ChemPhysChem

Cover image for Vol. 15 Issue 7

Special Issue: Liquid Crystals

May 19, 2014

Volume 15, Issue 7

Pages 1225–1518

  1. Cover Pictures

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
    1. You have free access to this content
      Cover Picture: Non-Uniform Helix Unwinding of Cholesteric Liquid Crystals in Cells with Interdigitated Electrodes (ChemPhysChem 7/2014) (page 1225)

      Dr. Mariacristina Rumi, Vincent P. Tondiglia, Dr. Lalgudi V. Natarajan, Dr. Timothy J. White and Dr. Timothy J. Bunning

      Version of Record online: 9 MAY 2014 | DOI: 10.1002/cphc.201490030

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      The cover image shows optical polarizing micrographs of a cholesteric liquid crystal in a cell with interdigitated electrodes for various applied voltages (increasing from top to bottom). On p. 1311 T. J. Bunning et al. report that in cells with narrow gaps between the electrodes, the pitch elongation is not uniform through the thickness of the cell, as a result of electric field gradients. This leads to different voltage-induced color changes in the selective reflection band depending on the side of illumination of the cell, as illustrated by the reflection mode micrographs on the left and right side of the cover image.

    2. You have free access to this content
      Inside Cover: 1,2,4-Oxadiazole-Based Bent-Core Liquid Crystals with Cybotactic Nematic Phases (ChemPhysChem 7/2014) (page 1226)

      Dr. Govindaswamy Shanker, Dr. Marko Prehm, Dr. Mamatha Nagaraj, Prof. Dr. Jagdish K. Vij, Marvin Weyland, Dr. Alexey Eremin and Prof. Dr. Carsten Tschierske

      Version of Record online: 9 MAY 2014 | DOI: 10.1002/cphc.201490031

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      The picture shows optical texture, XRD pattern and current response curve under a triangular wave field as typically observed for the cybotactic nematic phases formed by the liquid crystalline 3,5-diphenyl-1,2,4-oxadiazoles reported by C. Tschierske et al. on p. 1323.

  2. Graphical Abstract

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
  3. News

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
  4. Essay

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
    1. Liquid-Crystal Science from 1888 to 1922: Building a Revolution (pages 1245–1250)

      Dr. Michel Mitov

      Version of Record online: 31 JAN 2014 | DOI: 10.1002/cphc.201301064

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      Amazement, doubt, controversy, struggle, and finally acceptance were the successive steps of liquid-crystals' history from 1888 to 1907. The recognition of the liquid-crystalline states of matter by the scientific community required more than two decades. This Essay looks back to the early years of liquid-crystal research, at the junction between the nineteenth and twentieth centuries.

  5. Minireviews

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
    1. You have full text access to this OnlineOpen article
      The Nematic Phases of Bent-Core Liquid Crystals (pages 1251–1260)

      Prof. Helen F. Gleeson, Dr. Sarabjot Kaur, Dr. Verena Görtz, Dr. Abdel Belaissaoui, Dr. Stephen Cowling and John W. Goodby

      Version of Record online: 2 APR 2014 | DOI: 10.1002/cphc.201400014

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      Bent on stability: The nematic liquid-crystal phases formed by bent-core molecules have remarkable properties. This Minireview reports recent progress in stabilizing the nematic phase at accessible temperatures, concentrating on oxadiazole-based materials. It also describes recent measurements of their physical properties, including optical, dielectric, elastic, and flexoelectric coefficients, and electric field effects (see graphic).

    2. Optical Imaging of Liquid Crystals at the Nanoscale (pages 1261–1269)

      Prof. Charles Rosenblatt

      Version of Record online: 13 FEB 2014 | DOI: 10.1002/cphc.201300978

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      Coming closer: Near-field scanning optical microscopy (NSOM) is exploited to provide three-dimensional structure and dynamic information about liquid crystals at scales as small as a few nanometers. (Image courtesy of Prof. Antonio De Luca.)

    3. Lamellar Lα Mesophases Doped with Inorganic Nanoparticles (pages 1270–1282)

      Dr. Doru Constantin and Dr. Patrick Davidson

      Version of Record online: 24 FEB 2014 | DOI: 10.1002/cphc.201301187

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      Soft but ordered hybrids: Inserting inorganic nanoparticles into soft lyotropic mesophases yields systems with new functional properties. Achieving macroscopic-scale orientation is essential for complete characterization of these new materials, whether by structural, dynamic or spectroscopic techniques.

    4. Metal Nanoparticles with Liquid-Crystalline Ligands: Controlling Nanoparticle Superlattice Structure and Properties (pages 1283–1295)

      Dr. Wiktor Lewandowski, Dr. Michał Wójcik and Prof. Ewa Górecka

      Version of Record online: 30 APR 2014 | DOI: 10.1002/cphc.201301194

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      Melting gold with a liquid crystal: Liquid crystals are ideal ligands for self-assembling nanoparticles. They induce formation of various phases (see picture) made of spherical as well as rod-like nanoparticles. Importantly, the discussed approach gives access to functional assemblies that exhibit plasmonic anisotropy and dynamic tunability of structure, evidencing great potential for technological advance in materials science.

  6. Concept

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
    1. Systems with Competing Interlayer Interactions and Modulations in One Direction: Finding their Structures (pages 1297–1309)

      Prof. Dr. Mojca Čepič

      Version of Record online: 29 APR 2014 | DOI: 10.1002/cphc.201301101

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      One, two, three: Complex structures in polar smectics with commensurate or incommensurate modulations to layer thickness (see picture, commensurate periods are marked yellow) can be studied within the framework of a discrete phenomenological model. Three methods are presented and their appropriateness, advantages and disadvantages are discussed. Examples are given as an illustration for each method.

  7. Articles

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Essay
    6. Minireviews
    7. Concept
    8. Articles
    1. Non-Uniform Helix Unwinding of Cholesteric Liquid Crystals in Cells with Interdigitated Electrodes (pages 1311–1322)

      Dr. Mariacristina Rumi, Vincent P. Tondiglia, Dr. Lalgudi V. Natarajan, Dr. Timothy J. White and Dr. Timothy J. Bunning

      Version of Record online: 2 JAN 2014 | DOI: 10.1002/cphc.201300995

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      Asymmetrical mirrors: Cholesteric liquid crystals in cells with interdigitated electrodes can yield different reflection spectra from the two sides of the cell (see picture) for certain values of the voltage applied between the electrodes, due to non-uniform unwinding of the helical structure.

    2. 1,2,4-Oxadiazole-Based Bent-Core Liquid Crystals with Cybotactic Nematic Phases (pages 1323–1335)

      Dr. Govindaswamy Shanker, Dr. Marko Prehm, Dr. Mamatha Nagaraj, Prof. Dr. Jagdish K. Vij, Marvin Weyland, Dr. Alexey Eremin and Prof. Dr. Carsten Tschierske

      Version of Record online: 3 MAR 2014 | DOI: 10.1002/cphc.201301070

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      Between order and disorder: Variation of the molecular structure of bent 1,2,4-oxadiazoles (see picture) leads to insights into the molecular organization in their special nematic phases. These nematic phases have cybotactic cluster structures with strongly tilted aromatic cores and local polar and biaxial order. This gives rise to dielectric reorientation of the polar domains under an applied electric field and local periodic order on a 2D lattice in a magnetic field.

    3. From the Molecular Structure to Spectroscopic and Material Properties: Computational Investigation of a Bent-Core Nematic Liquid Crystal (pages 1336–1344)

      Cristina Greco, Dr. Alberto Marini, Elisa Frezza and Prof. Alberta Ferrarini

      Version of Record online: 27 JAN 2014 | DOI: 10.1002/cphc.201301030

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      Properly bent! An integrated methodology is developed, which enables to consistently analyze the molecular and material behavior of nematic liquid crystals. The methodology is applied to A131, a representative bent-core mesogen, for which the 13C NMR chemical shifts and the elastic constants of the nematic phase are simultaneously predicted. It is shown how the different properties are affected by the bent molecular shape.

    4. Quinquephenyl: The Simplest Rigid-Rod-Like Nematic Liquid Crystal, or is it? An Atomistic Simulation (pages 1345–1355)

      Dr. Yoann Olivier, Dr. Luca Muccioli and Prof. Claudio Zannoni

      Version of Record online: 15 APR 2014 | DOI: 10.1002/cphc.201301126

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      Not so rigid or straight after all! The nematic–isotropic and the other transition temperatures of p-quinquephenyl are determined by using atomistic molecular-dynamics simulations. The rigidity of p-quinquephenyl, often taken for granted, is assessed, and an aspect ratio that changes with temperature is found. The distribution is relatively broad due to internal torsion and bending.

    5. Order and Conformation of Biphenyl in Cyanobiphenyl Liquid Crystals: A Combined Atomistic Molecular Dynamics and 1H NMR Study (pages 1356–1367)

      Dr. Antonio Pizzirusso, Dr. Maria Enrica Di Pietro, Prof. Giuseppina De Luca, Prof. Giorgio Celebre, Prof. Marcello Longeri, Dr. Luca Muccioli and Prof. Claudio Zannoni

      Version of Record online: 1 APR 2014 | DOI: 10.1002/cphc.201400082

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      A happy marriage: Combination of 1H nuclear magnetic resonance experiments and molecular dynamics atomistic simulations validates the computational model and extends the range of information that can be gained on flexible solutes in liquid crystals.

    6. Sign Inversion of the Spontaneous Polarization in a “de Vries”-Type Ferroelectric Liquid Crystal (pages 1368–1375)

      Dorothee Nonnenmacher, Prof. Dr. Robert P. Lemieux, Prof. Dr. Mikhail A. Osipov and Prof. Dr. Frank Giesselmann

      Version of Record online: 25 MAR 2014 | DOI: 10.1002/cphc.201301154

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      The peculiar polarization-tilt coupling in a ferroelectric liquid crystal, where the director tilt appears stepwise in a first-order phase transition while the spontaneous electric polarization grows continuously but super-linearly, is now explained by the coincidence of the ferroelectric phase transition and a polarization-sign inversion point.

    7. Orthogonal Orientation of Chromonic Liquid Crystals by Rubbed Polyamide Films (pages 1376–1380)

      Aya Mcguire, Dr. Youngwoo Yi and Prof. Dr. Noel A. Clark

      Version of Record online: 27 JAN 2014 | DOI: 10.1002/cphc.201301040

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      Molecular tonguegroove alignment: Stacks of sunset yellow molecules in water are aligned with their axes, n, perpendicular to the rubbing direction of polyamide (PA) films in contact with them (see picture). This is due to interaction between molecular grooves of the stacks formed by head-to-tail stacking and stretched polymer chains. This molecular tongue–groove interaction model is interesting for the control of interfacial self-assembly of the molecular aggregates.

    8. Synthesis of Liquid Crystal Silane-Functionalized Gold Nanoparticles and Their Effects on the Optical and Electro-Optic Properties of a Structurally Related Nematic Liquid Crystal (pages 1381–1394)

      Javad Mirzaei, Dr. Martin Urbanski, Prof. Heinz-S. Kitzerow and Prof. Torsten Hegmann

      Version of Record online: 24 FEB 2014 | DOI: 10.1002/cphc.201301052

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      Stable silane shell to the rescue: Thermally and chemically robust gold nanoparticles (NPs) capped with mesogenic groups through silane conjugation show very distinct optical and electro-optic effects in a nematic liquid crystal. Surprisingly, capping a NP with a mesogen that is structurally dissimilar to that of the host has the most drastic effect on the electro-optic properties of the host.

    9. Nanoparticle Doping in Nematic Liquid Crystals: Distinction between Surface and Bulk Effects by Numerical Simulations (pages 1395–1404)

      Dr. Martin Urbanski, Javad Mirzaei, Prof. Dr. Torsten Hegmann and Prof. Dr. Heinz-S. Kitzerow

      Version of Record online: 31 JAN 2014 | DOI: 10.1002/cphc.201301054

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      NPs at the edge: Functionalized nanoparticles can have a great impact on the electro-optic response of a nematic host, both when dispersed in the bulk and when residing at the LC/substrate interface. Dispersions featuring a combination of both possible effects are studied and a method for distinguishing bulk and surface effects is presented. Experimental data is confirmed by numerical simulations.

    10. Stress-Sensor Device Based on Flexoelectric Liquid Crystalline Membranes (pages 1405–1412)

      Dr. Alejandro D. Rey, Dr. Phillip Servio and Dr. Edtson Emilio Herrera Valencia

      Version of Record online: 2 OCT 2013 | DOI: 10.1002/cphc.201300600

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      Stressed out: Membrane flexoelectricity is an electromechanical coupling process that describes membrane bending under electric fields and membrane electrical polarization through bending. A stress-sensor device for mechanically loaded solids, consisting of a soft flexoelectric thin membrane attached to the loaded deformed solid, is proposed, formulated, and characterized. The device model, based on the integration of the thermodynamics of polarizable membranes with isotropic solid elasticity, can identify the elastic, electromechanical, and geometrical parameters involved in electrical signal generation.

    11. Tuning Quantum-Dot Organization in Liquid Crystals for Robust Photonic Applications (pages 1413–1421)

      Andrea L. Rodarte, Zachary S. Nuno, Blessing H. Cao, Ronald J. Pandolfi, Makiko T. Quint, Prof. Sayantani Ghosh, Prof. Jason E. Hein and Prof. Linda S. Hirst

      Version of Record online: 12 FEB 2014 | DOI: 10.1002/cphc.201301007

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      Dots with liquid-crystalline ligands are synthesized and dispersed in the nematic and cholesteric phases at different concentrations. Fluorescence microscopy, scanning confocal photoluminescence microscopy, and X-ray diffraction reveal details of the quantum-dot (QD) cluster packing. Spectroscopic measurements demonstrate the applicability of the QDs for photonic applications.

    12. Thermodynamics and 2H NMR Study on the Insertion of Small Quinones into a Discotic Nematic Lyotropic Liquid Crystal (pages 1422–1431)

      Dr. Víctor Eduardo Bahamonde-Padilla, Prof. José Javier López-Cascales, Prof. Ramiro Araya-Maturana, Dr. Maximiliano Martínez-Cifuentes and Prof. Boris Enrique Weiss López

      Version of Record online: 8 APR 2014 | DOI: 10.1002/cphc.201301146

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      The thermodynamics associated with the insertion of two antioxidant-active quinone molecules embedded into a discotic nematic lyotropic liquid crystal, employed as a simple model of cell membrane, are studied with a combined approach entailing 2H NMR experiments and molecular dynamics. Key parameters related to the enthalpy, entropy, and free energy of the insertion process are investigated. An estimation of the liquid crystal microviscosity is also provided.

    13. Elongation of Discotic Liquid Crystal Strands and Lubricant Effects (pages 1432–1446)

      Dr. Surjya Sarathi Bhattacharyya and Prof. Yves Galerne

      Version of Record online: 2 DEC 2013 | DOI: 10.1002/cphc.201300687

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      Strandard or nematic-like behavior? By pulling a strand in the disordered columnar phase, unexpected mechanical behaviors at the macroscopic scale are revealed, which essentially depend on the effective length of the columns of molecules compared to the strand length. The differentiation between the standard (a) and the nematic-like behavior (b) is made.

    14. Low-Temperature Properties of Polymer-Stabilised Liquid-Crystal Blue Phases (pages 1447–1451)

      Gihwan Lim, Prof. Yasushi Okumura, Prof. Hiroki Higuchi and Prof. Hirotsugu Kikuchi

      Version of Record online: 7 APR 2014 | DOI: 10.1002/cphc.201301142

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      Hierarchical dynamics of polymer-stabilised blue phases are studied by means of dielectric relaxation time and electrooptical response, which showed different temperature dependences obeying the Vogel–Fulcher and Arrhenius equations (the picture shows the Arrhenius relations). The polymer concentration affects the electrooptical effect but not the rotation of the LC molecules in PSBPs.

    15. Discontinuous Thermal Diffusivity Change due to the Anchoring Transition of a Liquid Crystal on a Perfluoropolymer Surface (pages 1452–1456)

      Michiru Uehara, Satoshi Aya, Dr. Fumito Araoka, Prof. Ken Ishikawa, Prof. Hideo Takezoe and Prof. Junko Morikawa

      Version of Record online: 13 FEB 2014 | DOI: 10.1002/cphc.201300975

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      The thermal diffusivity of a liquid crystal on a polymer surface is measured using a temperature wave method. Abrupt changes in thermal diffusivity are observed in the nematic phase due to the discontinuous anchoring transition between the planar and homeotropic states. Not only is this transition detected, the anisotropy of the thermal diffusivity in the liquid crystal is measured as well.

    16. Nanostructures of Nematic Materials of Laterally Branched Molecules (pages 1457–1462)

      Randall Breckon, Saonti Chakraborty, Cuiyu Zhang, Nicholas Diorio, Prof. James T. Gleeson, Prof. Samuel Sprunt, Prof. Robert J. Twieg and Prof. Antal Jákli

      Version of Record online: 22 AUG 2013 | DOI: 10.1002/cphc.201300578

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      Branching out: The synthesis and small angle X-ray scattering (SAXS) characterization of twenty laterally branched mesogenic molecules, with a varying degree of flexibility in their lateral branch, is reported. The SAXS studies reveal the presence of short-range ordered smectic-like nanostructures in the nematic phase with varied tilt angles and characteristic correlation lengths These branched compounds are classified into four different categories (see picture).

    17. Anomalous Behavior in the Crossover between the Negative and Positive Biaxial Nematic Mesophases in a Lyotropic Liquid Crystal (pages 1463–1469)

      Prof. Dr. Erol Akpinar, Dennys Reis and Prof. Dr. Antonio M. Figueiredo Neto

      Version of Record online: 1 APR 2014 | DOI: 10.1002/cphc.201301003

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      Disorientation: In the crossover between negative equation image and positive biaxial nematic equation image phases, a liquid crystal in the magnetic field does not keep its orientation. Conoscopic patterns in different phases (see picture) show that the fringes lose their symmetrical appearance during crossover and regain their characteristic shapes in the uniaxial calamitic phase (NC).

    18. Effect of Alignment on a Liquid Crystal/Split-Ring Resonator Metasurface (pages 1470–1476)

      Bernhard Atorf, Holger Mühlenbernd, Dr. Mulda Muldarisnur, Prof. Dr. Thomas Zentgraf and Prof. Dr. Heinz Kitzerow

      Version of Record online: 31 JAN 2014 | DOI: 10.1002/cphc.201301069

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      The way it′s bedded: A metasurface comprising a two-dimensional array of split-ring resonators with resonance frequencies in the near-infrared region is fabricated and embedded in a uniformly aligned liquid crystal. Tunable resonance frequencies are observed. Direction and size of their spectral shifts depend on the excited mode, the initial liquid crystal alignment, the temperature, and the applied voltage.

    19. Macroscopic Control of Helix Orientation in Films Dried from Cholesteric Liquid-Crystalline Cellulose Nanocrystal Suspensions (pages 1477–1484)

      Ji Hyun Park, JungHyun Noh, Christina Schütz, German Salazar-Alvarez, Prof. Giusy Scalia, Prof. Lennart Bergström and Prof. Jan P. F. Lagerwall

      Version of Record online: 26 MAR 2014 | DOI: 10.1002/cphc.201400062

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      Film star: A new method for drying cholesteric liquid-crystalline cellulose nanocrystal suspensions into solid films avoids phase coexistence and, with an applied circular shear flow, yields unprecedented structural control. The commonly observed mosaic-like structure, with randomly varying orientation of the cholesteric helix axis, is replaced by a macroscopically uniform film with improved optical properties (see figure).

    20. Conformational Properties and Orientational Order of a de Vries Liquid Crystal Investigated through NMR Spectroscopy (pages 1485–1495)

      Dr. Valentina Domenici, Dr. Moreno Lelli, Dr. Mario Cifelli, Dr. Vera Hamplova, Dr. Alessandro Marchetti and Prof. Carlo Alberto Veracini

      Version of Record online: 31 JAN 2014 | DOI: 10.1002/cphc.201301036

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      Insight in models: A combination of solid-state NMR techniques applied to the SmA and SmC* phases of a de Vries liquid crystal show that a conformational change occurs at the mesophase transition, contributing to the debate about the models describing de Vries smectogens.

    21. Molecular Theory of Phase Separation in Nematic Liquid Crystals Doped with Spherical Nanoparticles (pages 1496–1501)

      Prof. Mikhail A. Osipov and Dr. Maxim V. Gorkunov

      Version of Record online: 3 MAR 2014 | DOI: 10.1002/cphc.201301048

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      Transit: A molecular-statistical theory is developed which enables one to describe the nematic-isotropic phase transition in liquid crystals doped with spherical nanoparticles taking into account the effects of phase separation.

    22. Chiral Isotropic Sponge Phase of Hexatic Smectic Layers of Achiral Molecules (pages 1502–1507)

      Dr. Dong Chen, Dr. Yongqiang Shen, Jose Aguero, Dr. Eva Korblova, Prof. David M. Walba, Dr. Nadia Kapernaum, Prof. Frank Giesselmann, Prof. Junji Watanabe, Prof. Joseph E. Maclennan, Prof. Matthew A. Glaser and Prof. Noel A. Clark

      Version of Record online: 20 DEC 2013 | DOI: 10.1002/cphc.201300912

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      Phased out: A low-temperature dark conglomerate phase is reported in the bent-core liquid crystal W624. In the neat material, the disordered focal conics strongly resemble a disordered sponge phase (left). In mixtures with a calamitic liquid crystal, the intralayer molecular order of this phase is enhanced, leading to a more ordered, bicontinuous structure (middle), similar to the cubic phase observed in lyotropic systems (right).

    23. Freely Floating Smectic Films (pages 1508–1518)

      Kathrin May, Kirsten Harth, Torsten Trittel and Prof. Dr. Ralf Stannarius

      Version of Record online: 1 APR 2014 | DOI: 10.1002/cphc.201301183

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      Bursting the bubble: The shape dynamics and rupture scenarios of freely floating smectic bubbles were studied using microgravity experiments. The images show snapshots of the rupture of a smectic A bubble, recorded with a high-speed camera.

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