brazil); Departamento de Física, Universidade Federal Rural de Pernambuco, 52171-900 Recife, PE (Brazil); Fumeron, Sébastien [Institut Jean Lamour, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre les Nancy (France); Pereira, Erms [Escola Politécnica de Pernambuco, Universidade de Pernambuco, Rua Benfíca, 455, Madalena, 50720-001 Recife, PE (Brazil)

    2016-09-07

    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. - Highlights: • An escaped radial disclination as a thermal diode made by a nematic liquid crystal. • Rectifying effects comparable to those caused by carbon and boron nitride nanotubes. • Thermal rectification increasing with radius and decreasing with height of the tube. • Asymmetric BCs cause rectification from the spatial asymmetry produced by the escape. • Symmetric BCs provide rectifications smaller than those yields by asymmetric BCs.

  14. Calculation of Optical Parameters of Liquid Crystals

    Science.gov (United States)

    Kumar, A.

    2007-12-01

    Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.

  15. Terahertz spectroscopic analysis of crystal orientation in polymers

    Science.gov (United States)

    Azeyanagi, Chisato; Kaneko, Takuya; Ohki, Yoshimichi

    2018-05-01

    Terahertz time-domain spectroscopy (THz-TDS) is attracting keen attention as a new spectroscopic tool for characterizing various materials. In this research, the possibility of analyzing the crystal orientation in a crystalline polymer by THz-TDS is investigated by measuring angle-resolved THz absorption spectra for sheets of poly(ethylene terephthalate), poly(ethylene naphthalate), and poly(phenylene sulfide). The resultant angle dependence of the absorption intensity of each polymer is similar to that of the crystal orientation examined using pole figures of X-ray diffraction. More specifically, THz-TDS can indicate the alignment of molecules in polymers.

  16. Biaxial nematic liquid crystals theory, simulation and experiment

    CERN Document Server

    Luckhurst, Geoffrey R

    2015-01-01

    Liquid Crystals are a state of matter that have properties between those of conventional liquid and those of a solid crystal. Thermotropic liquid crystals react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Since the accidental discovery of the chiral nematic (ordered) phase in 1888 many liquid crystal phases have been found, sometimes by chance and sometimes by design. The existence of one such phase was predicted by Freiser in 197

  17. Ultrabroadband terahertz spectroscopy of a liquid crystal

    DEFF Research Database (Denmark)

    Vieweg, N.; Fischer, B. M.; Reuter, M.

    2012-01-01

    Liquid crystals (LCs) are becoming increasingly important for applications in the terahertz frequency range. A detailed understanding of the spectroscopic parameters of these materials over a broad frequency range is crucial in order to design customized LC mixtures for improved performance. We p...... show that the spectra are dominated by multiple strong spectral features mainly at frequencies above 4 THz, originating from intramolecular vibrational modes of the weakly LC molecules....

  18. Nanoparticle guests in lyotropic liquid crystals

    Science.gov (United States)

    Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

    In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

  19. Liquid Crystal Microlenses for Autostereoscopic Displays

    Directory of Open Access Journals (Sweden)

    José Francisco Algorri

    2016-01-01

    Full Text Available Three-dimensional vision has acquired great importance in the audiovisual industry in the past ten years. Despite this, the first generation of autostereoscopic displays failed to generate enough consumer excitement. Some reasons are little 3D content and performance issues. For this reason, an exponential increase in three-dimensional vision research has occurred in the last few years. In this review, a study of the historical impact of the most important technologies has been performed. This study is carried out in terms of research manuscripts per year. The results reveal that research on spatial multiplexing technique is increasing considerably and today is the most studied. For this reason, the state of the art of this technique is presented. The use of microlenses seems to be the most successful method to obtain autostereoscopic vision. When they are fabricated with liquid crystal materials, extended capabilities are produced. Among the numerous techniques for manufacturing liquid crystal microlenses, this review covers the most viable designs for its use in autostereoscopic displays. For this reason, some of the most important topologies and their relation with autostereoscopic displays are presented. Finally, the challenges in some recent applications, such as portable devices, and the future of three-dimensional displays based on liquid crystal microlenses are outlined.

  20. Adsorption phenomena and anchoring energy in nematic liquid crystals

    CERN Document Server

    Barbero, Giovanni

    2005-01-01

    Despite the large quantity of phenomenological information concerning the bulk properties of nematic phase liquid crystals, little is understood about the origin of the surface energy, particularly the surface, interfacial, and anchoring properties of liquid crystals that affect the performance of liquid crystal devices. Self-contained and unique, Adsorption Phenomena and Anchoring Energy in Nematic Liquid Crystals provides an account of new and established results spanning three decades of research into the problems of anchoring energy and adsorption phenomena in liquid crystals.The book contains a detailed discussion of the origin and possible sources of anchoring energy in nematic liquid crystals, emphasizing the dielectric contribution to the anchoring energy in particular. Beginning with fundamental surface and anchoring properties of liquid crystals and the definition of the nematic phase, the authors explain how selective ion adsorption, dielectric energy density, thickness dependence, and bias voltage...

  1. Guided mode studies of smectic liquid crystals

    International Nuclear Information System (INIS)

    Hodder, B.

    2000-03-01

    Recently there has been considerable interest in the use of ferroelectric liquid crystals in low power, fast switching display devices. At present the voltage switching process in surface stabilised ferroelectric liquid crystal (SSFLC) devices is not fully understood and a convenient theory for such cells has yet to be found. It is the primary aim of this work to characterise the optic tensor configuration (director profile) in thin cells (∼ 3.5 μm) containing ferroelectric liquid crystal (FLC) material. These results form a benchmark by which continuum theories may be tested. Polarised microscopy is, perhaps, the most common optical probe of liquid crystal cells. It should be appreciated that this technique is fundamentally limited, as the results are deduced from an integrated optical response of any given cell, and cannot be used to spatially resolve details of the director profile through the cell. The guided mode techniques used in this study are the primary non-integral probe and enable detailed spatial resolution of the director profile within liquid crystal cells. Analysis of guided mode data from cells containing homeotropically aligned FLC reveals the temperature dependence of the optical biaxiality and cone angle for a 40% chiral mixture of the commercially available FLC SCE8*. From these optical biaxiality measurements the temperature dependence of the biaxial order parameter C is determined. Guided mode studies of cells containing homogeneously aligned SCE8* (the conventional alignment for SSFLC devices) reveal the 0V equilibrium director profile from which a cone and chevron model is constructed. Subsequent studies of voltage induced elastic deformations of the director profile are presented and compared with a single elastic constant continuum theory which is shown to be inadequate. Optical guided mode techniques are not directly sensitive to the smectic layer configuration but X-ray scattering is. Here, for the first time, results are presented

  2. Alcohol-responsive, hydrogen-bonded, cholesteric liquid-crystal networks

    NARCIS (Netherlands)

    Chang, C.; Bastiaansen, C.W.M.; Broer, D.J.; Kuo, H.-L.

    2012-01-01

    Hydrogen-bridged, cholesteric liquid-crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed

  3. Permanent Electric Dipole-Dipole Interactions in Lyotropic Polypeptide Liquid Crystals

    OpenAIRE

    MORI, Norio; Norio, MORI; Research Associate, Department of Industrial Chemistry

    1981-01-01

    The interaction energy between two adjacent α-helical molecules was calculated taking into account for permanent electric dipoles locating orl the helical core of a polymer mainchain in order to explain the cholesteric structure of lyotropic polypeptide liquid crystals. It was concluded that the dipole-dipole interactions were responsible for the formation of the cholesteric structure.

  4. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    Science.gov (United States)

    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

  5. Relation between anchorings of liquid crystals and conformation changes in aligning agents by the Langmuir-Blodgett film technique investigation

    International Nuclear Information System (INIS)

    Zhu, Y.; Lu, Z.; Wei, Y.

    1995-01-01

    The anchoring direction of liquid crystals on a solid substrate surface depends upon many parameters characterizing the liquid-crystal--substrate interface, a variation of which may change this anchoring direction leading to the so-called anchoring transition. Here, based on the Langmuir-Blodgett film technique, we present two model systems to study the relation between anchoring directions and the conformation changes in aligning agents. A double-armed crown ether liquid crystal and a side chain polymer liquid crystal at an air-water interface both show phase transitions, accompanied by conformation changes. However, when the monolayers in different phases were transferred onto solid substrates to orient liquid crystals, we found that for the crown ether material the conformation change can alter the anchoring of liquid crystals between homeotropic and homogeneous alignments, while for the polymer liquid crystal, despite the conformation changes, the liquid crystals can only be aligned homeotropically. The involved mechanisms were briefly discussed in terms of the Landau-type phenomenological theory

  6. Electrically tunable liquid crystal photonic bandgap fiber laser

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei

    2010-01-01

    We demonstrate electrical tunability of a fiber laser by using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an al...

  7. Macro-Micro Simulation for Polymer Crystallization in Couette Flow

    Directory of Open Access Journals (Sweden)

    Chunlei Ruan

    2017-12-01

    Full Text Available Polymer crystallization in manufacturing is a process where quiescent crystallization and flow-induced crystallization coexists, and heat/mass transfer on a macroscopic level interacts with crystal morphology evolution on a microscopic level. Previous numerical studies on polymer crystallization are mostly concentrated at a single scale; they only calculate macroscale parameters, e.g., temperature and relative crystallinity, or they only predict microstructure details, e.g., crystal morphology and mean size of crystals. The multi-scale numerical works that overcome these disadvantages are unfortunately based on quiescent crystallization, in which flow effects are neglected. The objective of this work is to build up a macro-micro model and a macro-micro algorithm to consider both the thermal and flow effects on the crystallization. Our macro-micro model couples two parts: mass and heat transfer of polymeric flow at the macroscopic level, and nucleation and growth of spherulites and shish-kebabs at the microscopic level. Our macro-micro algorithm is a hybrid finite volume/Monte Carlo method, in which the finite volume method is used at the macroscopic level to calculate the flow and temperature fields, while the Monte Carlo method is used at the microscopic level to capture the development of spherulites and shish-kebabs. The macro-micro model and the macro-micro algorithm are applied to simulate polymer crystallization in Couette flow. The effects of shear rate, shear time, and wall temperature on the crystal morphology and crystallization kinetics are also discussed.

  8. Synthesis and Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 5. Influence of Mesogenic Group and Interconnecting Group on the Thermotropic Behavior of the Resulting Polymers

    Science.gov (United States)

    1992-07-22

    Scheme I. The first nucleophilic displacement of halide of an n-haloalkan-l-ol with 4-cyano-4’-hydroxybiphenyl employed potassium carbonate in...21 𔃼 polysiloxanes, 23.24 and polyacrylates . 2- All these polymers exhibit an odd-even effect. If one considers the total number of atoms between the...0.019 mol) and 4’-methoxy-4-hydroxybiphenyl (4.0g, 0.020 tool) were heated at 100°C in 40 mL of dimethylformamide in the presence of potassium carbonate

  9. Invited review liquid crystal models of biological materials and silk spinning.

    Science.gov (United States)

    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. Copyright © 2011 Wiley Periodicals, Inc.

  10. Crystallization of Polymers Investigated by Temperature-Modulated DSC

    Directory of Open Access Journals (Sweden)

    Maria Cristina Righetti

    2017-04-01

    Full Text Available The aim of this review is to summarize studies conducted by temperature-modulated differential scanning calorimetry (TMDSC on polymer crystallization. This technique can provide several advantages for the analysis of polymers with respect to conventional differential scanning calorimetry. Crystallizations conducted by TMDSC in different experimental conditions are analysed and discussed, in order to illustrate the type of information that can be deduced. Isothermal and non-isothermal crystallizations upon heating and cooling are examined separately, together with the relevant mathematical treatments that allow the evolution of the crystalline, mobile amorphous and rigid amorphous fractions to be determined. The phenomena of ‘reversing’ and ‘reversible‘ melting are explicated through the analysis of the thermal response of various semi-crystalline polymers to temperature modulation.

  11. Liquid metals as electrodes in polymer light emitting diodes

    NARCIS (Netherlands)

    Andersson, G.G.; Gommans, H.H.P.; Denier van der Gon, A.W.; Brongersma, H.H.

    2003-01-01

    We demonstrate that liquid metals can be used as cathodes in light emitting diodes (pLEDs). The main difference between the use of liquid cathodes and evaporated cathodes is the sharpness of the metal–polymer interface. Liquid metal cathodes result in significantly sharper metal–organic interfaces

  12. Liquid crystal-based hydrophone arrays

    Science.gov (United States)

    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.

  13. Liquid Photonic Crystals for Mesopore Detection.

    Science.gov (United States)

    Zhu, Biting; Fu, Qianqian; Chen, Ke; Ge, Jianping

    2018-01-02

    Nitrogen adsorption-desorption for mesopore characterization requires the using of expensive instrumentation, time-consuming processes, and the consumption of liquid nitrogen. Herein, a new method is developed to measure the pore parameters through mixing a mesoporous substance with a supersaturated SiO 2 colloidal solution at different temperatures, and subsequent rapid measurement of reflection changes of the precipitated liquid photonic crystals. The pore volumes and diameters of mesoporous silica were measured according to the positive correlation between unit mass reflection change (Δλ/m) and pore volume (V), and the negative correlation between average absorption temperature (T) and pore diameter (D). This new approach may provide an alternative method for fast, convenient and economical characterization of mesoporous materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Control of liquid crystal molecular orientation using ultrasound vibration

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Satoki [Faculty of Life and Medical Sciences, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321 (Japan); Wave Electronics Research Center, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321 (Japan); Koyama, Daisuke; Matsukawa, Mami [Wave Electronics Research Center, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321 (Japan); Faculty of Science and Engineering, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321 (Japan); Shimizu, Yuki; Emoto, Akira [Faculty of Science and Engineering, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321 (Japan); Nakamura, Kentaro [Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259-R2-26, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan)

    2016-03-07

    We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5–25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distribution of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.

  15. Modified dynamical equation for dye doped nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Manohar, Rajiv, E-mail: rajlu1@rediffmail.co [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India); Misra, Abhishek Kumar; Srivastava, Abhishek Kumar [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India)

    2010-04-15

    Dye doped liquid crystals show changed dielectric properties in comparison to pure liquid crystals. These changes are strongly dependent on the concentration of dye. In the present work we have measured dielectric properties of standard nematic liquid crystals E-24 and its two guest host mixtures of different concentrations with Anthraquinone dye D5. The experimental results are fitted using linear response and in the light of this we have proposed some modifications in the dynamical equation for the nematic liquid crystals by introducing two new variables as dye concentration coefficients. The limitations of the proposed equation in high temperature range have also been discussed. With the help of the proposed dynamical equation for the guest-host liquid crystals (GHLCs) it is possible to predict the various parameters like rotational viscosity, dielectric anisotropy and relaxation time for GHLCs at other concentrations of dye in liquid crystals theoretically.

  16. Molecular engineering of chiral colloidal liquid crystals using DNA origami

    Science.gov (United States)

    Siavashpouri, Mahsa; Wachauf, Christian H.; Zakhary, Mark J.; Praetorius, Florian; Dietz, Hendrik; Dogic, Zvonimir

    2017-08-01

    Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials.

  17. Bistable cholesteric liquid crystal light shutter with multielectrode driving.

    Science.gov (United States)

    Li, Cheng-Chang; Tseng, Heng-Yi; Pai, Tsung-Wei; Wu, Yu-Ching; Hsu, Wen-Hao; Jau, Hung-Chang; Chen, Chun-Wei; Lin, Tsung-Hsien

    2014-08-01

    An electrically activated bistable light shutter that exploits polymer-stabilized cholesteric liquid crystal film was developed. Under double-sided three-terminal electrode driving, the device can be bistable and switched between focal conic and homeotropic textures with a uniform in-plane and vertical electrical field. The transparent state with a transmittance of 80% and the opaque/scattering state with a transmittance of 13% can be realized without any optical compensation film, and each can be simply switched to the other by applying a pulse voltage. Also, gray-scale selection can be performed by varying the applied voltage. The designed energy-saving bistable light shutter can be utilized to preserve privacy and control illumination and the flow of energy.

  18. Ultraweak azimuthal anchoring of a nematic liquid crystal on a planar orienting photopolymer

    International Nuclear Information System (INIS)

    Nespoulous, Mathieu; Blanc, Christophe; Nobili, Maurizio

    2007-01-01

    The search of weak anchoring is an important issue for a whole class of liquid crystal displays. In this paper we present an orienting layer showing unreached weak planar azimuthal anchoring for 4-n-pentyl-4 ' -cyanobiphenyl nematic liquid crystal (5CB). Azimuthal extrapolation lengths as large as 80 μm are easily obtained. Our layers are made with the commercial photocurable polymer Norland optical adhesive 60. The anisotropy of the film is induced by the adsorption of oriented liquid crystal molecules under a 2 T magnetic field applied parallel to the surfaces. We use the width of surface π-walls and a high-field electro-optical method to measure, respectively, the azimuthal and the zenithal anchorings. The azimuthal anchoring is extremely sensitive to the ultraviolet (UV) dose and it also depends on the magnetic field application duration. On the opposite, the zenithal anchoring is only slightly sensitive to the preparation parameters. All these results are discussed in terms of the adsorption/desorption mechanisms of the liquid crystal molecules on the polymer layer and of the flexibility of the polymer network

  19. Multistability in planar liquid crystal wells

    KAUST Repository

    Luo, Chong; Majumdar, Apala; Erban, Radek

    2012-01-01

    A planar bistable liquid crystal device, reported in Tsakonas, is modeled within the Landau-de Gennes theory for nematic liquid crystals. This planar device consists of an array of square micrometer-sized wells. We obtain six different classes of equilibrium profiles and these profiles are classified as diagonal or rotated solutions. In the strong anchoring case, we propose a Dirichlet boundary condition that mimics the experimentally imposed tangent boundary conditions. In the weak anchoring case, we present a suitable surface energy and study the multiplicity of solutions as a function of the anchoring strength. We find that diagonal solutions exist for all values of the anchoring strength W≥0, while rotated solutions only exist for W≥W c>0, where W c is a critical anchoring strength that has been computed numerically. We propose a dynamic model for the switching mechanisms based on only dielectric effects. For sufficiently strong external electric fields, we numerically demonstrate diagonal-to-rotated and rotated-to-diagonal switching by allowing for variable anchoring strength across the domain boundary. © 2012 American Physical Society.

  20. Multistability in planar liquid crystal wells

    KAUST Repository

    Luo, Chong

    2012-06-08

    A planar bistable liquid crystal device, reported in Tsakonas, is modeled within the Landau-de Gennes theory for nematic liquid crystals. This planar device consists of an array of square micrometer-sized wells. We obtain six different classes of equilibrium profiles and these profiles are classified as diagonal or rotated solutions. In the strong anchoring case, we propose a Dirichlet boundary condition that mimics the experimentally imposed tangent boundary conditions. In the weak anchoring case, we present a suitable surface energy and study the multiplicity of solutions as a function of the anchoring strength. We find that diagonal solutions exist for all values of the anchoring strength W≥0, while rotated solutions only exist for W≥W c>0, where W c is a critical anchoring strength that has been computed numerically. We propose a dynamic model for the switching mechanisms based on only dielectric effects. For sufficiently strong external electric fields, we numerically demonstrate diagonal-to-rotated and rotated-to-diagonal switching by allowing for variable anchoring strength across the domain boundary. © 2012 American Physical Society.

  1. Electrically Tuned Microwave Devices Using Liquid Crystal Technology

    Directory of Open Access Journals (Sweden)

    Pouria Yaghmaee

    2013-01-01

    Full Text Available An overview of liquid crystal technology for microwave and millimeter-wave frequencies is presented. The potential of liquid crystals as reconfigurable materials arises from their ability for continuous tuning with low power consumption, transparency, and possible integration with printed and flexible circuit technologies. This paper describes physical theory and fundamental electrical properties arising from the anisotropy of liquid crystals and overviews selected realized liquid crystal devices, throughout four main categories: resonators and filters, phase shifters and delay lines, antennas, and, finally, frequency-selective surfaces and metamaterials.

  2. Liquid crystal templating as an approach to spatially and temporally organise soft matter.

    Science.gov (United States)

    van der Asdonk, Pim; Kouwer, Paul H J

    2017-10-02

    Chemistry quickly moves from a molecular science to a systems science. This requires spatial and temporal control over the organisation of molecules and molecular assemblies. Whilst Nature almost by default (transiently) organises her components at multiple different length scales, scientists struggle to realise even relatively straightforward patterns. In the past decades, supramolecular chemistry has taught us the rules to precisely engineer molecular assembly at the nanometre scale. At higher length scales, however, we are bound to top-down nanotechnology techniques to realise order. For soft, biological matter, many of these top-down techniques come with serious limitations since the molecules generally show low susceptibilities to the applied stimuli. A new method is based on liquid crystal templating. In this hierarchical approach, a liquid crystalline host serves as the scaffold to order polymers or assemblies. Being a liquid crystal, the host material can be ordered at many different length scales and on top of that, is highly susceptible to many external stimuli, which can even be used to manipulate the liquid crystal organisation in time. As a result, we anticipate large control over the organisation of the materials inside the liquid crystalline host. Recently, liquid crystal templating was also realised in water. This suddenly makes this tool highly applicable to start organising more delicate biological materials or even small organisms. We review the scope and limitations of liquid crystal templating and look out to where the technique may lead us.

  3. Liquid crystalline thermosetting polymers as protective coatings for aerospace

    NARCIS (Netherlands)

    Guerriero, G.L.

    2012-01-01

    Environmental regulations are driving the development of new aerospace coating systems, mainly to eliminate chromates and reduce volatile organic compound (VOC) emissions. Among the various potential options for new coating materials, liquid crystalline polymers (LCPs) are attractive due to their

  4. Chromatic dispersion of liquid crystal infiltrated capillary tubes and photonic crystal fibers

    DEFF Research Database (Denmark)

    Rasmussen, Per Dalgaard; Lægsgaard, Jesper; Bang, Ole

    2006-01-01

    We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic...

  5. Shear Strength of Stabilized Kaolin Soil Using Liquid Polymer

    Science.gov (United States)

    Azhar, A. T. S.; Fazlina, M. I. S.; Nizam, Z. M.; Fairus, Y. M.; Hakimi, M. N. A.; Riduan, Y.; Faizal, P.

    2017-08-01

    The purpose of this research is to investigate the suitability of polymer in soil stabilization by examining its strength to withstand compressive strength. Throughout this research study, manufactured polymer was used as a chemical liquid soil stabilizer. The liquid polymer was diluted using a proposed dilution factor of 1 : 3 (1 part polymer: 3 parts distilled water) to preserve the workability of the polymer in kaolin mixture. A mold with a diameter of 50 mm and a height of 100 mm was prepared. Kaolin soil was mixed with different percentages of polymer from 10%, 15%, 20%, 25%, 30% and 35% of the mass of the kaolin clay sample. Kaolin mixtures were tested after a curing period of 3 days, 7 days, 14 days and 28 days respectively. The physical properties were determined by conducting a moisture content test and Atterberg limit test which comprise of liquid limit, plastic limit and shrinkage limit. Meanwhile, the mechanical properties of the soil shear strength were identified through an unconfined compressive strength (UCS) test. Stabilized kaolin soil showed the highest compressive strength value when it was mixed with 35% of polymer compared to other percentages that marked an increment in strength which are 45.72% (3 days), 67.57% (7 days), 81.73% (14 days) and 77.84% (28 days). Hence, the most effective percentage of liquid polymer which should be used to increase the strength of kaolin soil is 35%.

  6. Liquid Core Waveguides by UV Modification of Nanoporous Polymer

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Gopalakrishnan, Nimi; Sagar, Kaushal Shashikant

    2011-01-01

    Liquid core waveguides are fabricated from a self-assembled nanoporous polymer, with a porosity of 40%. The high porosity results in an effective refractive index of 1.26 for visible light, i.e. below the refractive index of aqueous solutions. However, since the polymer is hydrophobic, fluids...

  7. Polymers selection for a liquid inoculant of Azospirillum brasilense ...

    African Journals Online (AJOL)

    In this study, we used a method of accelerated degradation to select a polymer and a concentration to maintain cell stability of a liquid inoculant based on the strain C16 Azospirillum brasilense. A screening at 45°C was made to compare the protectant effect of five polymers on the viability of the strain (p/v): carrageenan ...

  8. Alignment technology and applications of liquid crystal devices

    CERN Document Server

    Takatoh, Kohki; Hasegawa, Ray; Koden, Mitsushiro; Itoh, Nobuyuki; Hasegawa, Masaki

    2005-01-01

    Alignment phenomena are characteristic of liquid crystalline materials, and understanding them is critically important in understanding the essential features and behavior of liquid crystals and the performance of Liquid Crystal Devices (LCDs). Furthermore, in LCD production lines, the alignment process is of practical importance. Alignment Technologies and Applications of Liquid Crystal Devices demonstrates both the fundamental and practical aspects of alignment phenomena in liquid crystals. The physical basis of alignment phenomena is first introduced in order to aid the understanding of the various physical phenomena observed in the interface between liquid crystalline materials and alignment layer surfaces. Methods for the characterization of surfaces, which induce the alignment phenomena, and of the alignment layer itself are introduced. These methods are useful for the research of liquid crystalline materials and devices in academic research as well as in industry. In the practical sections, the alignme...

  9. Unconventional phase transitions in liquid crystals

    Science.gov (United States)

    Kats, E. I.

    2017-12-01

    According to classical textbooks on thermodynamics or statistical physics, there are only two types of phase transitions: continuous, or second-order, in which the latent heat L is zero, and first-order, in which L ≠ 0. Present-day textbooks and monographs also mention another, stand-alone type—the Berezinskii-Kosterlitz-Thouless transition, which exists only in two dimensions and shares some features with first- and second-order phase transitions. We discuss examples of non-conventional thermodynamic behavior (i.e., which is inconsistent with the theoretical phase transition paradigm now universally accepted). For phase transitions in smectic liquid crystals, mechanisms for nonconventional behavior are proposed and the predictions they imply are examined.

  10. Microwave modulation characteristics of twisted liquid crystals with chiral dopant

    Directory of Open Access Journals (Sweden)

    Rui Yuan

    2017-01-01

    Full Text Available Adding a chiral dopant in twisted nematic (TN liquid crystal cell can stabilize the orientation of liquid crystal molecules, particularly in high TN (HTN or super TN (STN liquid crystal cells. The difference in pitches in liquid crystal is induced by the chiral dopant, and these different pitches affect the orientation of liquid crystal director under an external applied voltage and influence the characteristics of microwave modulation. To illustrate this point, the microwave phase shift per unit length (MPSL versus voltage is calculated on the basis of the elastic theory of liquid crystal and the finite-difference iterative method. Enhancing the pitch induced by the chiral dopant in liquid crystal increases the MPSLs, but the stability of the twisted structures is decreased. Thus, appropriate pitches of 100d, 4d, and 2d can be applied in TN, HTN, and STN cells with cell gap d to enhance the characteristics of microwave modulation and stabilize the structures in twisted cell. This method can improve the characteristics of liquid crystal microwave modulators such that the operating voltage and the size of such phase shifters can be decreased.

  11. Electrically modulated transparent liquid crystal-optical grating projection

    DEFF Research Database (Denmark)

    Buss, Thomas; Smith, Cameron; Kristensen, Anders

    2013-01-01

    A transparent, fully integrated electrically modulated projection technique is presented based on light guiding through a thin liquid crystal layer covering sub-wavelength gratings. The reported device operates at 10 V with response times of 4.5 ms. Analysis of the liquid crystal alignment shows...

  12. A helical naphthopyran dopant for photoresponsive cholesteric liquid crystals

    OpenAIRE

    Kim, Yuna; Frigoli, Michel; Vanthuyne, Nicolas; Tamaoki, Nobuyuki

    2017-01-01

    The first photoresponsive cholesteric liquid crystal comprising a photoisomerizable helical naphthopyran derivative dopant and a nematic liquid crystal is reported. An unprecedented helical twisting power switching ratio of over 90% allowed us to demonstrate multi-cycle rotational motion of micro-objects by UV light irradiation.

  13. Liquid-crystal intraocular adaptive lens with wireless control

    NARCIS (Netherlands)

    Simonov, A.N.; Vdovine, G.V.; Loktev, M.

    2007-01-01

    We present a prototype of an adaptive intraocular lens based on a modal liquid-crystal spatial phase modulator with wireless control. The modal corrector consists of a nematic liquid-crystal layer sandwiched between two glass substrates with transparent low- and high-ohmic electrodes, respectively.

  14. Polarization-independent nematic liquid crystal waveguides for optofluidic applications

    NARCIS (Netherlands)

    d'Alessandro, A.; Martini, L.; Gilardi, G.; Beccherelli, R.; Asquini, R.

    2015-01-01

    We present the fabrication and the characterization of waveguides made of a nematic liquid crystal infiltrated in poly(dimethylsiloxane) channels. They are made by means of cast and molding technique and patterned using soft photolithography. The orientation of the nematic liquid crystal molecules

  15. A New Prediction Method for Organic Liquids Sorption into Polymers

    Czech Academy of Sciences Publication Activity Database

    Randová, A.; Bartovská, L.; Izák, Pavel; Friess, K.

    2015-01-01

    Roč. 475, FEB 1 (2015), s. 545-551 ISSN 0376-7388 R&D Projects: GA ČR(CZ) GAP106/12/0569; GA MŠk(CZ) LD14094 Institutional support: RVO:67985858 Keywords : organic liquids * liquid non-solvents * polymers Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 5.557, year: 2015

  16. Tunable bandpass filter based on photonic crystal fiber filled with multiple liquid crystals

    DEFF Research Database (Denmark)

    Scolari, Lara; Tartarini, G.; Borelli, E.

    2007-01-01

    A tunable bandpass filter based on a photonic crystal fiber filled with two different liquid crystals is demonstrated. 130 nm bandwidth tunability is achieved by tuning the temperature from 30degC to 90degC.......A tunable bandpass filter based on a photonic crystal fiber filled with two different liquid crystals is demonstrated. 130 nm bandwidth tunability is achieved by tuning the temperature from 30degC to 90degC....

  17. Insertion of liquid crystal molecules into hydrocarbon monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Piotr, E-mail: ppopov@kent.edu; Mann, Elizabeth K. [Department of Physics, Kent State University, Kent, Ohio 44242 (United States); Lacks, Daniel J. [Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106 (United States); Jákli, Antal [Liquid Crystal Institute, Kent State University, Kent, Ohio 44242-0001 (United States)

    2014-08-07

    Atomistic molecular dynamics simulations were carried out to investigate the molecular mechanisms of vertical surface alignment of liquid crystals. We study the insertion of nCB (4-Cyano-4{sup ′}-n-biphenyl) molecules with n = 0,…,6 into a bent-core liquid crystal monolayer that was recently found to provide good vertical alignment for liquid crystals. The results suggest a complex-free energy landscape for the liquid crystal within the layer. The preferred insertion direction of the nCB molecules (core or tail first) varies with n, which can be explained by entropic considerations. The role of the dipole moments was found to be negligible. As vertical alignment is the leading form of present day liquid crystal displays (LCD), these results will help guide improvement of the LCD technology, as well as lend insight into the more general problem of insertion of biological and other molecules into lipid and surfactant layers.

  18. UV response on dielectric properties of nano nematic liquid crystal

    Directory of Open Access Journals (Sweden)

    Kamal Kumar Pandey

    2018-03-01

    Full Text Available In this work, we investigate the effect of UV light irradiation on the dielectric parameters of nematic liquid crystal (5CB and ZnO nanoparticles dispersed liquid crystal. With addition of nanoparticles in nematic LC are promising new materials for a variety of application in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however we optimize the properties of liquid crystal and understand how the UV light irradiation interact the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor have discussed the pure nematic LC and dispersed/doped system after, during and before UV light exposure. The dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz–10 MHz in the nematic mesophase range. Keywords: Dielectric permittivity, Relaxation frequency, Nematic liquid crystal, UV light irradiation

  19. Liquid filling of photonic crystal fibres for grating writing

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Canning, John; Lægsgaard, Jesper

    2007-01-01

    liquid filling of photonic crystal fibres reduces the scattering from air–glass interfaces during Bragg grating writing in many layered photonic crystal fibres. Within experimental uncertainty, the grating index modulation of a grating written in germanium-doped photonic crystal fibre with 10 rings...

  20. Magnetic, electric and optic properties of liquid crystals

    International Nuclear Information System (INIS)

    Florea, St.C.

    1980-01-01

    We study the nematic liquid crystals of thermotrop type. We also studied the crystals whose mesomorphism occured both at temperature increasing and decreasing and during the supercooling phase (monotrope). Investigation results performed by us have had in view the following: clearing up and experimental support of a new mechanism of nuclear relaxation in liquid crystals, proposed by author; usage of experimental techniques and methods for to characterize and test some mesomorph media used in very important applications, such as color TV. (author)

  1. (Meth)acrylate liquid crystalline polymers for membrane applications

    Czech Academy of Sciences Publication Activity Database

    Rabie, F.; Sedláková, Zdeňka; Sheth, S.; Marand, E.; Martin, S. M.; Poláková, Lenka

    2015-01-01

    Roč. 132, č. 43 (2015), 42694_1-42694_8 ISSN 0021-8995 Institutional support: RVO:61389013 Keywords : copolymers * liquid crystals * membranes Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.866, year: 2015

  2. Liquid Crystal Gel Reduces Age Spots by Promoting Skin Turnover

    OpenAIRE

    Mina Musashi; Ariella Coler-Reilly; Teruaki Nagasawa; Yoshiki Kubota; Satomi Kato; Yoko Yamaguchi

    2014-01-01

    Studies have shown that liquid crystals structurally resembling the intercellular lipids in the stratum corneum can beneficially affect the skin when applied topically by stimulating the skin’s natural regenerative functions and accelerating epidermal turnover. In the present study, the effects of applying low concentrations of a liquid crystal gel of our own creation were evaluated using epidermal thickening in mouse skin as an assay for effective stimulation of epidermal turnover. A liquid ...

  3. Hybrid polymer photonic crystal fiber with integrated chalcogenide glass nanofilms

    DEFF Research Database (Denmark)

    Markos, Christos; Kubat, Irnis; Bang, Ole

    2014-01-01

    The combination of chalcogenide glasses with polymer photonic crystal fibers (PCFs) is a difficult and challenging task due to their different thermo-mechanical material properties. Here we report the first experimental realization of a hybrid polymer-chalcogenide PCF with integrated As2S3 glass...... nanofilms at the inner surface of the air-channels of a poly-methyl-methacrylate (PMMA) PCF. The integrated high refractive index glass films introduce distinct antiresonant transmission bands in the 480-900 nm wavelength region. We demonstrate that the ultra-high Kerr nonlinearity of the chalcogenide glass...

  4. Ionic Liquid-Doped Gel Polymer Electrolyte for Flexible Lithium-Ion Polymer Batteries

    Science.gov (United States)

    Zhang, Ruisi; Chen, Yuanfen; Montazami, Reza

    2015-01-01

    Application of gel polymer electrolytes (GPE) in lithium-ion polymer batteries can address many shortcomings associated with liquid electrolyte lithium-ion batteries. Due to their physical structure, GPEs exhibit lower ion conductivity compared to their liquid counterparts. In this work, we have investigated and report improved ion conductivity in GPEs doped with ionic liquid. Samples containing ionic liquid at a variety of volume percentages (vol %) were characterized for their electrochemical and ionic properties. It is concluded that excess ionic liquid can damage internal structure of the batteries and result in unwanted electrochemical reactions; however, samples containing 40–50 vol % ionic liquid exhibit superior ionic properties and lower internal resistance compared to those containing less or more ionic liquids.

  5. Ionic Liquid-Doped Gel Polymer Electrolyte for Flexible Lithium-Ion Polymer Batteries

    Directory of Open Access Journals (Sweden)

    Ruisi Zhang

    2015-05-01

    Full Text Available Application of gel polymer electrolytes (GPE in lithium-ion polymer batteries can address many shortcomings associated with liquid electrolyte lithium-ion batteries. Due to their physical structure, GPEs exhibit lower ion conductivity compared to their liquid counterparts. In this work, we have investigated and report improved ion conductivity in GPEs doped with ionic liquid. Samples containing ionic liquid at a variety of volume percentages (vol % were characterized for their electrochemical and ionic properties. It is concluded that excess ionic liquid can damage internal structure of the batteries and result in unwanted electrochemical reactions; however, samples containing 40–50 vol % ionic liquid exhibit superior ionic properties and lower internal resistance compared to those containing less or more ionic liquids.

  6. The liquid protein phase in crystallization: a case study—intact immunoglobulins

    Science.gov (United States)

    Kuznetsov, Yurii G.; Malkin, Alexander J.; McPherson, Alexander

    2001-11-01

    A common observation by protein chemists has been the appearance, for many proteins in aqueous solutions, of oil like droplets, or in more extreme cases the formation of a second oil like phase. These may accompany the formation of precipitate in "salting out" or "salting in' procedures, but more commonly appear in place of any precipitate. Such phase separations also occur, with even greater frequency, in the presence of polymeric precipitants such as polyethyleneglycol (PEG). In general the appearance of a second liquid phase has been taken as indicative of protein aggregation, though an aggregate state distinctly different from that characteristic of amorphous precipitate. While the latter is thought to be composed of linear and branched assemblies, polymers of a sort, the oil phase suggests a more compact, three-dimensional, but fluid state. An important property of an alternate, fluid phase is that it can mediate transitions between other states, for example, between protein molecules free in solution and protein molecules immobilized in amorphous precipitate or crystals. The "liquid protein" phase can be readily observed in many crystallization experiments either prior to the appearance of visible crystals, or directly participating in the crystal growth process. In some cases the relationship between the liquid phase and developing crystals is intimate. Crystals grow directly from the liquid phase, or appear only after the visible formation of the liquid phase. We describe here our experience with a class of macromolecules, immunoglobulins, and particularly IDEC-151, an IgG specific for CD4 on human lymphocytes. This protein has been crystallized from a Jeffamine-LiSO 4 mother liquor and, its crystallization illustrates many of the features associated with the liquid protein, or protein rich phase.

  7. Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Armas-Pérez, Julio C. [Institute; División; Li, Xiao [Institute; Martínez-González, José A. [Institute; Smith, Coleman [Institute; Hernández-Ortiz, J. P. [Departamento; Nealey, Paul F. [Institute; Materials; de Pablo, Juan J. [Institute; Materials

    2017-08-17

    Liquid crystals are known to be particularly sensitive to orientational cues provided at surfaces or interfaces. In this work, we explore theoretically, computationally, and experimentally the behavior of liquid crystals on isolated nanoscale patterns with controlled anchoring characteristics at small length scales. The orientation of the liquid crystal is controlled through the use of chemically patterned polymer brushes that are tethered to a surface. This system can be engineered with remarkable precision, and the central question addressed here is whether a characteristic length scale exists at which information encoded on a surface is no longer registered by a liquid crystal. To do so, we adopt a tensorial description of the free energy of the hybrid liquidcrystal surface system, and we investigate its morphology in a systematic manner. For long and narrow surface stripes, it is found that the liquid crystal follows the instructions provided by the pattern down to 100 nm widths. This is accomplished through the creation of line defects that travel along the sides of the stripes. We show that a "sharp" morphological transition occurs from a uniform undistorted alignment to a dual uniform/splay-bend morphology. The theoretical and numerical predictions advanced here are confirmed by experimental observations. Our combined analysis suggests that nanoscale patterns can be used to manipulate the orientation of liquid crystals at a fraction of the energetic cost that is involved in traditional liquid crystal-based devices. The insights presented in this work have the potential to provide a new fabrication platform to assemble low power bistable devices, which could be reconfigured upon application of small external fields.

  8. Ionic diffusion and salt dissociation conditions of lithium liquid crystal electrolytes.

    Science.gov (United States)

    Saito, Yuria; Hirai, Kenichi; Murata, Shuuhei; Kishii, Yutaka; Kii, Keisuke; Yoshio, Masafumi; Kato, Takashi

    2005-06-16

    Salt dissociation conditions and dynamic properties of ionic species in liquid crystal electrolytes of lithium were investigated by a combination of NMR spectra and diffusion coefficient estimations using the pulsed gradient spin-echo NMR techniques. Activation energies of diffusion (Ea) of ionic species changed with the phase transition of the electrolyte. That is, Ea of the nematic phase was lower than that of the isotropic phase. This indicates that the aligned liquid crystal molecules prepared efficient conduction pathways for migration of ionic species. The dissociation degree of the salt was lower compared with those of the conventional electrolyte solutions and polymer gel electrolytes. This is attributed to the low concentration of polar sites, which attract the dissolved salt and promote salt dissociation, on the liquid crystal molecules. Furthermore, motional restriction of the molecules due to high viscosity and molecular oriented configuration in the nematic phase caused inefficient attraction of the sites for the salt. With a decreased dissolved salt concentration of the liquid crystal electrolyte, salt dissociation proceeded, and two diffusion components attributed to the ion and ion pair were detected independently. This means that the exchange rate between the ion and the ion pair is fairly slow once the salt is dissociated in the liquid crystal electrolytes due to the low motility of the medium molecules that initiate salt dissociation.

  9. H-Bond stabilized columnar discotic liquid crystals

    NARCIS (Netherlands)

    Paraschiv, I.

    2007-01-01

    Since 1977, more than 2300 publications on discotic (disk-like) liquid crystalline materials have appeared. Discotic liquid crystals, which usually consist of polyaromatic molecules surrounded by long peripheral alkyl tails, can form liquid crystalline mesophases in a wide temperature range. Within

  10. A thermodynamic framework for the study of crystallization in polymers

    Science.gov (United States)

    Rao, I. J.; Rajagopal, K. R.

    In this paper, we present a new thermodynamic framework within the context of continuum mechanics, to predict the behavior of crystallizing polymers. The constitutive models that are developed within this thermodynamic setting are able to describe the main features of the crystallization process. The model is capable of capturing the transition from a fluid like behavior to a solid like behavior in a rational manner without appealing to any adhoc transition criterion. The anisotropy of the crystalline phase is built into the model and the specific anisotropy of the crystalline phase depends on the deformation in the melt. These features are incorporated into a recent framework that associates different natural configurations and material symmetries with distinct microstructural features within the body that arise during the process under consideration. Specific models are generated by choosing particular forms for the internal energy, entropy and the rate of dissipation. Equations governing the evolution of the natural configurations and the rate of crystallization are obtained by maximizing the rate of dissipation, subject to appropriate constraints. The initiation criterion, marking the onset of crystallization, arises naturally in this setting in terms of the thermodynamic functions. The model generated within such a framework is used to simulate bi-axial extension of a polymer film that is undergoing crystallization. The predictions of the theory that has been proposed are consistent with the experimental results (see [28] and [7]).

  11. 3D holographic polymer photonic crystal for superprism application

    Science.gov (United States)

    Chen, Jiaqi; Jiang, Wei; Chen, Xiaonan; Wang, Li; Zhang, Sasa; Chen, Ray T.

    2007-02-01

    Photonic crystal based superprism offers a new way to design new optical components for beam steering and DWDM application. 3D photonic crystals are especially attractive as they could offer more control of the light beam based on the needs. A polygonal prism based holographic fabrication method has been demonstrated for a three-dimensional face-centered-cubic (FCC)-type submicron polymer photonic crystal using SU8 as the photo-sensitive material. Therefore antivibration equipment and complicated optical alignment system are not needed and the requirement for the coherence of the laser source is relaxed compared with the traditional holographic setup. By changing the top-cut prism structure, the polarization of the laser beam, the exposure and development conditions we can achieve different kinds of triclinic or orthorhombic photonic crystals on demand. Special fabrication treatments have been introduced to ensure the survivability of the fabricated large area (cm2) nano-structures. Scanning electron microscopy and diffraction results proved the good uniformity of the fabricated structures. With the proper design of the refraction prism we have achieved a partial bandgap for S+C band (1460-1565nm) in the [111] direction. The transmission and reflection spectra obtained by Fourier transform infrared spectroscopy (FTIR) are in good agreement with simulated band structure. The superprism effects around 1550nm wavelength for the fabricated 3D polymer photonic crystal have been theoretically calculated and such effects can be used for beam steering purpose.

  12. Cholesteric Liquid Crystal Based Reflex Color Reflective Displays

    Science.gov (United States)

    Khan, Asad

    2012-02-01

    Bistable color cholesteric liquid crystal displays are unique LCDs that exhibit high reflectivity, good contrast, extremely low power operation, and are amenable to versatile roll-to-roll manufacturing. The display technology, now branded as Reflex has been in commercialized products since 1996. It has been the subject of extensive research and development globally by a variety of parties in both academic and industrial settings. Today, the display technology is in volume production for applications such as dedicated eWriters (Boogie Board), full color electronic skins (eSkin), and displays for smart cards. The flexibility comes from polymerization induced phase separation using unique materials unparalleled in any other display technology. The blend of monomers, polymers, cross linkers, and other components along with nematic liquid crystals and chiral dopants is created and processed in such ways so as to enable highly efficient manufactrable displays using ultra thin plastic substrates -- often as thin as 50μm. Other significant aspects include full color by stacking or spatial separation, night vision capability, ultra high resolution, as well as active matrix capabilities. Of particular note is the stacking approach of Reflex based displays to show full color. This approach for reflective color displays is unique to this technology. Owing to high transparency in wavelength bands outside the selective reflection band, three primarily color layers can be stacked on top of each other and reflect without interfering with other layers. This highly surprising architecture enables the highest reflectivity of any other reflective electronic color display technology. The optics, architecture, electro-topics, and process techniques will be discussed. This presentation will focus on the physics of the core technology and color, it's evolution from rigid glass based displays to flexible displays, development of products from the paradigm shifting concepts to consumer

  13. Liquid crystal true 3D displays for augmented reality applications

    Science.gov (United States)

    Li, Yan; Liu, Shuxin; Zhou, Pengcheng; Chen, Quanming; Su, Yikai

    2018-02-01

    Augmented reality (AR) technology, which integrates virtual computer-generated information into the real world scene, is believed to be the next-generation human-machine interface. However, most AR products adopt stereoscopic 3D display technique, which causes the accommodation-vergence conflict. To solve this problem, we have proposed two approaches. The first is a multi-planar volumetric display using fast switching polymer-stabilized liquid crystal (PSLC) films. By rapidly switching the films between scattering and transparent states while synchronizing with a high-speed projector, the 2D slices of a 3D volume could be displayed in time sequence. We delved into the research on developing high-performance PSLC films in both normal mode and reverse mode; moreover, we also realized the demonstration of four-depth AR images with correct accommodation cues. For the second approach, we realized a holographic AR display using digital blazed gratings and a 4f system to eliminate zero-order and higher-order noise. With a 4k liquid crystal on silicon device, we achieved a field of view (FOV) of 32 deg. Moreover, we designed a compact waveguidebased holographic 3D display. In the design, there are two holographic optical elements (HOEs), each of which functions as a diffractive grating and a Fresnel lens. Because of the grating effect, holographic 3D image light is coupled into and decoupled out of the waveguide by modifying incident angles. Because of the lens effect, the collimated zero order light is focused at a point, and got filtered out. The optical power of the second HOE also helps enlarge FOV.

  14. Crystal-liquid-gas phase transitions and thermodynamic similarity

    CERN Document Server

    Skripov, Vladimir P; Schmelzer, Jurn W P

    2006-01-01

    Professor Skripov obtained worldwide recognition with his monograph ""Metastable liquids"", published in English by Wiley & Sons. Based upon this work and another monograph published only in Russia, this book investigates the behavior of melting line and the properties of the coexisting crystal and liquid phase of simple substances across a wide range of pressures, including metastable states of the coexisting phases. The authors derive new relations for the thermodynamic similarity for liquid-vapour phase transition, as well as describing solid-liquid, liquid-vapor and liquid-liquid phase tra

  15. New scintillating media based on liquid crystals for particle detectors

    International Nuclear Information System (INIS)

    Barnik, M.I.; Yudin, S.G.; Vasil'chenko, V.G.; Golovkin, S.V.; Medvedkov, A.M.; Solovjev, A.S.

    2000-01-01

    The study results of optical, photoluminiscent and scintillation properties of a liquid crystal 4-pentyl-4'-cyanobiphenyl are presented. The scintillation light output of this liquid crystal is about 35% of crystal anthracene, its main decay time constants are 4 and 14 ns, and the maximum of light emission spectrum is about 400 nm. The light output of a dissolution of green emitting light scintillation dopant R6 in the liquid crystal is about 120% of crystal anthracene. The light output of the frozen dissolution measured at -112 deg. C is about 2.5 times higher as observed at +20 deg. C. In the uniaxially oriented liquid crystal, the predominant intensity direction of emitted light is pointed perpendicular to the liquid crystal director and an appreciable part of the emitted light is elliptically polarized. The possibility to use scintillation properties of liquid crystals is considered both for the improvement of existing particle detector characteristics and for the creation of new gated particle detectors

  16. New scintillating media based on liquid crystals for particle detectors

    CERN Document Server

    Barnik, M I; Vasilchenko, V G; Golovkin, S V; Medvedkov, A M; Soloviev, A S

    2000-01-01

    The study results of optical, photoluminiscent and scintillation properties of a liquid crystal 4-pentyl-4'-cyanobiphenyl are presented. The scintillation light output of this liquid crystal is about 35% of crystal anthracene, its main decay time constants are 4 and 14 ns, and the maximum of light emission spectrum is about 400 nm. The light output of a dissolution of green emitting light scintillation dopant R6 in the liquid crystal is about 120% of crystal anthracene. The light output of the frozen dissolution measured at -112 deg. C is about 2.5 times higher as observed at +20 deg. C. In the uniaxially oriented liquid crystal, the predominant intensity direction of emitted light is pointed perpendicular to the liquid crystal director and an appreciable part of the emitted light is elliptically polarized. The possibility to use scintillation properties of liquid crystals is considered both for the improvement of existing particle detector characteristics and for the creation of new gated particle detectors.

  17. Computer simulation of confined liquid crystal dynamics

    International Nuclear Information System (INIS)

    Webster, R.E.

    2001-11-01

    Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

  18. Computer simulation of confined liquid crystal dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Webster, R.E

    2001-11-01

    Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

  19. Transport and spectroscopic studies of liquid and polymer electrolytes

    Science.gov (United States)

    Bopege, Dharshani Nimali

    Liquid and polymer electrolytes are interesting and important materials to study as they are used in Li rechargeable batteries and other electrochemical devices. It is essential to investigate the fundamental properties of electrolytes such as ionic conductivity, diffusion, and ionic association to enhance battery performance in different battery markets. This dissertation mainly focuses on the temperature-dependent charge and mass transport processes and ionic association of different electrolyte systems. Impedance spectroscopy and pulsed field gradient nuclear magnetic resonance spectroscopy were used to measure the ionic conductivity and diffusion coefficients of ketone and acetate based liquid electrolytes. In this study, charge and mass transport in non-aqueous liquid electrolytes have been viewed from an entirely different perspective by introducing the compensated Arrhenius formalism. Here, the conductivity and diffusion coefficient are written as an Arrhenius-like expression with a temperature-dependent static dielectric constant dependence in the exponential prefactor. The compensated Arrhenius formalism reported in this dissertation very accurately describes temperature-dependent conductivity data for acetate and ketone-based electrolytes as well as temperature-dependent diffusion data of pure solvents. We found that calculated average activation energies of ketone-based electrolytes are close to each other for both conductivity and diffusion data (in the range 24-26 kJ/mol). Also, this study shows that average activation energies of acetate-based electrolytes are higher than those for the ketone systems (in the range 33-37 kJ/mol). Further, we observed higher dielectric constants and ionic conductivities for both dilute and concentrated ketone solutions with temperature. Vibrational spectroscopy (Infrared and Raman) was used to probe intermolecular interactions in both polymer and liquid electrolytes, particularly those which contain lithium

  20. Liquid crystals in micron-scale droplets, shells and fibers

    Science.gov (United States)

    Urbanski, Martin; Reyes, Catherine G.; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P. F.

    2017-04-01

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  1. Liquid crystals in micron-scale droplets, shells and fibers

    International Nuclear Information System (INIS)

    Urbanski, Martin; Reyes, Catherine G; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P F

    2017-01-01

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  2. Stability of Disclinations in Nematic Liquid Crystals

    International Nuclear Information System (INIS)

    Wang Yusheng; Yang Guohong; Tian Lijun; Duan Yishi

    2006-01-01

    In the light of φ-mapping method and topological current theory, the stability of disclinations around a spherical particle in nematic liquid crystals is studied. We consider two different defect structures around a spherical particle: disclination ring and point defect at the north or south pole of the particle. We calculate the free energy of these different defects in the elastic theory. It is pointed out that the total Frank free energy density can be divided into two parts. One is the distorted energy density of director field around the disclinations. The other is the free energy density of disclinations themselves, which is shown to be concentrated at the defect and to be topologically quantized in the unit of (k-k 24 )π/2. It is shown that in the presence of saddle-splay elasticity a dipole (radial and hyperbolic hedgehog) configuration that accompanies a particle with strong homeotropic anchoring takes the structure of a small disclination ring, not a point defect.

  3. Optical defect modes in chiral liquid crystals

    International Nuclear Information System (INIS)

    Belyakov, V. A.; Semenov, S. V.

    2011-01-01

    An analytic approach to the theory of optical defect modes in chiral liquid crystals (CLCs) is developed. The analytic study is facilitated by the choice of the problem parameters. Specifically, an isotropic layer (with the dielectric susceptibility equal to the average CLC dielectric susceptibility) sandwiched between two CLC layers is studied. The chosen model allows eliminating the polarization mixing and reducing the corresponding equations to the equations for light of diffracting polarization only. The dispersion equation relating the defect mode (DM) frequency to the isotropic layer thickness and an analytic expression for the field distribution in the DM structure are obtained and the corresponding dependences are plotted for some values of the DM structure parameters. Analytic expressions for the transmission and reflection coefficients of the DM structure (CLC-defect layer-CLC) are presented and analyzed for nonabsorbing, absorbing, and amplifying CLCs. The anomalously strong light absorption effect at the DM frequency is revealed. The limit case of infinitely thick CLC layers is considered in detail. It is shown that for distributed feedback lasing in a defect structure, adjusting the lasing frequency to the DM frequency results in a significant decrease in the lasing threshold. The DM dispersion equations are solved numerically for typical values of the relevant parameters. Our approach helps clarify the physics of the optical DMs in CLCs and completely agrees with the corresponding results of the previous numerical investigations.

  4. Structural Transitions in Cholesteric Liquid Crystal Droplets

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A.; Rahimi, Mohammad; Roberts, Tyler F.; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L.; de Pablo, Juan J.

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  5. Shear flow in smectic A liquid crystals

    International Nuclear Information System (INIS)

    Stewart, I W; Stewart, F

    2009-01-01

    This paper considers the onset of a shear-induced instability in a sample of smectic A liquid crystal. Unlike many previous models, the usual director n need not necessarily coincide with the local smectic layer normal a; the traditional Oseen constraint (∇xa=0) is not imposed when flow is present. A recent dynamic theory for smectic A (Stewart 2007 Contin. Mech. Thermodyn. 18 343-60) will be used to examine a stationary instability in a simple model when the director reorientation and smectic layer distortions are, firstly, assumed not to be coupled to the velocity and, secondly, are supposed coupled to the velocity. A critical shear rate at which the onset of the instability occurs will be identified, together with an accompanying critical director tilt angle and critical wavenumber for the associated smectic layer undulations. Despite some critical phenomena being largely unaffected by any coupling to the flow, it will be shown that the influence of some material parameters, especially the smectic layer compression constant B 0 and the coupling constant B 1 , upon the critical shear rate and critical tilt angle can be greatly affected by flow.

  6. Convolving optically addressed VLSI liquid crystal SLM

    Science.gov (United States)

    Jared, David A.; Stirk, Charles W.

    1994-03-01

    We designed, fabricated, and tested an optically addressed spatial light modulator (SLM) that performs a 3 X 3 kernel image convolution using ferroelectric liquid crystal on VLSI technology. The chip contains a 16 X 16 array of current-mirror-based convolvers with a fixed kernel for finding edges. The pixels are located on 75 micron centers, and the modulators are 20 microns on a side. The array successfully enhanced edges in illumination patterns. We developed a high-level simulation tool (CON) for analyzing the performance of convolving SLM designs. CON has a graphical interface and simulates SLM functions using SPICE-like device models. The user specifies the pixel function along with the device parameters and nonuniformities. We discovered through analysis, simulation and experiment that the operation of current-mirror-based convolver pixels is degraded at low light levels by the variation of transistor threshold voltages inherent to CMOS chips. To function acceptable, the test SLM required the input image to have an minimum irradiance of 10 (mu) W/cm2. The minimum required irradiance can be further reduced by adding a photodarlington near the photodetector or by increasing the size of the transistors used to calculate the convolution.

  7. 2D director calculation for liquid crystal optical phased array

    International Nuclear Information System (INIS)

    Xu, L; Zhang, J; Wu, L Y

    2005-01-01

    A practical numerical model for a liquid crystal cell is set up based on the geometrical structure of liquid crystal optical phased arrays. Model parameters include width and space of electrodes, thickness of liquid crystal layer, alignment layers and glass substrates, pre-tilted angles, dielectric constants, elastic constants and so on. According to electrostatic field theory and Frank-Oseen elastic continuum theory, 2D electric potential distribution and 2D director distribution are calculated by means of the finite difference method on non-uniform grids. The influence of cell sizes on director distribution is analyzed. The fringe field effect between electrodes is also discussed

  8. Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Joanna Ptasinski

    2014-03-01

    Full Text Available In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

  9. Liquid crystals beyond displays chemistry, physics, and applications

    CERN Document Server

    Li, Quan

    2012-01-01

    The chemistry, physics, and applications of liquid crystals beyond LCDs Liquid Crystals (LCs) combine order and mobility on a molecular and supramolecular level. But while these remarkable states of matter are most commonly associated with visual display technologies, they have important applications for a variety of other fields as well. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications considers these, bringing together cutting-edge research from some of the most promising areas of LC science. Featuring contributions from respected researchers from around the globe, th

  10. Tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal structure

    International Nuclear Information System (INIS)

    Huang, Wenbin; Pu, Donglin; Qiao, Wen; Wan, Wenqiang; Liu, Yanhua; Ye, Yan; Wu, Shaolong; Chen, Linsen

    2016-01-01

    A continuously tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal cavity is demonstrated. The triangular-lattice resonator was initially fabricated through multiple interference exposure and was then replicated into a low refractive index polymer via UV-nanoimprinting. The blend of a blue-emitting conjugated polymer and a red-emitting one was used as the gain medium. Three periods in the scalene triangular-lattice structure yield stable tri-wavelength laser emission (625.5 nm, 617.4 nm and 614.3 nm) in six different directions. A uniformly aligned liquid crystal (LC) layer was incorporated into the cavity as the top cladding layer. Upon heating, the orientation of LC molecules and thus the effective refractive index of the lasing mode changes which continuously shifts the lasing wavelength. A maximum tuning range of 12.2 nm was observed for the lasing mode at 625.5 nm. This tunable tri-wavelength polymer laser is simple constructed and cost-effective. It may find application in the fields of biosensors and photonic integrated circuits. (paper)

  11. NATO Advanced Research Workshop on Incommensurate Crystals, Liquid Crystals, and Quasi-Crystals

    CERN Document Server

    Clark, N

    1988-01-01

    In this NATO-sponsored Advanced Research Workshop we succeeded in bringing together approximately forty scientists working in the three main areas of structurally incommensurate materials: incommensurate crystals (primarily ferroelectric insulators), incommensurate liquid crystals, and metallic quasi-crystals. Although these three classes of materials are quite distinct, the commonality of the physics of the origin and descrip­ tion of these incommensurate structures is striking and evident in these proceedings. A measure of the success of this conference was the degree to which interaction among the three subgroups occurred; this was facili­ tated by approximately equal amounts of theory and experiment in the papers presented. We thank the University of Colorado for providing pleasant housing and conference facilities at a modest cost, and we are especially grate­ ful to Ann Underwood, who retyped all the manuscripts into camera-ready form. J. F. Scott Boulder, Colorado N. A. Clark v CONTENTS PART I: INCO...

  12. Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Yogesh K. Murugesan

    2010-12-01

    Full Text Available Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications.

  13. Electric properties of a liquid crystalline methacrylic polymer

    International Nuclear Information System (INIS)

    Gonzalez Henriquez, C.M.; Soto Bustamante, E.A.; Haase, W.

    2009-01-01

    The formation of a liquid crystalline polymer called PM6R8 is reported. The polymers were obtained with different concentration of AIBN as initiator (0.25, 0.50, 1 and 2mg in 5ml solution) and time of reaction (24, 36 and 48 hours). The compounds were characterized by 1 H-NMR, differential thermal analysis (DTA), X-ray diffractometer and pyroelectric measurements. For the polymer a smectic C 2 phase occurs over broad temperature range, which is a possible explanation for the electric signal. The arrangement of the molecules within of the crystalline lattice is related with the kinetic of precipitation. (author)

  14. Crystallization in melts of short, semiflexible hard polymer chains: An interplay of entropies and dimensions

    Science.gov (United States)

    Shakirov, T.; Paul, W.

    2018-04-01

    What is the thermodynamic driving force for the crystallization of melts of semiflexible polymers? We try to answer this question by employing stochastic approximation Monte Carlo simulations to obtain the complete thermodynamic equilibrium information for a melt of short, semiflexible polymer chains with purely repulsive nonbonded interactions. The thermodynamics is obtained based on the density of states of our coarse-grained model, which varies by up to 5600 orders of magnitude. We show that our polymer melt undergoes a first-order crystallization transition upon increasing the chain stiffness at fixed density. This crystallization can be understood by the interplay of the maximization of different entropy contributions in different spatial dimensions. At sufficient stiffness and density, the three-dimensional orientational interactions drive the orientational ordering transition, which is accompanied by a two-dimensional translational ordering transition in the plane perpendicular to the chains resulting in a hexagonal crystal structure. While the three-dimensional ordering can be understood in terms of Onsager theory, the two-dimensional transition can be understood in terms of the liquid-hexatic transition of hard disks. Due to the domination of lateral two-dimensional translational entropy over the one-dimensional translational entropy connected with columnar displacements, the chains form a lamellar phase. Based on this physical understanding, orientational ordering and translational ordering should be separable for polymer melts. A phenomenological theory based on this understanding predicts a qualitative phase diagram as a function of volume fraction and stiffness in good agreement with results from the literature.

  15. Magnetic, electrical and optical properties of liquid crystals

    International Nuclear Information System (INIS)

    Florea, S.C.

    1980-01-01

    This thesis lays stress on the study of thermotrop nematic liquid crystals. But the crystals whose mesomorphism is achieved by an increase and decrease in temperature and the crystal category exhibiting a mesomorphism in a deep freezing phase are also studied. The results of the research carried out in the laboratory of ''active media, lasers and matter-radiation interactions'' of the Institute for Physics and Technology of Radiation Apparata as well as in the laboratories of liquid crystals and nuclear magnetic resonance of the Polytechnical Institute of Bucharest during seven years have had in view two main objectives: to elucidate and prove experimentally a new mechanism of nuclear relaxation in liquid crystals, proposed by the author; to use the current experimental techniques and methods applied in the above-mentioned laboratories to characterize and test some foreign mesomorphic media which are synthesized locally, providing a wide range of applications, such as colour television. (author)

  16. Static and dynamic continuum theory liquid crystals a mathematical introduction

    CERN Document Server

    Stewart, Iain W

    2004-01-01

    Providing a rigorous, clear and accessible text for graduate students regardless of scientific background, this text introduces the basic continuum theory for nematic liquid crystals in equilibria, and details its various simple applications.

  17. Controlling chirality with helix inversion in cholesteric liquid crystals

    NARCIS (Netherlands)

    Katsonis, Nathalie Hélène; Lacaze, E.; Ferrarini, A.

    2012-01-01

    The helical organization of cholesteric liquid crystals is omnipresent in living matter. Achieving control over the structure of the cholesteric helix consequently holds great potential for developing stimuli-responsive materials matching the level of sophistication of biological systems. In

  18. Heat and electrical conductivity of thermotropic liquid crystals

    International Nuclear Information System (INIS)

    Saidov, N.S.; Majidov, H.; Saburov, B.S.; Safarov, M.M.

    1989-01-01

    A results of thermal conduction and electrical conduction of chemo tropic liquid crystals are brought in this article. An installation dependence formula of thermal conduction investigating things from the electrical conduction and temperatures is constructed

  19. Liquid crystalline thermosetting polymers as protective coatings for aerospace

    OpenAIRE

    Guerriero, G.L.

    2012-01-01

    Environmental regulations are driving the development of new aerospace coating systems, mainly to eliminate chromates and reduce volatile organic compound (VOC) emissions. Among the various potential options for new coating materials, liquid crystalline polymers (LCPs) are attractive due to their unique combination of mechanical properties and chemical resistance. Their use, however, has been limited mainly due to poor adhesion properties. Thermotropic liquid crystalline thermosets displayed ...

  20. Variational Approach in the Theory of Liquid-Crystal State

    Science.gov (United States)

    Gevorkyan, E. V.

    2018-03-01

    The variational calculus by Leonhard Euler is the basis for modern mathematics and theoretical physics. The efficiency of variational approach in statistical theory of liquid-crystal state and in general case in condensed state theory is shown. The developed approach in particular allows us to introduce correctly effective pair interactions and optimize the simple models of liquid crystals with help of realistic intermolecular potentials.

  1. New developments in flexible cholesteric liquid crystal displays

    Science.gov (United States)

    Schneider, Tod; Davis, Donald J.; Franklin, Sean; Venkataraman, Nithya; McDaniel, Diaz; Nicholson, Forrest; Montbach, Erica; Khan, Asad; Doane, J. William

    2007-02-01

    Flexible Cholesteric liquid crystal displays have been rapidly maturing into a strong contender in the flexible display market. Encapsulation of the Cholesteric liquid crystal permits the use of flexible plastic substrates and roll-to-roll production. Recent advances include ultra-thin displays, laser-cut segmented displays of variable geometry, and smart card applications. Exciting technologies such as simultaneous laser-edge sealing and singulation enable high volume production, excellent quality control and non-traditional display geometries and formats.

  2. Liquid Crystals of Lithium Dodecylbenzenesulfonate for Electric Double Layer Capacitors

    International Nuclear Information System (INIS)

    Kuzmin, Andrey Vasil’evich; Yurtov, Evgeny V.

    2016-01-01

    Ionic lyotropic liquid crystals based on lithium dodecylbenzenesulfonate were used as electrolytes for electric double layer capacitors with carbon fibrous electrodes. The capacitors were tasted by cyclic voltammetry, galvanostatic charge and discharge, and impedance spectroscopy. The highest specific capacitance was achieved for electrical double layer capacitor equipped with ionic lyotropic liquid crystal of lithium dodecylbenzenesulfonate 35 wt% in water. The specific capacitance of capacitor was calculated from galvanostatic discharge curves – 15 F/g of carbon fibrous material

  3. All-optical image processing with nonlinear liquid crystals

    Science.gov (United States)

    Hong, Kuan-Lun

    Liquid crystals are fascinating materials because of several advantages such as large optical birefringence, dielectric anisotropic, and easily compatible to most kinds of materials. Compared to the electro-optical properties of liquid crystals widely applied in displays and switching application, transparency through most parts of wavelengths also makes liquid crystals a better candidate for all-optical processing. The fast response time of liquid crystals resulting from multiple nonlinear effects, such as thermal and density effect can even make real-time processing realized. In addition, blue phase liquid crystals with spontaneously self-assembled three dimensional cubic structures attracted academic attention. In my dissertation, I will divide the whole contents into six parts. In Chapter 1, a brief introduction of liquid crystals is presented, including the current progress and the classification of liquid crystals. Anisotropy and laser induced director axis reorientation is presented in Chapter 2. In Chapter 3, I will solve the electrostrictive coupled equation and analyze the laser induced thermal and density effect in both static and dynamic ways. Furthermore, a dynamic simulation of laser induced density fluctuation is proposed by applying finite element method. In Chapter 4, two image processing setups are presented. One is the intensity inversion experiment in which intensity dependent phase modulation is the mechanism. The other is the wavelength conversion experiment in which I can read the invisible image with a visible probe beam. Both experiments are accompanied with simulations to realize the matching between the theories and practical experiment results. In Chapter 5, optical properties of blue phase liquid crystals will be introduced and discussed. The results of grating diffractions and thermal refractive index gradient are presented in this chapter. In addition, fiber arrays imaging and switching with BPLCs will be included in this chapter

  4. Order parameters in smectic liquid crystals

    International Nuclear Information System (INIS)

    Beldon, Stephen M.

    2001-01-01

    This thesis explores some of the important mechanisms for switching in smectic liquid crystals. It is mainly concerned with the interaction of the electric field and various order parameters in smectic phases. Distortion of these order parameters and also the layer structures associated with smectics are discussed in depth. Initial work is concentrated on the electroclinic effect of commercially available FLC mixtures, where experimental results suggest the presence of non-uniformity in the molecular director profile. Two possible models are suggested assuming a variation of the order parameter θ through the cell. The first model assumes that the smectic layers remain bookshelf-like, and the second that the layers tilt in a vertical chevron structure when a cone angle is induced electroclinically or otherwise. The latter model is the first 'order parameter' model of an electric field induced vertical chevron. The presence of non-uniformity in the director profile is sensed by a method similar to wavelength extinction spectroscopy. Investigations are undertaken on racemic smectic materials with high dielectric biaxiality. Modelling of such a material reveals a new electroclinic effect which shows a discrete second order phase transition on application of a field. It is suggested that a bistable electroclinic effect stabilised with a high frequency ac field may be realised if a residual polarisation is present in the high biaxiality material, and that this might be useful in the displays industry. Experimental investigations of such a material confirm the above effects close to the smectic A-C transition. Finally a higher order smectic phase, the smectic I* phase, is considered. The distortion of the hexagonal bond orientational order is investigated experimentally during application of an electric field. The first dynamic model of the switching process is presented, showing good agreement with the experimental results. It is suggested that the bond orientational

  5. Liquid crystals: a new topic in physics for undergraduates

    International Nuclear Information System (INIS)

    Pavlin, Jerneja; Čepič, Mojca; Vaupotič, Nataša

    2013-01-01

    This paper presents a teaching module about liquid crystals. Since liquid crystals are linked to everyday student experiences and are also a topic of current scientific research, they are an excellent candidate for a modern topic to be introduced into education. We show that liquid crystals can provide a pathway through several fields of physics such as thermodynamics, optics and electromagnetism. We discuss what students should learn about liquid crystals and what physical concepts they should know before considering them. In the presentation of the teaching module, which consists of a lecture and experimental work in a chemistry and physics laboratory, we focus on experiments on phase transitions, polarization of light, double refraction and colours. A pilot evaluation of the module was performed among pre-service primary school teachers who have no special preference for natural sciences. The evaluation shows that the module is very efficient in transferring knowledge. A prior study showed that the informally obtained pre-knowledge on liquid crystals of the first-year students from several different fields of study was negligible. Since social science students are the least interested in natural sciences, it can be expected that students in any study programme will on average achieve at least as good qualitative knowledge of phenomena related to liquid crystals as the group involved in the pilot study. (paper)

  6. Tunable photoluminescence of porous silicon by liquid crystal infiltration

    International Nuclear Information System (INIS)

    Ma Qinglan; Xiong Rui; Huang Yuanming

    2011-01-01

    The photoluminescence (PL) of porous silicon films has been investigated as a function of the amount of liquid crystal molecules that are infiltrated into the constricted geometry of the porous silicon films. A typical nematic liquid crystal 4-pentyl-4'-cyanobiphenyl was employed in our experiment as the filler to modify the PL of porous silicon. It is found that the originally red PL of porous silicon films can be tuned to blue by simply adjusting the amount of liquid crystal molecules in the microchannels of the porous films. The chromaticity coordinates are calculated for the recorded PL spectra. The mechanism of the tunable PL is discussed. Our results have demonstrated that the luminescent properties of porous silicon films can be efficiently tuned by liquid crystal infiltration. - Highlights: → Liquid crystal infiltration can tune the photoluminescence of porous silicon. → Red emission of porous silicon can be switched to blue by the infiltration. → Chromaticity coordinates are calculated for the tuned emissions. → White emission is realized for porous silicon by liquid crystal infiltration.

  7. Simulation of liquid crystals. Disclinations and surface modification

    International Nuclear Information System (INIS)

    Downton, M.

    2001-01-01

    In this thesis we investigate the behaviour of molecular models liquid crystals in several different situations. Basic introductory material on liquid crystals and computer simulations is discussed in the first two chapters, we then discuss the research. The third chapter investigates the interaction between a liquid crystal and a modified surface. A confined system of hard spherocylinders in a slab geometry is examined. The surface consists of planar hard walls with elongated molecules grafted perpendicularly onto them. The concentration of grafted molecules is varied to give different surfaces. Several different behaviours are found including planar, homeotropic and tilted anchorings of the liquid crystal. Molecular dynamics simulations of a nematic liquid crystal in slab geometry with twisted boundary conditions are performed. By arranging the initial configuration suitably it is possible to create a simulation cell with two regions of opposite twist separated by a strength half disclination line. The properties of the line are examined both with and without an applied external field. Finally, we again examine the system of grafted molecules on a flat substrate using an atomistic model of both the liquid crystal and the surface molecules. Again the effect of varying the density of grafted molecules is found to change the anchoring characteristics of the surface; both homeotropic and planar anchorings are observed. (author)

  8. Lyotropic chromonic liquid crystals: From viscoelastic properties to living liquid crystals

    Science.gov (United States)

    Zhou, Shuang

    Lyotropic chromonic liquid crystal (LCLC) represents a broad range of molecules, from organic dyes and drugs to DNA, that self-assemble into linear aggregates in water through face-to-face stacking. These linear aggregates of high aspect ratio are capable of orientational order, forming, for example nematic phase. Since the microscopic properties (such as length) of the chromonic aggregates are results of subtle balance between energy and entropy, the macroscopic viscoelastic properties of the nematic media are sensitive to change of external factors. In the first part of this thesis, by using dynamic light scattering and magnetic Frederiks transition techniques, we study the Frank elastic moduli and viscosity coefficients of LCLC disodium cromoglycate (DSCG) and sunset yellow (SSY) as functions of concentration c , temperature T and ionic contents. The elastic moduli of splay (K1) and bend (K3) are in the order of 10pN, about 10 times larger than the twist modulus (K2). The splay modulus K1 and the ratio K1/K3 both increase substantially as T decreases or c increases, which we attribute to the elongation of linear aggregates at lower T or higher c . The bend viscosity is comparable to that of thermotropic liquid crystals, while the splay and twist viscosities are several orders of magnitude larger, changing exponentially with T . Additional ionic additives into the system influence the viscoelastic properties of these systems in a dramatic and versatile way. For example, monovalent salt NaCl decreases bend modulus K3 and increases twist viscosity, while an elevated pH decreases all the parameters. We attribute these features to the ion-induced changes in length and flexibility of building units of LCLC, the chromonic aggregates, a property not found in conventional thermotropic and lyotropic liquid crystals form by covalently bound units of fixed length. The second part of the thesis studies a new active bio-mechanical hybrid system called living liquid crystal

  9. Slippage and nanorheology of thin liquid polymer films

    International Nuclear Information System (INIS)

    Bäumchen, Oliver; Fetzer, Renate; Klos, Mischa; Lessel, Matthias; Marquant, Ludovic; Hähl, Hendrik; Jacobs, Karin

    2012-01-01

    Thin liquid films on surfaces are part of our everyday life; they serve, e.g., as coatings or lubricants. The stability of a thin layer is governed by interfacial forces, described by the effective interface potential, and has been subject of many studies in recent decades. In recent years, the dynamics of thin liquid films has come into focus since results on the reduction of the glass transition temperature raised new questions on the behavior of especially polymeric liquids in confined geometries. The new focus was fired by theoretical models that proposed significant implication of the boundary condition at the solid/liquid interface on the dynamics of dewetting and the form of a liquid front. Our study reflects these recent developments and adds new experimental data to corroborate the theoretical models. To probe the solid/liquid boundary condition experimentally, different methods are possible, each bearing advantages and disadvantages, which will be discussed. Studying liquid flow on a variety of different substrates entails a view on the direct implications of the substrate. The experimental focus of this study is the variation of the polymer chain length; the results demonstrate that inter-chain entanglements and in particular their density close to the interface, originating from non-bulk conformations, govern the liquid slip of a polymer. (paper)

  10. Cholesteric colloidal liquid crystals from phytosterol rod-like particles

    NARCIS (Netherlands)

    Rossi, L.; Sacanna, S.; Velikov, K.P.

    2011-01-01

    We report the first observation of chiral colloidal liquid crystals of rod-like particles from a low molecular weight organic compound— phytosterols. Based on the particles shape and crystal structure, we attribute this phenomenon to chiral distribution of surface charge on the surface of

  11. Mechanisms of Photo-Induced Deformations of Liquid Crystal Elastomers

    Science.gov (United States)

    Dawson, Nathan; Kuzyk, Mark; Neal, Jeremy; Luchette, Paul; Palffy-Muhoray, Peter

    2010-03-01

    Over a century ago, Alexander Graham Bell invented the photophone, which he used to transmit mechanical information on a beam of light. We report on the use of an active Fabry-Perot interferometer to encode and detect mechanical information using the photomechanical effect of a liquid crystal elastomer (LCE) that is placed at a critical point between the reflectors. These are the first steps in the creation of ultra smart materials which require a large photomechanical response. Thus, understanding the underlying mechanisms is critical. Only limited studies of the mechanisms of the photomechanical effect, such as photo-isomerization, photo-reorientation and thermal effects have been studied in azo-dye-doped LCEs and in azo-dye-doped polymer fibers have been reported. The focus of our present work is to use the Fabry-Perot transducer geometry to study the underlying mechanisms and to determine the relevant material parameters that are used to develop theoretical models of the response. We use various intensity-modulated optical wave forms to determine the frequency response of the material, which are used to predict the material response.

  12. NMR studies of liquid crystals and molecules dissolved in liquid crystal solvents

    Energy Technology Data Exchange (ETDEWEB)

    Drobny, Gary Peter [Univ. of California, Berkeley, CA (United States)

    1982-11-01

    This thesis describes several studies in which nuclear magnetic resonance (nmr) spectroscopy has been used to probe the structure, orientation and dynamics of liquid crystal mesogens and molecules dissolved in liquid crystalline phases. In addition, a modern high field nmr spectrometer is described which has been used to perform such nmr studies. Chapter 1 introduces the quantum mechanical formalisms used throughout this thesis and briefly reviews the fundamentals of nuclear spin physics and pulsed nmr spectroscopy. First the density operator is described and a specific form for the canonical ensemble is derived. Then Clebsch-Gordon coefficients, Wigner rotation matrices, and irreducible tensor operators are reviewed. An expression for the equilibrium (Curie) magnetization is obtained and the linear response of a spin system to a strong pulsed r.f. irradiation is described. Finally, the spin interaction Hamiltonians relevant to this work are reviewed together with their truncated forms. Chapter 2 is a deuterium magnetic resonance study of two 'nom' liquid crystals which possess several low temperature mesomorphic phases. Specifically, deuterium quadrupolar echo spectroscopy is used to determine the orientation of the liquid crystal molecules in smectic phases, the changes in molecular orientation and motion that occur at smectic-smectic phase transitions, and the order of the phase transitions. For both compounds, the phase sequence is determined to be isotropic, nematic, smectic A, smectic C, smectic BA, smectic BC, and crystalline. The structure of the smectic A phase is found to be consistent with the well-known model of a two dimensional liquid in which molecules are rapidly rotating about their long axes and oriented at right angles to the plane of the layers. Molecules in the smectic C phase are found to have their long axes tilted with respect to the layer normal, and the tilt angle is temperature dependent, increasing from

  13. Liquid polymers for using in a holographic ionizing radiation dosimeter

    International Nuclear Information System (INIS)

    Nicolau-Rebigan, S.

    1979-01-01

    Some liquid polymeric systems for using in the holographic ionizing radiation dosimeter are presented. It is shown that the action of radiation on polymers leads to the destruction of the polymeric chains or to perform them, the both processes being applied in radiation dosimetry. Some advantages of the holographic dosimeter are outlined comparatively with those common used. (author)

  14. Rapid, facile synthesis of conjugated polymer zwitterions in ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Page, Zachariah A. [Polymer Science & Engineering Department; Conte Center for Polymer Research; University of Massachusetts; Amherst, USA; Liu, Feng [Polymer Science & Engineering Department; Conte Center for Polymer Research; University of Massachusetts; Amherst, USA; Russell, Thomas P. [Polymer Science & Engineering Department; Conte Center for Polymer Research; University of Massachusetts; Amherst, USA; Emrick, Todd [Polymer Science & Engineering Department; Conte Center for Polymer Research; University of Massachusetts; Amherst, USA

    2014-01-01

    Ionic liquids (ILs) were utilized for the rapid air-stable Suzuki polymerization of polar zwitterionic thiophene monomers, precluding the need for volatile organic solvents, phosphine ligands and phase transfer catalysts typically used in conjugated polymer synthesis.

  15. Liquid crystallinity in flexible and rigid rod polymers

    International Nuclear Information System (INIS)

    Pickett, Galen T.; Schweizer, Kenneth S.

    2000-01-01

    We apply an anisotropic version of the polymer reference interaction site model (PRISM) integral equation description of flexible polymers to analyze athermal liquid crystallinity. The polymers are characterized by a statistical segment length, σ o , and by a physical hard-core thickness, d, that prevents the overlap of monomers on different chains. At small segment densities, ρ, the microscopic length scale d is irrelevant (as it must be in the universal semidilute regime), but becomes important in concentrated solutions and melts. Under the influence of the excluded volume interactions alone, the chains undergo a lyotropic, first-order isotropic-nematic transition at a concentration dependent upon the dimensionless ''aspect ratio,'' σ o /d. The transition becomes weaker as d→0, becoming second order, as has been previously shown. We extend the theory to describe the transition of rigid, thin rods, and discuss the evolution of the anisotropic liquid structure in the ordered phase. (c) 2000 American Institute of Physics

  16. Synthesis of Isothianaphthene (ITN and 3,4-Ethylenedioxy-Thiophene (EDOT-Based Low-Bandgap Liquid Crystalline Conjugated Polymers

    Directory of Open Access Journals (Sweden)

    Hiromasa Goto

    2013-05-01

    Full Text Available Copolymers, consisting of isothianaphthene and phenylene derivatives with liquid crystal groups, were synthesized via Migita-Kosugi-Stille polycondensation reaction. IR absorption, UV-vis optical absorption, and PL spectroscopy measurements were carried out. Thermotropic liquid crystallinity of the polymers with bandgap of ~2.5 eV was confirmed.

  17. Advanced Electroactive Single Crystal and Polymer Actuator Concepts for Passive Optics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes large stroke and high precision piezoelectric single crystal and electroactive polymer actuator concepts?HYBrid Actuation System (HYBAS)...

  18. Recent Advances in Discotic Liquid Crystal-Assisted Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ashwathanarayana Gowda

    2018-03-01

    Full Text Available This article primarily summarizes recent advancement in the field of discotic liquid crystal (DLC nanocomposites. Discotic liquid crystals are nanostructured materials, usually 2 to 6 nm size and have been recognized as organic semiconducting materials. Recently, it has been observed that the dispersion of small concentration of various functionalized zero-, one- and two-dimensional nanomaterials in the supramolecular order of mesophases of DLCs imparts negligible impact on liquid crystalline properties but enhances their thermal, supramolecular and electronic properties. Synthesis, characterization and dispersion of various nanoparticles in different discotics are presented.

  19. Fabrication of Phase-Change Polymer Colloidal Photonic Crystals

    Directory of Open Access Journals (Sweden)

    Tianyi Zhao

    2014-01-01

    Full Text Available This paper presents the preparation of phase-change polymer colloidal photonic crystals (PCs by assembling hollow latex spheres encapsulated with dodecanol for the first time. The monodispersed hollow latex spheres were obtained by phase reversion of monodispersed core-shell latex spheres in the n-hexane, which dissolves the PS core and retains the PMMA/PAA shell. The as-prepared phase-change colloidal PCs show stable phase-change behavior. This fabrication of phase-change colloidal PCs would be significant for PC’s applications in functional coatings and various optic devices.

  20. Single mode dye-doped polymer photonic crystal lasers

    International Nuclear Information System (INIS)

    Christiansen, Mads B; Buß, Thomas; Smith, Cameron L C; Petersen, Sidsel R; Jørgensen, Mette M; Kristensen, Anders

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e.g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be −0.045 or −0.066 nm K -1 , depending on the material

  1. Single mode dye-doped polymer photonic crystal lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...... emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e. g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be -0.045 or -0...

  2. Quantum Dot/Liquid Crystal Nanocomposites in Photonic Devices

    Directory of Open Access Journals (Sweden)

    Andrea L. Rodarte

    2015-07-01

    Full Text Available Quantum dot/liquid crystal nano-composites are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however, we need to control and stabilize nano-particle dispersion in different liquid crystal host phases and understand how the particles behave in an anisotropic fluid. An ideal system will allow for the controlled assembly of either well-defined nano-particle clusters or a uniform particle distribution. In this paper, we investigate mesogen-functionalized quantum dots for dispersion in cholesteric liquid crystal. These nanoparticles are known to assemble into dense stable packings in the nematic phase, and such structures, when localized in the liquid crystal defects, can potentially enhance the coupling between particles and a cholesteric cavity. Controlling the dispersion and assembly of quantum dots using mesogenic surface ligands, we demonstrate how resonant fluid photonic cavities can result from the co-assembly of luminescent nanoparticles in the presence of cholesteric liquid crystalline ordering.

  3. Do protein crystals nucleate within dense liquid clusters?

    International Nuclear Information System (INIS)

    Maes, Dominique; Vorontsova, Maria A.; Potenza, Marco A. C.; Sanvito, Tiziano; Sleutel, Mike; Giglio, Marzio; Vekilov, Peter G.

    2015-01-01

    The evolution of protein-rich clusters and nucleating crystals were characterized by dynamic light scattering (DLS), confocal depolarized dynamic light scattering (cDDLS) and depolarized oblique illumination dark-field microscopy. Newly nucleated crystals within protein-rich clusters were detected directly. These observations indicate that the protein-rich clusters are locations for crystal nucleation. Protein-dense liquid clusters are regions of high protein concentration that have been observed in solutions of several proteins. The typical cluster size varies from several tens to several hundreds of nanometres and their volume fraction remains below 10 −3 of the solution. According to the two-step mechanism of nucleation, the protein-rich clusters serve as locations for and precursors to the nucleation of protein crystals. While the two-step mechanism explained several unusual features of protein crystal nucleation kinetics, a direct observation of its validity for protein crystals has been lacking. Here, two independent observations of crystal nucleation with the proteins lysozyme and glucose isomerase are discussed. Firstly, the evolutions of the protein-rich clusters and nucleating crystals were characterized simultaneously by dynamic light scattering (DLS) and confocal depolarized dynamic light scattering (cDDLS), respectively. It is demonstrated that protein crystals appear following a significant delay after cluster formation. The cDDLS correlation functions follow a Gaussian decay, indicative of nondiffusive motion. A possible explanation is that the crystals are contained inside large clusters and are driven by the elasticity of the cluster surface. Secondly, depolarized oblique illumination dark-field microscopy reveals the evolution from liquid clusters without crystals to newly nucleated crystals contained in the clusters to grown crystals freely diffusing in the solution. Collectively, the observations indicate that the protein-rich clusters in

  4. On the molecular anisotropy of liquid crystalline and flexible polymer systems

    Science.gov (United States)

    van Horn, Brett L.

    The demand for products of ever increasing quality or for novel applications has required increasing attention to or manipulation of the anisotropy of manufactured parts. Oriented plastics are used everywhere from recording film to automotive body parts to monofilament fishing line. Liquid crystals are also used in a wide array of applications including their dominance in the flat panel display industry, color changing temperature sensors, and woven bullet resistant fabrics. Anisotropy can also be detrimental, for instance sometimes leading to poor fracture resistance or low yield stress along specific directions. Controlling and measuring anisotropy of materials has become increasingly important, but doing so is wrought with challenges. Measuring physical properties of isotropic liquids, such as water or most oils can be done in a straightforward fashion. Their viscosities and densities, for example, have unique values under a given set of conditions. With anisotropic fluids, like liquid crystals, the viscosity, for instance, will not only depend upon temperature, concentration, etc. but also upon the direction of observation, degree of anisotropy, source of anisotropy, and so forth. This added degree of complexity complicates our ability to define the state of the material at which the measurements are made and generally necessitates the use of more sophisticated measurement strategies or techniques. This work presents techniques and tools for investigating anisotropy in liquid crystalline and stretched polymeric systems. Included are the use of conoscopy for the determination of birefringence and orientation of nematic liquid crystals and stretched polymers, the shear response of flow aligning nematic liquid crystal monodomains, and the design of a novel linear rheometer that allows for in situ optical or scattering investigations.

  5. Visual Sensor for Sterilization of Polymer Fixtures Using Embedded Mesoporous Silicon Photonic Crystals.

    Science.gov (United States)

    Kumeria, Tushar; Wang, Joanna; Chan, Nicole; Harris, Todd J; Sailor, Michael J

    2018-01-26

    A porous photonic crystal is integrated with a plastic medical fixture (IV connector hub) to provide a visual colorimetric sensor to indicate the presence or absence of alcohol used to sterilize the fixture. The photonic crystal is prepared in porous silicon (pSi) by electrochemical anodization of single crystal silicon, and the porosity and the stop band of the material is engineered such that the integrated device visibly changes color (green to red or blue to green) when infiltrated with alcohol. Two types of self-reporting devices are prepared and their performance compared: the first type involves heat-assisted fusion of a freestanding pSi photonic crystal to the connector end of a preformed polycarbonate hub, forming a composite where the unfilled portion of the pSi film acts as the sensor; the second involves generation of an all-polymer replica of the pSi photonic crystal by complete thermal infiltration of the pSi film and subsequent chemical dissolution of the pSi portion. Both types of sensors visibly change color when wetted with alcohol, and the color reverts to the original upon evaporation of the liquid. The sensor performance is verified using E. coli-infected samples.

  6. Dynamics of Active Nematic Liquid Crystals

    Science.gov (United States)

    DeCamp, Stephen J.

    liquid crystal by assembling microtubule bundles into a quasi-2D film confined to a large, flat oil-water interface. Internal stresses generated by kinesin motors drive the system far from equilibrium which precludes a uniformly aligned nematic ground state through the continuous creation and annihilation of +/-1/2 motile defects. First, we demonstrate that the nematic is extensile by observing the deformation of a photobleached spot which undergoes extension along the nematic director and contraction perpendicular to the director. We map the experimentally tunable parameter, ATP concentration, to the intrinsic activity of the sample measured by the characteristic time of the contractile dynamics. Then, we characterize the flow of individual microtubules by measuring their relative velocity within the nematic and find a flow field consistent with a force dipole but where the magnitude of the extension and contraction velocity are proportional to the separation between the filaments. The extensile and contractile flow velocities can be tuned by the ATP concentration and can be as large as 6 mum/s. Then we spatially map microtubule concentration, alignment, and flow near topological defect cores. We test a theory which predicts that flows are directly proportional to the local alignment of the nematic and find our results inconsistent with that theory. Finally, we measure large scale velocity and vorticity distributions as well as vortex area distributions and find agreement with other recent theoretical predictions. Next, we turn our attention to the complex behavior of defects in the active nematic. Using defect tracking algorithms developed by Gabriel S. Redner, we measure the +/-1/2 defect velocity and lifetime distributions as well as MSD and average defect density. We find that average velocities, lifetimes, and densities are tunable by varying the ATP concentration. The MSDs reveal that motile +1/2 defects stream ballistically through the sample (up to 15 mum

  7. Printable optical sensors based on H-bonded supramolecular cholesteric liquid crystal networks.

    Science.gov (United States)

    Herzer, Nicole; Guneysu, Hilal; Davies, Dylan J D; Yildirim, Derya; Vaccaro, Antonio R; Broer, Dirk J; Bastiaansen, Cees W M; Schenning, Albertus P H J

    2012-05-09

    A printable H-bonded cholesteric liquid crystal (CLC) polymer film has been fabricated that, after conversion to a hygroscopic polymer salt film, responds to temperature and humidity by changing its reflection color. Fast-responding humidity sensors have been made in which the reflection color changes between green and yellow depending on the relative humidity. The change in reflection band is a result of a change in helix pitch in the film due to absorption and desorption of water, resulting in swelling/deswelling of the film material. When the polymer salt was saturated with water, a red-reflecting film was obtained that can potentially act as a time/temperature integrator. Finally, the films were printed on a foil, showing the potential application of supramolecular CLC materials as low-cost, printable, battery-free optical sensors.

  8. INERA Workshop 2016: Membrane and Liquid Crystal Nanostructures (MELINA 2016)

    International Nuclear Information System (INIS)

    2017-01-01

    We are pleased to introduce the Proceedings of the INERA Workshop “Membrane and Liquid Crystal Nanostructures” (MELINA 2016). This meeting was held from 3 th to 6 th of September 2016 in Varna (Bulgaria) and was organized by the Institute of Solid State Physics, Bulgarian Academy of Sciences (ISSP-BAS) in the frames of the Project INERA “Research and Innovation Capacity Strengthening of ISSP-BAS in Multifunctional Nanostructures” REGPOT-2012-2013-1 NMP (http://www.inera.org). The workshop venue was the “Saints Constantine and Helena” Resort - a beautiful complex on the Bulgarian Black Sea coast within a landscaped park 10 km north of downtown Varna, close to the Euxinograd royal summer palace, park and winery. The aim of this workshop was to bring together researchers with interests in interdisciplinary areas in order to report the recent results of their scientific work, to discuss the state-of-the-art and perspectives and communicate new ideas. Several experimental and theoretical streams in the field of nanostructured liquid crystal systems and nanocomposites; soft and living matter physics; membrane biophysics; nanostructures in polymer and lipid membranes; characterization of soft nanomaterials were merged and directed towards a constructive discussion and solutions of a wide variety of actual problems in these important scientific areas. Participants from 9 countries presented 20 oral and 15 poster presentations in 5 topical areas. INERA Workshop MELINA 2016 provided very good opportunities for direct contacts, interesting discussions and interactive exchange of ideas between the participants. It also became a meeting point where INERA partners could plan and organize their future efficient collaborations and joint research projects of common interest. The editors would like to thank all authors for their high-quality contributions. The papers submitted for publication in the Proceedings were refereed according to the publishing standards of the

  9. Liquid crystals with novel terminal chains as ferroelectric liquid crystal hosts

    International Nuclear Information System (INIS)

    Cosquer, G.Y.

    2000-02-01

    Changes to the molecular structure of liquid crystals can have a significant effect upon their mesomorphism and ferroelectric properties. Most of the research in liquid crystal for display applications concentrates on the design and synthesis of novel mesogenic cores to which straight terminal alkyl or alkoxy chains are attached. However, little is known about the effects upon the mesomorphism and ferroelectric properties of varying the terminal chains. The compounds prepared in this work have a common core - a 2,3-difluoroterphenyl unit with a nine-atom alkyl (nonyl) or alkoxy (octyloxy) chain at the 4-position, but with an unusual chain at the 4''-position. In some cases the terminal chain contains hetero atoms such as silicon, oxygen, chlorine and bromine or has a bulky end group. In total 46 final materials were synthesised in an attempt to understand the effect of an unusual terminal chains on mesomorphism and for some of these compounds the effect upon the switching times when added to a standard ferroelectric mixture were investigated. It was found that most compounds containing a bulky end group only displayed a smectic C phase, compounds with a halogen substituent as an end unit displayed a smectic A phase and that increasing the chain flexibility by introducing an oxygen atom in the chain reduces the melting and clearing points. The electro-optical measurements carried out on ferroelectric mixtures containing a bulky end group compound showed that shorter switching times were produced than for the ferroelectric mixture containing a straight chain compound. It is suggested that a bulky end group diminishes te extent of interlayer mixing in the chiral smectic C phase and therefore the molecules move more easily with ferroelectric switching. (author)

  10. Nanoscience with liquid crystals from self-organized nanostructures to applications

    CERN Document Server

    Li, Quan

    2014-01-01

    This book focuses on the exciting topic of nanoscience with liquid crystals: from self-organized nanostructures to applications. The elegant self-organized liquid crystalline nanostructures, the synergetic characteristics of liquid crystals and nanoparticles, liquid crystalline nanomaterials, synthesis of nanomaterials using liquid crystals as templates, nanoconfinement and nanoparticles of liquid crystals are covered and discussed, and the prospect of fabricating functional materials is highlighted. Contributions, collecting the scattered literature of the field from leading and active player

  11. Thermal degradation of polymer systems having liquid crystalline oligoester segment

    Directory of Open Access Journals (Sweden)

    Renato Matroniani

    Full Text Available Abstract Block copolymers and blends comprised by liquid crystalline oligoester and polystyrene were prepared and their thermal stability were characterized by thermogravimetric analysis (TGA. The samples have shown three main decomposition temperatures due to (1 lost of flexible chain and decomposition of mesogenic segment, (2 decomposition of polystyrene and (3 final decomposition of oligoester rigid segment. Both copolymers and polymer blends presented lower thermal stability compared to polystyrene and oligoester. The residual mass after heating at 600 °C in copolymers and polymer blends were lower than those found in the oligoesters. A degradative process of aromatic segments of oligoester induced by decomposition of polystyrene is suggested.

  12. Light scattering from crystals, glasses and liquids

    International Nuclear Information System (INIS)

    Subbaswamy, K.R.

    1984-09-01

    The theory of inelastic light scattering from a model system in the crystalline, disordered and liquid phases is analyzed. The roles of disorder induced first order scattering and second order scattering are clarified in the context of the classical liquid. The correlation functions appropriate for the various contributions are identified and useful ways of processing experimental data are pointed out. (author)

  13. Liquid crystals: high technology materials for potential applications

    International Nuclear Information System (INIS)

    Saeed, M.A.; Badaruddin; Rizvi, T.Z.

    1993-01-01

    Liquid crystals have very rapidly emerged as a basis of many high technology fields within the last few decades. These materials because of their intriguing physical properties are regarded as the fourth state of matter. At present the applications of liquid crystals are established in digital display devices, electro-optical switches, optical computing, acousto-optics, thermo-indicators, laser thermo-recording, photo-chemical image recording and optical communication networks. More recently due to the concept of molecularly based electronics (MBE): the logical extreme for miniaturization of electronic device, liquid crystals are foreseen to play a vital role in the future optics based technologies. This paper gives a brief introduction to liquid crystals, the types of meso phases found in these materials together with their applications in research and industry. Some technical details of the construction liquid crystal cells for some typical applications in digital displays and other electro optical devices have also been discussed with special emphasis on relevant physical processes occurring at molecular level. (author)

  14. Photonics of liquid-crystal structures: A review

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Blinov, L M; Barnik, M I; Lazarev, V V; Umanskii, B A; Shtykov, N M [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2011-07-15

    The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.

  15. Optical Study of Liquid Crystal Doped with Multiwalled Carbon Nanotube

    Science.gov (United States)

    Gharde, Rita A.; Thakare, Sangeeta Y.

    2014-11-01

    Liquid crystalline materials have been useful for display devices i.e watches, calculators, automobile dashboards, televisions, multi media projectors etc. as well as in electro tunable lasers, optical fibers and lenses. Carbon nanotube is chosen as the main experimental factor in this study as it has been observed that Carbon Nano Tube influence the existing properties of liquid crystal host and with the doping of CNT can enhance1 the properties of LC. The combination of carbon nanotube (CNT) and liquid crystal (LC) materials show considerable interest in the scientific community due to unique physical properties of CNT in liquid crystal. Dispersion of CNTs in LCs can provide us a cheap, simple, versatile and effective means of controlling nanotube orientation on macroscopic scale with no restrictions on nanotube type. LCs have the long range orientational order rendering them to be anisotropic phases. If CNTs can be well dispersed in LC matrix, they will align with their long axes along the LC director to minimize distortions of the LC director field and the free energy. In this paper, we doped liquid crystal (Cholesteryl Nonanoate) by a small amount of multiwall carbon nanotube 0.05% and 0.1% wt. We found that by adding carbon nanotube to liquid crystals the melting point of the mixture is decreased but TNI is increased. It has been also observed that with incereas in concentration of carbon nanotube into liquid crystal shows conciderable effect on LC. The prepared samples were characterized using various techniques to study structural, thermal and optical properties i.e PMS, FPSS, UV-Vis spectroscopy, FT-IR measurements, and DTA.

  16. Electrodeposition of Polymer Nanostructures using Three Diffuse Double Layers: Polymerization beyond the Liquid/Liquid Interfaces

    Science.gov (United States)

    Divya, Velpula; Sangaranarayanan, M. V.

    2018-04-01

    Nanostructured conducting polymers have received immense attention during the past few decades on account of their phenomenal usefulness in diverse contexts, while the interface between two immiscible liquids is of great interest in chemical and biological applications. Here we propose a novel Electrode(solid)/Electrolyte(aqueous)/Electrolyte(organic) Interfacial assembly for the synthesis of polymeric nanostructures using a novel concept of three diffuse double layers. There exist remarkable differences between the morphologies of the polymers synthesized using the conventional electrode/electrolyte method and that of the new approach. In contrast to the commonly employed electrodeposition at liquid/liquid interfaces, these polymer modified electrodes can be directly employed in diverse applications such as sensors, supercapacitors etc.

  17. 2D mesoscale colloidal crystal patterns on polymer substrates

    Science.gov (United States)

    Bredikhin, Vladimir; Bityurin, Nikita

    2018-05-01

    The development of nanosphere lithography relies on the ability of depositing 2D colloidal crystals comprising micro- and nano-size elements on substrates of different materials. One of the most difficult problems here is deposition of coatings on hydrophobic substrates, e.g. polymers, from aqueous colloidal solutions. We use UV photooxidation for substrate hydrophilization. We demonstrate a new method of producing a two-dimensional ordered array of polymer microparticles (polystyrene microspheres ∼1 μm in diameter) on a polymer substrate (PMMA). We show that implementation of the new deposition technique for directed self-assembly of microspheres on an UV irradiated surface provides an opportunity to obtain coatings on a hydrophilized PMMA surface of large area (∼5 cm2). UV irradiation of the surface through masks allows creating 2D patterns consisting of mesoscale elements formed by the deposited self-assembled microparticles owing to the fact that the colloidal particles are deposited only on the irradiated area leaving the non-irradiated sections intact.

  18. Flexible Bistable Smectic-A Liquid Crystal Device Using Photolithography and Photoinduced Phase Separation

    Directory of Open Access Journals (Sweden)

    Yang Lu

    2012-01-01

    Full Text Available A flexible bistable smectic-A liquid crystal (SmA LC device using pixel-isolated mode was demonstrated, in which SmA LC molecules were isolated in pixels by vertical polymer wall and horizontal polymer layer. The above microstructure was achieved by using ultraviolet (UV photolithography and photoinduced phase separation. The polymer wall was fabricated by photolithography, and then the SmA LC was encapsulated in pixels between polymer wall through UV-induced phase separation, in which the polymer wall acts as supporting structure from mechanical pressure and maintains the cell gap from bending, and the polymer layer acts as adhesive for tight attachment of two substrates. The results demonstrated that all the intrinsic bistable properties of the SmA LC are preserved, and good electrooptical characteristics such as high contrast ratio and excellent stability of the bistable states were characterized. This kind of SmA bistable flexible display has high potential to be used as electronic paper, smart switchable reflective windows, and so forth.

  19. Reverse-mode thermoresponsive light attenuators produced by optical anisotropic composites of nematic liquid crystals and reactive mesogens

    Science.gov (United States)

    Kakiuchida, Hiroshi; Ogiwara, Akifumi

    2018-04-01

    Polymer network liquid crystals (PNLCs) whose optical transmittance state switches between transparence at low temperatures and haze at high temperatures were fabricated from mixtures of nematic liquid crystals (LCs) and reactive mesogens (RMs). This PNLC structure is simple but effective, namely, consists of micro-scale domains of orientation-ordered LCs and anisotropically polymerized RMs. The domains form through photopolymerization induced phase separation with inhomogeneous irradiation projected by laser speckling techniques. This irradiation method enables you to control the size and shape of phase-separation domains, and these PNLCs can be applied to novel thermoresponsive optical devices; optical isolators, thermometric sheets, and smart windows.

  20. Endovascular treatment of intracranial aneurysms using liquid polymer injection

    International Nuclear Information System (INIS)

    Liu Jianmin; Huang Qinghai; Xu Yi; Hong Bo

    2004-01-01

    Objective: To report our preliminary clinical experience in embolization of intracranial aneurysms with liquid polymer (Onyx). Methods: One case of posterior communicating artery aneurysm was treated with Onyx and microcoils, while the other one with multiple basilar aneurysms was treated by Onyx combined with stent-coiling technique. Results: All the aneurysms were totally occluded with patency of parent arteries. There was no procedure-related complication. The patients recovered well during clinical follow-up for 3 months. The angiographic follow-up in one patient showed the result was stable and Onyx was totally apart from the flow in parent artery. Conclusions: Short-term result suggests that endovascular treatment of intracranial aneurysms with liquid polymer is safe and effective, however more experience is needed. (authors)

  1. Old and new ideas in ferroelectric liquid crystal technology

    Science.gov (United States)

    Lagerwall, Sven T.; Matuszczyk, M.; Matuszczyk, T.

    1998-02-01

    Ferroelectric liquid crystals (FLC) are to conventional liquid crystal what Gallium Arsenide is to Silicon in the semiconductor area. The first generation of FLC displays in now present on the market and has some outstanding features based on the symmetric bistability which may be achieved in these materials. One of the greatest challenges for the next generation is to achieve an analog grey scale out of an essentially digital principle. We will analyze in some detail which major problems had to be solved to reach the present state and show how the final steps could be taken toward a new state-of-the-art level in liquid crystal devices. In the last decade university research and industrial R and D have almost equally contributed to treat the very serious complications caused by the so-called chevron structures We will review this important topic in particular detail.

  2. Young-Laplace equation for liquid crystal interfaces

    Science.gov (United States)

    Rey, Alejandro D.

    2000-12-01

    This letter uses the classical theories of liquid crystal physics to derive the Young-Laplace equation of capillary hydrostatics for interfaces between viscous isotropic (I) fluids and nematic liquid crystals (NLC's), and establishes the existence of four energy contributions to pressure jumps across these unusual anisotropic interfaces. It is shown that in addition to the usual curvature contribution, bulk and surface gradient elasticity, elastic stress, and anchoring energy contribute to pressure differentials across the interface. The magnitude of the effect is proportional to the elastic moduli of the NLC, and to the bulk and surface orientation gradients that may be present in the nematic phase. In contrast to the planar interface between isotropic fluids, flat liquid crystal interfaces support pressure jumps if elastic stresses, bulk and surface gradient energy, and/or anchoring energies are finite.

  3. Vitrification and Crystallization of Phase-Separated Metallic Liquid

    Directory of Open Access Journals (Sweden)

    Yun Cheng

    2017-02-01

    Full Text Available The liquid–liquid phase separation (LLPS behavior of Fe50Cu50 melt from 3500 K to 300 K with different rapid quenching is investigated by molecular dynamics (MD simulation based on the embedded atom method (EAM. The liquid undergoes metastable phase separation by spinodal decomposition in the undercooled regime and subsequently solidifies into three different Fe-rich microstructures: the interconnected-type structure is kept in the glass and crystal at a higher cooling rate, while the Fe-rich droplets are found to crystalize at a lower cooling rate. During the crystallization process, only Fe-rich clusters can act as the solid nuclei. The twinning planes can be observed in the crystal and only the homogeneous atomic stacking shows mirror symmetry along the twinning boundary. Our present work provides atomic-scale understanding of LLPS melt during the cooling process.

  4. Shrink, twist, ripple and melt: Studies of frustrated liquid crystals

    Science.gov (United States)

    Fernsler, Jonathan G.

    Complex structures can arise out of a simple system with more than one competing influence on its behavior. The protypical example of this is the two-dimensional triangular lattice Ising model. The ferromagnetic model has two simple degenerate ground states of all spins up or down, but the antiferromagnetic model is a frustrated system. Its geometry does not allow satisfaction of the antiferro condition everywhere, which produces complex ordered structures with dimerization of the spins [1]. Without frustration, the complex structures and phase behavior are lost. All of the topics discussed in this thesis concern smectic liquid crystals. Liquid crystals are perhaps uniquely adept at manifesting frustrated phases. Their combination of periodicity in one or more dimensions allows ordered structures, yet their fluid nature in remaining dimensions allows creation of defects and extraordinarily complex structures in ways that a normal crystal could not tolerate. Liquid crystals contain a huge menagerie of frustrated phases and effects including the polarization modulated [2], vortex lattice [3], twist grain boundary [4], and blue [5] phases, as well as frustrated structures such as cholesteric or SmC* helix unwinding [6], defect lattices in thin films [7], and bend melted grain boundary defects [8], arising from boundary conditions and field effects. In this thesis, we study four liquid crystal systems that show unusual phase behavior or complex structures, deriving from the effects of frustration. Frustration, despite some human prejudices against the word, leaves nature all the more interesting and beautiful.

  5. NMR and molecular dynamics of small solutes in liquid crystals

    International Nuclear Information System (INIS)

    Luyten, P.R.

    1984-01-01

    NMR relaxation measurements, using a wide variety of modern pulse techniques, can yield valuable information about molecular motions. In this thesis the applicability of theories developed to describe spin relaxation phenomena in partially ordered media is studied for small solutes in liquid crystals. 1 H, 2 H, 13 C and 14 N relaxation measurements are interpreted by means of a model, in which fast anisotropic re-orientational motion in an orienting potential combined with contributions from cooperative fluctuations in the surrounding liquid crystal molecules, induce the observed frequency dependent relaxation behavior. (orig.)

  6. A Microwave Tunable Bandpass Filter for Liquid Crystal Applications

    Science.gov (United States)

    Cao, Weiping; Jiang, Di; Liu, Yupeng; Yang, Yuanwang; Gan, Baichuan

    2017-07-01

    In this paper, a novel microwave continuously tunable band-pass filter, based on nematic liquid crystals (LCs), is proposed. It uses liquid crystal (LC) as the electro-optic material to mainly realize frequency shift at microwave band by changing the dielectric anisotropy, when applying the bias voltage. According to simulation results, it achieves 840 MHz offset. Comparing to the existing tunable filter, it has many advantages, such as continuously tunable, miniaturization, low processing costs, low tuning voltage, etc. Thus, it has shown great potentials in frequency domain and practical applications in modern communication.

  7. Flexoelectricity in an oxadiazole bent-core nematic liquid crystal

    OpenAIRE

    Kaur, Sarabjot; Panov, V. P.; Greco, C.; Ferrarini, A.; Görtz, Verena; Goodby, John W.; Gleeson, Helen F.

    2014-01-01

    We have determined experimentally the magnitude of the difference in the splay and bend flexoelectric coefficients, |e 1 − e 3|, of an oxadiazole bent-core liquid crystal by measuring the critical voltage for the formation of flexodomains together with their wave number. The coefficient |e 1 − e 3| is found to be a factor of 2–3 times higher than in most conventional calamitic nematic liquid crystals, varying from 8 pCm−1 to 20 pCm−1 across the ∼60 K—wide nematic regime. We have also calculat...

  8. A flexible optically re-writable color liquid crystal display

    Science.gov (United States)

    Zhang, Yihong; Sun, Jiatong; Liu, Yang; Shang, Jianhua; Liu, Hao; Liu, Huashan; Gong, Xiaohui; Chigrinov, Vladimir; Kowk, Hoi Sing

    2018-03-01

    It is very difficult to make a liquid crystal display (LCD) that is flexible. However, for an optically re-writable LCD (ORWLCD), only the spacers and the substrates need to be flexible because the driving unit and the display unit are separate and there are no electronics in the display part of ORWLCD. In this paper, three flexible-spacer methods are proposed to achieve this goal. A cholesteric liquid crystal colored mirror with a polarizer behind it is used as the colored reflective backboard of an ORWLCD. Polyethersulfone substrates and flexible spacers are used to make the optically re-writable cell insensitive to mechanical force.

  9. Synthesis of carbonated hydroxyapatite nanorods in liquid crystals

    Directory of Open Access Journals (Sweden)

    Daniella Dias Palombino de Campos

    2009-09-01

    Full Text Available Syntheses of calcium phosphate nanoparticles, carried out in systems formed from surfactant, oil and water, have resulted in materials with promising possibilities for application. The calcium phosphate particles were synthesized using two different liquid crystals, formed from RenexTM, cyclohexane and a salts solution. The morphology of the nanoparticles synthesized in the liquid crystals is similar to that of hydroxyapatite particles that form bone mineral, where collagen fibers connect these particles so as to form a composite. Therefore, the synthesis of calcium phosphate nanoparticles in the systems used in this work can advance current understanding of mineralization processes that result in the formation of bone mineral.

  10. Compact electrically controlled broadband liquid crystal photonic bandgap fiber polarizer

    DEFF Research Database (Denmark)

    Wei, Lei; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2009-01-01

    An electrically controlled liquid crystal photonic-bandgap fiber polarizer is experimentally demonstrated. A maximum 21.3dB electrically tunable polarization extinction ratio is achieved with 45° rotatable transmission axis as well as switched on and off in 1300nm–1600nm.......An electrically controlled liquid crystal photonic-bandgap fiber polarizer is experimentally demonstrated. A maximum 21.3dB electrically tunable polarization extinction ratio is achieved with 45° rotatable transmission axis as well as switched on and off in 1300nm–1600nm....

  11. Bistable switching in dual-frequency liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Barnik, M I [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2006-06-15

    Various bistable switching modes in nematic liquid crystals with frequency inversion of the sign of dielectric anisotropy are revealed and investigated. Switching between states with different helicoidal distributions of the director field of a liquid crystal, as well as between uniform and helicoidal states, is realized by dual-frequency waveforms of a driving voltage. A distinctive feature of the dual-frequency switching is that the uniform planar distribution of the director field may correspond to a thermodynamically equilibrium state, and the chirality of an LC is not a necessary condition for switching to a helicoidal state.

  12. Hydrothermal decomposition of liquid crystal in subcritical water

    International Nuclear Information System (INIS)

    Zhuang, Xuning; He, Wenzhi; Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao

    2014-01-01

    Highlights: • Hydrothermal technology can effectively decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. • The decomposition rate reached 97.6% under the optimized condition. • Octoxy-4'-cyanobiphenyl was mainly decomposed into simple and innocuous products. • The mechanism analysis reveals the decomposition reaction process. - Abstract: Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4′-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4′-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H 2 O 2 supply, pH value 6, temperature 275 °C and reaction time 5 min, 97.6% of 4-octoxy-4′-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment

  13. Large three-dimensional photonic crystals based on monocrystalline liquid crystal blue phases.

    Science.gov (United States)

    Chen, Chun-Wei; Hou, Chien-Tsung; Li, Cheng-Chang; Jau, Hung-Chang; Wang, Chun-Ta; Hong, Ching-Lang; Guo, Duan-Yi; Wang, Cheng-Yu; Chiang, Sheng-Ping; Bunning, Timothy J; Khoo, Iam-Choon; Lin, Tsung-Hsien

    2017-09-28

    Although there have been intense efforts to fabricate large three-dimensional photonic crystals in order to realize their full potential, the technologies developed so far are still beset with various material processing and cost issues. Conventional top-down fabrications are costly and time-consuming, whereas natural self-assembly and bottom-up fabrications often result in high defect density and limited dimensions. Here we report the fabrication of extraordinarily large monocrystalline photonic crystals by controlling the self-assembly processes which occur in unique phases of liquid crystals that exhibit three-dimensional photonic-crystalline properties called liquid-crystal blue phases. In particular, we have developed a gradient-temperature technique that enables three-dimensional photonic crystals to grow to lateral dimensions of ~1 cm (~30,000 of unit cells) and thickness of ~100 μm (~ 300 unit cells). These giant single crystals exhibit extraordinarily sharp photonic bandgaps with high reflectivity, long-range periodicity in all dimensions and well-defined lattice orientation.Conventional fabrication approaches for large-size three-dimensional photonic crystals are problematic. By properly controlling the self-assembly processes, the authors report the fabrication of monocrystalline blue phase liquid crystals that exhibit three-dimensional photonic-crystalline properties.

  14. Using Quartz Crystal Microbalance for Field Measurement of Liquid Viscosities

    Directory of Open Access Journals (Sweden)

    Qingsong Bai

    2016-01-01

    Full Text Available The field measurement of liquid viscosities, especially the high viscous liquids, is challenging and often requires expensive equipment, long processing time, and lots of reagent. We use quartz crystal microbalances (QCMs operating in solution which are also sensitive to the viscosity and density of the contacting solution. QCMs are typically investigated for sensor applications in which one surface of QCM completely immersed in Newtonian liquid, but the viscous damping in liquids would cause not only large frequency shifts but also large losses in the quality factor Q leading to instability and even cessation of oscillation. A novel mass-sensitivity-based method for field measurement of liquid viscosities using a QCM is demonstrated in this paper and a model describing the influence of the liquid properties on the oscillation frequency is established as well. Two groups of verified experiments were performed and the experimental results show that the presented method is effective and possesses potential applications.

  15. Multi-scale entropic depletion phenomena in polymer liquids

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Debapriya [Department of Materials Science, University of Illinois, Urbana, Illinois 61801 (United States); Schweizer, Kenneth S., E-mail: kschweiz@illinois.edu [Department of Materials Science, University of Illinois, Urbana, Illinois 61801 (United States); Department of Chemistry, University of Illinois, Urbana, Illinois 61801 (United States); Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    2015-06-07

    We apply numerical polymer integral equation theory to study the entropic depletion problem for hard spheres dissolved in flexible chain polymer melts and concentrated solutions over an exceptionally wide range of polymer radius of gyration to particle diameter ratios (R{sub g}/D), particle-monomer diameter ratios (D/d), and chain lengths (N) including the monomer and oligomer regimes. Calculations are performed based on a calibration of the effective melt packing fraction that reproduces the isobaric dimensionless isothermal compressibility of real polymer liquids. Three regimes of the polymer-mediated interparticle potential of mean force (PMF) are identified and analyzed in depth. (i) The magnitude of the contact attraction that dominates thermodynamic stability scales linearly with D/d and exhibits a monotonic and nonperturbative logarithmic increase with N ultimately saturating in the long chain limit. (ii) A close to contact repulsive barrier emerges that grows linearly with D/d and can attain values far in excess of thermal energy for experimentally relevant particle sizes and chain lengths. This raises the possibility of kinetic stabilization of particles in nanocomposites. The barrier grows initially logarithmically with N, attains a maximum when 2R{sub g} ∼ D/2, and then decreases towards its asymptotic long chain limit as 2R{sub g} ≫ D. (iii) A long range (of order R{sub g}) repulsive, exponentially decaying component of the depletion potential emerges when polymer coils are smaller than, or of order, the nanoparticle diameter. Its amplitude is effectively constant for 2R{sub g} ≤ D. As the polymer becomes larger than the particle, the amplitude of this feature decreases extremely rapidly and becomes negligible. A weak long range and N-dependent component of the monomer-particle pair correlation function is found which is suggested to be the origin of the long range repulsive PMF. Implications of our results for thermodynamics and miscibility are

  16. Magneto-optic dynamics in a ferromagnetic nematic liquid crystal

    OpenAIRE

    Potisk, Tilen; Mertelj, Alenka; Sebastian, Nerea; Osterman, Natan; Lisjak, Darja; Brand, Helmut R.; Pleiner, Harald; Svenšek, Daniel

    2018-01-01

    We investigate dynamic magneto-optic effects in a ferromagnetic nematic liquid crystal experimentally and theoretically. Experimentally we measure the magnetization and the phase difference of the transmitted light when an external magnetic field is applied. As a model we study the coupled dynamics of the magnetization, M, and the director field, n, associated with the liquid crystalline orientational order. We demonstrate that the experimentally studied macroscopic dynamic behavior reveals t...

  17. Liquid Crystals - The 'Fourth' Phase of Matter

    Indian Academy of Sciences (India)

    possibilities of novel technological applications. Liquid crystalline materials ... advanced instrumentation, including laptops and futuristic flat panel displays. .... The twist grain-boundary phase is formed when the layers of a smectic A phase are .... the optic axis) is uniformly oriented parallel to the glass plate. (see Figure IIa).

  18. Fast-switching initially-transparent liquid crystal light shutter with crossed patterned electrodes

    Directory of Open Access Journals (Sweden)

    Joon Heo

    2015-04-01

    Full Text Available We propose an initially transparent light shutter using polymer-networked liquid crystals with crossed patterned electrodes. The proposed light shutter is switchable between the transparent and opaque states, and it exhibits a fast response time and a low operating voltage. In the transparent state, the light shutter has high transmittance; in the opaque state, it can block the background image and provides black color. We expect that the proposed light shutter can be applied to see-through displays and smart windows.

  19. Packaging consideration of two-dimensional polymer-based photonic crystals for laser beam steering

    Science.gov (United States)

    Dou, Xinyuan; Chen, Xiaonan; Chen, Maggie Yihong; Wang, Alan Xiaolong; Jiang, Wei; Chen, Ray T.

    2009-02-01

    In this paper, we report the theoretical study of polymer-based photonic crystals for laser beam steering which is based on the superprism effect as well as the experiment fabrication of the two dimensional photonic crystals for the laser beam steering. Superprism effect, the principle for beam steering, was separately studied in details through EFC (Equifrequency Contour) analysis. Polymer based photonic crystals were fabricated through double exposure holographic interference method using SU8-2007. The experiment results were also reported.

  20. Crystal nuclei templated nanostructured membranes prepared by solvent crystallization and polymer migration

    Science.gov (United States)

    Wang, Bo; Ji, Jing; Li, Kang

    2016-09-01

    Currently, production of porous polymeric membranes for filtration is predominated by the phase-separation process. However, this method has reached its technological limit, and there have been no significant breakthrough over the last decade. Here we show, using polyvinylidene fluoride as a sample polymer, a new concept of membrane manufacturing by combining oriented green solvent crystallization and polymer migration is able to obtain high performance membranes with pure water permeation flux substantially higher than those with similar pore size prepared by conventional phase-separation processes. The new manufacturing procedure is governed by fewer operating parameters and is, thus, easier to control with reproducible results. Apart from the high water permeation flux, the prepared membranes also show excellent stable flux after fouling and superior mechanical properties of high pressure load and better abrasion resistance. These findings demonstrate the promise of a new concept for green manufacturing nanostructured polymeric membranes with high performances.

  1. NOCHAR Polymers: An Aqueous and Organic Liquid Solidification Process for Cadarache LOR (Liquides Organiques Radioactifs) - 13195

    International Nuclear Information System (INIS)

    Vaudey, Claire-Emilie; Renou, Sebastien; Porco, Julien; Kelley, Dennis; Cochaud, Chantal; Serrano, Roger

    2013-01-01

    To handle the Very Low Level Waste (VLLW) and the Low Level Waste (LLW) in France, two options can be considered: the incineration at CENTRACO facility and the disposal facility on ANDRA sites. The waste acceptance in these radwaste routes is dependent upon the adequacy between the waste characteristics (physical chemistry and radiological) and the radwaste route specifications. If the waste characteristics are incompatible with the radwaste route specifications (presence of significant quantities of chlorine, fluorine, organic component etc or/and high activity limits), it is necessary to find an alternative solution that consists of a waste pre-treatment process. In the context of the problematic Cadarache LOR (Liquides Organiques Radioactifs) waste streams, two radioactive scintillation cocktails have to be treated. The first one is composed of organic liquids at 13.1 % (diphenyloxazol, mesitylene, TBP, xylene) and water at 86.9 %. The second one is composed of TBP at 8.6 % and water at 91.4 %. They contain chlorine, fluorine and sulphate and have got alpha/beta/gamma spectra with mass activities equal to some kBq.g -1 . Therefore, tritium is present and creates the second problematic waste stream. As a consequence, in order for disposal acceptance at the ANDRA site, it is necessary to pre-treat the waste. The NOCHAR polymers as an aqueous and organic liquid solidification process seem to be an adequate solution. Indeed, these polymers constitute an important variety of products applied to the treatment of radioactive aqueous and organic liquids (solvent, oil, solvent/oil mixing etc) and sludge through a mechanical and chemical solidification process. For Cadarache LOR, N910 and N960 respectively dedicated to the organic and aqueous liquids solidification are considered. With the N910, the organic waste solidification occurs in two steps. As the organic liquid travels moves through the polymer strands, the strands swell and immobilise the liquid. Then as the

  2. Micro-fabricated Liquid Encapsulated Energy Harvester with Polymer Barrier Layer as Liquid Electret Interface

    International Nuclear Information System (INIS)

    Bu, L; Xu, H Y; Xu, B J; Song, L

    2014-01-01

    This paper addresses the electret discharge issue for liquid based electret energy harvesters. An interface structure of PDMS/PTFE polymer barrier layer between liquid and electrets is introduced, achieving 75% charge retain rate over 100h, compared with 0% without the proposed layer over 100h. Further, the PDMS/PTFE layer is introduced into liquid encapsulated energy harvester (LEEH) and is compatible with micro-fabrication process. The retain rate of device voltage is about 47%∼65% over 100h. At 100h after corona charging, the device generates maximally 3.7V, 0.55μW @1Hz rotation

  3. Coupled effects of director orientations and boundary conditions on light induced bending of monodomain nematic liquid crystalline polymer plates

    International Nuclear Information System (INIS)

    You, Yue; Ding, Shurong; Huo, Yongzhong; Xu, Changwei

    2012-01-01

    A photo-chromic liquid crystal polymers (LCPs) is a smart material for large light-activated variation or bending to transfer luminous energy into mechanical energy. We study the light induced behavior by modeling planar and homeotropic nematic network polymer plates. We effectively illustrate some reported experimental outcomes and theoretically predict some possible bending patterns. This paper constructs an understanding between the bending behaviors and interactions among the alignments, aspect ratios and boundary conditions, etc. Our work provides information on optimizing light induced bending in the process of micro-opto-mechanical system (MOMS) design. (paper)

  4. Penetration of RBD palm olein in a lyotropic liquid crystal

    International Nuclear Information System (INIS)

    Hamdan bin Suhaimi; Anuar bin Kasim

    1993-01-01

    The inner structure of lamellar liquid crystal before and after addition of RDB palm olein was characterised employing small-angle X-ray scattering (SAXS) technique and optical microscopy. Results show that the addition of RDB palm olein to both layered structure indicate a temporary disturbance resulting in penetration of RDB palm olein into the layered structure

  5. Liquid Crystal Gel Reduces Age Spots by Promoting Skin Turnover

    Directory of Open Access Journals (Sweden)

    Mina Musashi

    2014-07-01

    Full Text Available Studies have shown that liquid crystals structurally resembling the intercellular lipids in the stratum corneum can beneficially affect the skin when applied topically by stimulating the skin’s natural regenerative functions and accelerating epidermal turnover. In the present study, the effects of applying low concentrations of a liquid crystal gel of our own creation were evaluated using epidermal thickening in mouse skin as an assay for effective stimulation of epidermal turnover. A liquid crystal gel was also applied topically to human facial skin, and analysis was conducted using before-and-after photographs of age spots, measurements of L* values that reflect degree of skin pigmentation, single-layer samples of the stratum corneum obtained via tape-stripping, and measurements of trans-epidermal water loss that reflect the status of the skin’s barrier function. The results suggested that cost-effective creams containing as low as 5% liquid crystal gel might be effective and safely sold as skin care products targeting age spots and other problems relating to uneven skin pigmentation.

  6. On asymptotic isotropy for a hydrodynamic model of liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Dai, M.; Feireisl, Eduard; Rocca, E.; Schimperna, G.; Schonbek, M.E.

    2016-01-01

    Roč. 97, 3-4 (2016), s. 189-210 ISSN 0921-7134 Grant - others:European Research Council(XE) MATHEF(320078) Institutional support: RVO:67985840 Keywords : liquid crystal * Q-tensor description * long-time behavior Subject RIV: BA - General Mathematics Impact factor: 0.933, year: 2016 http://content.iospress.com/articles/asymptotic-analysis/asy1348

  7. On a hyperbolic system arising in liquid crystals modeling

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Rocca, E.; Schimperna, G.; Zarnescu, A.

    2018-01-01

    Roč. 15, č. 1 (2018), s. 15-35 ISSN 0219-8916 EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : dissipative solution * liquid crystal * weak-strong uniqueness Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.940, year: 2016 https://www.worldscientific.com/doi/abs/10.1142/S0219891618500029

  8. Liquid crystal elastomer coatings with programmed response of surface profile

    NARCIS (Netherlands)

    Babakhanova, G.; Turiv, T.; Guo, Y.; Hendrikx, M.; Wei, Q.H.; Schenning, A.P.H.J.; Broer, D.J.; Lavrentovich, O.D.

    2018-01-01

    Stimuli-responsive liquid crystal elastomers with molecular orientation coupled to rubber-like elasticity show a great potential as elements in soft robotics, sensing, and transport systems. The orientational order defines their mechanical response to external stimuli, such as thermally activated

  9. Ultraviolet-pumped liquid-crystal dye-laser

    International Nuclear Information System (INIS)

    Bertolotti, M.; Sbrolli, L.; Scudieri, F.; Papa, T.

    1981-01-01

    The possibility offered by the orientation properties of liquid crystals as a matrix for dye lasers is shown. In particular, the linear polarization of emitted light can be changed by acting with an external magnetic field on the molecular nematic director. (author)

  10. Advances in chemical physics advances in liquid crystals

    CERN Document Server

    Prigogine, Ilya; Vij, Jagdish K

    2009-01-01

    Prigogine and Rice's highly acclaimed series, Advances in Chemical Physics, provides a forum for critical, authoritative reviews of current topics in every area of chemical physics. Edited by J.K. Vij, this volume focuses on recent advances in liquid crystals with significant, up-to-date chapters authored by internationally recognized researchers in the field.

  11. Optical monitoring of gases with cholesteric liquid crystals

    NARCIS (Netherlands)

    Han, Y.; Pacheco Morillo, K.B.; Bastiaansen, C.W.M.; Broer, D.J.; Sijbesma, R.P.

    2010-01-01

    A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The

  12. Alignment of carbon nanotubes in nematic liquid crystals

    NARCIS (Netherlands)

    Schoot, van der P.P.A.M.; Popa-Nita, V.; Kralj, S.

    2008-01-01

    The self-organizing properties of nematic liquid crystals can be used to align carbon nanotubes dispersed in them. Because the nanotubes are so much thinner than the elastic penetration length, the alignment is caused by the coupling of the unperturbed director field to the anisotropic interfacial

  13. Chiral HPLC and physical characterisation of orthoconic antiferroelectric liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Vojtylová, Terézia; Żurowska, M.; Milewska, K.; Hamplová, Věra; Sýkora, D.

    2016-01-01

    Roč. 43, č. 9 (2016), s. 1244-1250 ISSN 0267-8292 R&D Projects: GA MŠk(CZ) LD14007; GA ČR GA15-02843S Institutional support: RVO:68378271 Keywords : liquid crystals * chiral HPLC * orthoconic antiferroelectric LC Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.661, year: 2016

  14. The finite-size effect in thin liquid crystal systems

    Science.gov (United States)

    Śliwa, I.

    2018-05-01

    Effects of surface ordering in liquid crystal systems confined between cell plates are of great theoretical and experimental interest. Liquid crystals introduced in thin cells are known to be strongly stabilized and ordered by cell plates. We introduce a new theoretical method for analyzing the effect of surfaces on local molecular ordering in thin liquid crystal systems with planar geometry of the smectic layers. Our results show that, due to the interplay between pair long-range intermolecular forces and nonlocal, relatively short-range, surface interactions, both orientational and translational orders of liquid crystal molecules across confining cells are very complex. In particular, it is demonstrated that the SmA, nematic, and isotropic phases can coexist. The phase transitions from SmA to nematic, as well as from nematic to isotropic phases, occur not simultaneously in the whole volume of the system but begin to appear locally in some regions of the LC sample. Phase transition temperatures are demonstrated to be strongly affected by the thickness of the LC system. The dependence of the corresponding shifts of phase transition temperatures on the layer number is shown to exhibit a power law character. This new type of scaling behavior is concerned with the coexistence of local phases in finite systems. The influence of a specific character of interactions of molecules with surfaces and other molecules on values of the resulting critical exponents is also analyzed.

  15. On asymptotic isotropy for a hydrodynamic model of liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Dai, M.; Feireisl, Eduard; Rocca, E.; Schimperna, G.; Schonbek, M.E.

    2016-01-01

    Roč. 97, 3-4 (2016), s. 189-210 ISSN 0921-7134 Grant - others:European Research Council(XE) MATHEF(320078) Institutional support: RVO:67985840 Keywords : liquid crystal * Q-tensor description * long-time behavior Subject RIV: BA - General Mathematics Impact factor: 0.933, year: 2016 http://content.iospress.com/articles/asymptotic- analysis /asy1348

  16. Metric approach for sound propagation in nematic liquid crystals

    Science.gov (United States)

    Pereira, E.; Fumeron, S.; Moraes, F.

    2013-02-01

    In the eikonal approach, we describe sound propagation near topological defects of nematic liquid crystals as geodesics of a non-Euclidian manifold endowed with an effective metric tensor. The relation between the acoustics of the medium and this geometrical description is given by Fermat's principle. We calculate the ray trajectories and propose a diffraction experiment to retrieve information about the elastic constants.

  17. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert

    2011-07-01

    Full Text Available The chain polymer [{Cd(μ-X2py2}1∞] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  18. Identifying the primitive path mesh in entangled polymer liquids

    International Nuclear Information System (INIS)

    Sukumaran, Sathish K.; Kremer, Kurt; Grest, Gary Stephen; Everaers, Ralf

    2004-01-01

    Similar to entangled ropes, polymer chains cannot slide through each other. These topological constraints, the so-called entanglements, dominate the viscoelastic behavior of high-molecular-weight polymeric liquids. Tube models of polymer dynamics and rheology are based on the idea that entanglements confine a chain to small fluctuations around a primitive path which follows the coarse-grained chain contour. To establish the microscopic foundation for these highly successful phenomenological models, we have recently introduced a method for identifying the primitive path mesh that characterizes the microscopic topological state of computer-generated conformations of long-chain polymer melts and solutions. Here we give a more detailed account of the algorithm and discuss several key aspects of the analysis that are pertinent for its successful use in analyzing the topology of the polymer configurations. We also present a slight modification of the algorithm that preserves the previously neglected self-entanglements and allows us to distinguish between local self-knots and entanglements between distant sections of the same chain. Our results indicate that the latter make a negligible contribution to the tube and that the contour length between local self-knots, N 1k is significantly larger than the entanglement length N e

  19. Modeling of the (liquid + liquid) equilibrium of polydisperse hyperbranched polymer solutions by lattice-cluster theory

    International Nuclear Information System (INIS)

    Enders, Sabine; Browarzik, Dieter

    2014-01-01

    Graphical abstract: - Highlights: • Calculation of the (liquid + liquid) equilibrium of hyperbranched polymer solutions. • Description of branching effects by the lattice-cluster theory. • Consideration of self- and cross association by chemical association models. • Treatment of the molar-mass polydispersity by the use of continuous thermodynamics. • Improvement of the theoretical results by the incorporation of polydispersity. - Abstract: The (liquid + liquid) equilibrium of solutions of hyperbranched polymers of the Boltorn type is modeled in the framework of lattice-cluster theory. The association effects are described by the chemical association models CALM (for self association) and ECALM (for cross association). For the first time the molar mass polydispersity of the hyperbranched polymers is taken into account. For this purpose continuous thermodynamics is applied. Because the segment-molar excess Gibbs free energy depends on the number average of the segment number of the polymer the treatment is more general than in previous papers on continuous thermodynamics. The polydispersity is described by a generalized Schulz–Flory distribution. The calculation of the cloud-point curve reduces to two equations that have to be numerically solved. Conditions for the calculation of the spinodal curve and of the critical point are derived. The calculated results are compared to experimental data taken from the literature. For Boltorn solutions in non-polar solvents the polydispersity influence is small. In all other of the considered cases polydispersity influences the (liquid + liquid) equilibrium considerably. However, association and polydispersity influence phase equilibrium in a complex manner. Taking polydispersity into account the accuracy of the calculations is improved, especially, in the diluted region

  20. Characterization of polyacrylamide-stabilized Pf1 phage liquid crystals for protein NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Trempe, Jean-Francois; Morin, Frederick G.; Xia Zhicheng; Marchessault, Robert H.; Gehring, Kalle [McGill University, Department of Biochemistry and Department of Chemistry (Canada)], E-mail: kalle@bri.nrc.ca

    2002-01-15

    A new polymer-stabilized nematic liquid crystal has been characterized for the measurement of biomolecular residual dipolar couplings. Filamentous Pf1 phage were embedded in a polyacrylamide matrix that fixes the orientation of the particles. The alignment was characterized by the quadrupolar splitting of the {sup 2}H NMR water signal and by the measurement of {sup 1}H-{sup 15}N residual dipolar couplings (RDC) in the archeal translation elongation factor 1{beta}. Protein dissolved in the polymer-stabilized medium orients quantitatively as in media without polyacrylamide. We show that the quadrupolar splitting and RDCs are zero in media in which the Pf1 phage particles are aligned at the magic angle. This allows measurement of J and dipolar couplings in a single sample.

  1. Characterization of polyacrylamide-stabilized Pf1 phage liquid crystals for protein NMR spectroscopy

    International Nuclear Information System (INIS)

    Trempe, Jean-Francois; Morin, Frederick G.; Xia Zhicheng; Marchessault, Robert H.; Gehring, Kalle

    2002-01-01

    A new polymer-stabilized nematic liquid crystal has been characterized for the measurement of biomolecular residual dipolar couplings. Filamentous Pf1 phage were embedded in a polyacrylamide matrix that fixes the orientation of the particles. The alignment was characterized by the quadrupolar splitting of the 2 H NMR water signal and by the measurement of 1 H- 15 N residual dipolar couplings (RDC) in the archeal translation elongation factor 1β. Protein dissolved in the polymer-stabilized medium orients quantitatively as in media without polyacrylamide. We show that the quadrupolar splitting and RDCs are zero in media in which the Pf1 phage particles are aligned at the magic angle. This allows measurement of J and dipolar couplings in a single sample

  2. Interaction Studies between Newly Synthesized Photosensitive Polymer and Ionic Liquids

    Directory of Open Access Journals (Sweden)

    In Tae Kim

    2015-01-01

    Full Text Available In this information age, different kinds of photosensitive materials have been used in the manufacture of information storage devices. But these photosensitive materials have the bane of low diffraction efficiency. In order to solve this problem, we have synthesized a novel photosensitive polymer from epoxy-based azopolymers (with three types of azochromophores. Furthermore, we have studied the interaction between this newly synthesized azopolymer and ionic liquids (ILs. For this purpose, we have used the ammonium and imidazolium families of ILs, such as diethylammonium dihydrogen phosphate (DEAP, tributylammonium methyl sulfate (TBMS, triethylammonium 4-aminotoluene-3-sulfonic acid (TASA, and 1-methylimidazolium chloride ([Mim]Cl. To investigate the molecular interaction between azopolymer and ILs, we have used the following spectroscopic methods of analysis: UV-visible spectroscopy, photoluminescence (PL spectroscopy, Fourier transformed infrared spectroscopy (FT-IR, and confocal Raman spectroscopy. In this study, we have developed new photosensitive materials by combining polymer with ILs.

  3. Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

    OpenAIRE

    Scolari, Lara; Gauza, Sebastian; Xianyu, Haiqing; Zhai, Lei; Eskildsen, Lars; Alkeskjold, Thomas Tanggaard; Wu, Shin-Tson; Bjarklev, Anders Overgaard

    2009-01-01

    We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability ...

  4. Piezo-optical and electro-optical behaviour of nematic liquid crystals dispersed in a ferroelectric copolymer matrix

    International Nuclear Information System (INIS)

    Ganesan, Lakshmi Meena; Wirges, Werner; Gerhard, Reimund; Mellinger, Axel

    2010-01-01

    Polymer-dispersed liquid crystals (PDLCs) are composite materials that consist of micrometre-sized liquid-crystal (LC) droplets embedded in a polymer matrix. From ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and a nematic LC, PDLC films containing 10 and 60 wt% LC were prepared, and their electro-optical and piezo-optical behaviour was investigated. The electric field that is generated by the application of mechanical stress leads to changes in the transmittance of the PDLC film through a combination of piezoelectric and electro-optical effects. Such a piezo-optical PDLC material may be useful, e.g., in sensing and visualization applications.

  5. Time-resolved crystallization of deeply cooled liquid hydrogen isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnel, Matthias

    2014-02-15

    This thesis serves two main purposes: 1. The introduction of a novel experimental method to investigate phase change dynamics of supercooled liquids 2. First-time measurements for the crystallization behaviour for hydrogen isotopes under various conditions (1) The new method is established by the synergy of a liquid microjet of ∼ 5 μm diameter and a scattering technique with high spatial resolution, here linear Raman spectroscopy. Due to the high directional stability and the known velocity of the liquid filament, its traveling axis corresponds to a time axis static in space. Utilizing evaporative cooling in a vacuum environment, the propagating liquid cools down rapidly and eventually experiences a phase transition to the crystalline state. This temporal evolution is probed along the filament axis, ultimately resulting in a time resolution of 10 ns. The feasibility of this approach is proven successfully within the following experiments. (2) A main object of study are para-hydrogen liquid filaments. Raman spectra reveal a temperature gradient of the liquid across the filament. This behaviour can quantitatively be reconstructed by numerical simulations using a layered model and is rooted in the effectiveness of evaporative cooling on the surface and a finite thermal conductivity. The deepest supercoolings achieved are ∼ 30% below the melting point, at which the filament starts to solidify from the surface towards the core. With a crystal growth velocity extracted from the data the appropriate growth mechanism is identified. The crystal structure that initially forms is metastable and probably the result of Ostwald's rule of stages. Indications for a transition within the solid towards the stable equilibrium phase support this interpretation. The analog isotope ortho-deuterium is evidenced to behave qualitatively similar with quantitative differences being mass related. In further measurements, isotopic mixtures of para-hydrogen and ortho-deuterium are

  6. Time-resolved crystallization of deeply cooled liquid hydrogen isotopes

    International Nuclear Information System (INIS)

    Kuehnel, Matthias

    2014-02-01

    This thesis serves two main purposes: 1. The introduction of a novel experimental method to investigate phase change dynamics of supercooled liquids 2. First-time measurements for the crystallization behaviour for hydrogen isotopes under various conditions (1) The new method is established by the synergy of a liquid microjet of ∼ 5 μm diameter and a scattering technique with high spatial resolution, here linear Raman spectroscopy. Due to the high directional stability and the known velocity of the liquid filament, its traveling axis corresponds to a time axis static in space. Utilizing evaporative cooling in a vacuum environment, the propagating liquid cools down rapidly and eventually experiences a phase transition to the crystalline state. This temporal evolution is probed along the filament axis, ultimately resulting in a time resolution of 10 ns. The feasibility of this approach is proven successfully within the following experiments. (2) A main object of study are para-hydrogen liquid filaments. Raman spectra reveal a temperature gradient of the liquid across the filament. This behaviour can quantitatively be reconstructed by numerical simulations using a layered model and is rooted in the effectiveness of evaporative cooling on the surface and a finite thermal conductivity. The deepest supercoolings achieved are ∼ 30% below the melting point, at which the filament starts to solidify from the surface towards the core. With a crystal growth velocity extracted from the data the appropriate growth mechanism is identified. The crystal structure that initially forms is metastable and probably the result of Ostwald's rule of stages. Indications for a transition within the solid towards the stable equilibrium phase support this interpretation. The analog isotope ortho-deuterium is evidenced to behave qualitatively similar with quantitative differences being mass related. In further measurements, isotopic mixtures of para-hydrogen and ortho-deuterium are

  7. Time-resolved crystallization of deeply cooled liquid hydrogen isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnel, Matthias

    2014-02-15

    This thesis serves two main purposes: 1. The introduction of a novel experimental method to investigate phase change dynamics of supercooled liquids 2. First-time measurements for the crystallization behaviour for hydrogen isotopes under various conditions (1) The new method is established by the synergy of a liquid microjet of ∼ 5 μm diameter and a scattering technique with high spatial resolution, here linear Raman spectroscopy. Due to the high directional stability and the known velocity of the liquid filament, its traveling axis corresponds to a time axis static in space. Utilizing evaporative cooling in a vacuum environment, the propagating liquid cools down rapidly and eventually experiences a phase transition to the crystalline state. This temporal evolution is probed along the filament axis, ultimately resulting in a time resolution of 10 ns. The feasibility of this approach is proven successfully within the following experiments. (2) A main object of study are para-hydrogen liquid filaments. Raman spectra reveal a temperature gradient of the liquid across the filament. This behaviour can quantitatively be reconstructed by numerical simulations using a layered model and is rooted in the effectiveness of evaporative cooling on the surface and a finite thermal conductivity. The deepest supercoolings achieved are ∼ 30% below the melting point, at which the filament starts to solidify from the surface towards the core. With a crystal growth velocity extracted from the data the appropriate growth mechanism is identified. The crystal structure that initially forms is metastable and probably the result of Ostwald's rule of stages. Indications for a transition within the solid towards the stable equilibrium phase support this interpretation. The analog isotope ortho-deuterium is evidenced to behave qualitatively similar with quantitative differences being mass related. In further measurements, isotopic mixtures of para-hydrogen and ortho-deuterium are

  8. Liquid crystals for organic thin-film transistors

    Science.gov (United States)

    Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-Ichi

    2015-04-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

  9. Magneto-optic dynamics in a ferromagnetic nematic liquid crystal

    Science.gov (United States)

    Potisk, Tilen; Mertelj, Alenka; Sebastián, Nerea; Osterman, Natan; Lisjak, Darja; Brand, Helmut R.; Pleiner, Harald; Svenšek, Daniel

    2018-01-01

    We investigate dynamic magneto-optic effects in a ferromagnetic nematic liquid crystal experimentally and theoretically. Experimentally we measure the magnetization and the phase difference of the transmitted light when an external magnetic field is applied. As a model we study the coupled dynamics of the magnetization, M , and the director field, n , associated with the liquid crystalline orientational order. We demonstrate that the experimentally studied macroscopic dynamic behavior reveals the importance of a dynamic cross-coupling between M and n . The experimental data are used to extract the value of the dissipative cross-coupling coefficient. We also make concrete predictions about how reversible cross-coupling terms between the magnetization and the director could be detected experimentally by measurements of the transmitted light intensity as well as by analyzing the azimuthal angle of the magnetization and the director out of the plane spanned by the anchoring axis and the external magnetic field. We derive the eigenmodes of the coupled system and study their relaxation rates. We show that in the usual experimental setup used for measuring the relaxation rates of the splay-bend or twist-bend eigenmodes of a nematic liquid crystal one expects for a ferromagnetic nematic liquid crystal a mixture of at least two eigenmodes.

  10. Mixing effects in the crystallization of supercooled quantum binary liquids

    International Nuclear Information System (INIS)

    Kühnel, M.; Kalinin, A.; Fernández, J. M.; Tejeda, G.; Moreno, E.; Montero, S.; Tramonto, F.; Galli, D. E.; Nava, M.; Grisenti, R. E.

    2015-01-01

    By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH 2 ) or orthodeuterium (oD 2 ) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH 2 and oD 2 crystal growth rates, similarly to what found in our previous work on supercooled pH 2 -oD 2 liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites

  11. Mixing effects in the crystallization of supercooled quantum binary liquids

    Energy Technology Data Exchange (ETDEWEB)

    Kühnel, M.; Kalinin, A. [Institut für Kernphysik, J. W. Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); Fernández, J. M.; Tejeda, G.; Moreno, E.; Montero, S. [Laboratory of Molecular Fluid Dynamics, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain); Tramonto, F.; Galli, D. E. [Laboratorio di Calcolo Parallelo e di Simulazioni di Materia Condensata, Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Nava, M. [Laboratorio di Calcolo Parallelo e di Simulazioni di Materia Condensata, Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, CH-6900 Lugano (Switzerland); Grisenti, R. E. [Institut für Kernphysik, J. W. Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); GSI - Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

    2015-08-14

    By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH{sub 2}) or orthodeuterium (oD{sub 2}) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH{sub 2} and oD{sub 2} crystal growth rates, similarly to what found in our previous work on supercooled pH{sub 2}-oD{sub 2} liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites.

  12. Optimized Wavelength-Tuned Nonlinear Frequency Conversion Using a Liquid Crystal Clad Waveguide

    Science.gov (United States)

    Stephen, Mark A. (Inventor)

    2018-01-01

    An optimized wavelength-tuned nonlinear frequency conversion process using a liquid crystal clad waveguide. The process includes implanting ions on a top surface of a lithium niobate crystal to form an ion implanted lithium niobate layer. The process also includes utilizing a tunable refractive index of a liquid crystal to rapidly change an effective index of the lithium niobate crystal.

  13. New theories for smectic and nematic liquid crystalline polymers

    International Nuclear Information System (INIS)

    Dowell, F.

    1987-01-01

    A summary of results from new statistical-physics theories for both backbone and side-chain liquid crystalline polymers (LCPs) and for mixtures with LCPs is presented. Thermodynamic and molecular ordering properties (including odd-even effects) 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. These theories can also be applied to combined LCPs. Since these theories have no ad hoc or arbitrarily adjustable parameters, these theories have been used to design new LCPs and new solvents and to predict and explain properties

  14. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    International Nuclear Information System (INIS)

    Wahle, Markus; Kitzerow, Heinz-Siegfried

    2015-01-01

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage

  15. Formation of Gd coordination polymer with 1D chains mediated by Bronsted acidic ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Qianqian; Han, Ying [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai (China); Lin, Hechun, E-mail: hclin@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai (China); Zhang, Yuanyuan; Duan, Chungang [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai (China); Peng, Hui, E-mail: hpeng@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China)

    2017-03-15

    One dimensional coordination polymer Gd[(SO{sub 4})(NO{sub 3})(C{sub 2}H{sub 6}SO){sub 2}] (1) is prepared through the mediation of Bronsted acid ionic liquid, which crystallized in the monoclinic space of C2/c. In this polymer, adjacent Gd atoms are linked by two SO{sub 4}{sup 2-} ions to generate a 1-D chain, and all oxygen atoms in SO{sub 4}{sup 2-} groups are connected to three nearest Gd atoms in µ{sup 3}:η{sup 1}:η{sup 1}:η{sup 2} fashion. Gd, S and N from SO{sub 4}{sup 2-} and NO{sub 3}{sup -} are precisely coplanar. The planar is coordinated by a pair of DMSO molecules, which is parallel and linked by hydrogen bonding to form a three-dimensional supramolecular network. Magnetic susceptibility measurement of 1 reveals weak antiferromagnetic interactions between the Gd (III) ions. It exhibits relatively large magneto-caloric effect with –ΔS{sub m}=28.8 J Kg{sup −1} K{sup −1} for ΔH=7 T. - Graphical abstract: Coordination polymer Gd[(SO{sub 4})(NO{sub 3})(C{sub 2}H{sub 6}SO){sub 2}] was obtained mediated by Bronsted acid Ionic Liquid, which presents a 1-D chains collected by SO{sub 4}{sup 2-} groups. Magnetic susceptibility of the polymer reveals weak antiferromagnetic interactions between the Gd(III) ions with the relatively large magneto-caloric effect of –ΔS{sub m}=28.8 J Kg{sup −1} K{sup −1} for ΔH= 7T.

  16. Variation along liquid isomorphs of the driving force for crystallization

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Adrjanowicz, Karolina; Niss, Kristine

    2017-01-01

    at a reference temperature. More general analysis allows interpretation of experimental data for molecular liquids such as dimethyl phthalate and indomethacin, and suggests that the isomorph scaling exponent γ in these cases is an increasing function of density, although this cannot be seen in measurements......We investigate the variation of the driving force for crystallization of a supercooled liquid along isomorphs, curves along which structure and dynamics are invariant. The variation is weak, and can be predicted accurately for the Lennard-Jones fluid using a recently developed formalism and data...

  17. Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure.

    Science.gov (United States)

    Adamová, Gabriela; Gardas, Ramesh L; Nieuwenhuyzen, Mark; Puga, Alberto V; Rebelo, Luís Paulo N; Robertson, Allan J; Seddon, Kenneth R

    2012-07-21

    A series of alkyltributylphosphonium chloride ionic liquids, prepared from tributylphosphine and the respective 1-chloroalkane, C(n)H(2n+1)Cl (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 or 14), is reported. This work is a continuation of an extended series of tetraalkylphosphonium ionic liquids, where the focus is on the variability of n and its impact on the physical properties, such as melting points/glass transitions, thermal stability, density and viscosity. Experimental density and viscosity data were interpreted using QPSR and group contribution methods and the crystal structure of propyl(tributyl)phosphonium chloride is detailed.

  18. Large Electro-Optic Kerr-Effect in Ionic Liquid Crystals: Connecting Features of Liquid Crystals and Polyelectrolytes.

    Science.gov (United States)

    Schlick, Michael Christian; Kapernaum, Nadia; Neidhardt, Manuel; Wöhrle, Tobias; Stöckl, Yannick; Laschat, Sabine; Gießelmann, Frank

    2018-06-06

    The electro-optic Kerr effect in the isotropic phase of two ionic liquid crystals (ILCs) is investigated and compared to the Kerr effect in non-ionic liquid crystals (LCs) with same phase sequences, namely direct isotropic to hexagonal columnar transitions and direct isotropic to smectic-A transitions. Up to electric field amplitudes of some 106 V m-1, the optical birefringence induced in the isotropic phases follows Kerr's law and strongly increases when the temperature approaches the transition temperature into the particular liquid crystalline phase. Close to the transition, maximum Kerr constants in the order of 10-11 m V-2 are found, which are more than ten times higher than the Kerr constant of nitrobenzene, a strongly dipolar fluid with a huge Kerr effect applied in optical shutters and phase modulators. In comparison to their non-ionic LC counterparts the Kerr effect in ILCs is found to be enhanced in magnitude, but slowed-down in speed, showing rise times in the order of ten milliseconds. These remarkable differences are attributed to the presence of counterion polarization well-known from complex ionic fluids such as polyelectrolytes or ionic micellar solutions. ILCs thus combine the Kerr effect features of liquid crystals and complex ionic fluids. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Multi-Scale Responses of Liquid Crystals Triggered by Interfacial Assemblies of Cleavable Homopolymers.

    Science.gov (United States)

    Kim, Young-Ki; Huang, Yuran; Tsuei, Michael; Wang, Xin; Gianneschi, Nathan C; Abbott, Nicholas L

    2018-04-22

    Liquid crystals (LCs) offer the basis of stimuli-responsive materials that can amplify targeted molecular events into macroscopic outputs. However, general and versatile design principles are needed to realize the full potential of these materials. To this end, we report the synthesis of two homopolymers with mesogenic side chains that can be cleaved upon exposure to either H 2 O 2 (polymer P1) or UV light (polymer P2). Optical measurements reveal that the polymers dissolve in bulk LC and spontaneously assemble at nematic LC-aqueous interfaces to impose a perpendicular orientation on the LCs. Subsequent addition of H 2 O 2 to the aqueous phase or exposure of the LC to UV was shown to trigger a surface-driven ordering transition to a planar orientation and an accompanying macroscopic optical output. Differences in the dynamics of the response to each stimulus are consistent with sequential processing of P1 at the LC-aqueous interface (H 2 O 2 ) and simultaneous transformation of P2 within the LC (UV). The versatility of the approach is demonstrated by creating stimuli-responsive LCs as films or microdroplets, and by dissolving mixtures of P1 and P2 into LCs to create LC materials that respond to two stimuli. Overall, our results validate a simple and generalizable approach to the rational design of polymers that can be used to program stimuli-responsiveness into LC materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Crystallization of glass-forming liquids: Specific surface energy

    International Nuclear Information System (INIS)

    Schmelzer, Jürn W. P.; Abyzov, Alexander S.

    2016-01-01

    A generalization of the Stefan-Skapski-Turnbull relation for the melt-crystal specific interfacial energy is developed in terms of the generalized Gibbs approach extending its standard formulation to thermodynamic non-equilibrium states. With respect to crystal nucleation, this relation is required in order to determine the parameters of the critical crystal clusters being a prerequisite for the computation of the work of critical cluster formation. As one of its consequences, a relation for the dependence of the specific surface energy of critical clusters on temperature and pressure is derived applicable for small and moderate deviations from liquid-crystal macroscopic equilibrium states. Employing the Stefan-Skapski-Turnbull relation, general expressions for the size and the work of formation of critical crystal clusters are formulated. The resulting expressions are much more complex as compared to the respective relations obtained via the classical Gibbs theory. Latter relations are retained as limiting cases of these more general expressions for moderate undercoolings. By this reason, the formulated, here, general relations for the specification of the critical cluster size and the work of critical cluster formation give a key for an appropriate interpretation of a variety of crystallization phenomena occurring at large undercoolings which cannot be understood in terms of the Gibbs’ classical treatment.

  1. High-speed imaging polarimetry using liquid crystal modulators

    Directory of Open Access Journals (Sweden)

    Ambs P.

    2010-06-01

    Full Text Available This paper deals with dynamic polarimetric imaging techniques. The basics of modern polarimetry have been known for one and a half century, but no practical high-speed implementation providing the full polarization information is currently available. Various methods are reviewed which prove to be a trade-off between the complexity of the optical set-up and the amount of polarimetric information they provide (ie the number of components of the Stokes vector. Techniques using liquid crystal devices, incepted in the late 1990's, are emphasized. Optical set-ups we implemented are presented. We particularly focus on high-speed techniques (i.e. faster than 200 Hz using ferroelectric liquid crystal devices.

  2. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    International Nuclear Information System (INIS)

    Middha, Manju; Kumar, Rishi; Raina, K. K.

    2014-01-01

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence

  3. Modeling texture transitions in cholesteric liquid crystal droplets

    Science.gov (United States)

    Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew

    2012-02-01

    Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.

  4. Dynamics of cylindrical domain walls in smectic C liquid crystals

    International Nuclear Information System (INIS)

    Stewart, I W; Wigham, E J

    2009-01-01

    An analysis of the dynamics of cylindrical domain walls in planar aligned samples of smectic C liquid crystals is presented. A circular magnetic field, induced by an electric current, drives a time-dependent reorientation of the corresponding radially dependent director field. Nonlinear approximations to the relevant nonlinear dynamic equation, derived from smectic continuum theory, are solved in a comoving coordinated frame: exact solutions are found for a π-wall and numerical solutions are calculated for π/2-walls. Each calculation begins with an assumed initial state for the director that is a prescribed cylindrical domain wall. Such an initial wall will proceed to expand or contract as its central core propagates radially inwards or outwards, depending on the boundary conditions for the director, the elastic constants, the magnitude of the field and the sign of the magnetic anisotropy of the liquid crystal

  5. Thermodynamic properties of a liquid crystal carbosilane dendrimer

    Science.gov (United States)

    Samosudova, Ya. S.; Markin, A. V.; Smirnova, N. N.; Ogurtsov, T. G.; Boiko, N. I.; Shibaev, V. P.

    2016-11-01

    The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6-370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C p ° ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) are calculated from the obtained experimental data for the region of T → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at T = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.

  6. Proton irradiation of liquid crystal based adaptive optical devices

    International Nuclear Information System (INIS)

    Buis, E.J.; Berkhout, G.C.G.; Love, G.D.; Kirby, A.K.; Taylor, J.M.; Hannemann, S.; Collon, M.J.

    2012-01-01

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (10 10 p/cm 2 ). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  7. Proton irradiation of liquid crystal based adaptive optical devices

    Energy Technology Data Exchange (ETDEWEB)

    Buis, E.J., E-mail: ernst-jan.buis@tno.nl [cosine Science and Computing BV, Niels Bohrweg 11, 2333 CA Leiden (Netherlands); Berkhout, G.C.G. [cosine Science and Computing BV, Niels Bohrweg 11, 2333 CA Leiden (Netherlands); Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Love, G.D.; Kirby, A.K.; Taylor, J.M. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Hannemann, S.; Collon, M.J. [cosine Research BV, Niels Bohrweg 11, 2333 CA Leiden (Netherlands)

    2012-01-01

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (10{sup 10}p/cm{sup 2}). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  8. Color Gamut of a Nematic Liquid Crystal Display

    Science.gov (United States)

    Shimomura, Teruo; Mada, Hitoshi; Kobayashi, Shunsuke

    1980-05-01

    The theoretical color gamut of a nematic liquid crystal display is described. The color gamut of a tunable birefringence mode and a guest host mode are revealed with the CIE chromaticity diagram and color solid. In order to account for the quantitative color gamut, color matching between the given chromaticity coordinates and those calculated is investigated. Color matching is performed by a combination of three liquid crystal subcells (A, B, C), where each subcell receives the voltage VA, VB, VC or contains the dye amount a, b, c. Calculation of the value of voltage or dye amount was executed by the matrix representation method. The calculated data are in good agreement with the given data within 0.50 CIE-UNIT color difference in the 1964 CIE (U*, V*, W*) color scale.

  9. Thermal expansion accompanying the glass-liquid transition and crystallization

    Directory of Open Access Journals (Sweden)

    M. Q. Jiang

    2015-12-01

    Full Text Available We report the linear thermal expansion behaviors of a Zr-based (Vitreloy 1 bulk metallic glass in its as-cast, annealed and crystallized states. Accompanying the glass-liquid transition, the as-cast Vitreloy 1 shows a continuous decrease in the thermal expansivity, whereas the annealed glass shows a sudden increase. The crystallized Vitreloy 1 exhibits an almost unchanged thermal expansivity prior to its melting. Furthermore, it is demonstrated that the nucleation of crystalline phases can induce a significant thermal shrinkage of the supercooled liquid, but with the growth of these nuclei, the thermal expansion again dominates. These results are explained in the framework of the potential energy landscape, advocating that the configurational and vibrational contributions to the thermal expansion of the glass depend on both, structure and temperature.

  10. Electrically Tunable Reflective Terahertz Phase Shifter Based on Liquid Crystal

    Science.gov (United States)

    Yang, Jun; Xia, Tianyu; Jing, Shuaicheng; Deng, Guangsheng; Lu, Hongbo; Fang, Yong; Yin, Zhiping

    2018-02-01

    We present a reflective spatial phase shifter which operates at terahertz regime above 325 GHz. The controllable permittivity of the nematic liquid crystals was utilized to realize a tunable terahertz (THz) reflective phase shifter. The reflective characteristics of the terahertz electromagnetic waves and the liquid crystal parameters were calculated and analyzed. We provide the simulation results for the effect of the incident angle of the plane wave on the reflection. The experiment was carried out considering an array consisting of 30 × 30 patch elements, printed on a 20 × 20 mm quartz substrate with 1-mm thickness. The phase shifter provides a tunable phase range of 300° over the frequency range of 325 to 337.6 GHz. The maximum phase shift of 331° is achieved at 330 GHz. The proposed phase shifter is a potential candidate for THz applications, particularly for reconfigurable reflectarrays.

  11. Soft Elasticity in Main Chain Liquid Crystal Elastomers

    Directory of Open Access Journals (Sweden)

    Anselm C. Griffin

    2013-06-01

    Full Text Available Main chain liquid crystal elastomers exhibit several interesting phenomena, such as three different regimes of elastic response, unconventional stress-strain relationship in one of these regimes, and the shape memory effect. Investigations are beginning to reveal relationships between their macroscopic behavior and the nature of domain structure, microscopic smectic phase structure, relaxation mechanism, and sample history. These aspects of liquid crystal elastomers are briefly reviewed followed by a summary of the results of recent elastic and high-resolution X-ray diffraction studies of the shape memory effect and the dynamics of the formation of the smectic-C chevron-like layer structure. A possible route to realizing auxetic effect at molecular level is also discussed.

  12. A numerical method for eigenvalue problems in modeling liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Baglama, J.; Farrell, P.A.; Reichel, L.; Ruttan, A. [Kent State Univ., OH (United States); Calvetti, D. [Stevens Inst. of Technology, Hoboken, NJ (United States)

    1996-12-31

    Equilibrium configurations of liquid crystals in finite containments are minimizers of the thermodynamic free energy of the system. It is important to be able to track the equilibrium configurations as the temperature of the liquid crystals decreases. The path of the minimal energy configuration at bifurcation points can be computed from the null space of a large sparse symmetric matrix. We describe a new variant of the implicitly restarted Lanczos method that is well suited for the computation of extreme eigenvalues of a large sparse symmetric matrix, and we use this method to determine the desired null space. Our implicitly restarted Lanczos method determines adoptively a polynomial filter by using Leja shifts, and does not require factorization of the matrix. The storage requirement of the method is small, and this makes it attractive to use for the present application.

  13. Liquid crystal blue phases: stability, field effects and alignment

    OpenAIRE

    Gleeson, HF; Miller, RJ; Tian, L; Görtz, V; Goodby, JW

    2015-01-01

    The blue phases are fascinating structures in liquid crystals, fluids that exhibit cubic structures that have true crystalline order. The blue phases were discovered in the 1970s and were the subject of extensive research in the 1980s, when a deep understanding of many of their properties was established. The discovery that the blue phases could be stabilised to exist over wide temperature ranges meant that they became more than scientific curiosities and led to a recent resurgence in researc...

  14. Two-Dimensional Spatial Solitons in Nematic Liquid Crystals

    International Nuclear Information System (INIS)

    Zhong Weiping; Xie Ruihua; Goong Chen; Belic, Milivoj; Yang Zhengping

    2009-01-01

    We study the propagation of spatial solitons in nematic liquid crystals, using the self-similar method. Analytical solutions in the form of self-similar solitons are obtained exactly. We confirm the stability of these solutions by direct numerical simulation, and find that the stable spatial solitons can exist in various forms, such as Gaussian solitons, radially symmetric solitons, multipole solitons, and soliton vortices.

  15. Smectic liquid crystal cell with heat pulse and laser

    International Nuclear Information System (INIS)

    Mash, D.H.

    1984-01-01

    A method of operating a homeotropically aligned smectic liquid crystal cell in which the cell is turned from a clear to a scattering state by illumination with an intense flash of light after which a focused laser beam is scanned across the layer to leave clear tracks where homeotropic alignment has been restored thereby producing a display providing, in projection, bright lines on a dark background

  16. Liquid crystal foil for the detection of breast cancer

    Science.gov (United States)

    Biernat, Michał; Trzyna, Marcin; Byszek, Agnieszka; Jaremek, Henryk

    2016-09-01

    Breast cancer is the most common malignant tumor in females around the world, representing 25.2% of all cancers in women. About 1.7 million women were diagnosed with breast cancer worldwide in 2012 with a death rate of about 522,0001,2. The most frequently used methods in breast cancer screening are imaging methods, i.e. ultrasonography and mammography. A common feature of these methods is that they inherently involve the use of expensive and advanced equipment. The development of advanced computer systems allowed for the continuation of research started already in the 1980s3 and the use of contact thermography in breast cancer screening. The physiological basis for the application of thermography in medical imaging diagnostics is the so-called dermothermal effect related to higher metabolism rate around focal neoplastic lesion. This phenomenon can occur on breast surface as localized temperature anomalies4. The device developed by Braster is composed of a detector that works on the basis of thermotropic liquid crystals, image acquisition device and a computer system for image data processing and analysis. Production of the liquid crystal detector was based on a proprietary CLCF technology (Continuous Liquid Crystal Film). In 2014 Braster started feasibility study to prove that there is a potential for artificial intelligence in early breast cancer detection using Braster's proprietary technology. The aim of this study was to develop a computer system, using a client-server architecture, to an automatic interpretation of thermographic pictures created by the Braster devices.

  17. Directional Scattering of Semiconductor Nanoparticles Embedded in a Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Braulio García-Cámara

    2014-04-01

    Full Text Available Light scattering by semiconductor nanoparticles has been shown to be more complex than was believed until now. Both electric and magnetic responses emerge in the visible range. In addition, directional effects on light scattering of these nanoparticles were recently obtained. In particular, zero backward and minimum-forward scattering are observed. These phenomena are very interesting for several applications such as, for instance, optical switches or modulators. The strong dependence of these phenomena on the properties of both the particle and the surrounding medium can be used to tune them. The electrical control on the optical properties of liquid crystals could be used to control the directional effects of embedded semiconductor nanoparticles. In this work, we theoretically analyze the effects on the directional distribution of light scattering by these particles when the refractive index of a surrounded liquid crystal changes from the ordinary to the extraordinary configuration. Several semiconductor materials and liquid crystals are studied in order to optimize the contrast between the two states.

  18. Evidence for several dipolar quasi-invariants in liquid crystals

    Science.gov (United States)

    Bonin, C. J.; González, C. E.; Segnorile, H. H.; Zamar, R. C.

    2013-10-01

    The quasi-equilibrium states of an observed quantum system involve as many constants of motion as the dimension of the operator basis which spans the blocks of all the degenerate eigenvalues of the Hamiltonian that drives the system dynamics, however, the possibility of observing such quasi-invariants in solid-like spin systems in Nuclear Magnetic Resonance (NMR) is not a strictly exact prediction. The aim of this work is to provide experimental evidence of several quasi-invariants, in the proton NMR of small spin clusters, like nematic liquid crystal molecules, in which the use of thermodynamic arguments is not justified. We explore the spin states prepared with the Jeener-Broekaert pulse sequence by analyzing the time-domain signals yielded by this sequence as a function of the preparation times, in a variety of dipolar networks, solids, and liquid crystals. We observe that the signals can be explained with two dipolar quasi-invariants only within a range of short preparation times, however at longer times liquid crystal signals show an echo-like behaviour whose description requires assuming more quasi-invariants. We study the multiple quantum coherence content of such signals on a basis orthogonal to the z-basis and see that such states involve a significant number of correlated spins. Therefore, we show that the NMR signals within the whole preparation time-scale can only be reconstructed by assuming the occurrence of multiple quasi-invariants which we experimentally isolate.

  19. Smectic liquid crystals in anisotropic colloidal silica gels

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Dennis [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Borthwick, Matthew A [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Leheny, Robert L [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2004-05-19

    We report x-ray scattering studies of the smectic liquid crystal octylcyano-biphenol (8CB) confined by strained colloidal silica gels. The gels, comprised of aerosil particles, possess an anisotropic structure that stabilizes long-range nematic order in the liquid crystal while introducing random field effects that disrupt the smectic transition. The short-range smectic correlations that form within this environment are inconsistent with the presence of a topologically ordered state predicted for 3D random field XY systems and are quantitatively like the correlations of smectics confined by isotropic gels. Detailed analysis reveals that the quenched disorder suppresses the anisotropic scaling of the smectic correlation lengths observed in the pure liquid crystal. These results and additional measurements of the smectic-A to smectic-C transition in 4-n-pentylphenylthiol-4'-n-octyloxybenzoate (8barS5) indicate that the observed smectic behaviour is dictated by random fields coupling directly to the smectic order while fields coupling to the nematic director play a subordinate role.

  20. The opto-thermal effect on encapsulated cholesteric liquid crystals

    Science.gov (United States)

    Liu, Yu-Sung; Lin, Hui-Chi; Yang, Kin-Min

    2017-12-01

    In this study, we implemented a micro-encapsulated CLC electronic paper that is optically addressed and electrically erasable. The mechanism that forms spot diameters on the CLC films is discussed and verified through various experimental parameters, including the thickness of CLCs and Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) (PEDOT:PSS), pump intensity, and pumping time. The opto-thermal effect, brought on by the PEDOT:PSS absorbing layer, causes the spot diameters on the cholesteric liquid crystal thin films to vary. According to our results, the spot diameter is larger for a sample with a thinner cholesteric liquid crystal layer with the same excitation conditions and same thickness of the PEDOT layer. The spot diameter is also larger for a sample with a thicker PEDOT under the same excitation conditions and same thickness of the cholesteric liquid crystal layer. We proposed a simple heat-conducting model to explain the experimental results, which qualitatively agree with this theoretical model.

  1. THz waveguides, devices and hybrid polymer-chalcogenide photonic crystal fibers

    DEFF Research Database (Denmark)

    Bao, Hualong; Markos, Christos; Nielsen, Kristian

    2014-01-01

    In this contribution, we review our recent activities in the design, fabrication and characterization of polymer THz waveguides. Besides the THz waveguides, we finally will also briefly show some of our initial results on a novel hybrid polymer photonic crystal fiber with integrated chalcogenide...

  2. IR Sensor Synchronizing Active Shutter Glasses for 3D HDTV with Flexible Liquid Crystal Lenses

    Directory of Open Access Journals (Sweden)

    Jeong In Han

    2013-12-01

    Full Text Available IR sensor synchronizing active shutter glasses for three-dimensional high definition television (3D HDTV were developed using a flexible liquid crystal (FLC lens. The FLC lens was made on a polycarbonate (PC substrate using conventional liquid crystal display (LCD processes. The flexible liquid crystal lens displayed a maximum transmission of 32% and total response time of 2.56 ms. The transmittance, the contrast ratio and the response time of the flexible liquid crystal lens were superior to those of glass liquid crystal lenses. Microcontroller unit and drivers were developed as part of a reception module with power supply for the IR sensor synchronizing active shutter glasses with the flexible liquid crystal lens prototypes. IR sensor synchronizing active shutter glasses for 3D HDTV with flexible liquid crystal lenses produced excellent 3D images viewing characteristics.

  3. (Surfactant + polymer) interaction parameter studied by (liquid + liquid) equilibrium data of quaternary aqueous solution containing surfactant, polymer, and salt

    Energy Technology Data Exchange (ETDEWEB)

    Foroutan, Masumeh [Physical Chemistry Department, School of Chemistry, College of Science, University of Tehran, 14155-6455 Tehran (Iran, Islamic Republic of)], E-mail: foroutan@khayam.ut.ac.ir; Heidari, Nosrat; Mohammadlou, Maryam [Chemistry Department, Faculty of Science, Uremia University, Uremia (Iran, Islamic Republic of); Sojahrood, Amin Jafari [Physics Department, Faculty of Science, Uremia University, Uremia (Iran, Islamic Republic of)

    2009-02-15

    (Liquid + liquid) equilibrium (LLE) data of quaternary aqueous system containing polyoxyethylene (20) cetyl ether (with abbreviation name Brij 58, non-ionic surfactant), diammonium hydrogen phosphate, and poly ethylene glycol (PEG) with three molar masses {l_brace}M{sub W} = (1000, 6000, and 35,000) g . mol{sup -1}{r_brace} have been determined experimentally at T = 313.15 K. Furthermore, the Flory-Huggins theory with two electrostatic terms (Debye-Hueckel and Pitzer-Debye-Hueckel equations) have been used to calculate the phase behavior of the quaternary systems and (surfactant + polymer) interaction parameter as well as interaction parameters between other species. Temperature dependency of the parameters of the Flory-Huggins theory has been obtained. Also an effort have been done to show that addition of PEG as well as increasing the temperature can shift the binodal curves of the ternary aqueous system containing surfactant and salt to lower mole fraction of salt. Also the effect of polymer molar mass on the binodal diagram displacement has been discussed.

  4. Autophobicity and layering behavior of thin liquid-crystalline polymer films.

    NARCIS (Netherlands)

    Wielen, van der M.W.J.; Cohen Stuart, M.A.; Fleer, G.J.

    1998-01-01

    The stability against breaking-up of thin spin-coated films of liquid-crystalline polymers depends on the film thickness and annealing temperature. This study concerns side-chain liquid-crystalline polymers, based on alternating copolymers of maleic anhydride and mesogenic alkenes. The mesogenic

  5. Liquid crystal designs for high-contrast field sequential color liquid crystal on silicon (LCoS) microdisplays (Invited Paper)

    Science.gov (United States)

    Anderson, James; Chen, Cheng; Bos, Philip J.

    2005-04-01

    Single or dual panel microdisplay systems are becoming more popular in the marketplace. Consequently, Liquid Crystal on Silicon (LCoS) microdisplays are constantly being pushed to achieve faster switching times as well as higher contrast, while becoming simpler and allowing simpler optics engine design. Currently, most products use a Twisted Nematic (TN) mode with a retardation film. The most promising solution in research now is the Vertically Aligned Nematic (VAN) mode, which does not require a retarder.

  6. Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Tercjak, A; Garcia, I; Mondragon, I [Materials-Technologies Group, Departamento IngenierIa Quimica y M Ambiente, Escuela Politecnica, Universidad PaIs Vasco/Euskal Herriko Unibertsitatea, Plaza Europa 1, E-20018 Donostia-San Sebastian (Spain)], E-mail: scptesza@sc.ehu.es, E-mail: inaki.mondragon@ehu.es

    2008-07-09

    Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface.

  7. Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal.

    Science.gov (United States)

    Tercjak, A; Garcia, I; Mondragon, I

    2008-07-09

    Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface.

  8. Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

    International Nuclear Information System (INIS)

    Tercjak, A; Garcia, I; Mondragon, I

    2008-01-01

    Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface

  9. Effect of temperature on the morphology and electro-optical properties of liquid crystal physical gel

    International Nuclear Information System (INIS)

    Leaw, W.L.; Mamat, C.R.; Triwahyono, S.; Jalil, A.A.; Bidin, N.

    2016-01-01

    Liquid crystal physical gels were (thermally) prepared with cholesteryl stearate as a gelator in nematic liquid crystal, 4-cyano-4′-pentylbiphenyl. The electro-optical performance of liquid crystal physical gels is almost entirely dependent on the gels' inherent morphology. This study involved an empirical investigation of the relationships among all of the gelation temperature, morphology, and electro-optical properties. Besides continuous cooling at room temperature, isothermal cooling was also performed at both 18 and 0 °C, corresponding to near-solid and solid phases of 4-cyano-4′-pentylbiphenyl respectively. Nevertheless, the liquid crystal physical gel was also isothermally rapidly cooled using liquid nitrogen. Polarizing optical microscopy showed that the gel structure became thinner when isothermal cooling was carried out. These thinner gel aggregates then interconnected to form larger liquid crystal domains. Moreover, it was also revealed that the gel networks were randomized. Electron spin resonance results showed that the liquid crystal director orientation was severely randomized in the presence of gel networks. Conversely, isothermal cooling using liquid nitrogen generated a higher liquid crystal director orientation order. The 6.0 wt% cholesteryl stearate/4-cyano-4′-pentylbiphenyl physical gel that was isothermally cooled using liquid nitrogen showed the lowest response time in a twisted nematic mode optical cell. - Graphical abstract: Liquid crystal physical gel was prepared using nematic liquid crystal, 4-cyano-4′-pentylbiphenyl and cholesteryl stearate as gelator. Isothermal cooling at lower temperature produced thinner gel network and larger liquid crystal domain. - Highlights: • 5CB nematic liquid crystal was successfully gelled by cholesteryl stearate gelator. • The morphology of gel network was controlled by different cooling conditions. • Thinner gel network was formed by the rapid cooling using liquid nitrogen. • Enhanced

  10. Effect of temperature on the morphology and electro-optical properties of liquid crystal physical gel

    Energy Technology Data Exchange (ETDEWEB)

    Leaw, W.L. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Mamat, C.R., E-mail: che@kimia.fs.utm.my [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Triwahyono, S. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Jalil, A.A. [Department of Chemical Engineering, Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Centre of Hydrogen Energy, Institute of Future Energy, Univerisiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Bidin, N. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia)

    2016-12-01

    Liquid crystal physical gels were (thermally) prepared with cholesteryl stearate as a gelator in nematic liquid crystal, 4-cyano-4′-pentylbiphenyl. The electro-optical performance of liquid crystal physical gels is almost entirely dependent on the gels' inherent morphology. This study involved an empirical investigation of the relationships among all of the gelation temperature, morphology, and electro-optical properties. Besides continuous cooling at room temperature, isothermal cooling was also performed at both 18 and 0 °C, corresponding to near-solid and solid phases of 4-cyano-4′-pentylbiphenyl respectively. Nevertheless, the liquid crystal physical gel was also isothermally rapidly cooled using liquid nitrogen. Polarizing optical microscopy showed that the gel structure became thinner when isothermal cooling was carried out. These thinner gel aggregates then interconnected to form larger liquid crystal domains. Moreover, it was also revealed that the gel networks were randomized. Electron spin resonance results showed that the liquid crystal director orientation was severely randomized in the presence of gel networks. Conversely, isothermal cooling using liquid nitrogen generated a higher liquid crystal director orientation order. The 6.0 wt% cholesteryl stearate/4-cyano-4′-pentylbiphenyl physical gel that was isothermally cooled using liquid nitrogen showed the lowest response time in a twisted nematic mode optical cell. - Graphical abstract: Liquid crystal physical gel was prepared using nematic liquid crystal, 4-cyano-4′-pentylbiphenyl and cholesteryl stearate as gelator. Isothermal cooling at lower temperature produced thinner gel network and larger liquid crystal domain. - Highlights: • 5CB nematic liquid crystal was successfully gelled by cholesteryl stearate gelator. • The morphology of gel network was controlled by different cooling conditions. • Thinner gel network was formed by the rapid cooling using liquid nitrogen.

  11. Possible use of ionic polymers for treatment of radioactive liquid waste

    International Nuclear Information System (INIS)

    Siyam, T.; Nofal, M.; Eldessouky, M.I.; Aly, H.F.

    1992-01-01

    Water-soluble nonionic polymers such as polyacrylamide is recently introduced for treatment of radioactive liquid waste. Eater-soluble ionic polymers such as: poly (sodium acrylate) [anionic polymer], poly (acrylamide-CO-sodium acrylate) [anionic copolymer] and poly (acrylamide-sodium acrylate-diallyldiethylammonium chloride) [amphoteric terpolymer] were prepared by gamma radiation-initiated polymerization of the corresponding monomer solutions. The prepared polymers were assessed for use in treatment of radionuclides that might be present in radioactive waste effluents. It was found that the polymer efficiency for cobalt-60 was affected by the composition of the copolymer and the degree of ionization of the polymer. The efficiency of the polymer increases with increasing the concentration of the polymer. The mechanism of sludge formation for each type of polymer was discussed. It was found that the anionic copolymer is more selective for cobalt than the prepared polymers. Amphoteric terpolymer has different selectivity for cations and anions. 3 figs, 1 tab

  12. Strength of Drug–Polymer Interactions: Implications for Crystallization in Dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, Pinal; Suryanarayanan, Raj

    2016-09-07

    We investigated the influence of the strength of drug–polymer interactions on the crystallization behavior of a model drug in amorphous solid dispersions (ASDs). Ketoconazole ASDs were prepared with each poly(acrylic acid), poly(2-hydroxyethyl methacrylate), and polyvinylpyrrolidone. Over a wide temperature range in the supercooled region, the α-relaxation time was obtained, which provided a measure of molecular mobility. Isothermal crystallization studies were performed in the same temperature interval using either a synchrotron (for low levels of crystallinity) or a laboratory X-ray (for crystallization kinetics) source. The stronger the drug–polymer interaction, the longer was the delay in crystallization onset time, indicating an increase in physical stability. Stronger drug–polymer interactions also translated to a decrease in the magnitude of the crystallization rate constant. In amorphous ketoconazole as well as in the dispersions, the coupling coefficient, a measure of the extent of coupling between relaxation and crystallization times was ~0.5. This value was unaffected by the strength of drug–polymer interactions. On the basis of these results, the crystallization times in ASDs were predicted at temperatures very close to Tg, using the coupling coefficient experimentally determined for amorphous ketoconazole. The predicted and experimental crystallization times were in good agreement, indicating the usefulness of the model.

  13. Fresnel Lenses fabricated by femtosecond laser micromachining on Polymer 1D Photonic Crystal

    Directory of Open Access Journals (Sweden)

    Guduru Surya S.K.

    2013-11-01

    Full Text Available We report the fabrication of micro Fresnel lenses by femtosecond laser surface ablation on polymer 1D photonic crystals. This device is designed to focus the transmitted wavelength of the photonic crystal and filter the wavelengths corresponding to the photonic band gap region. Integration of such devices in a wavelength selective light harvesting and filtering microchip can be achieved.

  14. Optical tuning of photonic bandgaps in dye-doped nematic liquid crystal photonic crystal fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard; Hermann, David Sparre

    2005-01-01

    An all-optical modulator is demonstrated, which utilizes a pulsed 532 nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid crystal. In order to investigate the time response of the LCPBG fiber device, a low-power CW probe...... laser was coupled into the fiber together with the pulsed pump laser of 2.3 mW and we have demonstrated a modulation frequency of up to 2 kHz....

  15. Electrically Rotatable Polarizer Using One-Dimensional Photonic Crystal with a Nematic Liquid Crystal Defect Layer

    Directory of Open Access Journals (Sweden)

    Ryotaro Ozaki

    2015-09-01

    Full Text Available Polarization characteristics of defect mode peaks in a one-dimensional (1D photonic crystal (PC with a nematic liquid crystal (NLC defect layer have been investigated. Two different polarized defect modes are observed in a stop band. One group of defect modes is polarized along the long molecular axis of the NLC, whereas another group is polarized along its short axis. Polarizations of the defect modes can be tuned by field-induced in-plane reorientation of the NLC in the defect layer. The polarization properties of the 1D PC with the NLC defect layer is also investigated by the finite difference time domain (FDTD simulation.

  16. Chirality transfer technique between liquid crystal microdroplets using microfluidic systems

    Science.gov (United States)

    Guo, Jin-kun; Lee, Doyeon; Song, Jang-kun

    2018-02-01

    Cholesteric liquid crystal (LC) microdroplet is applied in many areas, such as tunable laser, biosensor, information display and security identification, due to its unique optical properties. The topological structure, defects, and photonic crystallinity in the cholesteric liquid crystal (LC) microdroplet can be controlled through the chirality. Here we report an interesting phenomenon that chirality information can be shared among dispersed LC microdroplets in surfactant aqueous solution, which is driven by the transferring of chiral dopant molecules. As a result, we developed an artificial molecule transfer technology which could in situ vary the material composition within the isolated dispersed microdroplets. The molecular transfer is switchable and the transfer speed is controllable by tuning the molecular solubility in continuous phase. Based on this technique, we manipulated, forward and backward, the topological evolution and the photonic crystal band-gap of the dispersed LC droplet. This technique is an easy and powerful experimental tool, and it may be applicable to other fields in optical application, biology, chemistry and material science.

  17. Liquid Crystal Mediated Nano-assembled Gold Micro-shells

    Science.gov (United States)

    Quint, Makiko; Sarang, Som; Quint, David; Huang, Kerwyn; Gopinathan, Ajay; Hirst, Linda; Ghosh, Sayantani

    We have created 3D nano-assenbled micro-shell by using thermotropic liquid crystal (LC), 4-Cyano-4'-pentylbiphenyl (5CB), doped with mesogen-functionalized gold nanoparticles (AuNPs). The assembly process is driven by the isotropic-nematic phase transition dynamics. We uniformly disperse the functionalized AuNPs into isotropic liquid crystal matrix and the mixture is cooled from the isotropic to the nematic phase. During the phase transition, the separation of LC-AuNP rich isotropic and ordered 5CB rich domains cause the functionalized AuNPs to move into the shrinking isotropic regions. The mesogenic ligands are locally crystalized during this process, which leads to the formation of a spherical shell with a densely packed wall of AuNPs. These micro-shells are capable of encapsulating fluorescence dye without visible leakages for several months. Additionally, they demonstrate strong localized surface plasmon resonance, which leads to localized heating on optical excitation. This photothermal effect disrupts the structure, releasing contents within seconds. Our results exhibiting the capture and optically regulated release of encapsulated substances is a novel platform that combines drug-delivery and photothermal therapy in one versatile and multifunctional unit. This work is supported by the NSF Grants No. DMR-1056860, ECC-1227034, and a University of California Merced Faculty Mentor Fellowship.

  18. Soap, science, and flat-screen TVs a history of liquid crystals

    CERN Document Server

    Dunmur, David

    2011-01-01

    The terms 'liquid crystal' or 'liquid crystal display' (LCD) are well-known in the context of flat-screen televisions, but the properties and history of liquid crystals are little understood. This book tells the story of liquid crystals, from their controversial discovery at the end of the nineteenth century, to their eventual acceptance as another state of matter to rank alongside gases, liquids and solids. As their story unfolds, the scientists involved and their works are put into illuminating broader socio-political contexts. In recent years, liquid crystals have had a major impact on the display industry, culminating in the now widely available flat-screen televisions; this development is described in detail over three chapters, and the basic science behind it is explained in simple terms accessible to a general reader. New applications of liquid crystals in materials, bio-systems, medicine and technology are also explained.

  19. Synthesis of novel liquid crystal compounds and their blood compatibility as anticoagulative materials

    International Nuclear Information System (INIS)

    Tu Mei; Cha Zhenhang; Feng Bohua; Zhou Changren

    2006-01-01

    The objective of this study was to synthesize new types of cholesteric liquid crystal compounds and study the anticoagulative properties of their composite membranes. Three kinds of cholesteric liquid crystal compounds were synthesized and characterized by infrared spectroscopy, differential scanning calorimetry and optical polarizing microscope. The polysiloxane, as a substrate, was blended with three liquid crystal compounds and was then used as membranes. The anticoagulative property of different polysiloxane liquid crystal composite membranes was identified by the blood compatibility tests. Three cholesteryl liquid crystals synthesized in this work contained hydrophilic soft chains and presented iridescent texture owned by cholesteric liquid crystals in the range of their liquid crystal state temperature, but only cholesteryl acryloyl oxytetraethylene glycol carbonate was in the liquid crystal state at body temperature. When liquid crystals were blended with polysiloxane to form polysiloxane/liquid crystal composite membranes, the haemocompatibility of these membranes could be improved to some extent. The blood compatibility of composite membranes whose hydrophilic property was the best was more excellent than that of other composite membranes, fewer platelets adhered and spread, and showed little distortion on the surface of materials

  20. A roadmap to uranium ionic liquids: Anti-crystal engineering

    International Nuclear Information System (INIS)

    Yaprak, Damla; Spielberg, Eike T.; Baecker, Tobias; Richter, Mark; Mallick, Bert; Klein, Axel; Mudring, Anja-Verena

    2014-01-01

    In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C_4mim) cation. As dithiocarbamate ligands binding to the UO_2"2"+ unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. A roadmap to uranium ionic liquids: anti-crystal engineering.

    Science.gov (United States)

    Yaprak, Damla; Spielberg, Eike T; Bäcker, Tobias; Richter, Mark; Mallick, Bert; Klein, Axel; Mudring, Anja-Verena

    2014-05-19

    In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C4mim) cation. As dithiocarbamate ligands binding to the UO2(2+) unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Polymer-Derived In- Situ Metal Matrix Composites Created by Direct Injection of a Liquid Polymer into Molten Magnesium

    Science.gov (United States)

    Sudarshan; Terauds, Kalvis; Anilchandra, A. R.; Raj, Rishi

    2014-02-01

    We show that a liquid organic precursor can be injected directly into molten magnesium to produce nanoscale ceramic dispersions within the melt. The castings made in this way possess good resistance to tensile deformation at 673 K (400 °C), confirming the non-coarsening nature of these dispersions. Direct liquid injection into molten metals is a significant step toward inserting different chemistries of liquid precursors to generate a variety of polymer-derived metal matrix composites.

  3. Lithium ion intercalation in thin crystals of hexagonal TaSe2 gated by a polymer electrolyte

    Science.gov (United States)

    Wu, Yueshen; Lian, Hailong; He, Jiaming; Liu, Jinyu; Wang, Shun; Xing, Hui; Mao, Zhiqiang; Liu, Ying

    2018-01-01

    Ionic liquid gating has been used to modify the properties of layered transition metal dichalcogenides (TMDCs), including two-dimensional (2D) crystals of TMDCs used extensively recently in the device work, which has led to observations of properties not seen in the bulk. The main effect comes from the electrostatic gating due to the strong electric field at the interface. In addition, ionic liquid gating also leads to ion intercalation when the ion size of the gate electrolyte is small compared to the interlayer spacing of TMDCs. However, the microscopic processes of ion intercalation have rarely been explored in layered TMDCs. Here, we employed a technique combining photolithography device fabrication and electrical transport measurements on the thin crystals of hexagonal TaSe2 using multiple channel devices gated by a polymer electrolyte LiClO4/Polyethylene oxide (PEO). The gate voltage and time dependent source-drain resistances of these thin crystals were used to obtain information on the intercalation process, the effect of ion intercalation, and the correlation between the ion occupation of allowed interstitial sites and the device characteristics. We found a gate voltage controlled modulation of the charge density waves and a scattering rate of charge carriers. Our work suggests that ion intercalation can be a useful tool for layered materials engineering and 2D crystal device design.

  4. Liquid-crystal laser optics: design, fabrication, and performance

    International Nuclear Information System (INIS)

    Jacobs, S.D.; Cerqua, K.A.; Marshall, K.L.; Schmid, A.; Guardalben, M.J.; Skerrett, K.J.

    1988-01-01

    We describe the development of laser optics utilizing liquid crystals. Devices discussed constitute passive optical elements for both low-power and high-power laser systems, operating in either the pulsed or cw mode. Designs and fabrication methods are given in detail for wave plates, circular polarizers, optical isolators, laser-blocking notch filters, and soft apertures. Performance data in the visible to near infrared show these devices to be useful alternatives to other technologies based on conventional glasses, crystals, or thin films. The issue of laser damage is examined on the basis of off-line threshold testing and daily use in OMEGA, the 24-beam Nd:glass laser system at the Laboratory for Laser Energetics. Results demonstrate that long-term survivability has been achieved

  5. Asymmetric flavone-based liquid crystals: synthesis and properties

    Energy Technology Data Exchange (ETDEWEB)

    Timmons, Daren J. [Department of Chemistry, Virginia Military Institute, Lexington, VA, USA; Jordan, Abraham J. [Department of Chemistry, Virginia Military Institute, Lexington, VA, USA; Kirchon, Angelo A. [Department of Chemistry, Virginia Military Institute, Lexington, VA, USA; Murthy, N. Sanjeeva [New Jersey Center for Biomaterials, Rutgers, The State University of New Jersey, Piscataway, NJ, USA; Siemers, Troy J. [Department of Applied Mathematics, Virginia Military Institute, Lexington, VA, USA; Harrison, Daniel P. [Department of Chemistry, Virginia Military Institute, Lexington, VA, USA; Slebodnick, Carla [Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA

    2017-02-01

    A series of flavones (n-F) substituted at the 4', and 6 positions was prepared, characterised by NMR (1H,13C), HRMS, and studied for liquid crystal properties. The 4'-alkoxy,6-methoxyflavones (4-F–16-F) exhibit varying ranges of nematic and smectic A phases as evidenced by polarised optical microscopy and differential scanning calorimetry (DSC). As the tail length is increased, the smectic phase becomes more prevalent. Smectic phases for (8-F–16-F) were further analysed by powder X-ray diffraction (XRD), and the rate of structural transformations was explored by combined DSC/XRD studies. Flavonol 6-F–OH was also prepared but no mesogenic behaviour was observed. The molecular structures of 6-F and 6-F–OH were determined by single-crystal XRD and help to explain the differences in material properties. Additionally, fluorescence and electrochemical studies were conducted on solutions of n-F.

  6. Adaptable liquid crystal elastomers with transesterification-based bond exchange reactions.

    Science.gov (United States)

    Hanzon, Drew W; Traugutt, Nicholas A; McBride, Matthew K; Bowman, Christopher N; Yakacki, Christopher M; Yu, Kai

    2018-02-14

    Adaptable liquid crystal elastomers (LCEs) have recently emerged to provide a new and robust method to program monodomain LCE samples. When a constant stress is applied with active bond exchange reactions (BERs), polymer chains and mesogens gradually align in the strain direction. Mesogen alignment is maintained after removing the BER stimulus (e.g. by lowering the temperature) and the programmed LCE samples exhibit free-standing two-way shape switching behavior. Here, a new adaptable main-chain LCE system was developed with thermally induced transesterification BERs. The network combines the conventional properties of LCEs, such as an isotropic phase transition and soft elasticity, with the dynamic features of adaptable network polymers, which are malleable to stress relaxation due to the BERs. Polarized Fourier transform infrared measurements confirmed the alignment of polymer chains and mesogens after strain-induced programming. The influence of the creep stress, temperature, and time on the strain amplitude of two-way shape switching was examined. The LCE network demonstrates an innovative feature of reprogrammability, where the reversible shape-switching memory of programmed LCEs is readily deleted by free-standing heating as random BERs disrupt the mesogen alignment, so LCEs are reprogrammed after returning to the polydomain state. Due to the dynamic nature of the LCE network, it also exhibits a surface welding effect and can be fully dissolved in the organic solvent, which might be utilized for green and sustainable recycling of LCEs.

  7. Asymmetric electrooptic response in a nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Dascalu, Constanta [Politechnica University of Bucharest, Bucharest (Romania)

    2001-06-01

    An asymmetric electrooptic response in nematic liquid crystal (LC) has been obtained. The liquid crystal hybrid cell was made by using a standard configuration. One of the ITO (Indium Tin Oxide) electrodes was covered with a surfactant, which induces a homeotropic alignment. The second of the indium tin oxide electrodes was covered by a thin layer of photopolymer, which was previously mixed with an acid, which favours a process of release of protons. Such cations are responsible of electrochemical process in the LC leading to an asymmetric electrooptic response, which depend on the polarity of the applied electric field. This fact is due to an internal field, which change the effective voltage thresholds for the reorientation of the liquid crystal. During the anodic polarization, the optical switching is inhibited because the effective field decreases below the threshold value. On contrary for the opposite polarization the effective field is enough to determine a homeotropic alignment. [Spanish] Se ha obtenido una respuesta electro-optica asimetrica en cristales liquidos neumaticos. La celula hibrida de cristal liquido fue construida utilizando una configuracion estandar. Uno de los electrodos ITO fue cubierto con una pelicula delgada de material organico para inducir una alineacion homeotropa. El otro electrodo ITO fue cubierto con una pelicula delgada de fotopolimero anteriormente mezclada con un acido para favorecer la emision de protones. Estos cationes son responsables del proceso electroquimico en LC, conduciendo a una respuesta electro-optica asimetrica que depende de la polaridad del campo electrico aplicado. Este efecto es originado por un campo interno que cambia el umbral efectivo del voltaje para la reorientacion del cristal liquido. Durante la polarizacion anodica, la conmutacion optica se inhibe debido a que el campo efectivo disminuye abajo del valor del umbral. Por el contrario, para la polarizacion opuesta el campo efectivo es suficiente para

  8. Nematic liquid crystals on sinusoidal channels: the zigzag instability.

    Science.gov (United States)

    Silvestre, Nuno M; Romero-Enrique, Jose M; Telo da Gama, Margarida M

    2017-01-11

    Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.

  9. Local structural ordering in surface-confined liquid crystals

    Science.gov (United States)

    Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

    2017-06-01

    The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

  10. Electrothermally Driven Fluorescence Switching by Liquid Crystal Elastomers Based On Dimensional Photonic Crystals.

    Science.gov (United States)

    Lin, Changxu; Jiang, Yin; Tao, Cheng-An; Yin, Xianpeng; Lan, Yue; Wang, Chen; Wang, Shiqiang; Liu, Xiangyang; Li, Guangtao

    2017-04-05

    In this article, the fabrication of an active organic-inorganic one-dimensional photonic crystal structure to offer electrothermal fluorescence switching is described. The film is obtained by spin-coating of liquid crystal elastomers (LCEs) and TiO 2 nanoparticles alternatively. By utilizing the property of LCEs that can change their size and shape reversibly under external thermal stimulations, the λ max of the photonic band gap of these films is tuned by voltage through electrothermal conversion. The shifted photonic band gap further changes the matching degree between the photonic band gap of the film and the emission spectrum of organic dye mounting on the film. With rhodamine B as an example, the enhancement factor of its fluorescence emission is controlled by varying the matching degree. Thus, the fluorescence intensity is actively switched by voltage applied on the system, in a fast, adjustable, and reversible manner. The control chain of using the electrothermal stimulus to adjust fluorescence intensity via controlling the photonic band gap is proved by a scanning electron microscope (SEM) and UV-vis reflectance. This mechanism also corresponded to the results from the finite-difference time-domain (FDTD) simulation. The comprehensive usage of photonic crystals and liquid crystal elastomers opened a new possibility for active optical devices.

  11. Ionic conductivity of polymer gels deriving from alkali metal ionic liquids and negatively charged polyelectrolytes

    International Nuclear Information System (INIS)

    Ogihara, Wataru; Sun Jiazeng; Forsyth, Maria; MacFarlane, Douglas R.; Yoshizawa, Masahiro; Ohno, Hiroyuki

    2004-01-01

    We have prepared polymer gel electrolytes with alkali metal ionic liquids (AMILs) that inherently contain alkali metal ions. The AMIL consisted of sulfate anion, imidazolium cation, and alkali metal cation. AMILs were mixed directly with poly(3-sulfopropyl acrylate) lithium salt or poly(2-acrylamido-2-methylpropanesulfonic acid) lithium salt to form polymer gels. The ionic conductivity of these gels decreased with increasing polymer fraction, as in general ionic liquid/polymer mixed systems. At low polymer concentrations, these gels displayed excellent ionic conductivity of 10 -4 to 10 -3 S cm -1 at room temperature. Gelation was found to cause little change in the 7 Li diffusion coefficient of the ionic liquid, as measured by pulse-field-gradient NMR. These data strongly suggest that the lithium cation migrates in successive pathways provided by the ionic liquids

  12. Infrared laser-induced chaos and conformational disorder in a model polymer crystal: Melting vs ablation

    International Nuclear Information System (INIS)

    Sumpter, B.G.; Noid, D.W.; Voth, G.A.; Wunderlich, B.

    1990-01-01

    Molecular dynamics-based computer simulations are presented for the interaction of one and two infrared (IR) laser beams with a model polymer surface. When a single laser beam system is studied over a wide range of intensities, only melting of the polymer, or melting followed by bond dissociation, is observed for up to 100 picoseconds. In contrast, the two-laser simulation results exhibit a marked difference in the energy absorption behavior of the irradiated polymer which, in turn, results in multiple bond dissociations. The results for the one- and two-laser cases studied can be divided into four different classes of physical behavior: (a) the polymer remains in the solid state; (b) the polymer crystal melts; (c) the polymer ablates, but with significant melting (charring); or (d) the polymer ablates with minimal melting. Damage to the model polymer crystal from absorption of energy from either one or two lasers occurs through a mechanism that involves the competition between the absorption of energy and internal energy redistribution. The rate of energy loss from the absorption site(s) relative to the rate of absorption of energy from the radiation field determines rather the polymer melts or ablates (low absorption rates lead to melting or no change and high rates lead to ablation). A sufficiently large rate of energy absorption is only obtainable through the use of two lasers. Two lasers also significantly decrease the total laser intensity required to cause polymer crystal melting. The differences between the one- and two-laser cases are studied by adapting novel signal/subspace techniques to analyze the dynamical changes in the mode spectrum of the polymer as it melts

  13. A novel composite alignment layer for transflective liquid crystal display

    Energy Technology Data Exchange (ETDEWEB)

    Li Shuangyao; Li Xuan [State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Tao Du; Chigrinov, Vladimir; Kwok, Hoi Sing, E-mail: eechigr@ust.h [Center for Display Research, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2010-10-20

    A novel composite photoalignment layer for transflective liquid crystal displays is explored. The key technique is to introduce a functional photo-crosslinkage into a rewritable azodye material with proper mixing. Bearing good alignment quality derived from the azodye material, the composite layer provides strong azimuthal and polar anchoring energy comparable to that of rubbed polyimide layers. The capability of dual modes fabrication in one cell exhibited by azodyes could be well retained and the new alignment film exhibits a display resolution of up to 2 {mu}m. Furthermore, after exposure to strong LED unpolarized light the composite layer shows much better stability than that with a pure azodye material.

  14. Optical devices based on liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard

    2005-01-01

    the waveguiding mechanism of LC filled PCFs. The principle of tunable fibers based on LCs is thereafter discussed and an alignment and coating study of LC in capillaries is presented. Next, the Liquid Crystal Photonic BandGap (LCPBG) fiber is presented and the waveguiding mechanism is analyzed through plane...... hole. The presence of a LC in the holes of the PCF transforms the fiber from a Total Internal Reflection (TIR) guiding type into a Photonic BandGap (PBG) guiding type, where light is confined to the silica core by coherent scattering from the LC-billed holes. The high dielectric and optical anisotropy...

  15. The mathematics of instabilities in smectic C liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, D.A

    2001-07-01

    The theoretical effects of applying a magnetic or electric field to samples of smectic A and smectic C{sup *} liquid crystals are studied in this thesis. In Chapter 2 general background material on liquid crystals is introduced as well as the continuum theory which we shall use in subsequent chapters. We consider a planar sample of ferroelectric smectic C{sup *} liquid crystal in Chapter 3, where an electric field is applied perpendicular to the smectic layers. In particular, we obtain an exact solution to a dynamic equation which governs director reorientation (within a sample which is bounded in the z direction) which appears in the literature. We then consider the linear stability of this solution by applying a perturbation, in both space and time, and examine its growth. In Chapter 4 we again consider the stability of a planar sample of ferroelectric smectic C{sup *} when an electric field is applied perpendicular to the smectic planes. However, unlike in Chapter 3, we derive the relevant governing equation. After having introduced the relevant theory, the linear and nonlinear stability of a constant equilibrium state in both finite and infinite domains is examined. We then obtain information upon the relaxation times for each of these cases. The relaxation time gives an indication of how quickly the director relaxes back to equilibrium. The dynamic equation which is derived in Chapter 4 is extended in Chapter 5 to include the effects of lilting the applied electric field. The equilibrium equation which we then obtain is not tractable explicitly due to the form of the sinusoidal nonlinearity which appears in it. We therefore solve a simplified approximating dynamic equation as well as the full sinusoidal nonlinearity case numerically. In both cases the linear stability of the equilibrium solution is examined. Finally, in Chapter 6 we consider the layer deformations in a cylindrical sample of smectic A liquid crystal when a magnetic field is applied across the

  16. Liquid crystal nanoparticles for delivery of photosensitizers for photodynamic therapy

    Science.gov (United States)

    Nag, Okhil K.; Naciri, Jawad; Delehanty, James B.

    2018-02-01

    The main principle of photodynamic therapy (PDT) is to kill malignant cells by generation of reactive oxygen species (ROS). PDT appeared highly effective when ROS can be produced in subcellular location such as plasma membrane. The plasma membrane maintains the structural integrity of the cell and regulates multiple important cellular processes, such as endocytosis, trafficking, and apoptotic pathways, could be one of the best points to kill the cancer cells. Previously, we have developed a plasma membrane-targeted liquid crystal nanoparticle (LCNP) formulation that can be loaded with dyes or drugs. Here we highlight the utility of this LCNP for membrane targeted delivery and imaging for a photosensitizer (PS) for PDT applications.

  17. Diffraction and signal processing experiments with a liquid crystal microdisplay

    International Nuclear Information System (INIS)

    MartInez, Jose Luis; Moreno, Ignacio; Ahouzi, Esmail

    2006-01-01

    In this work, we show some diffraction experiments performed with a liquid crystal display (LCD) that shows how useful this device can be to teach and experience diffraction optics and signal processing experiments. The LCD acts as a programmable pixelated diffractive mask. The Fourier spectrum of the image displayed in the LCD is visualized through a simple free propagation diffraction experiment. This optical system allows easy testing of different diffractive elements. As a demonstration we include experimental results with well-known diffractive elements like diffraction gratings or Fresnel lenses, and with more complicated elements like computer-generated holograms

  18. Diffraction and signal processing experiments with a liquid crystal microdisplay

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, Jose Luis [Departamento de Ciencia y TecnologIa de Materiales, Universidad Miguel Hernandez de Elche, Alicante (Spain); Moreno, Ignacio [Departamento de Ciencia y TecnologIa de Materiales, Universidad Miguel Hernandez de Elche, Alicante (Spain); Ahouzi, Esmail [Institut National des Postes et Telecomunications (INTP), Madinat Al Irfane, Rabat (Morocco)

    2006-09-01

    In this work, we show some diffraction experiments performed with a liquid crystal display (LCD) that shows how useful this device can be to teach and experience diffraction optics and signal processing experiments. The LCD acts as a programmable pixelated diffractive mask. The Fourier spectrum of the image displayed in the LCD is visualized through a simple free propagation diffraction experiment. This optical system allows easy testing of different diffractive elements. As a demonstration we include experimental results with well-known diffractive elements like diffraction gratings or Fresnel lenses, and with more complicated elements like computer-generated holograms.

  19. Experimental investigations on weakly polar liquid crystal-aerosil composites

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, Chethan V; Prasad, S Krishna; Yelamaggad, C V [Centre for Liquid Crystal Research, Jalahalli, Bangalore 560013 (India)

    2006-01-25

    We have carried out differential scanning calorimetric and dielectric studies on composites of hydrophilic aerosil with a liquid crystal that does not possess a terminal polar group. While the shift in the nematic-isotropic transition temperature is in agreement with the general behaviour observed for such composites, the dielectric studies show, contrary to the commonly observed feature, that there is a systematic increase in the relaxation frequency associated with the rotation of the molecules around their short axis, as the aerosil concentration in the composite is increased.

  20. The mathematics of instabilities in smectic C liquid crystals

    International Nuclear Information System (INIS)

    Anderson, D.A.

    2001-01-01

    The theoretical effects of applying a magnetic or electric field to samples of smectic A and smectic C * liquid crystals are studied in this thesis. In Chapter 2 general background material on liquid crystals is introduced as well as the continuum theory which we shall use in subsequent chapters. We consider a planar sample of ferroelectric smectic C * liquid crystal in Chapter 3, where an electric field is applied perpendicular to the smectic layers. In particular, we obtain an exact solution to a dynamic equation which governs director reorientation (within a sample which is bounded in the z direction) which appears in the literature. We then consider the linear stability of this solution by applying a perturbation, in both space and time, and examine its growth. In Chapter 4 we again consider the stability of a planar sample of ferroelectric smectic C * when an electric field is applied perpendicular to the smectic planes. However, unlike in Chapter 3, we derive the relevant governing equation. After having introduced the relevant theory, the linear and nonlinear stability of a constant equilibrium state in both finite and infinite domains is examined. We then obtain information upon the relaxation times for each of these cases. The relaxation time gives an indication of how quickly the director relaxes back to equilibrium. The dynamic equation which is derived in Chapter 4 is extended in Chapter 5 to include the effects of lilting the applied electric field. The equilibrium equation which we then obtain is not tractable explicitly due to the form of the sinusoidal nonlinearity which appears in it. We therefore solve a simplified approximating dynamic equation as well as the full sinusoidal nonlinearity case numerically. In both cases the linear stability of the equilibrium solution is examined. Finally, in Chapter 6 we consider the layer deformations in a cylindrical sample of smectic A liquid crystal when a magnetic field is applied across the circular cross

  1. Controlling Active Liquid Crystal Droplets with Temperature and Surfactant Concentration

    Science.gov (United States)

    Shechter, Jake; Milas, Peker; Ross, Jennifer

    Active matter is the study of driven many-body systems that span length scales from flocking birds to molecular motors. A previously described self-propelled particle system was made from liquid crystal (LC) droplets in water with high surfactant concentration to move particles via asymmetric surface instabilities. Using a similar system, we investigate the driving activity as a function of SDS surfactant concentration and temperature. We then use an optical tweezer to trap and locally heat the droplets to cause hydrodynamic flow and coupling between multiple droplets. This system will be the basis for a triggerable assembly system to build and couple LC droplets. DOD AROMURI 67455-CH-MUR.

  2. Self-Assembled Supramolecular Architectures Lyotropic Liquid Crystals

    CERN Document Server

    Garti, Nissim

    2012-01-01

    This book will describe fundamentals and recent developments in the area of Self-Assembled Supramolecular Architecture and their relevance to the  understanding of the functionality of  membranes  as delivery systems for active ingredients. As the heirarchial architectures determine their performance capabilities, attention will be paid to theoretical and design aspects related to the construction of lyotropic liquid crystals: mesophases such as lamellar, hexagonal, cubic, sponge phase micellosomes. The book will bring to the reader mechanistic aspects, compositional c

  3. Distributed hydrophone array based on liquid crystal cell

    Science.gov (United States)

    Brodzeli, Zourab; Ladouceur, Francois; Silvestri, Leonardo; Michie, Andrew; Chigrinov, Vladimir; Guo, Grace Qi; Pozhidaev, Eugene P.; Kiselev, Alexei D.

    2012-02-01

    We describe a fibre 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 voltage-controlled Liquid Crystals (LC) and simple multiplexing method. The proposed method permits measurements of sound under water at multiple points along an optical fibre using low cost components (LC cells), standard single mode fibre, without complex interferometric measurement techniques, electronics or demodulation software.

  4. Adaptive Holography in Liquid Crystal Light-Valves

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Huignard

    2012-08-01

    Full Text Available By performing two-wave mixing experiments in a liquid crystal light-valve, optical beam amplification is obtained as a strongly resonant process to which a narrow frequency bandwidth is associated. This property is exploited to realize adaptive holographic interferometric systems able to efficiently detect displacements as small as fraction of picometers. Pressure radiation induced deformations of a reflecting membrane are measured with the same type of system. Then, when used with complex wavefronts, like speckle fields, the LCLV-based interferometer allows to detect extremely small phase modulations. The examples shown demonstrate the potentialities of the light-valve for dynamic holography applications.

  5. Imaging spectrometer using a liquid crystal tunable filter

    Science.gov (United States)

    Chrien, Thomas G.; Chovit, Christopher; Miller, Peter J.

    1993-09-01

    A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design. An overview of the prototype system is given along with a description of balloon experiment results. System model performance predictions are given for a future LCTF based imaging spectrometer design. System design considerations of LCTF imaging spectrometers are discussed.

  6. A novel composite alignment layer for transflective liquid crystal display

    International Nuclear Information System (INIS)

    Li Shuangyao; Li Xuan; Tao Du; Chigrinov, Vladimir; Kwok, Hoi Sing

    2010-01-01

    A novel composite photoalignment layer for transflective liquid crystal displays is explored. The key technique is to introduce a functional photo-crosslinkage into a rewritable azodye material with proper mixing. Bearing good alignment quality derived from the azodye material, the composite layer provides strong azimuthal and polar anchoring energy comparable to that of rubbed polyimide layers. The capability of dual modes fabrication in one cell exhibited by azodyes could be well retained and the new alignment film exhibits a display resolution of up to 2 μm. Furthermore, after exposure to strong LED unpolarized light the composite layer shows much better stability than that with a pure azodye material.

  7. Synthesis and characterization of liquid crystals and their thermoset films

    International Nuclear Information System (INIS)

    Ahn, Yong-Ho; Jung, Myung-Sup; Chang, Jin-Hae

    2010-01-01

    We prepared a series of aromatic liquid crystals (LCs) based on aromatic ester units with the reactive end groups methyl-maleimide and nadimide, and the resulting LCs were thermally cross-linked to produce liquid crystalline thermoset (LCT) films by means of solution-casting and heat treatment. The synthesized LCs and LCTs were characterized with Fourier transform infrared (FT-IR) spectroscopy, 1 H nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and polarizing optical microscopy with a hot stage. We found that all these LCs form nematic phases. The coefficients of thermal expansion (CTEs) of the LCT films are strongly affected by the reactive end group and the mesogen units in their main-chain structures. The methyl-maleimide-terminated biphenyl LCT was found to have the lowest CTE.

  8. Biaxiality in Nematic and Smectic Liquid Crystals. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satyendra [Kent State Univ., Kent, OH (United States); Li, Quan [Kent State Univ., Kent, OH (United States); Srinivasarao, Mohan [Georgia Inst. of Technology, Atlanta, GA (United States); Agra-Kooijman, Dena M. [Kent State Univ., Kent, OH (United States); Rey, Alejandro [McGill Univ., Montreal, QC (Canada)

    2017-01-24

    During the award period, the project team explored several phenomena in a diverse group of soft condensed matter systems. These include understanding of the structure of the newly discovered twist-bend nematic phase, solving the mystery of de Vries smectic phases, probing of interesting associations and defect structures in chromonic liquid crystalline systems, dispersions of ferroelectric nanoparticles in smectic liquid crystals, investigations of newly synthesized light sensitive and energy harvesting materials with highly desirable transport properties. Our findings are summarized in the following report followed by a list of 36 publications and 37 conference presentations. We achieved this with the support of Basic Sciences Division of the US DOE for which we are thankful.

  9. Tunable Channel Drop Filter in a Two-Dimensional Photonic Crystal Modulated by a Nematic Liquid Crystal

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Photonic crystals (PCs have many potential applications because of their ability to control light-wave propagation and because PC-based waveguides may be integrated into optical circuits. We propose a novel tunable PC channel drop filter based on nematic liquid crystals and investigate its properties numerically by using the finite-difference time-domain (FDTD method. The refractive indices of liquid crystals can be actively modulated after infiltrating nematic liquid crystals into the microcavity in PC waveguides with square lattices. Then we can control light propagation in a PC waveguide. We analyze the Q -factors and resonance frequencies of a tunable PC channel drop filter by considering various indices modulation of liquid crystals. The novel component can be used as wavelength division multiplexing in photonic integrated circuits.

  10. Integration of molecular machines into supramolecular materials: actuation between equilibrium polymers and crystal-like gels.

    Science.gov (United States)

    Mariani, Giacomo; Goujon, Antoine; Moulin, Emilie; Rawiso, Michel; Giuseppone, Nicolas; Buhler, Eric

    2017-11-30

    In this article, the dynamic structure of complex supramolecular polymers composed of bistable [c2]daisy chain rotaxanes as molecular machines that are linked by ureidopyrimidinones (Upy) as recognition moieties was studied. pH actuation of the integrated mechanically active rotaxanes controls the contraction/extension of the polymer chains as well as their physical reticulation. Small-angle neutron and X-ray scattering were used to study in-depth the nanostructure of the contracted and extended polymer aggregates in toluene solution. The supramolecular polymers comprising contracted nanomachines were found to be equilibrium polymers with a mass that is concentration dependent in dilute and semidilute regimes. Surprisingly, the extended polymers form a gel network with a crystal-like internal structure that is independent of concentration and reminiscent of a pearl-necklace network.

  11. Toward protic ionic liquid and organic ionic plastic crystal electrolytes for fuel cells

    International Nuclear Information System (INIS)

    Rana, Usman Ali; Forsyth, Maria; MacFarlane, Douglas R.; Pringle, Jennifer M.

    2012-01-01

    Highlights: ► Polymer electrolyte membrane fuel cells that can operate above 120 °C, without humidification, would be much more commercially viable. ► Protic ionic liquids and organic ionic plastic crystals are showing increasing promise as anhydrous proton conductors in fuel cells. ► Here we review the recent progress in these two areas. - Abstract: There is increasing demand for the development of anhydrous proton conducting electrolytes, most notably to allow the development of fuel cells that can operate at temperatures above 120 °C, without the need for constant and controlled humidification. The emerging field of protic ionic liquids (PILs) represents a promising new direction for this research and the development of these materials has made significant progress in recent years. In a related but as yet little-explored avenue, proton conducting organic ionic plastic crystals offer the potential advantage of providing a solid state matrix for anhydrous proton conductivity. Here we discuss the recent progress in these areas and identify the key challenges for future research.

  12. Polymerizable Ionic Liquid Crystals Comprising Polyoxometalate Clusters toward Inorganic-Organic Hybrid Solid Electrolytes

    Directory of Open Access Journals (Sweden)

    Takeru Ito

    2017-07-01

    Full Text Available Solid electrolytes are crucial materials for lithium-ion or fuel-cell battery technology due to their structural stability and easiness for handling. Emergence of high conductivity in solid electrolytes requires precise control of the composition and structure. A promising strategy toward highly-conductive solid electrolytes is employing a thermally-stable inorganic component and a structurally-flexible organic moiety to construct inorganic-organic hybrid materials. Ionic liquids as the organic component will be advantageous for the emergence of high conductivity, and polyoxometalate, such as heteropolyacids, are well-known as inorganic proton conductors. Here, newly-designed ionic liquid imidazolium cations, having a polymerizable methacryl group (denoted as MAImC1, were successfully hybridized with heteropolyanions of [PW12O40]3− (PW12 to form inorganic-organic hybrid monomers of MAImC1-PW12. The synthetic procedure of MAImC1-PW12 was a simple ion-exchange reaction, being generally applicable to several polyoxometalates, in principle. MAImC1-PW12 was obtained as single crystals, and its molecular and crystal structures were clearly revealed. Additionally, the hybrid monomer of MAImC1-PW12 was polymerized by a radical polymerization using AIBN as an initiator. Some of the resulting inorganic-organic hybrid polymers exhibited conductivity of 10−4 S·cm−1 order under humidified conditions at 313 K.

  13. Dye-Induced Enhancement of Optical Nonlinearity in Liquids and Liquid Crystals

    International Nuclear Information System (INIS)

    Muenster, R.; Jarasch, M.; Zhuang, X.; Shen, Y.

    1997-01-01

    Optical nonlinearity of liquid crystals (LC) in the isotropic phase can be enhanced by 1 order of magnitude by dissolving 0.1% of anthraquinone dye in the LC. The enhancement decreases by ∼30% when the LC transforms into the nematic phase. The same guest-host effect also exists in non-LC liquids. It can be explained by a model based on the change of guest-host interaction induced by optical excitations of the dye. copyright 1996 The American Physical Society

  14. A simple analytical thermo-mechanical model for liquid crystal elastomer bilayer structures

    Directory of Open Access Journals (Sweden)

    Yun Cui

    2018-02-01

    Full Text Available The bilayer structure consisting of thermal-responsive liquid crystal elastomers (LCEs and other polymer materials with stretchable heaters has attracted much attention in applications of soft actuators and soft robots due to its ability to generate large deformations when subjected to heat stimuli. A simple analytical thermo-mechanical model, accounting for the non-uniform feature of the temperature/strain distribution along the thickness direction, is established for this type of bilayer structure. The analytical predictions of the temperature and bending curvature radius agree well with finite element analysis and experiments. The influences of the LCE thickness and the heat generation power on the bending deformation of the bilayer structure are fully investigated. It is shown that a thinner LCE layer and a higher heat generation power could yield more bending deformation. These results may help the design of soft actuators and soft robots involving thermal responsive LCEs.

  15. Electro-optical memory of a nematic liquid crystal doped by multi-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    L. Dolgov

    2012-10-01

    Full Text Available A pronounced irreversible electro-optical response (memory effect has been recently observed for nematic liquid crystal (LC EBBA doped by multi-walled carbon nanotubes (MWCNTs near the percolation threshold of the MWCNTs (0.02÷0.05 wt. %. It is caused by irreversible homeotropic-to-planar reorientation of LC in an electric field. This feature is explained by electro-hydrodynamically stimulated dispergation of MWCNTs in LC and by the formation of a percolation MWCNT network which acts as a spatially distributed surface stabilizing the planar state of the LC. This mechanism is confirmed by the absence of memory in the EBBA/MWCNT composites, whose original structure is fixed by a polymer. The observed effect suggests new operation modes for the memory type and bistable LC devices, as well as a method for in situ dispergation of carbon nanotubes in LC cells.

  16. Director gliding in a nematic liquid crystal layer: Quantitative comparison with experiments

    Science.gov (United States)

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

    2018-03-01

    The interaction between nematic liquid crystals and polymer-coated substrates may lead to slow reorientation of the easy axis (so-called "director gliding") when a prolonged external field is applied. We consider the experimental evidence of zenithal gliding observed by Joly et al. [Phys. Rev. E 70, 050701 (2004), 10.1103/PhysRevE.70.050701] and Buluy et al. [J. Soc. Inf. Disp. 14, 603 (2006), 10.1889/1.2235686] as well as azimuthal gliding observed by S. Faetti and P. Marianelli [Liq. Cryst. 33, 327 (2006), 10.1080/02678290500512227], and we present a simple, physically motivated model that captures the slow dynamics of gliding, both in the presence of an electric field and after the electric field is turned off. We make a quantitative comparison of our model results and the experimental data and conclude that our model explains the gliding evolution very well.

  17. Effect of a novel amphipathic ionic liquid on lithium deposition in gel polymer electrolytes

    International Nuclear Information System (INIS)

    Choi, Nam-Soon; Koo, Bonjae; Yeon, Jin-Tak; Lee, Kyu Tae; Kim, Dong-Won

    2011-01-01

    Highlights: · Synthesis of a dimeric ionic liquid. · Gel polymer electrolytes providing uniform lithium deposit pathway. · An amphipathic ionic liquid locates at the interface between an electrolyte-rich phase and a polymer matrix in a gel polymer electrolyte. · The presence of PDMITFSI ionic liquid leads to the suppression of dendritic lithium formation on a lithium metal electrode. - Abstract: A novel dimeric ionic liquid based on imidazolium cation and bis(trifluoromethanesulfonyl) imide (TFSI) anion has been synthesized through a metathesis reaction. Its chemical shift values and thermal properties are identified via 1 H nuclear magnetic resonance (NMR) imaging and differential scanning calorimetry (DSC). The effect of the synthesized dimeric ionic liquid on the interfacial resistance of gel polymer electrolytes is described. Differences in the SEM images of lithium electrodes after lithium deposition with and without the 1,1'-pentyl-bis(2,3-dimethylimidazolium) bis(trifluoromethane-sulfonyl)imide (PDMITFSI) ionic liquid in gel polymer electrolytes are clearly discernible. This occurs because the PDMITFSI ionic liquid with hydrophobic moieties and polar groups modulates lithium deposit pathways onto the lithium metal anode. Moreover, high anodic stability for a gel polymer electrolyte with the PDMITFSI ionic liquid was clearly observed.

  18. Towards understanding hydrophobic recovery of plasma treated polymers: Storing in high polarity liquids suppresses hydrophobic recovery

    International Nuclear Information System (INIS)

    Bormashenko, Edward; Chaniel, Gilad; Grynyov, Roman

    2013-01-01

    The phenomenon of hydrophobic recovery was studied for cold air plasma treated polyethylene films. Plasma-treated polymer films were immersed into liquids with very different polarities such as ethanol, acetone, carbon tetrachloride, benzene and carbon disulphide. Hydrophobic recovery was studied by measurement of contact angles. Immersion into high polarity liquids slows markedly the hydrophobic recovery. We relate this slowing to dipole–dipole interaction of polar groups of the polymer with those of the liquids. This kind of interaction becomes decisive when polar groups of polymer chains are at least partially spatially fixed.

  19. Viewing angle switching of patterned vertical alignment liquid crystal display

    International Nuclear Information System (INIS)

    Lim, Young Jin; Jeong, Eun; Chin, Mi Hyung; Lee, Seung Hee; Ji, Seunghoon; Lee, Gi-Dong

    2008-01-01

    Viewing angle control of a patterned vertical alignment (PVA) liquid crystal display using only one panel is investigated. In conventional PVA modes, a vertically aligned liquid crystal (LC) director tilts down in four directions making 45 deg. with respect to crossed polarizers to exhibit a wide viewing angle. In the viewing angle control device, one pixel was divided into two sub-pixels such that the LC director in the main pixel is controlled to be tilted down in multiple directions making an angle with the polarizer, playing the role of main display with the wide viewing angle, while the LC director in the sub-pixel is controlled to be tilted down to the polarizer axis, playing the role of sub-pixel to the viewing angle control for the narrow viewing angle. Using sub-pixel control, light leakage or any type of information such as characters and image can be generated in oblique viewing directions without distorting the image quality in the normal direction, which will prevent others from peeping at the displayed image by overlapping the displayed image with the made image

  20. Optics of Confined Liquid Crystals for Gas Detection

    Science.gov (United States)

    Charles, William; Carrozzi, Daniel; Vigilia, Lee Anne; Wang, Xiaoyurui; Guzman, Violet; Shibayev, Petr; Fordham University Students of Undergraduate Physics Team

    Cholesteric liquid crystals (CLCs) of a wide range of viscosities were studied experimentally in relation to their use as gas sensors and sensors of volatile organic compounds (VOCs), specifically ethanol, cyclohexane, toluene, acetic acid, and pyridine. CLCs were obtained by mixing low molar mass liquid crystals (MBBA and cholesterol derivatives with siloxane based oligomers). The droplets of CLCs were placed in containers with controlled atmospheres. The shift of the selective reflection band, predominantly from shorter to longer wavelengths, and the color changes were observed in the CLC illuminated by light coming from the various directions. Visible optical changes were observed in droplets with viscosities of CLCs ranging from c.a. 4 Pa*s to 105 Pa*s. The most responsive droplets in which the shift of the selective reflection band occurs at lower concentrations of VOCs were prepared from CLC mixtures with the lowest viscosities. Higher viscosities of CLCs lead to a slower response to VOCs, but the rate of response is different for each pair of VOC and CLC with a certain viscosity. This finding opens a possibility for selective detection of VOCs by CLCs with different viscosities. The mechanism of VOCs diffusion, interaction with CLC matrix and optical changes is discusse

  1. Switchable Liquid Crystal Contact Lenses for the Correction of Presbyopia

    Directory of Open Access Journals (Sweden)

    James Bailey

    2018-01-01

    Full Text Available Presbyopia is an age-related disorder where the lens of the eye hardens so that focusing on near objects becomes increasingly difficult. This complaint affects everyone over the age of 50. It is becoming progressively more relevant, as the average age of the global population continues to rise. Bifocal or varifocal spectacles are currently the best solution for those that require near and far vision correction. However, many people prefer not to wear spectacles and while multifocal contact lenses are available, they are not widely prescribed and can require significant adaptation by wearers. One possible solution is to use liquid crystal contact lenses that can change focal power by applying a small electric field across the device. However, the design of these contact lenses must be carefully considered as they must be comfortable for the user to wear and able to provide the required change in focal power (usually about +2D. Progress towards different lens designs, which includes lens geometry, liquid crystal choices and suitable alignment modes, are reviewed. Furthermore, we also discuss suitable electrode materials, possible power sources and suggest some methods for switching the lenses between near and far vision correction.

  2. Intrinsic frame transport for a model of nematic liquid crystal

    Science.gov (United States)

    Cozzini, S.; Rull, L. F.; Ciccotti, G.; Paolini, G. V.

    1997-02-01

    We present a computer simulation study of the dynamical properties of a nematic liquid crystal model. The diffusional motion of the nematic director is taken into account in our calculations in order to give a proper estimate of the transport coefficients. Differently from other groups we do not attempt to stabilize the director through rigid constraints or applied external fields. We instead define an intrinsic frame which moves along with the director at each step of the simulation. The transport coefficients computed in the intrinsic frame are then compared against the ones calculated in the fixed laboratory frame, to show the inadequacy of the latter for systems with less than 500 molecules. Using this general scheme on the Gay-Berne liquid crystal model, we evidence the natural motion of the director and attempt to quantify its intrinsic time scale and size dependence. Through extended simulations of systems of different size we calculate the diffusion and viscosity coefficients of this model and compare our results with values previously obtained with fixed director.

  3. Investigation of the liquid crystal alignment layer: effect on electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Abderrahmen, Asma; Romdhane, Fayda Fekih; Gharbi, Abdelhafidh [Laboratoire de la matiere molle, Faculte des sciences, Tunis (Tunisia); Ouada, Hafedh Ben [Laboratoire de physique et chimie des interfaces, Faculte des sciences, 5000 Monastir (Tunisia)], E-mail: asma_abderrahmen@yahoo.fr

    2008-04-01

    We investigate the electrical behavior of a symmetric liquid crystal (LC) cell: elecrode-silane-LC-silane-electrode. The silane (chlorodimethyloctadecyl-silane) layer induces a homeotropic orientation of the nematic liquid crystal (NLC) molecules. The wettability technique is used to detect the change of the surface energy of the electrode upon cleaning and silane layer deposition. We report on the dynamic impedance measurements of the nematic liquid crystal cell. It is found that the silane alignment layer has a blocking effect on the liquid crystal (LC) cell. We also study the relaxation behavior of the cell which is later assimilated as an electrical equivalent circuit.

  4. Investigation of the liquid crystal alignment layer: effect on electrical properties

    International Nuclear Information System (INIS)

    Abderrahmen, Asma; Romdhane, Fayda Fekih; Gharbi, Abdelhafidh; Ouada, Hafedh Ben

    2008-01-01

    We investigate the electrical behavior of a symmetric liquid crystal (LC) cell: elecrode-silane-LC-silane-electrode. The silane (chlorodimethyloctadecyl-silane) layer induces a homeotropic orientation of the nematic liquid crystal (NLC) molecules. The wettability technique is used to detect the change of the surface energy of the electrode upon cleaning and silane layer deposition. We report on the dynamic impedance measurements of the nematic liquid crystal cell. It is found that the silane alignment layer has a blocking effect on the liquid crystal (LC) cell. We also study the relaxation behavior of the cell which is later assimilated as an electrical equivalent circuit

  5. muSR-Investigation of a Liquid Crystal Containing Iron Atoms

    CERN Document Server

    Mamedov, T N; Galyametdinov, Yu G; Gritsaj, K I; Herlach, D; Kormann, O; Major, J V; Rochev, V Ya; Stoikov, A V; Zimmermann, U

    2000-01-01

    The work is devoted to the investigation of properties of a liquid crystal whose molecule contains iron atom. The compounds of this type are of interest from the point of view of obtaining liquid crystals with magnetic properties. The temperature dependence of the polarization and relaxation rate of positive muon spin in the liquid crystal was measured in the temperature range 4-300 K. The results obtained do not contradict the suggestion that the iron ions from an antiferromagnetically-ordered structure in this liquid crystal at the temperatures below 80 K.

  6. Electro-Optical Characterization of Bistable Smectic A Liquid Crystal Displays

    Science.gov (United States)

    Buyuktanir, Ebru Aylin

    My dissertation focuses the characterization and optimization of the electro-optical properties of smectic A (SmA) based liquid crystal (LC) displays. I present the development of robust and flexible bistable SmA LC displays utilizing polymer dispersed liquid crystal (PDLC) technology. The SmA PDLC displays produced on plastic substrates present electrically reversible memory, high contrast ratio, paper-like sunlight readability, and wide viewing angle characteristics. In order to optimize the SmA PDLC display, I investigated polymerization conditions, such as polymer concentration effect, polymerization temperature, and UV-light intensity variations. I characterized the electro-optical responses-such as static-response, time-response, threshold characteristics, and contrast ratio values' of the optimized SmA PDLC display and compared them to those of the pure SmA LC. The best electro-optical performance of SmA PDLC formulation was obtained using the combination of low mW/cm 2 and high mW/cm2 UV-light curing intensity. The contrast ratio of the optimum SmA PDLC at a 5o collection angle was 83% of that of the pure SmA material on plastic substrates. I fabricated 2.5 x 2.5 in., 4 x 4 in., and 6 x 6 in. sized monochrome flexible SmA PDLC displays, as well as red, yellow, and fluorescent dyes colored SmA PDLC displays on plastic substrates. The electro-optic performance of the bistable SmA LC display consisting of a patterned field-induced polymer wall infrastructure was also studied and compared to those of pure SmA material. I found that the contrast ratio of the SmA LC encapsulated between polymer walls was much greater than that of the SmA PDLC system, approaching the contrast ratio value of the pure SmA material. I also improved the electro-optical characteristics of bistable SmA LC displays by adding ferroparticles into the system. Finally, I illustrated the unique capabilities of polarized confocal Raman microscopy (CRM) to resolve the orientational order of Sm

  7. NATO Advanced Study Institute on Electronic Structure of Polymers and Molecular Crystals

    CERN Document Server

    Ladik, János

    1975-01-01

    The NATO Advanced Study Institute on "Electronic Structure of Polymers and Molecular Crystals" was held at the Facultes Universi­ taires de Namur (F.U.N.) from September 1st till September 14th, 1974. We wish to express our appreciation to the NATO Scientific Affairs Division whose generous support made this Institute possible and to the Facultes Universitaires de Namur and the Societe Chimique de Belgique which provided fellowships and travel grants to a number of students. This volume contains the main lectures about the basic principles of the field and about different recent developments of the theory of the electronic structure of polymers and molecular crystals. The school started with the presentation of the basic SCF-LCAO theory of the electronic structure of periodic polymers and molecular crystals (contributions by Ladik, Andre & Delhalle) showing how a combination of quantum chemical and solid state physical methods can provide band structures for these systems. The numerical aspects of these ...

  8. A roadmap to uranium ionic liquids: Anti-crystal engineering

    Energy Technology Data Exchange (ETDEWEB)

    Yaprak, Damla; Spielberg, Eike T.; Baecker, Tobias; Richter, Mark; Mallick, Bert [Inorganic Chemistry III, Ruhr-University Bochum (Germany); Klein, Axel [Institut fuer Anorganische Chemie, Koeln Univ. (Germany); Mudring, Anja-Verena [Inorganic Chemistry III, Ruhr-University Bochum (Germany); Materials Science and Engineering, Iowa State University and Critical Materials Institute, Ames Laboratory, Ames, IA (United States)

    2014-05-19

    In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C{sub 4}mim) cation. As dithiocarbamate ligands binding to the UO{sub 2}{sup 2+} unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Effects of thermo-order-mechanical coupling on band structures in liquid crystal nematic elastomer porous phononic crystals.

    Science.gov (United States)

    Yang, Shuai; Liu, Ying

    2018-08-01

    Liquid crystal nematic elastomers are one kind of smart anisotropic and viscoelastic solids simultaneously combing the properties of rubber and liquid crystals, which is thermal sensitivity. In this paper, the wave dispersion in a liquid crystal nematic elastomer porous phononic crystal subjected to an external thermal stimulus is theoretically investigated. Firstly, an energy function is proposed to determine thermo-induced deformation in NE periodic structures. Based on this function, thermo-induced band variation in liquid crystal nematic elastomer porous phononic crystals is investigated in detail. The results show that when liquid crystal elastomer changes from nematic state to isotropic state due to the variation of the temperature, the absolute band gaps at different bands are opened or closed. There exists a threshold temperature above which the absolute band gaps are opened or closed. Larger porosity benefits the opening of the absolute band gaps. The deviation of director from the structural symmetry axis is advantageous for the absolute band gap opening in nematic state whist constrains the absolute band gap opening in isotropic state. The combination effect of temperature and director orientation provides an added degree of freedom in the intelligent tuning of the absolute band gaps in phononic crystals. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Enhanced transduction of photonic crystal dye lasers for gas sensing via swelling polymer film

    DEFF Research Database (Denmark)

    Smith, Cameron; Lind, Johan Ulrik; Christiansen, Mads Brøkner

    2011-01-01

    We present the enhanced transduction of a photonic crystal dye laser for gas sensing via deposition of an additional swelling polymer film. Device operation involves swelling of the polymer film during exposure to specific gases, leading to a change in total effective refractive index. Experimental...... in its application to other intracavity-based detection schemes to enable gas sensing. © 2011 Optical Society of America....

  11. Membrane-Based Technologies in the Pharmaceutical Industry and Continuous Production of Polymer-Coated Crystals/Particles.

    Science.gov (United States)

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

    2017-01-01

    Membrane technologies are of increasing importance in a variety of separation and purification applications involving liquid phases and gaseous mixtures. Although the most widely used applications at this time are in water treatment including desalination, there are many applications in chemical, food, healthcare, paper and petrochemical industries. This brief review is concerned with existing and emerging applications of various membrane technologies in the pharmaceutical and biopharmaceutical industry. The goal of this review article is to identify important membrane processes and techniques which are being used or proposed to be used in the pharmaceutical and biopharmaceutical operations. How novel membrane processes can be useful for delivery of crystalline/particulate drugs is also of interest. Membrane separation technologies are extensively used in downstream processes for bio-pharmaceutical separation and purification operations via microfiltration, ultrafiltration and diafiltration. Also the new technique of membrane chromatography allows efficient purification of monoclonal antibodies. Membrane filtration techniques of reverse osmosis and nanofiltration are being combined with bioreactors and advanced oxidation processes to treat wastewaters from pharmaceutical plants. Nanofiltration with organic solvent-stable membranes can implement solvent exchange and catalyst recovery during organic solvent-based drug synthesis of pharmaceutical compounds/intermediates. Membranes in the form of hollow fibers can be conveniently used to implement crystallization of pharmaceutical compounds. The novel crystallization methods of solid hollow fiber cooling crystallizer (SHFCC) and porous hollow fiber anti-solvent crystallization (PHFAC) are being developed to provide efficient methods for continuous production of polymer-coated drug crystals in the area of drug delivery. This brief review provides a general introduction to various applications of membrane technologies in

  12. Charge Transport and Phase Behavior of Imidazolium-Based Ionic Liquid Crystals from Fully Atomistic Simulations.

    Science.gov (United States)

    Quevillon, Michael J; Whitmer, Jonathan K

    2018-01-02

    Ionic liquid crystals occupy an intriguing middle ground between room-temperature ionic liquids and mesostructured liquid crystals. Here, we examine a non-polarizable, fully atomistic model of the 1-alkyl-3-methylimidazolium nitrate family using molecular dynamics in the constant pressure-constant temperature ensemble. These materials exhibit a distinct "smectic" liquid phase, characterized by layers formed by the molecules, which separate the ionic and aliphatic moieties. In particular, we discuss the implications this layering may have for electrolyte applications.

  13. Pulsed zero field NMR of solids and liquid crystals

    International Nuclear Information System (INIS)

    Thayer, A.M.

    1987-02-01

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs

  14. Ionic Liquid based polymer electrolytes for electrochemical sensors

    Directory of Open Access Journals (Sweden)

    Jakub Altšmíd

    2015-09-01

    Full Text Available Amperometric NO2 printed sensor with a new type of solid polymer electrolyte and a carbon working electrode has been developed. The electrolytes based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonylimide [EMIM][N(Tf2], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][CF3SO3] and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] ionic liquids were immobilized in poly(vinylidene fluoride matrix [PVDF]. The analyte, gaseous nitrogen dioxide, was detected by reduction at -500 mV vs. platinum pseudoreference electrode. The sensors showed a linear behavior in the whole tested range, i.e., 0 - 5 ppm and their sensitivities were in order of 0.3 x∙10-6 A/ppm. The sensor sensitivity was influenced by the electric conductivity of printing formulation; the higher the conductivity, the higher the sensor sensitivity. The rise/recovery times were in order of tens of seconds. The use of  screen printing technology and platinum pseudoreference electrode simplify the sensor fabrication and it does not have any negative effect on the sensor stability.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7371

  15. Synthesis of new solid polymer electrolyte and actuator based on PEDOT/NBR/ionic liquid

    Science.gov (United States)

    Cho, M. S.; Seo, H. J.; Nam, J. D.; Choi, H. R.; Koo, J. C.; Lee, Y.

    2006-03-01

    The conducting polymer actuator was presented. The solid polymer electrolyte based on nitrile rubber (NBR) activated with different ionic liquids was prepared. The three different grades of NBR films were synthesized by emulsion polymerization with different amount of acrylonitrile, 23, 35, and 40 mol. %, respectively. The effect of acrylonitrile content on the ionic conductivity and dielectric constant of solid polymer electrolytes was characterized. A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the NBR layer by using a chemical oxidation polymerization technique, and room temperature ionic liquids (RTIL) based on imidazolium salts, e.g. 1-butyl-3-methyl imidazolium X [where X= BF 4 -, PF 6 -, (CF 3SO II) IIN -], were absorbed into the composite film. The effects of the anion size of the ionic liquids on the displacement of the actuator were examined. The displacement increased with increasing the anion-size of the ionic liquids.

  16. (1-Butyl-4-methyl-pyridinium)[Cu(SCN)2]: a coordination polymer and ionic liquid.

    Science.gov (United States)

    Spielberg, Eike T; Edengeiser, Eugen; Mallick, Bert; Havenith, Martina; Mudring, Anja-Verena

    2014-04-25

    The compound (C4C1py)[Cu(SCN)2], (C4C1py = 1-Butyl-4-methyl-pyridinium), which can be obtained from CuSCN and the ionic liquid (C4C1py)(SCN), turns out to be a new organic-inorganic hybrid material as it qualifies both, as a coordination polymer and an ionic liquid. It features linked [Cu(SCN)2](-) units, in which the thiocyanates bridge the copper ions in a μ1,3-fashion. The resulting one-dimensional chains run along the a axis, separated by the C4C1py counterions. Powder X-ray diffraction not only confirms the single-crystal X-ray structure solution but proves the reformation of the coordination polymer from an isotropic melt. However, the materials shows a complex thermal behavior often encountered for ionic liquids such as a strong tendency to form a supercooled melt. At a relatively high cooling rate, glass formation is observed. When heating this melt in differential scanning calorimetry (DSC) and temperature-dependent polarizing optical microscopy (POM), investigations reveal the existence of a less thermodynamically stable crystalline polymorph. Raman measurements conducted at 10 and 100 °C point towards the formation of polyanionic chain fragments in the melt. Solid-state UV/Vis spectroscopy shows a broad absorption band around 18,870 cm(-1) (530 nm) and another strong one below 20,000 cm(-1) (<500 nm). The latter is attributed to the d(Cu(I))→π*(SCN)-MLCT (metal-to-ligand charge transfer) transition within the coordination polymer yielding an energy gap of 2.4 eV. At room temperature and upon irradiation with UV light, the material shows a weak fluorescence band at 15,870 cm(-1) (630 nm) with a quantum efficiency of 0.90(2) % and a lifetime of 131(2) ns. Upon lowering the temperature, the luminescence intensity strongly increases. Simultaneously, the band around 450 nm in the excitation spectrum decreases. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Creation of tunable absolute bandgaps in a two-dimensional anisotropic photonic crystal modulated by a nematic liquid crystal

    International Nuclear Information System (INIS)

    Liu Chenyang

    2008-01-01

    Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the tunable absolute bandgap in a two-dimensional anisotropic photonic crystal structures modulated by a nematic liquid crystal. The PC structure composed of an anisotropic-dielectric cylinder in the liquid crystal medium is studied by solving Maxwell's equations using the plane wave expansion method. The photonic band structures are found to exhibit absolute bandgaps for the square and triangular lattices. Numerical simulations show that the absolute bandgaps can be continuously tuned in the square and triangular lattices consisting of anisotropic-dielectric cylinders by infiltrating nematic liquid crystals. Such a mechanism of bandgap adjustment should open up a new application for designing components in photonic integrated circuits

  18. Thermal conductivity of Glycerol's liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures.

    Science.gov (United States)

    Andersson, Ove; Johari, G P

    2016-02-14

    To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κcrystal is 3.6-times the κliquid value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T(-0.95); (ii) the ratio κliquid (p)/κliquid (0.1 MPa) is 1.45 GPa(-1) at 280 K, which, unexpectedly, is about the same as κcrystal (p)/κcrystal (0.1 MPa) of 1.42 GPa(-1) at 298 K; (iii) κglass is relatively insensitive to T but sensitive to the applied p (1.38 GPa(-1) at 150 K); (iv) κglass-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κcrystal of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

  19. Thermal optical nonlinearity in photonic crystal fibers filled with nematic liquid crystals doped with gold nanoparticles

    Science.gov (United States)

    Lesiak, Piotr; Budaszewski, Daniel; Bednarska, Karolina; Wójcik, Michał; Sobotka, Piotr; Chychłowski, Miłosz; Woliński, Tomasz R.

    2017-05-01

    In this work we studied a newly reported class of nonlinear effects observed in 5CB liquid crystals doped with gold nanoparticles (GNPs). The size of the GNP was determined by direct TEM imaging and by X-ray scattering of the diluted NP solution. GNPs was coated by thiols with the ratio of mesogenic to n-alkyl thiols varying from 1:2 to 1:1. The research involved comparing properties of both undoped and doped 5CB (nematic LC) by infiltrating LC cell and microholes of the photonic crystal fiber (PCF) separately. In our experiment the PCF fiber type LMA-10 made by NKT Photonics as host material has been used.

  20. Switchable Photonic Crystals Using One-Dimensional Confined Liquid Crystals for Photonic Device Application.

    Science.gov (United States)

    Ryu, Seong Ho; Gim, Min-Jun; Lee, Wonsuk; Choi, Suk-Won; Yoon, Dong Ki

    2017-01-25

    Photonic crystals (PCs) have recently attracted considerable attention, with much effort devoted to photonic bandgap (PBG) control for varying the reflected color. Here, fabrication of a modulated one-dimensional (1D) anodic aluminum oxide (AAO) PC with a periodic porous structure is reported. The PBG of the fabricated PC can be reversibly changed by switching the ultraviolet (UV) light on/off. The AAO nanopores contain a mixture of photoresponsive liquid crystals (LCs) with irradiation-activated cis/trans photoisomerizable azobenzene. The resultant mixture of LCs in the porous AAO film exhibits a reversible PBG, depending on the cis/trans configuration of azobenzene molecules. The PBG switching is reliable over many cycles, suggesting that the fabricated device can be used in optical and photonic applications such as light modulators, smart windows, and sensors.