Radisson Resort Orlando-Celebration Conference ...

EMN MEETING ON LIQUID CRYSTAL

PROGRAM&ABSTRACT

Radisson Resort Orlando-Celebration Conference Venue

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PROGRAM&ABSTRACT

CONTENTS General Information ....................................................................................1 Registration Desk Hours .............................................................................1 Committees .................................................................................................1 Program-at-a-Glance ...................................................................................4 Meeting Program ........................................................................................6 Abstract Session ........................................................................................12 Author Index .............................................................................................65

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PROGRAM&ABSTRACT

General Information The EMN Meeting on Liquid Crystal 2016 will take place at Radisson Resort OrlandoCelebration, Orlando, USA. The conference will be held from Feb 16 to Feb 19, 2016. Workshops on selected focus topics in energy, materials and nanotechnology will include invited and contributed oral presentations from Tuesday to Thursday, and the poster session will be presented on the afternoon of Wednesday.

Registration Desk Hours The EMN Meeting on Liquid Crystal registration desk, located in front of meeting rooms of the Radisson Resort Orlando-Celebration, will be open during the following hours: Monday, Feb 15..................................................................................14:00pm -18:00pm Tuesday, Feb 16....................................................................................8:00am -18:00pm Wednesday, Feb 17...............................................................................8:00am -18:00pm Thursday, Feb 18..................................................................................8:00am -18:00pm

Committees International Advisory Committee Agnes Buka, Hungarian Academy of Sciences,Hungary Antonio d’Alessandro, Universita di Roma, Italy Andrzej Miniewicz, Wroclaw University of Technology Andy Y.-G. Fuh, National Cheng Kung University, Taiwan Corrie Imrie, University of Aberdeen,UK D.J. Broer, Eindhoven University of Technology, Netherlands Demetri J. Photinos, University of Patras,Greece 1


PROGRAM&ABSTRACT

Francesco Simoni, UniversitàPolitecnica delle Marche, Italy Giancarlo Galli, Universitàdi Pisa, Italy Helen Gleeson, University of Leeds, UK Harald Pleiner, Max Planck Institute for Polymer Research, Germany Igor Musevic, University of Ljubljana, Slovenia Ian Underwood, University of Edinburgh, UK Kristiaan Neyts，Ghent University,Belgium Liang-Chy Chien, Kent State University, USA Lachezar Komitov, University of Gothenburg, Sweden Lam Lui, San Jose State University, USA Mary O’Neill, University of Hull,UK Mikhail Osipov, University of Strathclyde,UK M P Allen, University of Warwick,UK Paolo Pasini, INFN Sezione di Bologna, Italy Randall Kamien, University of Pennsylvania, USA Robert P. Lemieux, University of Waterloo, Canada Satyendra Kumar, Kent State Univeristy, USA Shunsuke Kobayashi, Tokyo University of Science, Japan Sin-Doo Lee, Seoul National University, Korea Slobodan Zumer, University of Ljubljana, Slovenia Tomiki Ikeda, Chuo University, Japan 2


PROGRAM&ABSTRACT

International Program Committee Antonio Figueiredo Neto, University of São Paulo, Brazil Bill Milne, University of Cambridge, UK Panos J. Photinos, Southern Oregon University, USA Ruben R. Garcia, INAOE, Mexico Sierra Travieso, Teresa, University of Zaragoza, Spain Shin-Tson Wu, University of Central Florida, USA Tim Sluckin, University of Southampton, UK Timothy White, Air Force Research Laboratory, USA Vladimir G. Chigrinov, HKUST, HongKong Yanlei Yu, Fudan University, China

International Organizing Committee Cesare Umeton, University of Calabria, Italy Ibrahim Abdulhalim, Ben Gurion University in Israel, Israel Samo Kralj, University of Maribor, Slovenia (Homepage) Tsung-Hsien Lin, National Sun Yat Sen University,Taiwan Romeo Beccherelli, CNR (National Research Council), Italy

Local Committee Jiyu Fang, University of Central Florida, USA

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PROGRAM&ABSTRACT

Chair Zhiming Wang, University of Electronic Science and Technology of China, China Jiming Bao, University of Houston, USA

Program-at-a-Glance

Tuesday Morning, Feb 16 Room A (Egret/Heron)

Welcome Speech

8:05-8:15 AM

Keynote

8:15-8:50 AM

Liquid Crystal/Nanoparticle System

Liquid Crystals in Electro-optics and Display Applications Ⅰ

8:50-10:05 AM

10:20-12:00 AM

Tuesday Afternoon, Feb 16 Room A (Eagle)

Biological and Bio-inspired Liquid Crystals

Theory, Simulations and Modeling of Liquid Crystals Ⅰ

14:00-15:15 PM

15:3017:35 PM

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PROGRAM&ABSTRACT

Wednesday Morning, Feb 17 Room A (Eagle)

Liquid Crystal Polymers, Elastomers and Gels

8:05-9:45 AM

Theory, Simulations and Modeling of Liquid Crystals Ⅱ

10:00-12:05 PM

Wednesday Afternoon, Feb 17 Room A (Eagle)

Design and synthesis of Liquid Crystal Materials

14:00-15:15 PM

Theory, Simulations and Modeling of Liquid Crystals Ⅲ

15:45-17:50 PM

Wednesday Afternoon, Feb 17 Room B (Flsmingo)

Liquid Crystalline Phases and Phase Behavior

14:00-15:15 PM

Other Applications of Liquid Crystals

15:45-17:00 PM

Thursday Morning, Feb 18 Room A (Eagle)

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PROGRAM&ABSTRACT

Properties of Liquid Crystals

Lyotropic, Colloidal and Chromonic Liquid Crystals

8:05-10:10 AM

10:25-11:40 AM

Thursday Afternoon, Feb 18 Room A (Eagle)

Liquid Crystals in Electro-optics and Display Applications Ⅱ

14:00-15:40 PM

Liquid Crystal Photonics

15:55-18:00 PM

Meeting Program

7:00-8:05 AM

8:05-8:15 AM

Tuesday Feb. 16 Room A (Egret/Heron) Breakfast Opening Ceremony A01: Welcome Speech

General Chair, Zhiming Wang University of Electronic Science and Technology of China, China

Keynote Speaker A02: How the International Liquid Crystal Lui Lam 8:15-8:50 AM Society Was Founded San Jose State University, USA Session: Liquid Crystal/Nanoparticle System Chair: Lia Q. Amaral A03: Liquid crystal mixtures made of Regis Guegan 8:50-9:15 AM nanosheets and nonionic surfactants University of Orleans, France A04: The Helical Nanofilament phase for David M. Walba 9:15-9:40 AM organic electronics University of Colorado, USA Robert Repnik 9:40-10:05 AM A05: Controlled nanoparticle targeting University of Maribor, Slovenia 10:05-10:20 AM Session Break Session: Liquid Crystals in Electro-optics and Display Applications Ⅰ 6


10:20-10:45 AM

10:45-11:10 AM

11:10-11:35 AM

11:35-12: 00 AM 12:00-14:00 PM

14:00-14:25 PM

14:25-14:50 PM

14:50-15:15 PM 15:15-15:30 PM

15:30-15:55 PM 15:55-16:20 PM 16:20-16:45 PM

16:45-17:10 PM

17: 10-17:35 PM 18:00 PM

PROGRAM&ABSTRACT

Chair: Raisa Talroze A06: Graphene oxide liquid crystals for reflective displays without polarizing optics A07: How can an LCD power be saved while a fast-response LC is well-developed

Jiming Bao University of Houston, USA Fang-Cheng Lin National Chiao Tung University, Taiwan

A08: Investigation of the relationships between Hiroki Iwanaga molecular structures and properties of Corporate Research & Development anthraquinone dichroic dyes with phenylthio Center Toshiba Corporation, Japan groups and their application to GH-LCD A09: Smart Switching of Nematic LC over a 2D Malik Qasim Material Surface University of Cambridge, UK Lunch Break Tuesday Feb. 16 Room A (Eagle) Session: Biological and Bio-inspired Liquid Crystals Chair: David M. Walba A10: Liquid crystal droplets for biosensor Jiyu Fang applications University of Central Florida, USA A11: Phase transitions in nematic lyotropic Lia Q. Amaral systems and in biomembranes: the role of order / University of São Paulo, Brazil disorder of hydrocarbon chains A12: Liquid crystals used as diffraction grating Miguel Mora-Gonzalez and their applications to optical metrology Universidad de Guadalajara, Mexico Session Break Session: Theory, Simulations and Modeling of Liquid Crystals Ⅰ Chair: Vasily Oganesyan Harald Pleiner A13: Active Liquid Crystal Hydrodynamics Max Planck Institute, Germany A14: What is the ability of all-atom simulation Armand Soldera to depict accurately the Sm C phase? University of Sherbrooke, Canada A15: An Analysis of Chevrons in Thin Liquid Lei Z. Cheng Crystal Cells Olivet Nazarene University, USA A16: Molecular dynamics simulation methods Keiko. M. Aoki for anisotropic systems --from liquid crystals, Institute of Computational Fluid surfaces and beyond Dynamics, Japan A17: Topological defects dynamics in Kuang-Wu Lee microfluidic channel: A numerical study by Max Planck Institute, Germany multi-particle collision simulation Dinner Social 7


7:00-8:05

8:05-8:30 AM

8:30-8:55 AM

8:55-9:20 AM

9:20-9:45 AM 9:45-10:00 AM

10:00-10:25 AM

10:25-10:50 AM

10:50-11:15 AM

11:15-11:40 AM

11:40-12:05 PM 12:05-14:00 PM

14:00-14:25 PM 14:25-14:50 PM

PROGRAM&ABSTRACT

Wednesday Feb. 17 Room A (Eagle) Breakfast Session: Liquid Crystal Polymers, Elastomers and Gels Chair: Robert Lindquist A18: Challenges and Opportunities in PhotoWilliam S. Oates responsive Liquid Crystal Polymer Networks for Florida State University, USA Adaptive Structure Applications Raisa Talroze A19: Optical effects in nanocomposites of liquid Topchiev Institute of Petrochemical crystal polymers with nanoparticles Synthesis Russian Academy of Sciences, Russia A20: Thermally Conductive Liquid Crystal Shusuke Yoshihar Polyesters and Composites Kaneka Corporation, Japan Yuehang Xu A21: Microwave flexible devices with ultra thin University of Electronic Science and Liquid Crystal Polymers (LCP) Technology of China, China Session Break Session: Theory, Simulations and Modeling of Liquid Crystals Ⅱ Chair: Sachiko T. Nakagawa A22: Non-equilibrium behaviors of nematic Takeaki Araki liquid crystal confined in porous media Kyoto University, Japan A23: Application of MD simulations and EPR Vasily Oganesyan spectroscopy to liquid crystals: A combined University of East Anglia, UK approach A24: Cubic phases of lyotropic liquid crystals: Wojciech Gozdz monocrystals, thin films, cubosomes Polish Academy of Science, Warsaw Sylvan Brechet A25: Thermodynamics of a continuous medium Ecole Polytechnique Federale de with electric dipoles Lausanne, Switzerland A26: Molecular Simulation of Confined LiquidAziz Ghoufi Crystals and Clustomesogens UniversitéRennes 1, France Lunch Break Wednesday Feb. 17 Room A (Eagle) Session: Design and synthesis of Liquid Crystal Materials Chair: Miguel Mora-Gonzalez A27: Columnar and Smectic Self-Organization S. Holger Eichhorn of Unconventionally Shaped Mesogens University of Windsor, Canada A28 Pyrazinacenes, porphyrins and Jonathan P. Hill nanoparticles: liquid crystals and self-assemblies 8


PROGRAM&ABSTRACT National Institute for Materials Science (NIMS),Japan

14:50-15:15 PM 15:15-15:45 PM

15:45-16:10 PM

16:10-16:35 PM 16:35-17:00 PM 17:00-17:25 PM 17:25-17:50 PM 18: 00 PM

14:00-14:25 PM

14:25-14:50 PM

14:50-15:15 PM 15:15-15:45 PM

15:45-16:10 PM

16:10-16:35 PM

A29: Design, assembly, and emergent properties Joseph Reczek of columnar mixed-stack aromatic donorDenison University, USA acceptor liquid crystals Poster & Session Break Session: Theory, Simulations and Modeling of Liquid Crystals Ⅲ Chair: Armand Soldera Rolfe.G. Petschek A30: Hard Tetrahedra, Spatially Varying Liquid Case Western Reserve University, Crystal Order and Quasicrystals USA Sachiko T. Nakagawa A31: The phase transition during post annealing Okayama University of Science, Japan A32: Topological defect-antidefect depinning Luka Mesarec threshold for nematic shells Laboratory of Biophysics, Slovenia Piotr Surowka A33: From field theory to chiral fluids and back Harvard University, USA Rene D. M. Topf A34: Modes of Liquid Crystal Lasers Imperial College London, UK Dinner Social Wednesday Feb. 17 Room B (Flamingo) Session: Liquid Crystalline Phases and Phase Behavior Chair: Michael Debije Thomas G. Mason B01: Shape-Designed Triatic and Hexatic Liquid University of California Los Angeles, Crystals USA B02: Structure-propoerty relationships in twistCorrie Imrie bend nematogens University of Aberdeen,UK Francesco Vita B03: Insights into the nematic order of allUniversita Politecnica delle Marche, aromatic mesogens Italy Poster & Session Break Session: Other Applications of Liquid Crystals Chair: Seiji Fukushima B04: Roles of wide-band thermochromic liquid Koonlaya Kanokjaruvijit crystals in heat transfer measurement of jet Naresuan University, Thailand impingement coupled with a dimpled surface B05: Magneto-optical properties of LC Thierry Verbiest molecules and their magnetic sensing University of Leuven, Belgium applications 9

EMN MEETING ON LIQUID CRYSTAL 16:35-17:00 PM

B06: LC based non-display applications

PROGRAM&ABSTRACT Michael Wittek

18:00 AM

Social dinner Thursday Feb. 18 Room A (Eagle) 7:00-8:05 AM Breakfast Session: Properties of Liquid Crystals Chair: Corrie Imrie A35: Heat-driven rotation in isotropicJun Yoshioka 8:05-8:30 AM cholesteric coexistence system Waseda University, Japan A36: High Performance p-type Organic David Jones 8:30-8:55 AM Electronic Semiconductors for OPV with a High University of Melbourne, Australia Temperature Nematic Liquid Crystalline Phase A37: Surface and photophysical studies on C. Karthik 8:55-9:20 AM tricycloquinazoline based discotic liquid crystal Birla Institute of Technology and and its application as molecular probe Science, India A38: Photoinduced reorientation of methyl red David Statman 9:20-9:45 AM doped nematics: What we have learned Allegheny College, USA A39: Resonant soft X-ray scattering study of Chenhui Zhu 9:45-10:10 AM helical structures in liquid crystals - helical Lawrence Berkeley National nanofilament B4 and twist bend nematic phase Laboratory, USA 10:10-10:25 AM Session Break Session: Lyotropic, Colloidal and Chromonic Liquid Crystals Chair: Jonathan P. Hill A40: Unique behavior of lyotropic liquid Masanobu Sagisaka 10:25-10:50 AM crystals with anionic hybrid surfactants having Hirosaki University, Japan oxyethylated alkyl tail A41: Structure and transport of self-assembled Yuji Sasaki 10:50-11:15 AM colloidal particles in electro-hydrodynamic Hokkaido University, Japan convection of nematic liquid crystals A42: Self-organized structures of star-like Kun Zhao 11:15-11:40 AM concave colloids in 2D Tianjin University, China 12:00-14:00 AM Lunch Break Thursday Feb. 18 Room A (Eagle) Session: Liquid Crystals in Electro-optics and Display Applications Ⅱ Chair: Thierry Verbiest A43: Stratified Liquid Crystal Structures to Robert Lindquist 14:00-14:25 PM Enable Practical Electro-Optic Devices in University of Alabama in Huntsville, Terahertz Regime USA

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EMN MEETING ON LIQUID CRYSTAL 14:25-14:50 PM 14:50-15:15 PM

15:15-15:40 PM 15:40-15:55 PM

15:55-16:20 PM

16:20-16:45 PM

16:45-17:10 PM 17:10-17:35 PM

17:35-18:00 PM 18: 0 0 PM

PROGRAM&ABSTRACT

A44: Light scattering device using dye-doped Seiji Fukushima (polymer/liquid crystal) composite film Kagoshima University, Japan A45: Polymer-enhanced electro-optics in various Alexander Lorenz types of LCs Paderborn University, Germany A46: Study on the electro-optical properties of Mujtaba Ellahi PDLC films (Smart glass) using University Of Karachi, Pakistan Diethylenetriamine (DETA) hardener Session Break Session: Liquid Crystal Photonics Chair: David Jones A47: Electrically controllable multicolor Maria Penelope De Santo cholesteric laser University of Calabria, Italy Michael Debije A48: Controlling light in the built environment Eindhoven University of Technology, using liquid crystals Netherlands A49: Polar POLICRYPS Photonic Structures: Roberto Caputo Features and Possibilities Universita Della Calabria, Italy A50: Cholesteric liquid-crystal Bragg onion Matjaz Humar lasers Jozef Stefan Institute, Slovenia Joanna Ptasinski A51: Liquid Crystals for Photonic Integrated Space and Naval Warfare Systems Circuit Applications Center Pacific, USA Dinner Social

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PROGRAM&ABSTRACT

Abstract Session A02: How the International Liquid Crystal Society Was Founded Lam, Lui San Jose State University, USA [email protected] The International Liquid Crystal Society (ILCS), with nearly 900 members in 43 countries/territories on six continents, was founded in 1990, at the University of British Columbia during the 13th International Liquid Crystal Conference. The founding

A03: Liquid crystal mixtures made of nanosheets and nonionic surfactants R. Guégan1, N. Miyamoto2 1 Institut des Sciences de la Terre d’Orléans, UMR 7327 CNRS-Université d’Orléans, Orléans 45071, France Email:[email protected] 2 Department of Life, Environment and Materials Science, Graduate School of Fukuoka Institute of Technology, Fukuoka 811-0295, Japan Two dimensional (2D) atomic crystals or nanosheets resulting from the exfoliation of inorganic layered materials constitute exciting nano materials with fascinating properties showing transparency, semi-

process lasted three years starting 1987 and is quite different from the usual case concerning other learned societies. It was prompted by an event at the solid state lab at Orsay. The ILCS’s founding was initiated and orchestrated by the author who is the only one who knows the whole story [see Lam’s Chapter 10 in All About Science, eds. M. Burguete and L. Lam (World Scientific, 2014)]. In this talk, a personal account of the why and how as well as the background and crucial events is given. It is aimed at those working in or interested in science, liquid crystals in particular, and at historians of science.

conductivity and a lamellar liquid crystal (LC) phase that can be easily aligned at a macroscopic scale with weak magnetic or electric fields.1 Stability and microstructure of these hybrid systems result from the interplay of the attractive and repulsive forces between the colloidal exfoliated nanosheets. A small variation in the intersheet molecular force balance caused by variations in nanosheet concentration, pH or ionic strength variation, may induce a reorganization in the system, for instance phase separation or aggregation via an exclusion mechanism.2 Thus, while keeping its LC properties, the mixing between niobate nanosheets and alkylpoly(ethylene oxide) nonionic surfactants (CnEm) that selforganize in a variety of distinct morphologies such as hexagonal, cubic, lamellar lyotropic liquid crystalline phases represents a certain

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PROGRAM&ABSTRACT

challenge. 3-4

introduction of the amphiphilic molecules does not lead to any aggregation of the inorganic nanosheets that still show LC phases. Nevertheless, nonionic surfactant systems constrains the characteristic repeat distance of the nanosheets lamellar phase, which singularly evolves following the density of surfactant whihc show a mono lamellar domain within the intersheets distance.5

Fig1. Experimental protocol for the preparation of the colloidal suspensions resulting of the mixing of K4Nb6O17 niobate nanosheets lamellar phase and various liquid crystalline phases (here L1 phase) made of C12E5 nonionic surfactants.he Old Main, University of Arkansas.

1. F. Geng, R. Ma, A. Nakamura, K. Akatsuka, Y. Ebina, Y. Yamauchi, N. Miyamoto, Y. Tateyama, T. Sasaki, Nat Commun, 4, 1632 (2013). 2. I. Grillo, P. Levitz, T. Zemb, Eur. Phys. J. E, 5, 377 (2001). 3. R. Guégan, Soft Matter, 9, 10913 (2013).

In this contribution, we show that combining K4Nb6O17 niobate nanosheets and several alkylpoly(ethylene oxide) nonionic surfactants (C10E5 and C12E5) leads to interesting novel nanostructures. The

4. R. Guégan, Langmuir, 26, 19175 (2010). 5. R. Guégan, K. Sueyoshi, S. Anraku, S. Yamamoto, N. Miyamoto, ChemComm DOI: 10.1039/C5CC08948D (2016).

A04: The Helical Nanofilament phase for organic electronics

Email: [email protected], web site: http://walba.colorado.edu

David M. Walba1, Noel A. Clark2, Chenhui Zhu3, Alexander Hexemer3, Dong Ki Yoon4, Hanim Kim4, Eva Korblova1, Dong Chen2, and Michael Tuchband2

2Department of Physics, 390 UCB, and the Soft Materials Research Center, Univeristy of Colorado, Boulder, Colorado, USA

1Department of Chemistry and Biochemistry, 215 UCB, and the Soft Materials Research Center, University of Colorado, Boulder, Colorado, USA

3Advanced Light Source, Lawrence Berkeley National Lab, 1 Cyclotron Road Mail Stop 15-R317, Berkeley, California, USA 4Graduate School of Nanoscience and

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EMN MEETING ON LIQUID CRYSTAL Technology and KINC, KAIST, Daejeon, 305701, Republic of Korea The helical nanofilament (HNF) liquid crystal (LC) phase of bent core mesogens (also commonly termed the B4 phase) is among the most unique and exotic LC phases known. The structure involves a spontaneous hierarchical self assembly of molecules leading to a supramolecular twisted rod structure with a square cross section approximately 30 nm on a side, with the length of the filaments unconstrained, as indicated for the prototype material P-9-OPIMB (also termed NOBOW) (Figure 1). [1] Based upon solid state NMR data, [2] we have proposed that the helical nanofilaments actually represents an unusual assembly of organic crystalline nanoparticles, which form an LC phase, in the case of NOBOW existing in the temperature range between about 150°C and 110°C, which becomes a glass at temperatures below 110°C. That is, the HMF phase is not a typical molecular LC, but an LC of nanocrystals. Analysis of freeze fracture transmission electron microscopic (FFTEM) images of HNF samples suggest that the helix, with a pitch of approximately 240 nm, is coherent in the LC phase. However, lack of electron density contrast in the system has prevented experimental proof of this interesting aspect of the phase structure. Recently, the application of resonant soft x-ray scattering at the carbon K-edge, which is dependent upon molecular orientation as well as electron density,

A05: Controlled nanoparticle targeting

PROGRAM&ABSTRACT

affords proof of the coherence of the HNF helix in bulk samples. [3]

Fig1. Hierarchical structure of the helical nanofilament phase from the prototype mesogen P-9-OPIMB (NOBOW) Descriptions of the unique structure of these nanoparticles and their LC phases, the fascinating behavior of nanostructured composites of the NOBOW HNF phase with other compounds, approaches for alignment of the phase, and some possible applications, will be presented. 1. L. E. Hough, H. T. Jung, D. Krüerke, M. S. Heberling, M. Nakata, C. D. Jones, D. Chen, D. R. Link, J. Zasadzinski, G. Heppke, J. P. Rabe, W. Stocker, E. Körblova, D. M. Walba, M. A. Glaser, and N. A. Clark, Science 325, 456-460 (2009). 2. D. M. Walba, L. Eshdat, E. Korblova, and R. K. Shoemaker, Crystal Growth & Design 5, 2091-2099 (2005). 3. C. Zhu, C. Wang, A. T. Young, F. Liu, I. Gunkel, D. Chen, D. M. Walba, J. E. Maclennan, N. A. Clark, and A. Hexemer, Nano Lett 15, 3420-3424 (2015).

R. Repnik1, A.V. Dubtsov2, S.V. Pasechnik2, D.V. Shmeliova2, S. Kralj1 14

EMN MEETING ON LIQUID CRYSTAL E-mail: [email protected] , Phone: +386 41 792 567 1Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska 160, 2000 Maribor, Slovenia 2Moscow State University of Instrument Engineering and Computer Science, Stromynka 20, 107996 Moscow, Russia We present the study of interactions between nanoparticles (NPs) and nematic liquid crystalline (LC) ordering. In the 1st part of our presentation we analyse numerically impact of NP's surface conditions on NP positioning within a spatially nonhomogeneous nematic LC ordering. Our aim is to identify a general robust mechanism which could potentially allow for controlled targeting of specific NPs to desired areas within a LC medium. Landau-de Gennes approach in terms of the nematic tensor order parameter is used. For demonstrative purpose we consider a cylindrically shaped NP within a cylindrical cell enforcing hybrid orientational boundary conditions. We chose three qualitatively different NP's surface conditions in order to probe impact of different locally enforced topologies on NP targeting preferences. To be more specific, our chosen geometry possesses areas exhibiting essentially i) radial, ii) melted and iii) homogeneous nematic configuration. We inserted NP imposing locally either i) radial, ii) melted or iii) homogeneous nematic ordering. Our simulations reveal that NPs tend to migrate to regions which are most structurally compatible with their surface interaction imposed LC ordering tendency. Our simulations identified a general robust

PROGRAM&ABSTRACT

targeting mechanism revealing that a NP tends to move into a region within which LC ordering matches best with NP's local LC ordering tendency as it is intuitively expected. In such a way average elastic penalties are at least locally minimised. In the second part of the contribution we demonstrate that controlled targeting of specific NPs to desired positions could efficiently trigger a global LC structural transition using a relatively small NP concentration. For this purpose we studied both experimentally and theoretically impact of phospholipids on nematic ordering in nematic droplets dispersed in water containing concentration c of phospholipids. For c=0 the droplets exhibited bipolar nematic configurations. On increasing c we observed dramatic increase of droplets possessing radial structures above the threshold concentration cc>10-5 g/mL. We attributed this behaviour to adsorbed phospholipid molecules at the water-LC droplet interface, which locally enforce homeotropic anchoring. Therefore, for a high enough number of adsorbed phospholipid molecules the effective anchoring condition at the interface can be changed. Consequently, nematic structural transition is triggered. Note that bipolar and radial interference textures are optically significantly different and the structural transition are triggered for a relatively low vale of c. If combined for example with external electric or magnetic field such system could be exploited for sensitive determination of relatively low concentrations of phospholipids in water. The mechanism demonstrated in our study could be exploited for development of

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EMN MEETING ON LIQUID CRYSTAL sensitive sensors of specific NPs.

Acknowledgements

A06: Graphene oxide liquid crystals for reflective displays without polarizing optics Jiming Bao University of Houston E-mail: [email protected] The recent emergence of liquid crystals of atomically thin two dimensional (2D) materials not only has allowed us to explore novel phenomena of macroscopically aligned 2D nanomaterials but also has provided a route toward their controlled assembly into three-dimensional functional macrostructures. Using flow induced

A07: How can an LCD power be saved while a fast-response LC is well-developed Fang-Cheng Lin and Yi-Pai Huang Department of Photonics, National Chiao Tung University, 30010 Hsinchu, Taiwan Email: [email protected] Web site: http://tw.linkedin.com/in/fclin10 The optical throughput of current liquid

PROGRAM&ABSTRACT

This work was partially supported by the Ministry of Education and Science of the Russian Federation (grant No. 3.1921.2014/K, 9.1189.2014/K) and the RFBR (projects No. 14-03-31773 mol_a).

mechanical alignment, we prepared flakes of graphene oxide (GO) in different orientational orders and demonstrated that GO liquid crystals (LC) can be used as rewritable media for reflective displays without polarizing optics. With a wire or stick as a pen, we can make the surface of GO LC reflective and bright, and we can then manually draw lines, curves, and any patterns with dark appearance. The contrast between bright and dark features is due to anisotropic optical responses of ordered GO flakes. Since optical anisotropy is an intrinsic property of 2D structures, our observations and demonstration represent one of many potential applications of macroscopically aligned 2D nanomaterials.

crystal displays (LCDs) is only about 7% to yield a front-of-screen image. The main killer in an LCD is red, green and blue color filter which absorbs about 70% light from a backlight [1]. In contrast, a field-sequentialcolor LCD (FSC-LCD) does not require color filters to yield a color image by sequentially displaying three high luminance primary-color field-images (Fig. 1(a)). Therefore, it has higher optical throughput, higher resolution, high image saturation and lower power consumption. Hence, FSCLCDs are promising as next generation eco-

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Compromising between hardware requirement and image quality, 180Hz Stencil-FSC was implemented on a 65-inch color filter-less MVA-mode LCD with 32×24 RGB-LED backlight resolution (Figs. 2(a) and 2(b)). Using the IEC 62087 video according to the average of APLs (average picture levels) curve to evaluate display power consumption, 180Hz Stencil-FSC (52Watt in average) averagely reduced power consumption to 20% compared to a 65-inch conventional color filter LCD (250-Watt) (Fig. 2(c)). Conventional RGB mono-primary FSC method

Multi-color field Stencil-FSC method

Color breakup images

(a)

240-Hz (4-field)

180-Hz (3-field)

(b)

120-Hz (2-field)

(c)

(d)

Fig. 1. Schematic plot of (a) current RGBFSC method and proposed Stencil-FSC methods in (b) 240Hz, (c) 180Hz and (d) 120Hz.

(a)

(b)

120

Power consumption (W)

Stencil-FSC methods incorporate the localcolor-backlight-dimming technology [6] and gather the most luminance in a multi-color field and reduces the luminance of the residual field-image to successfully suppress color breakup. For practical applications, we developed the Stencil-FSC methods at 240Hz (four field-images) [3], 180Hz (three field-images) [4] and 120Hz (two fieldimages) [5] field rates to effectively suppress color breakup for large-sized TFT-LCDs (Fig. 1). A higher field rate driving has better image fidelity but needs a faster LC material and higher TFT mobility. Field rates of 120Hz, 180Hz and 240Hz, each field-image respectively has 8.3ms, 5.6ms and 4.2ms for data charging, LC responding and backlight flashing. Assuming 1.5ms for backlight flashing and 2ms for data charging in a fullHD (1080p) panel resolution with a proper backlight scanning technology, the rest time for LC response is respectively 4.8ms, 2.1ms and 0.7ms. Facing current LC response time in a commercial LCD is larger than 5ms, the 120Hz Stencil-FSC just matches this criterial but the color breakup suppression is limited and with just acceptable reproduced image fidelity. Additionally, we observe the 240Hz Stencil-FSC has best color breakup

suppression among these three methods from Fig. 1. However, an LC response time less than 1ms, such as blue phase and ferroelectric LC, still needs a breakthrough for commercialized applications.

100 80 60

Average power consumption = 52 W

40 20 0

1 478 955 1432 1909 2386 2863 3340 3817 4294 4771 5248 5725 6202 6679 7156 7633 8110 8587 9064 9541 10018 10495 10972 11449 11926 12403 12880 13357 13834 14311 14788 15265 15742 16219 16696 17173 17650 18127

displays. However, two main issues limit its commercial application. One is a color breakup phenomenon and the other is slow LC response [2]. Color breakup is caused by the relative movement between the human eye and the displayed image. The phenomenon degrades the image quality and leads to discomfort in human eyes. This paper introduces Stencil-FSC methods [3]-[5] to suppress the color breakup and discuss how fast LC response is needed.

PROGRAM&ABSTRACT

Frame (30 frames/sec)

(c)

Fig. 2. 65” FSC-LCD driven by 180Hz Stencil-FSC, including (a) locally color 17

EMN MEETING ON LIQUID CRYSTAL backlight image, and (b) the full displayed image. (c) A 52-Watt average power consumption (20% compared to a current 65inch LCD) 1. Y.-P. Huang et al., Journal of Display Tech., 7(12), 630-632 (2011). 2. Z. Ge et al., Applied Physics Letters, 94, 101104 (2009).

A08: Investigation of the relationships between molecular structures and properties of anthraquinone dichroic dyes with phenylthio groups and their application to GH-LCD

PROGRAM&ABSTRACT

3. F. C. Lin et al., J. Soc. Info. Display, 17(3), 221-228 (2009). 4. F. C. Lin et al., J. Display Technol., 6(3), 107-112 (2010). 5. F. C. Lin et al., J. Display Technol., 11(12), 1069-1075 (2015). 6. F. C. Lin et al., J. Display Technol., 4(2), 139-146 (2008).

yellow anthraquinone dyes with two phenylthio groups. Dyes 1-5 have the same two phenylthio groups at positions 1 and 5 of the anthraquinone skeleton. On the other hand, dyes 6-14 have two different phenylthio groups. [2]

Hiroki Iwanaga Corporate Research & Development Center, Toshiba Corporation, Kawasaki, Kanagawa 212-8582, Japan Email:[email protected] Solubility of dichroic dyes is the most important determinant of performances of GH-LCDs. [1] However; solubilities of dyes in fluorinated liquid crystals for TFT-LCDs are much smaller than those in cyanobiphenyl liquid crystals. In this presentation, relationships between molecular structures and properties of anthraquinone dichroic dyes are discussed and the optimal molecular structure for realizing large solubilities is proposed. Figure 1 shows the molecular structures of

Values of enthalpies of fusions (Hf) of dyes 1-5 are larger than those of dyes 6-14 and solubilities are smaller (Figure 2). The values

values are considered to have negative effects on solubility. Non-symmetric molecular structures have effects of reducing Hf values and increasing solubilities of dyes. Dye 8 has CF3 groups at meta-positions of phenylthio groups. Introduction of CF3 groups has remarkable effects of reducing bility. Study of solvatochromic behaviors [3] and comparison of solubilities of dyes in fluorinated liquid crystals and fluorinated solvents [2] indicate that dyes in liquid crystal phase have a specific solvation form

18


PROGRAM&ABSTRACT

different to that in isotropic phase. Dye 8 can adapt both phases and large solubilities are realized. These results contribute to improving the performances of GH-LCDs and I will also discuss color adjustment of GH-LCDs. [4] Me

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Figure 2. Correlation between enthalpy of fusions (Hf) and solubilities in fluorinated liquid crystals.

S

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References

F

13

14

1. Figure 1. Molecular structures of yellow anthraquinone dyes with two phenylthio groups.

H. Iwanaga, Materials 2, 1636 (2009).

2. H. Iwanaga and F. Aiga, Liq. Cryst. 38, 135 (2011). 3. H. Iwanaga, K. Naito and F. Effenberger, Liq. Cryst. 27, 115 (2000). 4. H. Iwanaga, K. Taira and Y. Nakai, Mol. Cryst. Liq. Cryst. 443, 105 (2005).

A09: Smart Switching of Nematic LC over a 2D Material Surface M. M. Qasim†, A. A. Khan, A. Kostanyan, P. R. Kidambi, P. Braeuninger-Weimer, A. Cabrero-Vilatela, D. J. Gardiner, S. Hofmann and T. D. Wilkinson. Centre of Molecular Materials for Photonics

and Electronics, Department of Engineering, University of Cambridge, 9 J.J. Thomson Avenue, Cambridge, CB3 0FA, UK *E-mail: [email protected] Engineering liquid crystal (LC) interactions and alignment at solid interfaces is crucial to display technologies and many other

19

EMN MEETING ON LIQUID CRYSTAL applications. Most LC displays currently make use of a uniaxially rubbed polymer alignment layer on top of a transparent conductive oxide layer. In order to allow new functionalities and form factors, alternative transparent conductor materials (TCMs) are being explored. In this context graphene films (2D atomic material) are highly interesting due to their flexibility, chemical inertness combined with their broad optical transparency and unusual electrical properties. While graphene flake based LC devices have been explored, continuous graphene films synthesised using chemical vapour deposition (CVD) are best suited as advanced TCMs and many of the processing and integrated manufacturing challenges can be addressed. The LC alignment effects on CVD graphene films can be exploited as an additional functionality for TCM applications to create new generation highly efficient nematic LC scattering displays. We demonstrate a simple hybrid graphene nematic LC (figure 1) light scattering device that utilises the as-

A10: Liquid crystal droplets for biosensor applications Jiyu Fang Department of Materials Science and Engineering, University of Central Florida, Orlando, FL Bile acids have long been used as a clinical biomarker for the diagnosis of liver disease because individuals suffering from liver

PROGRAM&ABSTRACT

grown poly-crystallinity of the CVD graphene electrode to allow efficient light scattering without the need of crossed polarisers or separate alignment layers/additives to achieve switching thresholds at very low electric fields (< 1Vµm-1) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications.

Fig 1. A schematic of Gr-ITO 10 m cell filled with nematic liquid crystal, (a) overall device operation (b) cell structure of the GrITO cell.

disease show a sharply increased concentration of bile acids. There has been great interest in developing optical probes for the simple and rapid detection of bile acids in biological fluids. In this talk, I will discuss our effort in tailoring the surface of liquid crystal (LC) droplets dispersed in aqueous solution by the adsorption of chitosan/surfactant complexes at the LCaqueous interface for the sensitive and selective detection of bile acids, in which the chitosan adsorbed at the surface of the

20

EMN MEETING ON LIQUID CRYSTAL droplets acts as a selective barricade and the director configuration of the LC inside the droplets serves a sensitive optical probe. We find that the detection limit of the chemically tailored LC droplets for bile acids can be tuned by changing the length of the surfactants and the number of the droplets.

PROGRAM&ABSTRACT

The Ag+ ion-triggered fast gelation of the chitosan/surfactant complex-tailored LC droplets casted on a glass substrate can lead to the formation of the LC droplet embedded hydrogel film, which allows us to in situ measure the response time of the LC droplets for bile acids.

A11: Phase transitions in nematic lyotropic systems and in biomembranes: the role of order / disorder of hydrocarbon chains Lia Q. Amaral 1 Department of Applied Physics, Institute of Physics, University of São Paulo, Brazil Email: [email protected] web site: http://portal.if.usp.br/fap/ptbr/membro-do-departamento/lia-queirozdo-amaral Recent results of studies in lyotropic systems with water / (detergents or lipids) / additives are discussed. Nematic phases with sodium dodecyl sulphate present unusual characteristics, with both a biaxial phase and coexistence of the two uniaxial phases [1]. The biaxial phase has a temperature range of stability, above which comes a coexistence region, with spinodal decomposition in the two uniaxial phases (cylindrical and discotic); Figure 1 shows a detail of the SDS phase diagram.

Fig. 1 Partial phase diagram of the system water/SDS/decanol, with molar ratio x = D2O/SDS as a function of temperature, for a fixed molar ratio decanol/SDS = 0.324. Results along the vertical lines at x = 32 and 36 are discussed in [1]. There is a nematic biaxial island NBX, two uniaxial phases ND (discotic) and NC (cylindrical), and a coexistence region (NC + ND). For D2O/SDS = 32 there is a phase transition sequence ND – NBX – (ND + NC). The bar represents a biaxial phase, stable between 3032.5ºC. A complex system with water / detergents / oils forms at room temperature a stable dermatological emulsion, with drops in the gel lamellar phase [2]. Aqueous dispersions of a charged anionic lipid, dimyristoylphosphatidylglycerol (DMPG) in low ionic strength have an abnormal melting

21

EMN MEETING ON LIQUID CRYSTAL transition, attributed to formation of pores within the melting regime [3], which is being now modeled with a detailed theory for Xray scattering. These lyotropic systems have been investigated by a variety of experimental techniques, and their behavior analyzed with theoretical modeling. In all cases the curvature separating aqueous and apolar regions defines the behavior of the system, together with the order-disorder transition of the chains. There is always a compromise between the chain interactions (in gel or

A12: Liquid crystals used as diffraction grating and their applications to optical metrology Miguel Mora-Gonzalez Science and Technology Department, University Center of los Lagos, University of Guadalajara. Lagos de Moreno, Jal., 47460, Mexico. [email protected] phone: 00(+52) 4747424314, ext. 66523. Keywords: optical metrology, diffraction, Ronchi test, axilens, non-invasive optical test. Abstract: Optical metrology is a discipline that contains a series of non-invasive techniques, which are used to measure

PROGRAM&ABSTRACT

liquid crystalline states), and the interactions between the hydrated polar heads. 1. L.Q. Amaral, O.R. Santos, W.S. Braga, N.M. Kimura and A.J. Palangana, Liquid Crystals 42, 240 (2015) 2. N.R. Maciel, E.C.V. Oliveira, C.H. Okuma, J.F. Topan, L.Q. Amaral and P. Rocha-Filho, Journal of Dispersion Science and Technology (accepted, 2015) 3. F.Spinozzi, L. Paccamiccio, P. Mariani and L.Q. Amaral, Langmuir 26, 6484 (2010)

deformations, aberrations, cracks, flatness, etc. in optically reflective and/or refractive surfaces. Since the beginning of the century, Liquid Crystal Displays (LCDs) have been used as diffraction gratings applied to diverse interferometers and non-invasive optical testing systems. Among our applications in optical metrology are the first implementation of an LCD as a Ronchi grating; the quasi-sinusoidal grating approach in the Ronchi test, approaching to the interferometric resolution; flatness measurement by an LCD grating applied in oblique-incidence interferometer; composed filtering in order to attenuate diffraction of pixels; labeling of nonplanar surfaces. Currently, our research team works in applied Liquid Crystal on Silicon (LCoS) or low-cost LCDs as axilens, in order to perform refracted devises with special focus characteristics.

22

EMN MEETING ON LIQUID CRYSTAL A13: Active Hydrodynamics

Liquid

Crystal

H. Pleiner1, D. Svenšek2, and H.R. Brand3 1 Max Planck Institute for Polymer Research, Mainz, Germany Email: [email protected], Website:http://www2.mpipmainz.mpg.de/~pl einer 2 Department of Physics, University of Ljubljana, Ljubljana, Slovenia 3 Theoretical Physics III, Bayreuth, Bayreuth, Germany

University

We study the dynamics of an active, polar dynamic liquid crystal that is embedded in a visco-elastic medium. Examples include the pattern-forming growth of bacteria [1] and the motion of molecular motors. These systems are active, since the entities move by themselves. They are driven (out of equilibrium) by internal chemical processes. In those systems there is orientational order, if there is motion. Because the ordered state only exists dynamically, but not statically, the macroscopic variable of choice is the velocity of the active units [2]. The passive visco-elastic medium is described by a relaxing strain tensor [3]. We derive the macroscopic equations for such a system including relative rotations [4,5] of the elastic medium with respect to the polar direction. We find novel static, reversible and irreversible cross-couplings within this twofluid (two-velocity) system. The dynamics is rather different compared to the case of

PROGRAM&ABSTRACT

passive, static polar nematic order [6]. In particular, we find a complicated normal mode structure that reflects the broken timereversal symmetry due to the nonequilibrium situation, an anisotropy of first sound and a possible second sound excitation due to the active velocity [1]. Various coupled relaxations of the elasticity, the relative rotations, and the active order are discussed [7]. We also comment critically the role of the so-called active term in the stress tensor [8] and we dwell on the thermodynamically correct description of the hydrodynamic advection and convection velocities [9]. 1. Y. Yamazaki, T. Ikeda, H. Shimada, F. Hiramatsu, N. Kobayashi, J. Wakita, H. Itoh, S. Kurosu, M. Nakatsuchi, T. Matsuyama, and M. Matsushita, Physica D 205, 136 (2005). 2. H. Pleiner, D. Svenšek, and H.R. Brand, Eur. Phys. J. E, 36, 135 (2013). 3. H. Pleiner, M. Liu, and H.R. Brand, Rheol. Acta 39, 560 (2000) and 43, 502 (2004). 4. P.G. de Gennes, in Liquid Crystals of One– and Two–Dimensional Order, edited by W. Helfrich and G. Heppke (Springer, New York, 1980). 5. A.M. Menzel, H. Pleiner, and H.R. Brand, J. Chem. Phys. 126, 234901 (2007). 6. H.R. Brand, H. Pleiner, and F. Ziebert, Phys. Rev. E, 74, 021713 (2006). 7. H. Pleiner, D. Svenšek, and H.R. Brand, to be published

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EMN MEETING ON LIQUID CRYSTAL 8. H.R. Brand, H. Pleiner, and D. Svenšek, Eur. Phys. J. E 37, 83 (2014). 9. H. Pleiner and J.L. Harden, in Nonlinear

A14: What is the ability of all-atom simulation to depict accurately the Sm C phase? François Porzio, Clément Wespiser, and Armand Soldera* Department of Chemistry, Centre Québécois sur les Matériaux Fonctionnels, Université de Sherbooke, Sherbrooke (Québec), J1K 2R1 Canada Email:[email protected] http:// http://lpcm.recherche.usherbrooke.ca Subtle differences in the molecular structure of mesogens can lead to very different experimental polymorphisms. The smectic C (SmC) phase can actually be exhibited by one isomer, and not the other, or the range of temperature can be completely different [1]. Unveiling the deep connection between atomic structure and the very existence of the SmC phase will lead to the design of new performing liquid crystalline materials for ferroelectric or non-linear optical applications [2]. In this presentation, we propose to combine results stemming from molecular dynamics simulation and experimental phase diagrams [3]. From a molecular simulation viewpoint, the use of isomers is of particular interest since they share the same force field parameters. Any

PROGRAM&ABSTRACT

Problems of Continuum Mechanics, Special issue of Notices of Universities. South of Russia. Natural sciences, p. 46 (2003) and arXiv:cond-mat/0404134.

changes observed in the computed properties are then attributed to differences in molecular characteristics only. We thus show that a strong negative long-range Coulomb interaction potential energy between molecules is required for a greater thermal stability of the SmC phase [4]. However, this thermal stability can be reduced depending on the strength of the short-range Coulomb potential energy, leading preferentially to the development of the crystalline phase instead of the mesophase, if the intermolecular interactions are too strong. Our approach is actually based on running molecular dynamics simulation from an initial SmC arrangement of molecules. By increasing the temperature, the molecules automatically adjust in a more favorable organization. Such modification in the imposed initial self-assembly is governed by values of the non-bonded energies. This conclusion can be applied to other mesophases.

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EMN MEETING ON LIQUID CRYSTAL Fig1. Correlation between experimental liquid crystal polymorphism and simulation data. 1. R. Vadnais, M.A. Beaudoin, A. Beaudoin, B. Heinrich, A. Soldera, J. Chem. Phys. 129, 164908, (2008). 2.

PROGRAM&ABSTRACT

Chem. Phys. Lett. 440, 116 (2007). 3. E. Levert, S. Lacelle, E. ZysmanColman, A. Soldera, J. Mol. Liq. 183, 59 (2013). 4. F. Porzio, E. Levert, R. Vadnais, and A. Soldera, J. Phys. Chem. B 118, 4037 (2014).

F. Perreault, B. Champagne, A. Soldera,

A15: An Analysis of Chevrons in Thin Liquid Crystal Cells Lei Z. Cheng Olivet Nazarene University, USA Email: [email protected] Keywords: chevron-like defects, smectic liquid crystals, Γ-convergence We analyze a model for the structure in a liquid crystal medium that arises when the material is cooled from the smectic-A to the chiral smectic-C phase in a surface-stabilized cell with prescribed boundary conditions

under a given electric field. This phenomenon causes V-shaped (chevron-like) defects to form in liquid crystal display devices and has attracted interest from both theoretical and practical points of view. The work investigates the nature of the chevron shaped defects in solutions to a family of minimization problems. Their energy densities are highly nonlinear and we use the notion of Γ-convergence as a way of identifying the solutions principal features. We single out the bulk smectic layer thickness as a small parameter, show that as this parameter tends to zero the energies Γconverge to a limiting energy, and characterize the minimizers for the limit problem. This work is joint with D.Phillips.

1Institute of Computational Fluid Dynamics (iCFD), 1-16-5 Haramachi, Meguro-ku, Tokyo, Japan A16: Molecular dynamics simulation methods for anisotropic systems --from liquid crystals, surfaces and beyond

Email:[email protected] 2Faculty of Science, Toho University, Funabashi, Chiba, Japan

Keiko M. Aoki1 2 3 3Faculty of Science and Engineering,

25

EMN MEETING ON LIQUID CRYSTAL Waseda University, Tokyo, Japan The solutions of symplectic integrators preserve the structure of Hamilton’s equations of motion. Recent molecular dynamics simulations using the symplectic integrator designed for soft matter [1] has revealed the importance of treating the pressure not as a scalar but as a tensor. The anisotropic fluctuation is extremely important not only in systems with anisotropy in the constituent molecules, such as liquid crystals [2, 3, 4, 5, 6], but also in metastable states, such as glass, of systems consisting of isotropic molecules [7]. The barostat of these molecular dynamic simulations allows us to treat anisotropic fluctuations of the volume. Systems under a given value of hydrostatic pressure [8] or surface tension [9] can be simulated. Based on this symplectic integrator, a thermodynamic approach to calculate entropy and heat capacity has been proposed and utilized to detect the 2nd order transition between crystal and hexatic smectic B phase [1, 2, 10]. The calculation methods and some relevant results will be presented.

PROGRAM&ABSTRACT

Fig.1: Hexatic Smectic B Liquid Crystal with Anisotropic Fluctuations. 1. K. M. Aoki, J. Phys. Soc. Japan 77, 044003 (2008) 2. K. M. Aoki, M. Yoneya, and H. Yokoyama, Phys. Rev. E 81, 021701 (2010) 3. K. M. Aoki and M. Yoneya, J. Phys. Soc. Japan 80, 124603 (2011) 4. K. M. Aoki, J. Phys. Soc. Japan 83, 104603 (2014) 5. K. M. Aoki and S. Ohnishi, Mol. Cryst. Liq. Cryst. 612, pp.64-71 (2015) 6. K. M. Aoki, Mol. Cryst. Liq. Cryst. 612, pp.72-80 (2015) 7. K. M. Aoki, S. Fujiwara, K. Sogo, S. Ohnishi, T. Yamamoto, Crystals, 3, pp.315332 (2013); JPS Conf. Proc. 1, 012038 (2014) 8. K. M. Aoki, M. Yoneya and H. Yokoyama, J. Chem. Phys. 120, pp.55765584 (2004) 9. K. M. Aoki, M. Yoneya and H. Yokoyama, J. Chem. Phys. 124, 064705 (2006) 10. K. M. Aoki, JPS Conf. Proc. 1, 016009 (2014)

A17: Topological defects dynamics in microfluidic channel: A numerical study by multi-particle collision simulation

Lee, Kuang-Wu Max-Planck-Institute for Dynamics and Self-

26

EMN MEETING ON LIQUID CRYSTAL Organization, Göttingen, Germany Email: [email protected] With the latest advances in microfluidic manipulations, novel usages of the microflow control have opened up windows for advanced designs of new materials. Many of their experimental setups the complex fluids, instead of simple isotropic fluid, are utilized to extend their peculiar physical characters in microscopic geometry. Despite their great success in those innovative laboratorial exercises, the analytical studies for this multi-scale complex system fall still behind. This is particularly because the system characteristic energies come close to its thermal energy; the hydrodynamic theory/numerics fail to describe the thermal

A18: Challenges and Opportunities in Photo-responsive Liquid Crystal Polymer Networks for Adaptive Structure Applications William S. Oates∗ Florida Center for Advanced Aero Propulsion (FCAAP) Department of Mechanical Engineering, Florida State University, Tallahassee, FL 32310 Email: [email protected] Complex light-matter microstructure interaction in azobenzene polymer networks is modeled to help explain a broad range of deformation states induced by different types of polarized light sources. This is achieved

PROGRAM&ABSTRACT

fluctuation related phenomenon. We introduce a new mesoscopic model for nematic liquid crystals (LCs).We extend the particle-based stochastic rotation dynamics method, which reproduces the Navier-Stokes equation, to anisotropic fluids by including a simplified Ericksen-Leslie formulation of nematodynamics. We verify the applicability of this hybrid model by studying the equilibrium isotropic-nematic phase transition and nonequilibrium problems, such as the dynamics of topological defects and the rheology of sheared LCs. Our simulation results show that this hybrid model captures many essential aspects of LC physics at the mesoscopic scale, while preserving microscopic thermal fluctuations. The dynamics of topological defects in the microfluidics channel will be discussed.

by coupling photo-responsive electronic material evolution with timedependent electromagnetics and polymer mechanics. This approach provides an explanation of the mechanisms contributing to light induced bending and twisting of free standing azobenzene polymer films and surface texture deformation from circularly or linearly polarized laser beams and optical vortex beams. The analysis includes a comparison of dipole and quadrupole forces within the charge density of the optical active microstructure and correlation of this behavior with optical absorption, photoisomerization, and polymer deformation. The necessity of higher order terms associated with field gradients are explored and compared to cases where only homogeneous, polarized light is applied to

27


PROGRAM&ABSTRACT

free standing films. The results have important implications on exciting azobenzene polymers with different light

sources to achieve photomechanical response.

A19: Optical effects in nanocomposites of liquid crystal polymers with nanoparticles

models will be discussed, namely, an interaction of functional groups in side chains of polymers responsible for LC formation with the surface of a semiconductor NPs and an attachment of the polymer backbone to the surface of plasmonic NPs :

R.V. Talroze1, A.A. Ezhov 1 G.A.Shandryuk , Ya.I. Derekov1, Tselikov2, A.S. Merekalov1

1,2

, G.I.

1 Topchiev Institute of Petrochemical Synthesis, Moscow, Russia. Email:[email protected] 2Department of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia3 Both low molecular weight and polymer liquid crystals (LCs) doped with metal and semiconductor nano-particles (NPs) attract the growing attention because the properties of such composites may differ significantly from those of pure soft materials. Some fundamental issues of hybrid organicinorganic composites created via introducing of nanometer scale colloidal particles (NPs) into LC polymer matrices will be discussed. The control of the processes of ordered structure formation in nanocomposites is driven by anisotropic polymer matrixes by means of chemical coupling of polymers with NPs, mesophase structure type and NP shape control. The binding of NPs by polymer macromolecule allows the embedding of NP in a polymer matrix at much higher content with no phase separation than just simple blending. In frameworks of that approach two different

a

desired

Such matrices may govern the distribution and assembly of NPs that are of wide-ranging interest for both fundamental science and technological applications. Several optical phenomena are detected that result from the coupling of NPs and hydrogen bonded LC polymers [1] in one system, namely: a redshift of the exciton photoluminescence (PL) band of CdSe quantum dots (QDs) in smectic matrix relatively to that of colloidal QDs in solution [2] and a splitting of the excitonic state in CdSe QDs while in smectic matrix which results in the increase of photoinduced optic translucence under the action of powerful laser pulses [3]. Cholesteric matrices provide other effects like a blue shift of QDs PL and polarized PL of QDs that appear due to selective reflection of light of a certain polarization characteristic for a cholesteric matrix. RAFT polymerization followed by the reduction of the end group allows creating polymers with the thiol end group capable of the stabilization of gold plasmonic NPs [4]. Optical properties of composite film are the combination of properties inherent to the cholesteric matrix and NPs. The reason is

28

EMN MEETING ON LIQUID CRYSTAL weak overlap of the spectral position of the stop band of the cholesteric polymer and the absorption bands of NPs. However the major result is that the composite with such a high content of NPs retains cholesteric ordering in combination with the lack of aggregation of the NPs.

PROGRAM&ABSTRACT

Acknowledgement This work was supported by the Russian Foundation for Basic Research (Grants № № 14-03-00737, 14-0390016, 15-03-31323 and Grant of the Program № 1 of the Presidium of Russian Academy of Sciences) 1. G. Shandryuk, E. Matukhina, R. Vasil’ev, A. Rebrov, G. Bondarenko, A. Merekalov, A. Gas’kov, Raisa V. Talroze. Macromolecules 41, 2178 (2008) 2. G. Tselikov, V. Timoshenko, J. Plenge, E. Rühl, A. Shatalova, G. Shandryuk, A. Merekalov, R. Talroze, Semiconductors 47, 647 (2013) 3. G.Tselikov,V. Timoshenko, L. Golovan’, Jürgen Plenge, A. Shatalova, G. Shandryuk, I. Kutergina, A. Merekalov, E. Rühl, R. Talroze. ChemPhysChem 17, 1071, (2015) 4. A. Ezhov, Y. Derikov, E.Chernikova, S. Abramchuk, G. Shandryuk, A. Merekalov, V. Panov, R. Talroze . Polymer 77, 113 (2015)

A20: Thermally Conductive Liquid Crystal Polyesters and Composites Shusuke Yoshihara1, Kazuaki Matsumoto1 1Frontier Materials Development Laboratories, Kaneka Co., Osaka, Japan Email:[email protected] Thermally conductive, electrically insulating

materials have attracted attention as useful substances for heat dissipation in electronic devices. The improvement of devices in size and performance results in the generation of a greater amount of heat in a smaller volume of space. To remove the heat, materials with higher thermal conductivity (TC) are demanded. Polymers are lightweight electrical insulators; however, their TC is typically very low (ca 0.2 W m−1 K−1).[1] Even with large concentrations of thermally

29

EMN MEETING ON LIQUID CRYSTAL conductive fillers, it is difficult to enhance the polymer composite TC because the polymer matrix plays a major role in the heat transfer process.

PROGRAM&ABSTRACT

served as a heat path with a TC of more than 1 W m−1 K−1 in composites at MgO content of more than 30 vol%, although the TC of the polydomain PB-10 is 0.52 W m−1 K−1.[4] The TC enhancement mechanism will be explained in this presentation.

Ff Fig.1 Chemical structure of PB-n

We found that smectic liquid crystal polydomain PB-n polyesters (Figure1) exhibit TC of 0.52 W m−1 K−1 due to a highly ordered structure. (Figure2) They show a parallel orientation of lamellae by shear flow during injection molding. The polymer chains are aligned in the normal direction (ND) with respect to the molding surface, leading to high TC (1.2 W m−1 K−1) in this direction.[2]

Fig.3 PB-10 composite TC vs. MgO content. PB-n technique enables the production of polymer materials with high TCs without a high filler content, and hence lightweight composites with good processability. Acknowledgement; We thank J. Watanabe and M. Tokita of Tokyo Institute of Technology for discussions.

Fig.2 Higher order structure of PB-10 Furthermore, the composites containing thermally conductive filler particles exhibit a dramatic enhancement in the TC.[2,3] Figure 3 shows the effect of MgO filler content on the PB-10 composites TC compared with the theoretical curves calculated using Bruggeman’s equation.[4] The solid and broken lines represent the calculated TC values with (matrix TC, filler TC)=(0.52, 42) and (1, 42), respectively. PB-10 matrix

A21: Microwave flexible devices with

1. Han, Z; Fina, A. Prog. Polym. Sci. 2011, 36, 914. 2. Yoshihara, S. et. al., Macromol. Chem. Phys. 2012, 213, 2213. 3. Yoshihara, S. et. al., J. Appl. Polym. Sci. 2014, 131, 39896. 4. Bruggeman, D. A. G. Ann. Phys. 1935, 24, 636.

ultra thin Liquid Crystal Polymers (LCP) 30

EMN MEETING ON LIQUID CRYSTAL Yuehang Xu University of Electronic Technology of China, China

Science

and

Email: [email protected] Recently, flexible electronic devices are in greatly demand for wearable and bioimplantable electronics. To collect signals or

A22: Non-equilibrium behaviors of nematic liquid crystal confined in porous media Takeaki Araki1 1PDepartment of Physics, Kyoto University, Sakyo-ku, Kyoto, Japan

PROGRAM&ABSTRACT

communication effectively, wireless systems are become the popular solution. Here, we would like to demonstrate a feasible way to realize Flexible Microwave Devices by using Ultra Thin Liquid Crystal Polymer (LCP). The performance of flexible microwave filters, antennas, and, rectennas are shown. The results that the LCP is a very good candidate for the substrate of flexible microwave devices.

configurations are long-lived since the energy barriers connecting them are larger than the thermal fluctuations. This results in non-ergodic glassy behaviors, analogous to a spin glass. We also found some of the remaining disclination lines are topologically constrained in the channels of the matrix. These constrained defects play an essential role in the memory effect.

Email:[email protected] Web site: http://statphys.scphys.kyotou.ac.jp/~araki/e-index.html It has been reported that a nematic liquid crystal in a porous material exhibits slow glassy relaxation and its resultant memory effect [1,2]. In a previous paper, we revealed that this memory effect is attributed to reconfiguration of the defect structure by means of Monte Carlo simulations [3]. In porous madia with strong anchoring, the director field of the nematic phase cannot align uniformly and hence, topological defects are stably formed. Since all the channels do not necessarily have disclination lines running through them, many metastable configurations can be found. The defect

In this work, we study flow behaviors of a nematic liquid crystal in a porous medium by means of lattice Boltzmann simulations [4]. Here, we employ a bicontinuous cubic porous matrix, in which the defect pattern can reach one of the global energy minimum states. This stable configuration is consisted of two types of disclination loops. Half of the loops are topologically locked and the other half are not. In a weak flow, both the locked and free defects are sustained, only showing small displacements of their positions. In an intermediate flow, the free defects move against the background flow. When the defects reach a critical distance, they are annihilated and new ones are generated at the original positions. This cycle is repeated and its period depends on the flow speed. In a

31

EMN MEETING ON LIQUID CRYSTAL strong flow, even the locked defects show similar repeated motions with a longer period. We also found that flow can switch the average orientation of the nematic phase. Owing to the topological locking, the new orientation is recorded even after the flow is stopped [5].

PROGRAM&ABSTRACT

1. G. P. Crawford and S. Zumer, Liquid Crystals in Complex Geometries Formed by Polymer and Porous Networks (Taylor and Francis, London, 1996). 2. M. Buscaglia et al., Rhys. Rev. E 74, 011706 (2006) and references therein. 3. T. Araki, M. Buscaglia, T. Bellini and H. Tanaka, Nature Materials 10, 303 (2011).

Fig1. Defect patterns of a nematic liquid crystal flowing in a porous matrix are shown. The imposed forces are (a) fz=0.001, (b) 0.003 and (c) 0.005. (d) Temporal changes in the averaged remnant order of a flowing nematic liquid crystal . Under a strong force, two oscillation modes are observed.

4. C. Care et al., Phys. Rev. E 67, 061703 (2003).

A23: Application of MD simulations and EPR spectroscopy to liquid crystals: A combined approach

can be readily introduced into LCs to probe the order and dynamics of LC molecules in different phases. EPR is a “fast” magnetic technique which is able to resolve molecular motions of partially ordered systems on the sub-nanosecond timescale. We combine experimental EPR with state-of-the-art molecular modeling and develop methods for prediction of EPR spectra from Molecular Dynamics (MD) simulations [4]. Such an approach bridges the gap between theory and experiment allowing unambiguous interpretation of EPR line shapes and enabling conclusions to be drawn about molecular motions and order in LC phases [2, 5, 6].

Vasily S. Oganesyan1 1 School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom Email: [email protected] http://www.uea.ac.uk/chemistry/people/profi le/v-oganesyan Electron Paramagnetic Resonance (EPR) with paramagnetic spin probes (SP) is a particularly valuable advanced spectroscopic method for studying both structure and dynamics of soft matter systems such as liquid crystals (LCs) [1-3]. Nitroxide SPs

5. T. Araki, Phys. Rev. Lett. 109, 257801 (2012).

For thermotropic nematic LCs structurally variable nitroxide SPs probing different aspects of LC dynamics have been employed 32

EMN MEETING ON LIQUID CRYSTAL resulting in different but highly complementary EPR spectra. Variable temperature EPR spectra of LCs doped with SPs were predicted directly from fully atomistic MD simulations using our novel MD-EPR simulation methodology [4]. They show excellent agreement with experiment. Using MD-EPR approach we were able to characterise in detail the dynamics and molecular order in different phases of 5CB and 8CB LCs including meta-stable states at the phase transitions [5, 6].

PROGRAM&ABSTRACT

provide information about the changes in the sizes and motions of surfactant aggregates across the phase transition regions. 1. V. S. Oganesyan in SPR: Electron Paramagnetic Resonance, (Eds: B. C. Gilbert, V. Chechik and D. M. Murphy), Royal Society of Chemistry, London, 24, 32-61, (2015). 2. V. S. Oganesyan, E. Kuprusevicius, H. Gopee, A. N. Cammidge, M. R. Wilson, Phys. Rev. Lett., 102, 013005, (2009) 3. H. Gopee, A. N. Cammidge, and V. S. Oganesyan, Angew. Chem. Int. Ed., 52, 34, 8917, (2013) 4. V. S. Oganesyan, Phys. Chem. Chem. Phys., 13, 10, 4724, (2011).

We also report the first application of a combination of MD simulations and EPR spectroscopy to lyotropic LCs such as sodium dodecyl sulphate (SDS) doped with the 5-DOXYL stearic acid SP. The SDS systems include pre-micellar, micellar and rod aggregations. This study uncovers the potential for such a synergistic approach to

5. F. Chami, M. R. Wilson and V. S. Oganesyan, Soft Matter, 8, 2823, (2012). 6. E. Kuprusevicius, R. Edge, H. Gopee, A.N. Cammidge, E.J.L. McInnes, M.R. Wilson, and V.S. Oganesyan, Chem. Eur. J., 16, (38), 11558, (2010).

A24: Cubic phases of lyotropic liquid crystals: monocrystals, thin films, cubosomes Wojciech Góźdź Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-

33


PROGRAM&ABSTRACT

224 Warsaw, Poland Email:[email protected], web site: http://ichf.edu.pl/wtg.html Bicontinuous cubic phases are composed of two disjoint water channels separated by a lipid bilayer. Examples of a unit cell of the cubic phases are shown in Fig. 1, where the surface represents the location of the bilayer. When a liquid crystal phase is in equilibrium with an isotropic phase an interface is formed. The structure of such an interface is presented in Fig. 1. Liquid crystals are anisotropic and the structure of the interface depends on the orientation of the unit cell with respect to the surface of the interface. Such interfaces are formed in monocrystals [3,4], thin films [2], and nanoparticles [1] formed from bicontinuous phases. We have determined the structure and stability of the interfaces for different phases and different orientations of the unit cell with respect to the interface surface. The calculations were performed withing the framework of the Landau-Brazovskii functional [1-3]. The results of the calculations were compared with the results of available experiments. Good agreement between the theoretical calculations and the experimental results was obtained. It has been shown that different phases have the stable interfaces for different orientations of the unit cell with respect to the interface. Such behavior influences the orientation of the lyotropic liquid crystals in thin films and the stability of different facets in monocrystals.

Fig1. The unit cell of diamond and gyroid phases with the most stable interfaces. The interfaces are perpendicular to the [111] and [110] directions for the diamod and gyroid phase respectively. The colors represent different sides of the surface. 1. Góźdź W.T., "Cubosome Topologies at Various Particle Sizes and Crystallographic Symmetries", Langmuir 31(49) , 1332113326, 2015 2. Richardson S.J., Staniec P.A., Newby G.E., Terrill N.J., Elliott J.M., Squires A.M., and Góźdź W.T., "Predicting the orientation of lipid cubic phase films ", Langmuir 30 , 13510-13515, 2014 3. Latypova L., Góźdź W.T., Pierański P., "Facets of lyotropic liquid crystals ", Langmuir 30(2) , 488-495, 2014 4. Latypova L., Góźdź W.T., Pierański P., "Symmetry, topology and faceting in bicontinuous lyotropic crystals", The Eur. Phys. J. E 36(88) , 9903, 2013

34


A25: Thermodynamics of a continuous medium with electric dipoles Sylvan Brechet Ecole Polytechnique Federale de Lausanne, Switzerland Email: [email protected] The non-equilibrium thermodynamics of an electrically charged, multicomponent fluid with spontaneous electric is analysed in the

A26: Molecular Simulation of Confined Liquid-Crystals and Clustomesogens

PROGRAM&ABSTRACT

presence of electromagnetic fields. Taking into account the chemical composition of the current densities and stress tensors leads to three different types of irreversible terms: scalars, vectors and pseudo-vectors. The scalar terms account for chemical reactivities, the vectorial terms account for transport and the pseudo-vectorial terms account for relaxation. The linear phenomenological relations, derived from the irreversible evolution, describe notably the Lehmann and electric Lehmann effects for liquid crystals in a transparent manner.

UniversitéRennes 1, France Email: [email protected]

Aziz Ghoufi

A27: Columnar and Smectic SelfOrganization of Unconventionally Shaped Mesogens S. Holger Eichhorn1, H. Taing1, H. Kayal1, C. Shuai1, M. Ahmida1, F. S. Raada1,2, B. R. Kaafarani2, N. D. Suhan1, and S. J. Loeb1 1Department of Chemistry & Biochemistry, University of Windsor, Windsor, ON, Canada Email:[email protected] Web site: http://www.mxu.edu/jdoe.htm 2Department

of

Chemistry,

American

University of Beirut, Beirut, Lebanon Two different approaches to liquid crystals of unconventional shape will be presented. The first approach explores the transition from smectic to polycatenar-type columnar to conventional columnar liquid crystals in different board-shaped aromatic organic dyes based on the quinoxalino[20,30:9,10] phenanthro[4,5-abc]phenazine (QPP) core. To use the QPP core as building block for columnar mesophases is not straightforward because the attachment of lateral flexible side chains directly to the core generated derivatives that display (lamellar) soft crystal rather than columnar liquid crystal phases

35

EMN MEETING ON LIQUID CRYSTAL due to their large in plane aspect ratios. Reduction of the effective in plane aspect ratio by employing new crucifix- or dumbbell-shaped cores generated compounds that form columnar mesophases over wide ranges of temperature (Fig. 1a).1,2 Some of their interesting electronic and optical properties will also be reported. a)

PROGRAM&ABSTRACT

structures of [2]rotaxanes that display SmA mesomorphism. The second approach describes the conversion of ionic [2] rotaxanes into smectic liquid crystals (Fig. 1b).3 Both, mesomorphism and thermal stability of the materials was largely enhanced by sheltering the ionic cores with an interlocked neutral macrocycle. The influence of the sheltering macrocycle, the numbers of charges on the core and the size and nature of the side chains (aliphatic vs siloxane) were probed. 1. A. O. El-Ballouli, et al., Tetrahedron. 71, 308 (2015).

b) 2. S. Chen, F. S. Read, M. Ahmida, B. R. Kaafarani and S. H. Eichhorn, Org. Lett. 15, 558 (2013).

Fig 1. a) Crucifix- and dumbbell-shaped quinoxalino[20,30:9,10]phenanthro[4,5abc]phenazine derivatives. b) General

A28 Pyrazinacenes, porphyrins and nanoparticles: liquid crystals and selfassemblies Jonathan P. Hill1, Gary J. Richards1, Yongshu Xie2, Misaho Akada1, Somobrata Acharya3, Katsuhiko Ariga1 1 International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

3. N. D. Suhan, S. J. Loeb, and S. H. Eichhorn, J. Am. Chem. Soc. 135 (1), 400 (2013)

2Department of Chemistry & Institute for Fine Chemicals, East China University of Science and Technology, Meilong Rd. 130, Shanghai, P. R. China 3Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadaypur, Kolkata 700 032, India Self-assembly of molecules implies intermolecular processes that can involve

Email:[email protected]

36

EMN MEETING ON LIQUID CRYSTAL hydrogen bonding, van der Waals interactions (e. g. pi-pi stacking), amphiphilicity, coordination chemistry and combinations of these. Here, we will discuss assembly processes of porphyrins, pyrazinacenes and oxoporphyrinogens (amongst others) including how their structures affect the final self-assembly form and any dynamic processes occurring in the structures. These include investigations of supramolecular activity at surfaces of an amphiphilic porphyrin trimers [1]. Liquid crystal materials are a very significant class of compounds used in display and other applications. We have selected pyrazinacenes [2] as being interesting for the development of a class of mesomorphic materials and their synthesis and properties will be described. We have also investigated the introduction of chalcogenide nanoparticles into liquid crystal blends and the results of those investigations will be briefly introduced [3].

A29: Design, assembly, and emergent properties of columnar mixed-stack aromatic donor-acceptor liquid crystals Joseph Reczek Denison University, USA Email: [email protected] The well-designed combination of complementary electron-rich and electronpoor aromatic molecules can lead to the self-

PROGRAM&ABSTRACT

Fig1. From left: a self-assembling amphiphilic porphyrin derivative, polarized optical microscopy texture of a pyrazinacene liquid crystalline lamellar phase, and selfassembled pyrazinacene nanotubes. 1. Y. Xie, M. Akada, J. P. Hill, Q. Ji, R. Charvet and K. Ariga, Chem. Commun. 47, 2285 (2011). 2. G. J. Richards, J. P. Hill, N. K. Subbaiyan, F. D’Souza, M. R. J. Elsegood, S. J. Teat, T. Mori and K. Ariga, J. Org. Chem. 74, 8914 (2009). 3. S. Acharya, S. Kundu, J. P. Hill, G. J. Richards and K. Ariga, Adv. Mater. 21, 989 (2009).

assembly of alternating face-centered columns. These bi-component materials are often thermotropic liquid crystals, termed donor-acceptor columnar liquid crystals (DACLCs). DACLCs display physical and optical properties distinct from their component molecules, and these properties can be tuned in modular fashion through the simple mixing of components. The mesophase structure and range of these materials can vary widely, in some cases leading to novel room-temperature columnar liquid crystals. Several materials show promising optical and electronic properties,

37


PROGRAM&ABSTRACT

exhibiting broad UV/Vis/NIR absorption from simple and stable organic compounds. The ability to independently tune optical and physical properties of these materials will be

discussed, as well as a brief look at their potential to serve as new functional organic materials.

A30: Hard Tetrahedra, Spatially Varying Liquid Crystal Order and Quasicrystals

crystalline phases we have shown that these phases are best understood as blue-phase like: they have helically varying liquid crystalline order in a number of different directions, with third and higher rank tensor liquid crystalline order. The phases that have been observed are described. We will discuss the Landau theory of such phases, the "naturalness" of quasicrystalline order in such phases as and possible "nearby" phases. Such quasicrystalline phases, particularly if they can be made icosahedral, may be of interest for photonic applications.

Rolfe.G. Petschek Case Western Reserve University, USA Email: [email protected] According to computer simulations hard tetrahedra transition from the isotropic to a complicated quasicrystalline phase. Using standard techniques for analyzing liquid

A31: The phase transition during post annealing S. T. Nakagawa Okayama Univ. of Science, 1-1 Ridai-Cho 700-0005 Okayama, Japan. Corresponding author: [email protected] Keywords: globally coupled map, complex system, applied statistics, postannealing, Ion implantation, molecular dynamics simulation, long-range-order parameter In this study, we thought to determine why post-annealing (PA) would require as many as 1010 repetitions of lattice vibrations to

restore damaged crystallinity. Using a molecular dynamics (MD) simulation, we investigated how PA proceeds in terms of the time-series of the long-range-order (LRO) parameter as LRO patterns. We monitored the LRO pattern in the case of a IIa-type diamond, from the beginning of ion impact via sub-keV N2 beam implantation to a few nanoseconds (ns), i.e., close to the feasible time limit for MD simulations. After the ion impact, the LRO parameter changed gradually from ‘LRO = 1’ (perfect crystal) to ‘LRO = 0’ (perfectly random). That is, the LRO pattern showing the crystal to amorphous transition was simply a decreasing curve. Nevertheless, since PA started, the LRO pattern was not simply an increasing curve but a complex one. We grouped LRO patterns into more than three

38


PROGRAM&ABSTRACT

types of phases and observed the transition between them. Such chaotic variations in the LRO pattern may reveal that the system is a ‘globally coupled map’ (GCM) of a complex system. A GCM is composed of coupled oscillators that develop slowly to exhibit several different phases over time; thus, the long duration required for PA may be attributable to the nature of a complex system.

PACS number(s): 89.75.-k (complex systems), 64.60.-Cn (Order-disorder transformations),

A32: Topological defect-antidefect depinning threshold for nematic shells

their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling positioning and local number of TDs.

Luka Mesarec,1, ∗ Aleˇs Igliˇc,1, † and Samo Kralj2, 3, 4, ‡ 1Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Trˇzaˇska 25, SI1000 Ljubljana, Slovenia 2Condensed Matter Physics Department, Joˇzef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia 3Joˇzef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia 4Faculty of Natural Sciences and Mathematics, University of Maribor, Koroˇska 160, 2000 Maribor, Slovenia Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. Topological origin makes their key features independent of systems’ microscopic details and therefore TDs display many universalities. Because of

64.70.-p specific phase transition, 61.72 Cc (Kinetics of defect formation and annealing), 05.10.-a (Computational methods in statistical physics and nonlinear dynamics)

We present a numerical study of TDs within nematic shells, effectively two dimensional closed soft films of nematic liquid crystal exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We study the equilibrium configurations of nematic shells within a twodimensional Landau-de Gennes tensorial formalism. Topological defects are characterized by their topological charge. The sum of the topological charges of all defects on the surface of any topology is constant as long as the surface topology remains unchanged. We introduce the Effective Topological Charge Cancellation mechanism controlling localized positional assembling tendency of TDs and formation of pairs {defect, antidefect} on curved surfaces. We study also the impact of relevant impurities (e.g. nanoparticles) which act as virtual topological charges.

39


PROGRAM&ABSTRACT

Using the electrostatic analogy, we estimate a critical depinning threshold to form pairs

{defect,antidefect} configurations.

A33: From field theory to chiral fluids and back

Parity-violating fluids in two spatial dimensions can appear in a variety of

contexts such as liquid crystal films, anyon fluids, and quantum Hall fluids. Nonetheless, the consequences of parity violation on the solutions to the equations of motion are largely unexplored. Such chiral flows can be captured by spontaneous formation of vortex clusters. I will present an effective description of point vortices in terms of an effective field theory. Moreover, I will discuss consequences of parity breaking on the boundaries of fluid flows.

A34: Modes of Liquid Crystal Lasers

Imperial College London, UK

Rene D. M. Topf

Email: [email protected]

B01: Shape-Designed Triatic and Hexatic Liquid Crystals

compressed to high densities, as revealed through optical microscopy. Entropy maximization at a particular applied 2D osmotic pressure controls the observed selfassembled structures. A given triangle in a triatic LC has three nearest neighbors which point away from this central triangle; at least quasi-long range orientational order is observed whereas the spatial pair correlation function does not show crystalline order. Thus, triatic LCs are distinguishably different than classic 2D hexatic LCs, in which a central particle has six nearest neighbors. Moreover, as the area fraction of triangles is increased, triatic LCs can undergo a local chiral symmetry breaking (L-CSB)

Piotr Surowka Harvard University, USA Email: [email protected]

Thomas G. Mason, Kun Zhao UCLA Department of Physics and Astronomy, UCLA Department of Chemistry and Biochemistry Email: [email protected] Two-dimensional (2D) Brownian systems of microscale lithographic equilateral triangles and rhombs, which effectively have hard interactions between their surfaces, form liquid crystal phases when slowly

in

dumb-bell

40


PROGRAM&ABSTRACT

transition, in which pairs of triangles can be analyzed in terms of right- or left-handed parallelograms. This L-CSB is caused by a competition between accessible translational and rotational microstates in the dense system. By contrast, in a 2D Brownian system of 72-degree rhombs, as the density is increased, we observe a pronounced and

robust hexatic LC phase en route to a rhombic crystal phase that exhibits longrange chiral symmetry breaking in individual crystallites. Overall, systems of hard lithographic colloids provide an interesting experimental platform for exploring the structure and dynamics of classic and novel LC phases.

B02: relationships nematogens

right handed and equal amounts of both types of helix are expected. To date, the Ntb phase has been observed for relatively few liquid crystal dimers and bent core mesogens. Given this very limited data set, the development of the empirical relationships linking molecular structure to the observation of this exciting new phase is very much at an embryonic stage. Here we present a range of new liquid crystal dimers which exhibit the Ntb phase and discuss structureproperty relationships in materials exhibiting this fascinating new phase.

Structure-propoerty in twist-bend

Corrie T Imrie,* Daniel A Paterson, Jordan P Abberley, Rebecca Walker and John MD Storey Department of Chemistry, University of Aberdeen, Meston Building, King’s College, Aberdeen, AB24 3UE, United Kingdom. *E-mail: [email protected] Liquid crystal dimers consist of molecules containing two mesogenic units linked by a flexible spacer and have been a rich source for the discovery of new types of mesophases.[1] Most recently, a nematicnematic transition has been reported for oddmembers of the α,ω-bis-4-(4’cyanobiphenyl)alkanes.[2,3] Cestari et al. assigned the lower temperature nematic as a twist-bend nematic phase, Ntb.[2] This was later confirmed in studies based on freeze fracture transmission electron microscopy.[4,5] In the Ntb phase, the achiral molecules form a helix and the director is titled with respect to the helical axis. The induced twist may be either left or

References [1] C. T. Imrie, P. A. Henderson, Chem. Soc. Rev. 2007, 36, 2096-2124. [2] M.Cestari et al, Phys. Rev. E 84, 031704 (2011). [3] V.P. Panov et al, Phys. Rev. Lett. 105, 167801 (2010). [4] V. Borshch et al, Nature Commun. 4, 2635 (2013). [5] D. Chen et al, Proc. Nat. Acad. Sci. 110, 15931 (2013).

41


B03: Insights into the nematic order of all-aromatic mesogens Francesco Vita1, M. Hegde2, E. T. Samulski3, O. Francescangeli1, T. Dingemans2 1Dipartimento di Scienze e Ingegneria della Materia, dell’Ambiente ed Urbanistica and CNISM, UniversitàPolitecnica della Marche, Ancona, Italy. Email:[email protected] 2Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands. 3Department of Chemistry, University of North Carolina, Chapel Hill, NC, USA. Rod-like all-aromatic mesogens, such as pquinquephenyl (PPPPP) and 2,6-biphenyl naphthalene (PPNPP, Fig. 1), exhibit an enantiotropic high-temperature nematic (N) phase. These rigid prototypical nematogens represent an ideal benchmark for scientists interested in relating theories of nematic order to experiment. However, the literature provides very few structural studies on this class of compounds, mainly due to the challenge of performing measurements at temperatures exceeding 400 °C on highly volatile samples. [1-2] Only recently a molecular dynamics characterization of PPPPP has been reported. [3] Here we discuss the results of a recent X-ray diffraction investigation on this class of nematogens. [4] The diffraction patterns

PROGRAM&ABSTRACT

observed in the aligned N phase differ substantially from those of conventional calamitics, displaying relatively narrow meridional arcs together with an unusually large number of higher-order reflections. We ascribe this effect to the lack of terminal alkyl chains in the molecular structure in conjunction with the formation of cybotactic clusters, i.e. groups of molecules exhibiting short-ranged smectic-like positional order. [5] In particular, the longitudinal correlation length associated to the molecular layering significantly exceeds the typical values found in conventional calamitics, being larger than ~3-5L (with L the molecular length) over most of the N range (Fig. 1). Finally, the orientational order parameter measured from the azimuthal broadening of the wide-angle diffraction features is compared with Maier-Saupe theoretical predictions.

Fig1. PPNPP molecular structure and temperature dependence of the longitudinal correlation length. In the inset, a typical Xray diffraction pattern of the vertically aligned N phase. The present results raise fundamental questions on the primary role of cybotaxis in determining the thermodynamic properties of the N phase. Although conjectured long ago, [6] this topic that has just begun to be 42

EMN MEETING ON LIQUID CRYSTAL elucidated (theoretically experimentally).

[7]

and

1. T. J. Dingemans, L. A. Madsen, N. A. Zafiropoulos, W. B. Lin and E. T. Samulski, Philos. Trans. R. Soc. London, Ser. A 364, 2681 (2006). 2. S. Kuiper, B. Norder, W. Jager, T. J. Dingemans, J. van Turnhout and S. J. Picken, J. Phys. Chem. B 115, 1416 (2011).

PROGRAM&ABSTRACT

4. F. Vita, M. Hegde, G. Portale, W. Bras, C. Ferrero, E. T. Samulski, O. Francescangeli and T. Dingemans, Soft Matter (2016). 5. E. T. Samulski, Liq. Cryst. 37, 669 (2010). 6. G. R. Luckhurst and C. Zannoni, Nature 267, 412 (1977). 7. S. Droulias, A. G. Vanakaras and D. J. Photinos, Liq. Cryst. 37, 969 (2010).

3. Y. Olivier, L. Muccioli and C. Zannoni, ChemPhysChem 15, 1345 (2014).

B04: Roles of wide-band thermochromic liquid crystals in heat transfer measurement of jet impingement coupled with a dimpled surface Koonlaya Kanokjaruvijit1, Martinez-Botas2

Ricardo

1Department of Mechanical Engineering, Naresuan University, Phitsanulok, Thailand 2Department of Mechanical Engineering, Imperial College London, United Kingdom Jet impingement is well-known as a highly effective method in heat augmentation, and has been used in many applications such as gas turbine engine, paper and fabric drying and cooling computer chips. Hence, there have been many attempts to modify the effectiveness of the jet impingement by coupling with different techniques such as channel flow, pin fins, convex and concave surfaces in order to stimulate more

turbulence. As a results, local and overall heat transfer in terms of either heat transfer coefficients or dimensionless number like Nusselt number (Nu = hL/k) must be reported as useful data. Thermochromic liquid crystals have been used widely as a means to measure local temperature through image processing as its high accuracy and flexibility. In this study, an array of inline jets impinging on an array of staggered dimples imprinted on an acrylic substrate was investigated using a transient wide-band liquid crystal technique. Effects of Reynolds number (Re = 5000-11500), jet-to-plate spacing (H/Dj = 28), dimple depth (d/Dd = 0.15, 0.25) and ratio of jet diameter to projected dimple diameter (Dj/Dd) were examined. In addition, crossflow scheme of the exits of spent air after impinging was also investigated by considering 3 schemes: minimum crossflow (spent air freely left), intermediate crossflow (spent air was forced by 2 opposite side walls

43

EMN MEETING ON LIQUID CRYSTAL to leave 2 opposite ways) and maximum crossflow (3 side walls forced spent air to form channel-like crossflow). Moreover, impinging positions were also taken into consideration such as onto dimples and onto flat portions next to dimples. The flat plate impingement was used as a baseline case. The experimental setup is shown in Figure 1 [1]. Oncoming air jets were set at Tb = 50oC. With the initial temperature, Ti, of 21oC, the surface temperature, Ts, was to be measured by liquid crystal color transformation. Onedimensional conduction was assumed with the heat penetration depth as x=2√αt [2]. Benchmark of the dimensionless temperature (θ=(T_s-T_i)/(T_b-T_i )) less than 0.4 [3] was brought into consideration leading to the selection of liquid crystal temperature range of 35-45oC, which gave the dimensionless temperature range of 0.5 to 0.85.

PROGRAM&ABSTRACT

change were calibrated against hue values. Hue value was selected to represent the redgreen-blue signal, because it follows color index criteria [4] as it is (1) simple and monotonic function of liquid crystal temperature and (2) insensitive to illumination strength. A mat heater with variac was placed on top of the liquid crystals coated acrylic substrate, at which 5 thermocouples were embedded inside a dimple, and 4 at the flat portions adjacent to that dimple. At each 0.5oC change, the color transformation from red (35oC) to blue (45oC) was recorded, and 9 data points were collected. A temperature against hue calibration curve was then achieved with the use of statistic tools in order to obtain the correlation. Figure 2 presents an example of such calibration curve of a dimpled plate of d/Dd = 0.15. The curve fitting gave a 6thorder polynomial correlation. The average uncertainty of the calibration was found 3%.

Heated Air Honeycomb sandwiched

Plenum

Drawer used to bypass flow

Orifice plate

before

and Target plate

with Liquid

Fig.2 Liquid crystal calibration curve of a dimpled plate of d/Dd = 0.15 [1].

Fig.1 Experimental setup scheme [1] Before beginning the experiments, the liquid crystal color transformation of temperature

When an experiment was carried out, the video camera started capturing images since the bypass drawer was opened to allow the flow through nozzles. After converting each pixel containing color information to a matrix of temperature, heat transfer

44

EMN MEETING ON LIQUID CRYSTAL coefficients, h, of each pixel was calculated via the transient heat transfer equation in equation (1) 𝜃 = 1 − 𝑒𝑥𝑝(𝛽2 )𝑒𝑟𝑓𝑐(𝛽)

aid of the channel-like crossflow the dimple edge helped promote turbulence by shifting the oncoming jets to impinge near dimple edges; hence the heat transfer was improved.

(1)

ℎ√𝑡 𝑖 where 𝜃 = 𝑇𝑇𝑠−𝑇 and 𝛽 = −𝑇 √𝜌𝑐𝑘 𝑏

PROGRAM&ABSTRACT

𝑖

Then, the heat transfer coefficients were converted to Nusselt numbers through Nu = hDj/k. Note that the heat conductivity, k, belongs to the fluid. The overall uncertainty of Nusselt number was 12% with taking 5% uncertainty of constants into account. Not only can the thermochromic liquid crystals give the heat transfer information, but also detects the trend of the flow near the surface. For instance, in the maximum crossflow scheme, the high heat transfer regime on the downstream half of the dimples and the flat portions next to the dimples was represented by green. Outside these regimes, the liquid crystals became orange showing the lower heat transfer. When compared to the flat plate impingement with the same setup conditions, the heat transfer was improved by maximum of 68%. Contrarily, the minimum crossflow scheme with dimples led to 8% heat transfer reduction compared to the flat plate. The liquid crystals color transformation showed the symmetry of color spectrum inside each dimple and lower heat transfer on the flat portions. Furthermore, the heat transfer enhancement was also found in the intermediate crossflow scheme, at which the high heat transfer regimes were at the vicinity of dimple edges in the direction of crossflow. This could suggest that with the

Considering the effect of dimple depth, better heat transfer improvement was found at the shallower dimples. The spectrum of green was shown inside both d/Dd = 0.15 and 0.25; however, more area of higher heat transfer outside each dimple was present for d/Dd = 0.15. This could explain that the spent air spent more time inside the deeper dimples causing the crossflow to lose more momentum. References [1] Kanokjaruvijit, K., "Heat transfer investigation of jet impingement coupled with dimples," Ph.D. Thesis, Imperial College London, 2004. [2] Schultz, D.L. and Jones, T.V., "Heat transfer measurement in short-duration hypersonic facilities," AGARD, 1973, No.165. [3] Martinez-Botas, R.F., "Annular cascade aerodynamics and heat transfer," D.Phil Thesis, University of Oxford, 1993. [4] Wang, Z., Ireland, P.T., Jones, T.V. and Davenport, R., "A colour image processing system for transient liquid crystal heat transfer experiments," ASME Paper, 93-GT282. [5] Kanokjaruvijit, K. and Martinez-Botas, R.F., "Heat transfer correlations of perpendicularly impinging jets on a

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hemispherical-dimpled surface," International Journal of Heat and Mass

Transfer 53 (2010) 3045-3056.

B05: Magneto-optical properties of LC molecules and their magnetic sensing applications

recently several organic molecules and polymers have been identified with very large Faraday responses. These are usually highly conjugated molecules such as trisubstituted benzene derivatives and conjugated polymers such as polythiophene [1,2].

Thierry Verbiest1, Rick Vleugels1 1Chemistry department, Leuven, Leuven, Belgium

University

of

Email:[email protected] Web site: http://www.verbiestgroup.org Faraday rotation is the rotation of the plane of polarization of light due to magnetically induced circular birefringence. It is a magneto-optical effect that was discovered by Michael Faraday in 1843 and it is now used in a wide range of applications, with optical isolators and magnetic field sensors probably the most important ones. Faraday

We will discuss our recent results on a series of disc-shaped molecules. Thin films of these molecules do not show any appreciable Faraday response when they are in their isotropic liquid state. In the crystalline phase, they show an appreciable Faraday response, but it is only in their discotic liquid crystalline state that they exhibit giant Faraday responses. The magnitude of the response is such that these systems could be used in highly sensitive magnetic field sensors. We hypothesize that aggregation and stacking effects are the origin of the observed Faraday effect.

Verdet constant, B the magnetic field parallel to the propagation of light, and L the path length. The actual origin of the effect is due to a different refractive index for left- and right-hand circularly polarized light, related to the presence of off-diagonal components in the dielectric tensor. Due to the presence of the magnetic field, Faraday rotation is a non-reciprocal effect. Faraday rotation is usually studied in inorganic materials, but

1. Vandendriessche, S., Van Cleuvenbergen, S., Willot, P., Hennrich, G., Srebro, M., V. K. Valev, V., Koeckelberghs, G., Clays, K., Autschbach, J., Verbiest, T. Chemistry of Materials, 25 (7), 1139 (2013)

B06: LC based non-display applications

Michael Wittek

2. Koeckelberghs, G., Vangheluwe, M., Van Doorsselaere, K., Robijns, E., Persoons, A., Verbiest, T., Macromolecular Rapid Communications, 27 (22), 1920 (2006)

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Email: [email protected]

antennas.

Overview of the use of LCs in non-display applications like Liquid Crystal Window Technology (LCT), Smart lighting and Smart

The LC technology applied and the requirements for LC material are discussed.

A35: Heat-driven rotation in isotropiccholesteric coexistence system

tried to induce the unidirectional rotation under the temperature gradient.

Jun Yoshioka, Yuka Tabe

In this study, we made the cholesteric liquid crystalline samples, adding the chiral dopant S811 (Merck) into the nematic liquid crystalline mixture of 5CB and No.270032 (LCC). The phase sequence of this sample

Faculty of Science and Engineering, Waseda University, Tokyo, Japan Email:[email protected] When temperature gradient is applied to the cholesteric (Ch) phase, director rotates unidirectionally. This phenomenon is called Lehmann rotation, and its rotational mechanism is explained by the Leslie’s theory phenomenologically [1]. However, this phenomenon is poorly reproducible; the experimental verification for the Lehmann rotation isn’t enough yet. In this situation, as the reproduction of the Lehmann rotation, in the coexistence state between the isotropic (I) and the Ch phase, it has been reported the unidirectional rotation is induced in the Ch droplets under the temperature gradient (Fig.1) [2][3]. However, while this phenomenon has been reproduced by several research groups, the Lehmann rotation in the bulk cholesteric liquid crystals is hardly reported. This suggests being isotropiccholesteric coexistence state is essentially required to induce the unidirectional rotation in the Ch droplets. To verify this hypothesis, we made the system where isotropic droplets are dispersed in the Ch liquid crystal and

Fig1. Heat-driven rotation in cholesteric isotropicis almost phase was droplet Ch-54̊Cdispersed -I+Ch-58̊Cin -I, which

independent of the concentration of the S811. The sample was sandwiched with two glass plates coated with Al4811 (JSR) for homeotropic anchoring. Heating the sample from the Ch phase, we made the isotropic droplets in the Ch liquid crystal. Observing them with polarized microscopy, we found spiral texture appears as shown in Fig.2. When the temperature gradient was applied to this system, the texture rotates unidirectionally. Here, the rotational direction was opposite from the direction in case of the cholesteric droplets in the

Fig2. Heat-driven rotation in the system where isotropic droplet is dispersed in

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EMN MEETING ON LIQUID CRYSTAL isotropic phase as shown in Fig.1 and 2. To clarify the physical origin of the rotation, we analyzed the flow-field in the system using photo-bleaching method. As a result, we found convective structures are induced in both the cholesteric and the isotropic droplets when the temperature gradient is

PROGRAM&ABSTRACT

applied. Here, in these systems, the direction of the convection was opposite with each other as shown in Fig.3. This result strongly indicates the physical origin of the rotation is derived from the coupling between the helical structure of the Ch liquid crystal and the convective structure induced by the temperature gradient. 1. S. Chandrasekhar, ”Liquid Crystals”(2nd ed.), Cambridge: Cambridge University Press (1992).

Fig.3. Schematic illustration of convective structure under temperature gradient (a) Ch droplet in isotropic phase (b) Isotropic droplet in Ch phase.

2. P. Oswald and A. Dequidt, Phys. Rev. Lett. 100, 217802 (2008). 3. J. Yoshioka, F. Ito, Y. Suzuki, H. Takahashi, H. Takizawa and Y. Tabe, Soft Matter, 10, 5869 (2014)

A36: High Performance p-type Organic Electronic Semiconductors for OPV with a High Temperature Nematic Liquid Crystalline Phase

Web site:

David J. Jones,1 Jegadesan Subbiah,1 Paul Geraghty,1 Mohammed Jemeel2 & Trevor A. Smith2

The Victorian Organic Solar Cell Consortium (VICOSC) has had a twopronged approach to the development of printed OPV. One arm has focused on the scale-up of the printing process, translating laboratory-based processes to commercially relevant systems. This work used commercial materials and off the shelf printers, where available, to develop a materials agnostic printing process.[1] New materials, with suitable properties, can be “dropped-into” the program. A parallel program has developed new materials via a rigorous stage-gated process resulting in high

1 School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria, Australia 3010 2 School of Chemistry, University of Melbourne, Melbourne, Victoria, Australia 3010 Email: [email protected]

http://www.chemistry.unimelb.edu.au/drdavid-jones

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EMN MEETING ON LIQUID CRYSTAL performance n- and p-type organic semiconductors for our use. A key to understanding the development of new materials was the interplay of the chromophore side-chains and their impact on materials performance.

Figure 1. a) Side-chain engineering of known chromophore to form BTR, b) UVVis of BTR, c) DSC curve of BTR, and POM images of BTR films at d) 185 oC, e) 195 oC and f) 197 oC. In recent work we have optimized side-chain placement of a known chromophore, Figure 1, by ensuring the side-chains are regioregular, which should allow the chromophore to lie flat.[2] The unexpected outcome was a nematic liquid crystalline material with significantly improved performance (now 9.6% PCE), excellent charge transport properties, reduced geminate recombination rates and excellent performance with active layers up to 400nm.

Figure 2. Oligomeric series of BTR

A37: Surface and photophysical studies on tricycloquinazoline based discotic liquid crystal and its application as molecular

PROGRAM&ABSTRACT

analogues for examination of structureproperty relationships in OPV. In our desire to better understand the structure property relationships of this class of p-type organic semiconductor we have synthesized a series of analogues through modification of the chromophore length to generate the series oligothiophenes, the monothiophene (BMR), the bisthiophene (BBR), the known terthiophene (BTR), the quaterthiophene (BQR) and the pentathiophene (BPR), Figure 2. BMR, BBR and BPR have clean melting points while BQR, like BTR shows a complicated series of phase transition. I will discuss the examination of chromophore length on the Nematic Liquid Crystalline properties and on materials development and performance resulting in materials with > 9% PCE in OPV. [1] Hwang, K.; Jung, Y.-S.; Heo, Y.-J.; Scholes, F. H.; Watkins, S. E.; Subbiah, J.; Jones, D. J.; Kim, D.-Y.; Vak, D., Adv. Mater. 2015, 27(7), 1241–1247. DOI: 10.1002/adma.201404598 [2] Sun, K.; Xiao, Z.; Lu, S.; Zajaczkowski, W.; Pisula, W.; Hanssen, E.; White, J. M.; Williamson, R. M.; Subbiah, J.; Ouyang, J.; Holmes, A. B.; Wong, W. W.; Jones, D. J., Nat Commun 2015, 6, 6013. DOI: 10.1038/ncomms7013

probe C. Karthik1*, V. Manjuladevi1, R. K. Gupta1

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EMN MEETING ON LIQUID CRYSTAL and Sandeep Kumar2 1Department of Physics, Birla Institute of Technology and Science, Pilani Rajasthan 333031, INDIA 2 Raman Research Institute, Sadashivnagar, Bengaluru, Karnataka, INDIA *E-mail: [email protected]

The study on molecular organization and structure formation at the nanometer length scale is important due to its application in the field of nanoscience and nanotechnology. The optical imagings of liquid crystals (LCs) provide vital physical insights related to molecular organization and the phase transitions. Over the past few years, the field of discotic liquid crystals (DLCs) has grown enormously because of the interesting electro-optical properties exhibited by the molecules. The cores of commonly studied discotic molecules are rich in pi-electrons, and such molecules are known to behave as

A38: Photoinduced reorientation of methyl red doped nematics: What we have learned David Statman Physics Department, Allegheny College, Meadville, PA 16335 USA

PROGRAM&ABSTRACT

p-type semiconductor with appropriate doping. The tricycloquinazoline (TCQ) based molecules are deficient in pi-electrons and are reported to behave as n-doped semiconducting materials. We report the surface behavior and solvatochromatic results of TCQ based molecules with 6 ethelenoxy side chains (AmTCQ) by forming Langmuir monolayer (LM) and Langmuir Blodgett (LB) films at different interfaces. The TCQ monolayer exhibits gas, low density liquid (L1) and high density liquid (L2) phases. The LB films of the AmTCQ molecules were deposited on solid substrates at different surface pressure and the nanostructures were studied using the atomic force microscopy (AFM) technique. Using infrared spectroscopy, it has been found that the transition dipole moment of TCQ molecule is planar to the surface. Solvatochromatic studies on AmTCQ molecule has been done without the aid of any dye. We have doped AmTCQ molecule into structurally similar DLC, hexa-alkoxy triphenylene (HAT5) molecule and have done fluorescence imaging. The fluorescence microscope images reveal the potential of AmTCQ molecules as a probe to study the optical properties of another DLC system.

Email: [email protected] It has long been known that photoinduced nematic director reorientation enhanced by the presence of dye is significantly greater when that dye is the azobenzene compound methyl red. It has been determined that the most significant contribution by methyl red is a surface effect involving charged species.

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In this talk, I will present our most recent results in which we compared the photoinduced reorientation of the easy axis on rubbed polyimide surfaces for the nematic

E7 doped with three isomers of methyl red; ortho, meta, and para. These results clarify the process by which photoinduced reorientation occurs.

A39: Resonant soft X-ray scattering study of helical structures in liquid crystals - helical nanofilament B4 and twist bend nematic phase

(e.g. B7 phase [1], SmAPFmod phase[2]). Typically hard X-rays are used due to its high penetrating power. However, in the hard Xray regime, the scattering contrast of some LC nanostructures can be extremely low due to their weak electron density modulation. Here we show that by utilizing the coupling between x-ray polarization and molecular bond orientation, it is possible to use polarized soft x-rays at carbon resonant edge to probe the helical pitch in, for example, the helical nanofilament B4 phase [3], and the newly discovered twist bend nematic phase [4,5], which are typically not accessible by conventional non-resonant x-ray scattering techniques. The in-situ temperature dependent studies of the helical pitch reveal new insights on both structure and the nature of its phase transition. These work indicate the great potential of resonant soft x-ray scattering in investigating liquid crystal phases, including twist grain boundary phase, blue phases and perhaps the polarization modulated SmAPF phase [2].

Chenhui Zhu1, Anthony Young1, Cheng Wang1, Alexander Hexemer1, Quan Li2, Oleg Lavrentovich2, David Walba3, Michael Tuchband4, Min Shuai4, Noel Clark4 1 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA 2 Liquid Crystal Institute, and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242 3 Dept. of Chemistry and Biochemistry, and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO, 80309 4 Dept. of Physics, and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO, 80309 Email: [email protected] Liquid crystals (LCs) form many interesting nano-scale structures, many of which can be probed with X-ray scattering techniques, such as layering in smectics, hexagonal packing of cylinders in discotics, and layer modulation/undulation in bent-core smectics

[1] D.A. Coleman, et al. Science, 301, 5637 (2003). [2] C. Zhu, et al. J. Am. Chem. Soc. 134, 9681 (2012). [3] C. Zhu, et al. Nano. Lett. 15, 3420 (2015). [4] D. Chen, et al. PNAS, DOI 1314654110

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(2015).

[5] V. Borshch, et al. Nat. Comm., 4, 2635 (2015).

A40: Unique behavior of lyotropic liquid crystals with anionic hybrid surfactants having oxyethylated alkyl tail

seconds. To investigate effects of the temperature-sensitive oxyethylene units on the hydrophilic/lipophilic balance (HLB) of the CB-B2ES bilayers, a fluorescence probe

Masanobu Sagisaka1, Yayoi Fujita1, Yusuke Nakanishi1, Hisayuki Takahashi1, Narumi Tsuyoshi1, Craig James1, Atsushi Yoshizawa1, Frédéric Guittard2, Julian Eastoe3 1Graduate school of Science and Technology, Hirosaki University, Hirosaki, Aomori, JAPAN Email:[email protected], web site: http://www.st.hirosaki-u.ac.jp/~lclab/ 2Univ. Nice Sophia-Antipolis, CNRS, Equipe Surfaces et Interfaces 3School of Chemistry, University of Bristol, Bristol, UK This study reports unusual behaviour of aqueous phase lamellar aggregates with a new class of hybrid surfactant, CB-B2ES having mesogenic units (6-[4-(4cyanophenyl)phenyloxy]hexyl) and temperature-sensitive oxyethylated (butoxyethoxyethyl) tails. These tails are poorly miscible and likely to micro-segregate if the surfactant molecules assemble. Lamellar aggregates appear at CB-B2ES concentrations higher than 5 wt% and were found to undergo repeat formation/breakdown periodically at 30 ˚C, with an average domain lifetime of ~ 10

1-pyrene-carboxaldehide (PyCHO) was solubilized in the mixtures to sense the micro-environmental polarities. Fluorimetric measurements (Fig.1) suggested that the polarity of CB-B2ES bilayers is very similar as for the non-ethoxylated CB-B2ES analogue at high temperatures (≥ 65 ºC). However, for CB-B2ES polarity increased with decreasing temperature, in contrast to the small decrease in polarity observed for analogous non-ethoxylated bilayers. This is consistent with increased hydration of the oxyethylene units in CB-B2ES bilayers at low temperatures. The periodic formation/breakdown and the coolinginduced hydrophilicity of the CB-B2ES lamellar aggregates, did not appear in the non-hybrid and/or non-ethoxylated surfactant systems. Therefore, the combination of two unsymmetrical tails, one containing oxyethylene units and the other

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EMN MEETING ON LIQUID CRYSTAL cyanobiphenyl terminal tips, must play an important role promote this unusual behaviour.

PROGRAM&ABSTRACT

a function of temperature. As a comparison, temperature dependencies of I1/I3 for pyrene solubilized in 10 wt% 8F-B2ES and 8FDeS/water mixtures are also shown.

Fig1. Changes in fluorescence peak maximum wavelength of PyCHO in water containing 5 wt% CB-8FS and CB-B2ES as

A41: Structure and transport of selfassembled colloidal particles in electrohydrodynamic convection of nematic liquid crystals Yuji Sasaki1 1 Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan Email:[email protected] The dispersion of the surface-modified particles in nematic liquid crystals (NLCs) exhibits unique physical properties compared to the isotropic counterpart. As is well known, when a spherical particle with perpendicular anchoring is immersed in a uniform director field, the asymmetric director distortion around particle can be approximated as an elastic dipole due to the appearance of a hyperbolic point defect. Recently, an unconventional electrophoretic motion of the elastic dipole is found under AC electric fields. [1] This liquid-crystalenabled electrophoresis (LCEEP) is caused by unbalancing AC electro-osmotic flow around the particle. [2] Other experiments demonstrate, for example, that the phenomenon can be used for the transport of an immiscible liquid droplet and a swarming

motion of particles by photoactivated surface. [3] When NLCs possess negative dielectric anisotropy, the elastic dipoles move in the rubbing direction of the planar cell, i.e., the direction is normal to the electric field. On the other hand, further increase of the electric field induces the electro-hydrodynamic convection whose microscopic texture is known as the Williams domains. [4] Here we present the results of the motion of elastic dipoles in the EHC region. We found that the LCEEP plays an important role for the dynamics besides the EHC flow. [5] Although the neighboring convective roll has a counter-rotating structure, single particles show a directed undulating motion by the persistent effect of the LCEEP. In particular, self-assembled dipolar colloids show a caterpillar-like motion as shown in Figure 1, which also enables cargo transportation of an oil droplet and a glass rod particle by attaching them with the elastic energy. This is a unique system which provides a regular motion in the direction of the cell thickness. Thus, we tried to characterize the undulating behavior not only by polarizing microscopy [6] but also by confocal laser-scanning microscopy to visualize the cross-sectional

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EMN MEETING ON LIQUID CRYSTAL appearance. [7]

PROGRAM&ABSTRACT

3. S. Hernàndez-Navarro, P. Tierno, J. Ignés-Mullol, and F. Sagués, Soft Matter 9, 7999 (2013). S. Hernàndez-Navarro, P. Tierno, J. A. Farrera, J. Ignés-Mullol, and F. Sagués, Angew. Chem., Int. Ed. 53, 10696 (2014). 4. R. Williams, J. Chem. Phys.39, 384 (1963).

Fig1. An undulating motion of a selfassembled colloidal chain in EHC. 1. O. D. Lavrentovich, I. Lazo, O. P. Pishnyak, Nature 467, 947 (2010). O. D. Lavrentovich, Soft Matter, 10, 1264 (2014). 2. I. Lazo, C. Peng, J. Xiang, S. V. Shiyanovskii, and O. D. Lavrentovich, Nat. Commun. 5 (2014).

5. Y. Sasaki, Y. Takikawa, V. S. R. Jampani, H. Hoshikawa, T. Seto, C. Bahr, S. Herminghaus, Y. Hidaka, and H. Orihara, Soft Matter 10, 8813 (2014). 6. Y. Nishioka, F. Kobayashi, N. Sakurai, Y. Sasaki, and H. Orihara, Liq. Cryst. in press. 7. Y. Sasaki, H. Hoshikawa, T. Seto, F. Kobayashi, V. S. R. Jampani, S. Herminghaus, C. Bahr, and H. Orihara, Langmuir 31, 3815 (2015)

. A42: Self-organized structures of star-like concave colloids in 2D Kun Zhao Tianjin University, China Email: [email protected] Concave-shaped colloids have a great potential in making metamaterial with specific structures including chiral and/or liquid crystalline structures. In this talk, I will show phase behavior of two example

concave colloids: square crosses and tri-stars. In a 2D square cross system, a sequence of isotropic phase – rhombic crystal – chiral square crystal is observed, contrary to the sequence of isotropic phase – nematic phase – D4 liquid crystalline phase found in a system of slender Onsager crosses in 3D. In a 2D tri-star system, an alternating strip crystal phase at higher surface fractions is formed. Our findings imply that a variety of structures can be formed through selforganization by selecting the shape of constituent concave particles and the dimensionality of the system.

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EMN MEETING ON LIQUID CRYSTAL A43: Stratified Liquid Crystal Structures to Enable Practical Electro-Optic Devices in Terahertz Regime Robert Lindquist1, 2, Abubaker Tareki1, Daniele Lo Forti1 1 Dept. of Electrical and Computer Engineering, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA 2 Center for Applied Optics, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA Email: [email protected], Electro-optic (EO) modulation of the amplitude and phase of electromagnetic waves using liquid crystals is commonplace in the optical and infrared regions. This effort has led to commercially available components used in spectral filtering, polarization management, beam steering, transmitters, displays, etc. However, electro-optic techniques have had limited success in the THz region due to several practical design challenges. The primary barrier for components is the long interaction lengths required to modulate a THz wave. Since the EO modulation depth is directly proportional to the multiplication of the change of permittivity and the ratio of

PROGRAM&ABSTRACT

interaction length over wavelength, THz systems with wavelengths ranging from 150 ome this barrier, longitudinal and transverse stratified sub-wavelength liquid crystal structures have been engineered and fabricated. The longitudinal component is shown in figure 1. The stratified structures introduce the challenge in the selection and design of the electrodes. The material properties of a conductive material in the THz region are significantly different than the infrared and optical region leading to large impedance mismatch at dielectric/electrode interfaces. Both simulation and experimental data will be presented.

Figure 1. Longitudinal stratified liquid crystal modulator in the terahertz regime.

A44: Light scattering device using dyedoped (polymer/liquid crystal) composite film

1 Department of Electrical and Electronics Engineering, Kagoshima University, Korimoto 1, Kagoshima-shi 890 Japan

Seiji Fukushima1, Hirotsugu Kikuchi2

Email:[email protected], web site: http://www.eee.kagoshima-

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EMN MEETING ON LIQUID CRYSTAL u.ac.jp/~fuku-lab/ 2Insitute for Materials Chemistry and Engineering, Kyushu University, Kasuga-shi, Fukuoka 816-8580 Japan In optical fiber communication systems, a lot of variable optical attenuators (VOAs) have been employed for some reasons such as light power equalization and optical surge reduction [1]. These devices must function at infrared wavelength of 1.3must be polarization insensitive. One of the solutions is a (polymer/liquid crystal) composite film (PLCF), which was originally developed as a gas and liquid permeable material [2]. Moreover, the PLCF was experimentally proven to have a good extinction at visible wavelength [3] and at infrared wavelengths especially when dichroic dyes are doped [4]. This paper reviews a structure, principle, and experimental results of the dye-doped PLCFs. The PLCF is sandwiched between two glass substrates with transparent electrode coatings [2]-[4]. Without any external voltages, nematic LC molecules are enclosed and aligned by surrounding polymer network, which results in a light scattering or opaque mode. When we apply >10 V to the PLCF, the nematic LC molecules are aligned in parallel to the electric field and the device becomes transparent. Even without dye doping, the PLCF exhibits excellent extinction at visible wavelengths. We can color the device at the opaque status by dichroic dye selection and can develop a white device by doping infrared-absorption dyes. For example, an anthraquinone derivative doped device looks pink. In

PROGRAM&ABSTRACT

contrast, a metal complex dye doped device has an excellent extinction of 17.1 dB at 1.523 m. Extinction dependence on wavelength, -4, suggests the extinction mechanism occurs due to Rayleigh scattering. It was experimentally proved that an aperture structure improves the extinction ratio when the sample is applied to the VOA. A polarization dependent loss (PDL) is one of the most important performances at optical fiber communication systems. Figure 1 shows transmission dependence on the applied voltage, where the data were obtained for the linear polarization with 8 deviation is lower than 0.1 dB for the LC voltage VLC of 20 V or higher. The worst deviation we measured was 7.6% or 0.32 dB, which was observed at 8V.

This paper is concluded as follows: The dyedoped PLCF is PDL-free so that it can be applied to the VOA at the infrared wavelengths. Moreover, it is advantageous from the view point of back light efficiency since there are no polarization losses when it is applied to a display.

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EMN MEETING ON LIQUID CRYSTAL 1. S. Fukushima, A. Ohki, S. Kanazawa, and A. Okada, Proc. of 21st Annual Meet. of IEEE Lasers and Electro-Optics Society, Newport Beach, CA, USA, 656-657 (2008). 2. T. Kajiyama, Y. Nagata, E. Maemura, and M. Takayanagi, Chem. Lett. 679-682 (1979). 3. S. Noguchi, H. Higuchi, S. Fukushima, A. Okada, and H. Kikuchi, Proc. of Kyushu-

A45: Polymer-enhanced electro-optics in various types of LCs Alexander Lorenz1, Larissa Braun2, Valeria Kolosova2 1Department of Chemistry, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany Email: [email protected], web site: http://www.uni-paderborn.de/person/328/ 2Stranski-Laboratory, TU Berlin, Str. des 17. Juni 124, 10623 Berlin, Germany Polymer enhanced liquid crystals with enhanced electro-optical properties [1-4] were obtained by generating polymer networks within a thin (4 – 6 µm) layer of a host liquid crystal. The host LC was doped with up to 10% of a mixture that contained both non-mesogenic and mesogenic acrylates and a small amount of photoinitiator. The doped LC was filled in LC test cells with planar electrodes and insitu cured. Both chiral and non-chiral variants of the host LCs were studied. In the

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Seibu Busan-Gyeongnam Joint Symp. on High Polymers (14th) and Fibers (12th), Kagoshima, Japan, 84, paper PB074 (2009). 4. S. Fukushima, K. Yoshinaga, T. Hachino, Y. Igarashi, S. Noguchi, H. Higuchi, and H. Kikuchi, CD-ROM of Asia Communications and Photonics Conference (ACP 2102), Guangzhou, China, paper AS4B.5 (2012).

chiral LC, different driving modes were studied (blue phase mode, uniformly standing/lying helix mode, focal conic mode) with focus on optical phase modulation1-2. Both blue phase mode and uniformly phase modulation. The sum of the response times ton+toff = 0.2 ms was detected in the blue phase mode. The sum of the response times (3.7 ms) was one order of magnitude higher in the uniformly standing helix mode. Both blue phase mode and uniformly standing helix mode required high electrical driving field strengths ED= 8 V/µm to yield ve test cells. A polymer enhanced nematic LC (without presence of chiral dopant) was studied in transparent test cells. Surprisingly, relatively fast electro-optic responses ton+toff =2.4 ms were detected. A comparison of the response times and the required electrical field shown (Fig. 1). The required electrical field strengths (ED = 3.8 V/µm) were much lower in the polymer enhanced nematic LC, which is desirable in electro-optical modulators.

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References 1. R. M. Hyman, A. Lorenz, S. M. Morris, and T. D. Wilkinson, Applied Optics 53, 6925 (2014). 2. R. M. Hyman, A. Lorenz, T. D. Wilkinson, Liquid Crystals, published online (2015), DOI: 10.1080/02678292.2015.1061146.

Fig1. Sums of response times and driving electric field strength ED in various polymer enhanced liquid crystals, based on the same host LC.

A46: Study on the electro-optical properties of PDLC films (Smart glass) using Diethylenetriamine (DETA) hardener Mujtaba Ellahi*1 and M.Y.Rafique2 H.E.J. Research Institute of Chemistry, International Centre for Chemical and Biological Sciences (ICCBS), University of Karachi, 75270 Karachi, Pakistan1. Department of Physics, Comsats Institute of Information Technology, Lahore 54000.Pakistan2. *Corresponding author. Mujtaba Ellahi. ([email protected].); Tel. & Fax: 0092-111-222-292, Ext-196, 0092-

3. A. Lorenz, D. J. Gardiner, S. M. Morris, F. Castles, M. M. Qasim, S. S. Choi, W.-S. Kim, H. J. Coles, T. D. Wilkinson, Appl. Phys. Lett. 104, 071102 (2014). 4. J. Yuan, G. Tan, D. Xu, F. Peng, A. Lorenz, S.-T. Wu, Optical Materials Express 5, 1341 (2015).

3332991136 Keywords: polymer dispersed liquid crystal, smart glass, epoxy resins, Diethylenetriamine, electrooptical properties (E-O). The author’s results obtained today and in previous works are summarized. The present work has been performed to investigate the effects of the structure and electro-optical (EO) properties of epoxy resin based polymer dispersed liquid crystal (PDLC) films smart glass using Diethylenetriamine (DETA) as hardener with 4-cyano-4ʹ-penthylbiphenyl (5CB) liquid crystal. In this study we have been prepared PDLC films by the thermal polymerization-induced phase separation (PIPS) method, with a thickness of 10.0 ±1.0

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PROGRAM&ABSTRACT

μm controlled by a polyethylene terephathalate (PET) spacer and optimal preparation condition were 25% and 30% 5CB LC respectively, with a curing time 7 hours at 70°c temperature. The morphology of phase separation, dispersed states of the PDLC films, and the microstructure of the polymer matrix with 5CB LC contents were characterized under scanning electron microscopy (SEM). In this study, the effects of DETA as a hardener on the curing process and the E-O properties of PDLC films were studied using liquid crystal device (LCD) parameters tester with a halogen tungsten lamp as an incident light source and the incident wavelength (λ) through the samples was fixed with the wavelength (λ) filter

(632.8nm). In addition, PDLC films were prepared with different amounts of DETA to investigate the best ratio of the hardener. Results showed that when the weight ratio of LC 5CB was 30% in PDLC and 2% of DETA hardener, then dispersed state of LC were well proportioned, and the variation of transmittance reached the highest value. The optical characterization of the PDLC film indicates an improvement of the angular transmission of visible light. Meanwhile, it is examined that by adjusting the mol% of hardener and LC 5CB content possesses good E-O properties with a low energy efficient method for preparing PDLC smart glass display technology.

A47: Electrically controllable multicolor cholesteric laser

Sciences of Tunis, University of Tunis El Manar, El Manar 2092 Tunis, Tunisia

M. P. De Santo1,2, Gia Petriashvili3, Ridha Hamdi4, Lotfi Saadaoui4 and Riccardo Barberi1,2

The Cholesteric Liquid Crystal (CLC) phase is a nematic phase with a self-organized periodical helical arrangement that acts as a one dimensional periodic structure. Due to this periodicity, visible light impinging on a cholesteric structure experiences a Bragg type reflection giving rise to a Photonic Band Gap (PBG). CLCs can change their PBG position by means of external or internal factors (electric and electromagnetic fields, temperature, local order). Due to this property, CLCs are of practical interest for various applications. In particular, lasing from dye doped - CLC was obtained for the first time by Ilchishin et al. in 1980 [1] and, many years later, lasing in several different LC systems has been widely investigated.

1Department of Physics, University of Calabria, Ponte P. Bucci 31C, 87036 Rende (CS), Italy and CNR-Nanotec UOS of Cosenza, c/o University of Calabria, 87036 Rende (CS), Italy Email: [email protected], web site: http://www.fis.unical.it 2Institute of Cybernetics of the Georgian Technical University, Euli str. 5, 0175, Tbilisi, Georgia 3Physics Laboratory of Soft Matter and Electromagnetic Modelling, Faculty of

Here, we present a strategy to obtain

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EMN MEETING ON LIQUID CRYSTAL multicolored lasing. The novelty of this system relies on the peculiar cell design. We have used a four layers cell, one layer containing the photoluminescent dye doped solution and the other three layers containing a cholesteric liquid crystals mixtures that act as mirrors. In ref [2,3] we have shown that lasing in a three layered structure, two cholesteric mixtures sandwiching a dye and glycerol mixture, can be considered as a defect mode type and multimode lasing within the photonic band gap with several emission peaks can be obtained. To achieve single mode lasing, two CLCs with different pitches can be used, obtaining laser emission at the wavelength in which the two PBGs overlap. In the present case, dual mode lasing is obtained, the first laser line at a wavelength in which the first and second cholesteric PBGs overlapped and the second laser line at the wavelength in which the second and third cholesteric PBGs overlapped (figure). Additionally, applying an electric field one of the two laser lines can be switched off [4]. Lasers that emit at several wavelengths, as Krypton and Argon lasers, are extremely useful in scientific research and for many applications in medicine and in optics.

PROGRAM&ABSTRACT

Figure. PBGs of the cholesteric layers and laser lines intensities. The shorter wavelength laser peaks on the violet line corresponds to the pumping light source, the other two laser lines with larger intensities correspond to the emission from the four layers sample cell. 1. I. P. Ilchishin, E. A. Tikhonov, V. G. Tishchenko, and M. T. Shpak, JETP Lett. 32, 24–27 (1980). 2. G. Petriashvili, M. A. Matranga, M. P. De Santo, G. Chilaya, and R. Barberi, Opt. Express 17 (6), 4553–4558 (2009). 3. G. Chilaya, A. Chanishvili, G. Petriashvili, R. Barberi, G. Cipparrone, A. Mazzulla, M. P. De Santo, H. Sellame and M. A. Matranga, Mol. Cryst. Liq. Cryst. 495 (1), 97–105 (2008). 4. L. Saadaoui, G. Petriashvili, M. P. De Santo, R. Hamdi, T. Othman, R. Barberi, Opt. Express 23 (17), 22922-22927 (2015).

A48: Controlling light in the built environment using liquid crystals

Michael Debije

60

EMN MEETING ON LIQUID CRYSTAL Dept. Chem. Engin. & Chemistry, Group of Functional Organic Materials and Devices, Eindhoven University of Technology, The Netherlands Email: [email protected] Buildings use 40% of all our energy in the western world. However, incorporating energy control/generation systems in the built environment is a challenge as they must be able to cover huge areas while remaining aesthetically pleasing. In this presentation, I will give examples of how we are using liquid crystals in the urban setting to address these challenges. To maintain interior temperatures in a room space, it is common to employ blinds, curtains, or more recent devices such as polymer dispersed liquid crystals or electrochromic materials. The problem with these solutions are that they all interfere with incident visible light, either by blocking the light creating a demand for artificial lighting or scattering it, which disrupts views of the external environment. In our work we utilize cholesteric liquid crystals with an adjustable, extended reflective bandwidth to selectively and reversibly control infrared influx while maintaining optical transparency to visible light, thereby allowing savings in both

A49: Polar POLICRYPS Photonic Structures: Features and Possibilities Roberto Caputo1,2, Domenico Alj1, Sathyanarayana Paladugu3, Giovanni 3,4 1 Volpe and Cesare Umeton

PROGRAM&ABSTRACT

cooling costs without having to compensate by the use of artificial lighting. Another challenge in the city is generation of electricity from sunlight. Standard photovoltaic (PV) panels have several limitations which make deployment in urban settings problematic: they require more direct sunlight and are quite negatively influenced by shading or fouling, and are often visually unappealing. A device that could be employed where PVs are inappropriate is the luminescent solar concentrator, which is a colorful fluorescent dye-embedded polymer plate that absorbs sunlight, re-emitting the light at longer wavelengths, a significant fraction of which is trapped in the high refractive index plate and directed to the edges where thin PV cells are placed to convert the light into electricity. The LSC generally performs equally well in direct and diffuse light conditions and is relatively robust. However, LSC performance has been limited by excessive light losses: this presentation will describe how we use liquid crystals to align fluorophores and take advantage of their anisotropy of emission to direct light more effectively, and how cholesteric liquid crystals can be used to better manage the emitted light to improve the fraction of photons leaving the edge of the device.

1 Department of Physics and CNRNANOTEC, 87036 Arcavacata di Rende (CS), Italy 2 Laboratoire de Nanotechnologie et d’Instrumentation Optique, ICD CNRS UMR n°6281, Universitéde Technologie de Troyes,

61

EMN MEETING ON LIQUID CRYSTAL CS 42060, 10004 Troyes, France

PROGRAM&ABSTRACT

rings are the aligned LC regions.

3 Soft Matter Lab, Department of Physics, Bilkent University, Ankara 06800, Turkey 4 UNAM-National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey Email: [email protected] The fabrication of POLICRYPS (POLymerLiquid-CRYstals-Polymer-Slices) structures with polar symmetry has been obtained as a natural evolution of the standard technique, which enables, the realization of highly efficient, switchable, planar diffraction gratings [1]. Performances exhibited in the Cartesian geometry are extended to the polar one by exploiting the spherical aberration produced by simple optical elements [2]. Devices containing birefringent materials may locally shape the polarization state of a light beam. In this contribution, we present one of such devices that enables converting a uniformly circularly polarized beam into a cylindrical vector beam (CVB) [3]. Fig1. Micrographs of a POLICRYPS polshape with radial symmetry. All the images are acquired with a polarized optical microscope between crossed polarizers and represent the same sample but at different magnifications. The yellow/light grey rings are the polymeric circles and the dark grey

A50: Cholesteric liquid-crystal Bragg onion lasers

Figure 1 shows some micrographs of the obtained structure representing the same sample, but at different magnifications, as observed at the polarized optical microscope between crossed polarizers. The Maltese cross confirms the expected radial alignment of the LC director between the polymeric rings of the structure. 1. L. De Sio, A. Veltri, R. Caputo, A. De Luca, G. Strangi, R. Bartolino, and C. Umeton, Liq. Cryst. Rev. 1, 2 (2013). 2. D. Alj, R. Caputo, and C. Umeton, Opt. Lett. 39, 6201 (2014). 3. D. Alj, S. Paladugu, G. Volpe, R. Caputo and C. Umeton, App. Phys. Lett. 107, 201101 (2015)

Matjaž Humar1,2 1 Wellman Center for Photomedicine,

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EMN MEETING ON LIQUID CRYSTAL Harvard Medical School, Massachusetts General Hospital, Cambridge, Massachusetts, USA 2 Condensed Matter Department, J. Stefan Institute, Ljubljana, Slovenia Email: [email protected], http://www.matjazhumar.com

web

site:

Dye doped cholesteric liquid crystals (CLCs) are well known for their use as laser sources [1]. Their periodic structure acts as a Bragg mirror making an optical cavity, while the fluorescent dye provides gain. The advantage of CLCs compared to solid state Bragg structures is their ability to self-assemble to complex structures in 3D without the need of slow and costly microfabrication methods. The second advantage is their sensitivity to external stimuli which enables large tunability and possibility to use them as sensors. One of the interesting geometry for CLC lasers is inside a droplet [2]. By mixing of a small quantity of dye doped CLC with a fluid that produces planar anchoring, thousands of spherulite type droplets can be produced [3]. The droplets have onion structure (Figure 1a and b) that confines light to the center of the droplet by Bragg reflection from the cholesteric layers. By illuminating a droplet with a pulsed laser, lasing from the center of the droplet can be achieved (Figure 1c and c). The laser emits light uniformly in all directions in space, acting as an isotropic point source of coherent light, a 3D laser. By changing the temperature, the lasing wavelength can be tuned up to 50 nm. By using a lower refractive index external liquid,

PROGRAM&ABSTRACT

also whispering-gallery modes [4] can be lasing at the same time as the Bragg lasing. Further, by choosing a longer pitch CLC, which has the optical bandgap in the infrared, the Bragg condition for reflection of visible light is at an angle smaller than 90 degrees. This causes a lasing mode that circulates inside the droplet and it is visible as a ring of light. The droplets can be also made from polimerizable CLCs. This enables the production of solid laser particles, which are mechanically more stable than droplets, as well show more stable lasing and are not sensitive to external stimuli. In conclusion, the CLC droplet lasers are one of the easiest lasers to make in general. It is only necessary to mix four components that are commercially available: liquid crystal, chiral dopant, laser dye and external liquid. The CLC droplet lasers could be used as a building blocks for many applications like integrated photonics, telecommunication, holography, imaging and sensing.

Fig1. a) CLC droplet in glycerol, b) structure of such droplet, c) lasing from the center of a CLC droplet and d) spectrum emitted by the 3D laser. 1. H. Coles, and S. Morris, Nature Photon. 4, 676-685 (2010). 2. M. Humar and I. Muševič, Opt. Express 18, 26995-27003 (2010). 3. J. Bezić, and S. Žumer, Liq. Cryst. 11, 593-619 (1992). 63

EMN MEETING ON LIQUID CRYSTAL 4.

M. Humar, M. Ravnik, S. Pajk, I.

PROGRAM&ABSTRACT

Muševič, Nature Photon. 3, 595-600 (2009).

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PROGRAM&ABSTRACT

Author Index *P – page in program A – page in abstract

Alexander Lorenz

P11, A60

Maria Penelope De Santo

P11, A62

Armand Soldera

P7, A25

Masanobu Sagisaka

P10, A54

Aziz Ghoufi

P8, A36

Matjaz Humar

P11, A65

C. Karthik

P10, A52

Michael Debije

P11, A63

Chenhui Zhu

P10, A53

Michael Wittek

P10, A48

Corrie Imrie

P9, A43

David Jones

P10, A50

Mujtaba Ellahi

P11, A61

P6, A13

Piotr Surowka

P9, A41

David Statman

P10, A53

Raisa Talroze

P8, A29

Fang-Cheng Lin

P7, A17

Regis Guegan

P6, A12

Francesco Vita

P9, A43

Rene D. M. Topf

P9, A42

David M. Walba

Miguel Mora-Gonzalez

P7, A23

65


PROGRAM&ABSTRACT

Harald Pleiner

P7, A24

Robert Lindquist

Hiroki Iwanaga

P7, A19

Robert Repnik

P6, A15

Jiming Bao

P7, A16

Roberto Caputo

P11, A64

Jiyu Fang

P7, A21

Rolfe.G. Petschek

P9, A39

Jonathan P. Hill

P8, A38

S. Holger Eichhorn

P8, A37

Joseph Reczek

P9, A39

Sachiko T. Nakagawa

P9, A40

Jun Yoshioka

P10, A49

Seiji Fukushima

P10, A57

P11, A58

Keiko. M. Aoki

P7, A26

Shusuke Yoshihara

P8, A30

Koonlaya Kanokjaruvijit

P9, A45

Sylvan Brechet

P8, A36

Kuang-Wu Lee

P7, A28

Takeaki Araki

P8, A32

Thierry Verbiest

P9, A47

Kun Zhao

P10, A57

Lei Z. Cheng

P7, A26

Thomas G. Mason

P9, A42

Lia Q. Amaral

P7, A22

Vasily Oganesyan

P8, A33

66


PROGRAM&ABSTRACT

Lui Lam

P6, A12

William S. Oates

P8, A28

Luka Mesarec

P9, A41

Wojciech Gozdz

P8, A35

Malik Qasim

P7, A20

Yuehang Xu

P8, A32

Yuji Sasaki

P10, A55

67