Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 33

Full-Text Articles in Physics

Imprinting The Quasi Bookshelf Texture Of A Ferroelectric Liquid Crystal Into Nano-Scaled Polymer Fibrils, S. H. Kim, S. Suresh, Liang-Chy Chien Oct 2013

Imprinting The Quasi Bookshelf Texture Of A Ferroelectric Liquid Crystal Into Nano-Scaled Polymer Fibrils, S. H. Kim, S. Suresh, Liang-Chy Chien

Liang-Chy Chien

Polymer-stabilized ferroelectric liquid crystals (PSFLCs) are made by photopolymerizing 3% reactive mesogenic monomer on a quasi bookshelf texture of a ferroelectric liquid crystal (FLC). We observe the formation of nano-scaled polymer fibrils templated by the two dimensionally ordered host. The polymer fibrils capture the orientation of the host with thin polymer fibrils interweaving the smectic layers. The SEM study highlights the difference in morphology of the polymer fibrils depending on polymerization conditions; that is, polymerizing with or without the presence of an electric field. The polymer networks suppress the cone of rotation of FLC and thus, facilitate the switching and ...


Three-Dimensional Orientational Order In The Bulk And On The Surface Of Polymer Films And Its Effect On Liquid-Crystal Alignment, O. V. Yaroshchuk, Yu. Zakrevskyy, Satyendra Kumar, J. Kelly, Liang-Chy Chien, J. Lindau Oct 2013

Three-Dimensional Orientational Order In The Bulk And On The Surface Of Polymer Films And Its Effect On Liquid-Crystal Alignment, O. V. Yaroshchuk, Yu. Zakrevskyy, Satyendra Kumar, J. Kelly, Liang-Chy Chien, J. Lindau

Liang-Chy Chien

The correlation between orientation ordering of polymer chains in the bulk of polymer film and at the polymer-liquid-crystal (LC) interface has been studied to determine it's role in LC alignment. The bulk and surface ordering of polymer were investigated by null ellipsometry and x-ray reflectivity, respectively. Two kinds of liquid-crystalline polymers were used; side-chain azopolymers with azochromophores containing hydrophobic OC(4)H(9) alkyl chain (P1) and strongly polar NO(2) group (P2) as the end substituents. The uniaxial tilt orientation of azochromophores in the films of both polymers was induced by the oblique irradiation with unpolarized UV light ...


Optical Studies Of The Liquid Crystal B2 Phase Formed By Banana-Shaped Molecules, D. A. Olson, M. Veum, A. Cady, M. V. D'Agostino, P. M. Johnson, H. T. Nguyen, Liang-Chy Chien, C. C. Huang Oct 2013

Optical Studies Of The Liquid Crystal B2 Phase Formed By Banana-Shaped Molecules, D. A. Olson, M. Veum, A. Cady, M. V. D'Agostino, P. M. Johnson, H. T. Nguyen, Liang-Chy Chien, C. C. Huang

Liang-Chy Chien

Null-transmission ellipsometry and depolarized light microscopy have been performed on free-standing films of three achiral banana-shaped compounds in the B2 phase. Our results support a two-layer unit cell previously proposed to explain the observed antiferroelectricity in thin films and bulk samples. We have studied thicker films than previously reported and have found no deviations in the film structure from the earlier findings. Moreover, we can determine the layer spacing, the molecular tilt from the layer normal, and the three principal indices of refraction in the molecular reference frame.


Light Induced Structures In Liquid Crystalline Side-Chain Polymers With Azobenzene Functional Groups, O. Yaroschuk, Tatiana Sergan, J. Lindau, S. Lee, J. Kelly, Liang-Chy Chien Oct 2013

Light Induced Structures In Liquid Crystalline Side-Chain Polymers With Azobenzene Functional Groups, O. Yaroschuk, Tatiana Sergan, J. Lindau, S. Lee, J. Kelly, Liang-Chy Chien

Liang-Chy Chien

We applied ellipsometry to study the distribution of azobenzene fragments in the films of two types of comblike polymers with azobenzene moieties in the side chains before and after ultraviolet ~UV! light irradiation. The polymer with an alkyl chain at the end of the azobenzene fragment forms structures with preferred homeotropic alignment of the fragments. Irradiation of this polymer with nonpolarized UV light at normal incidence induces a homeotropic alignment of azobenzene fragments. Oblique irradiation induces tilted structures. Polarized UV light irradiation at normal beam incidence induces biaxial structures with a fanlike distribution of azobenzene fragments and preferably out-of-plane alignment ...


Short Pitch Cholesteric Electro-Optical Device Stabilized By Nonuniform Polymer Network, Sang Kim, Liang-Chy Chien Oct 2013

Short Pitch Cholesteric Electro-Optical Device Stabilized By Nonuniform Polymer Network, Sang Kim, Liang-Chy Chien

Liang-Chy Chien

We have developed a method for stabilization of the uniform lying helix (ULH) texture of short pitch cholesterics in an electro-optical device, based on the flexoelectro-optic effect in such a texture. By using a small concentration of photoreactive liquid crystal monomer (less than 5 wt. %) and selecting the illumination conditions, we were able to create a nonuniform polymeric network in the liquid crystal bulk (localized essentially at both substrate surfaces) which stabilized efficiently the amplitude and the phase modulation modes of the device. Most importantly, the effect of the residual birefringence of the polymeric network in the field-unwound state of ...


Structure And Morphology Of Polymer-Stabilized Cholesteric Diffraction Gratings, Shin-Woong Kang, Samuel Sprunt, Liang-Chy Chien Oct 2013

Structure And Morphology Of Polymer-Stabilized Cholesteric Diffraction Gratings, Shin-Woong Kang, Samuel Sprunt, Liang-Chy Chien

Liang-Chy Chien

We report a study of polymer network morphology in planar diffraction gratings formed from polymer-stabilized cholesteric liquid crystals. Photopolymerizing a mesogenic monomer yields a regular sawtooth morphology, composed of polymer sheets running at an acute angle between thick, uniformly aligned bundles which reside on the opposing substrates. To explain this morphology and evidence of two grating vectors in the diffraction pattern, we propose a model for the liquid-crystal director where out-of-phase twists at the surfaces gear into an interior twist, which has half the period of the surface twist, via splay distortions running between the substrates. The morphology also changes ...


Control Of Reflectivity And Bistability In Displays Using Cholesteric Liquid-Crystals, Deng-Ke Yang, John West, Liang-Chy Chien, J. Doane Oct 2013

Control Of Reflectivity And Bistability In Displays Using Cholesteric Liquid-Crystals, Deng-Ke Yang, John West, Liang-Chy Chien, J. Doane

Liang-Chy Chien

It is demonstrated that the reflective properties and bistability of cholesteric liquid crystals can be controlled by proper surface treatment and dispersed polymers. Dispersing a polymer in the liquid crystal or using a cell with an inhomogeneous surface anchoring creates permanent defects which result in long-term bistability, high contrast at large viewing angles, and gray scale. The wide-angle, reflective feature makes cholesteric materials suitable for displays without backlights and bistability provides flicker-free operation.


Field-Induced And Polymer-Stabilized Two-Dimensional Cholesteric Liquid Crystal Gratings, Shin-Woong Kang, Liang-Chy Chien Oct 2013

Field-Induced And Polymer-Stabilized Two-Dimensional Cholesteric Liquid Crystal Gratings, Shin-Woong Kang, Liang-Chy Chien

Liang-Chy Chien

The authors experimentally demonstrate an electrically switchable gratings based on polymer-stabilized, field-induced two-dimensional square-lattice pattern of a cholesteric liquid crystal. A dependence of the two-dimensional diffraction patterns with the magnitude of applied voltage is observed for before and after the polymer stabilization. The diffraction efficiency reaches 84% calculated for the zero order light intensity at the applied voltage of 0.23 V/mu m for a 10 mu m thick sample.


Dynamical Studies Of Gratings Formed In Polymer-Dispersed Liquid Crystal Films, Andy Fuh, T. Ko, M. Tsai, C. Huang, Liang-Chy Chien Oct 2013

Dynamical Studies Of Gratings Formed In Polymer-Dispersed Liquid Crystal Films, Andy Fuh, T. Ko, M. Tsai, C. Huang, Liang-Chy Chien

Liang-Chy Chien

The use of polymer-dispersed liquid crystal films to fabricate gratings was demonstrated. The written gratings are permanent, but are electrically switchable. In this article, we report the results obtained from the dynamical studies of gratings formed in polymer-dispersed liquid crystal films having various liquid crystal-polymer mixing ratios. The results showed that during the initial phases of formation, a thermal grating effect dominated. Later, it was offset or quenched by the photopolymerization effect which eventually dominated and determined the characteristics of the final grating.


Photoinduced Three-Dimensional Orientational Order In Side Chain Liquid Crystalline Azopolymers, O. Yaroshchuk, K. Kiselev, Yu. Zakrevskyy, T. Bidna, J. Kelly, Liang-Chy Chien, J. Lindau Oct 2013

Photoinduced Three-Dimensional Orientational Order In Side Chain Liquid Crystalline Azopolymers, O. Yaroshchuk, K. Kiselev, Yu. Zakrevskyy, T. Bidna, J. Kelly, Liang-Chy Chien, J. Lindau

Liang-Chy Chien

We apply experimental technique based on the combination of methods dealing with principal refractive indices and absorption coefficients to study the photoinduced three-dimensional (3D) orientational order in the films of liquid crystalline (LC) azopolymers. The technique is used to identify 3D orientational configurations of trans azobenzene chromophores and to characterize the degree of ordering in terms of order parameters. We study two types of LC azopolymers which form structures with preferred in-plane and out-of-plane alignment of azochromophores, respectively. Using irradiation with the polarized light of two different wavelengths, we find that the kinetics of photoinduced anisotropy can be dominated by ...


A Polymer-Stabilized Single-Layer Color Cholesteric Liquid Crystal Display With Anisotropic Reflection, Shin-Ying Lu, Liang-Chy Chien Oct 2013

A Polymer-Stabilized Single-Layer Color Cholesteric Liquid Crystal Display With Anisotropic Reflection, Shin-Ying Lu, Liang-Chy Chien

Liang-Chy Chien

The authors report a method of fabricating single-layer color cholesteric liquid crystal displays from a polymer-stabilized cholesteric liquid crystal. The reflective wavelength can be electrically switched to reflect blue or green from a cell initially reflecting a red color. The color change is a result of the compression to the helical pitches in planar layers in response to the applied voltage. The unique feature of the polymer stabilization is in the fact that the electrically switched colors preserve good reflectivity and the colors are reversible with voltage ramping. Conspicuously, the polymer-stabilized cholesteric display exhibits anisotropic reflection and has a temperature ...


Helical Single-Lamellar Crystals Thermotropically Formed In A Synthetic Nonracemic Chiral Main-Chain Polyester, Christopher Y. Li, Donghang Yan, Stephen Z. D. Cheng, Feng Bai, Jason J. Ge, Bret H. Calhoun, Tianbai He, Liang-Chy Chien, Frank W. Harris, Bernard Lotz Oct 2013

Helical Single-Lamellar Crystals Thermotropically Formed In A Synthetic Nonracemic Chiral Main-Chain Polyester, Christopher Y. Li, Donghang Yan, Stephen Z. D. Cheng, Feng Bai, Jason J. Ge, Bret H. Calhoun, Tianbai He, Liang-Chy Chien, Frank W. Harris, Bernard Lotz

Liang-Chy Chien

Phase structures and transformation mechanisms of nonracemic chiral biological and synthetic polymers are fundamentally important topics in understanding their macroscopic responses in different environments. It has been known for many years that helical structures and morphologies can exist in low-ordered chiral liquid crystalline (LC) phases. However, when the chiral liquid crystals form highly ordered smectic liquid crystal phases, the helical morphology is suppressed due to the crystallization process. A double-twisted morphology has been observed in many liquid crystalline biopolymers such as dinoflaggellate chromosomes (in Prorocentrum micans) in an in vivo arrangement. Helical crystals grown from solution have been reported in ...


Nematic Director Orientation In A Liquid-Crystal-Dispersed Polymer - A Deuterium Nmr Approach, Ralf Stannarius, G. Crawford, Liang-Chy Chien, J. Doane Oct 2013

Nematic Director Orientation In A Liquid-Crystal-Dispersed Polymer - A Deuterium Nmr Approach, Ralf Stannarius, G. Crawford, Liang-Chy Chien, J. Doane

Liang-Chy Chien

The nuclear-magnetic-resonance (NMR) technique is employed to liquid-crystal-dispersed-polymer (LCDP) systems. Deuterium NMR is used to determine director distributions in LCDP cells in the presence of a magnetic field. The samples consist of a nematic liquid crystal mixed with small percentages of a monomer that is polymerized under different conditions after dissolving it in the liquid crystal. NMR spectra of the deuterated liquid-crystal molecules give information on orientation and order in such systems. The orientation of the polymer skeleton formed during the polymerization is found to be stable. It determines the orientation of the nematic director even in the presence of ...


A Novel Polymer Patterning Method Based On Pattern Forming States Of Liquid Crystals As Templates, Liang-Chy Chien, Samuel N. Sprunt, Shin-Woong Kang Oct 2013

A Novel Polymer Patterning Method Based On Pattern Forming States Of Liquid Crystals As Templates, Liang-Chy Chien, Samuel N. Sprunt, Shin-Woong Kang

Liang-Chy Chien

We describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength ...


Piezoelectric Effects In Cholesteric Elastomer Gels, C. C. Chang, Liang-Chy Chien, R. Meyer Oct 2013

Piezoelectric Effects In Cholesteric Elastomer Gels, C. C. Chang, Liang-Chy Chien, R. Meyer

Liang-Chy Chien

We report a piezolectric effect in cholesteric liquid crystalline elastomer gels. When we apply a shear stress to a cholesteric elastomer gel in the direction perpendicular to its helical axis, a polarization can be induced in the direction perpendicular to both the stress and the helix. This experimental observation agrees with the theory proposed by Pelcovits and Meyer [J. Phys. II France 5, 877 (1995)].


Formation And Localization Of Internal Polymer Columnar Structures In Liquid Crystal Cells, Qingbing Wang, Liang-Chy Chien, Satyendra Kumar Oct 2013

Formation And Localization Of Internal Polymer Columnar Structures In Liquid Crystal Cells, Qingbing Wang, Liang-Chy Chien, Satyendra Kumar

Liang-Chy Chien

Internal polymer columnar structures in liquid crystal (LC) cells have been produced using the method of thermally-induced phase separation of LC/prepolymer solution and solidified by photopolymerization. These polymer columns adhere to both substrates and enhance control of the LC cell spacing and mechanical stability. The existence and profile of the polymer columns were investigated by optical and scanning electron microscopy techniques. Supertwisted nematic LC cells with polymer columnar structures have been constructed using this method and their electro-optical characteristics measured.


Electro-Optical Study Of Nematic Elastomer Gels, C.C. Chang, Liang-Chy Chien, R. B. Meyer Oct 2013

Electro-Optical Study Of Nematic Elastomer Gels, C.C. Chang, Liang-Chy Chien, R. B. Meyer

Liang-Chy Chien

We report on an electro-optical study of a liquid-crystal-polymer composite system. This system is made by dissolving a small amount of acrylate monomers (8%) plus crosslinkers in a nematic liquid crystal, and then photopolymerizing the homogeneous mixture. These nematic gels show properties different from those of ordinary nematics or polymer stabilized liquid crystals. By studying the electric field induced Frederiks transition, some basic propel-ties of the nematic gels can be deduced. We compare the experimental results to a simple phenomenological model of the nematic gel, involving a characteristic length scale of order 1 mu m, which is also visible as ...


Switchable Diffraction Gratings Based On Inversion Of The Dielectric Anisotropy In Nematic Liquid Crystals, S. W. Kang, Samuel N. Sprunt, Liang-Chy Chien Oct 2013

Switchable Diffraction Gratings Based On Inversion Of The Dielectric Anisotropy In Nematic Liquid Crystals, S. W. Kang, Samuel N. Sprunt, Liang-Chy Chien

Liang-Chy Chien

A switchable liquid crystal diffraction grating, responsive to both the frequency and magnitude of an applied voltage, is demonstrated. The grating is based on polymer stabilization of modulated states of the liquid crystal optic axis induced at frequencies near a sign inversion of the dielectric anisotropy. In a particular case of frequency-based switching, 70% of the transmitted intensity of a 633 nm laser beam can be shifted into or out of a +/-12 degrees forward are by changing the frequency of an applied voltage between 10 and 16 kHz at a fixed amplitude of 27 V. (C) 2001 American Institute ...


Macroscopic Chirality Of A Liquid Crystal From Nonchiral Molecules, Antal Jákli, Geetha G. Nair, C. K. Lee, R. Sun, Liang-Chy Chien Oct 2013

Macroscopic Chirality Of A Liquid Crystal From Nonchiral Molecules, Antal Jákli, Geetha G. Nair, C. K. Lee, R. Sun, Liang-Chy Chien

Liang-Chy Chien

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


Double Twist In Helical Polymer "Soft" Crystals, Christopher Li, Stephen Cheng, Jason Ge, Feng Bai, John Zhang, Ian Mann, Frank Harris, Liang-Chy Chien, Donghang Yan, Tianbai He, Bernard Lotz Oct 2013

Double Twist In Helical Polymer "Soft" Crystals, Christopher Li, Stephen Cheng, Jason Ge, Feng Bai, John Zhang, Ian Mann, Frank Harris, Liang-Chy Chien, Donghang Yan, Tianbai He, Bernard Lotz

Liang-Chy Chien

In natural and synthetic materials having non-racemic chiral centers, chirality and structural ordering each play a distinct role in the formation of ordered states. Configurational chirality can be extended to morphological chirality when the phase, structures possess low liquid crystalline order. In the crystalline states the crystallization process suppresses the chiral helical morphology due to strong ordering interactions, In this Letter, we report the first observation of helical single lamellar crystals of synthetic non-racemic chiral polymers. Experimental evidence shows that the molecular chains twist along both the long and short axes of the helical lamellar crystals, which is the first ...


Liquid-Crystal Photoalignment Using Low-Molecular-Weight Photo-Cross-Linkable Composites, O. Yaroshchuk, L Cada, M. Sonpatki, Liang-Chy Chien Oct 2013

Liquid-Crystal Photoalignment Using Low-Molecular-Weight Photo-Cross-Linkable Composites, O. Yaroshchuk, L Cada, M. Sonpatki, Liang-Chy Chien

Liang-Chy Chien

A liquid-crystal (LC) photoalignment method, based on the use of low-molecular-weight photo-cross-linkable (LMWPC) composites is proposed. The basic idea of this method is that cross linking or both cross linking and polymerization of LMWPC composites are realized immediately on the substrate simultaneously with the photoalignment or as a stage of the backing process. Providing the advantages of a conventional photoalignment method, the use of LMWPC composites simplifies the synthesis and alignment procedure, makes possible wide range control of pretilt angles, and enhances the thermal stability of the LC alignment. The abilities of this method are demonstrated using a series of ...


Cholesteric Liquid-Crystal Polymer Dispersion For Haze-Free Light Shutters, Deng-Ke Yang, Liang-Chy Chien, J. Donae Oct 2013

Cholesteric Liquid-Crystal Polymer Dispersion For Haze-Free Light Shutters, Deng-Ke Yang, Liang-Chy Chien, J. Donae

Liang-Chy Chien

A new dispersion involving a polymer in low concentration with a cholesteric liquid crystal is reported. Two types of light modulators from these materials are described as a normal mode shutter which is opaque (light scattering) in the field-OFF state and transparent in the field-ON state and a reverse-mode shutter with the opposite field conditions. The transparent state of both cells is haze-free for all viewing angles making the material attractive for window applications and direct view displays.


Effect Of A Polymer Network On The Alignment And The Rotational Viscosity Of A Nematic Liquid-Crystal, Antal Jákli, D. Kim, Liang-Chy Chien, A. Saupe Oct 2013

Effect Of A Polymer Network On The Alignment And The Rotational Viscosity Of A Nematic Liquid-Crystal, Antal Jákli, D. Kim, Liang-Chy Chien, A. Saupe

Liang-Chy Chien

Polymer dispersions were made by photoinduced polymerization of 4,4'-bisacryloyl-biphenyl in liquid crystal 4-4'-cyano pentyl biphenyl as nematic solvent. Samples were prepared with 0.5, 1, and 1.5 wt % monomer. The polymerization was done in the isotropic phase. The rotational viscosities of the two lower concentration samples increased only moderately after UV curing (3 mW/cm2, 25 min). The 1.5 wt % sample gave under the same condition a nematic with a fairly rigid anisotropic network that did not realign in magnetic field up to 20 kG. We estimate that the mesh size of the network was ...


Polymer-Stabilized Diffraction Gratings From Cholesteric Liquid Crystals, S. N. Lee, Liang-Chy Chien, Samuel N. Sprunt Oct 2013

Polymer-Stabilized Diffraction Gratings From Cholesteric Liquid Crystals, S. N. Lee, Liang-Chy Chien, Samuel N. Sprunt

Liang-Chy Chien

We report the use of a low concentration polymer network to stabilize electric field-induced diffraction gratings in cholesteric liquid crystals. The stabilized gratings can be electrically switched between a zero-field "on" state, which exhibits approximately 75% diffraction efficiency, and a moderate field (typically 3 V/mu m) "off" state. Grating spacings between 1.7 and 30 mu m are obtained in a 10 mu m thick cell by variation of the concentration of chiral dopant used to form the cholesteric liquid crystal. (C) 1998 American Institute of Physics.


Reversible Actuating And Writing Behaviours Of A Head-To-Side Connected Main-Chain Photochromic Liquid Crystalline Polymer, Dae-Yoon Kim, Sang-A Lee, Hyong Jong Choi, Liang-Chy Chien, Myong-Hoon Lee, Kwang-Un Jeong Dec 2012

Reversible Actuating And Writing Behaviours Of A Head-To-Side Connected Main-Chain Photochromic Liquid Crystalline Polymer, Dae-Yoon Kim, Sang-A Lee, Hyong Jong Choi, Liang-Chy Chien, Myong-Hoon Lee, Kwang-Un Jeong

Liang-Chy Chien

A photochromic liquid crystalline (LC) polymer {4-butoxy-2'-(4-hex-5-enyloxy)-4'-(4-hex-5-enyl-oxybenzyloxy)azobenzene, abbreviated as PLCP} was newly synthesized via the acrylic diene metathesis polymerization (H. J. Choi, et al., J. Mater. Chem., 2009, 19, 7124). Utilizing the combined techniques of differential scanning calorimetry, cross-polarized optical microscopy, and wide-angle X-ray diffraction (WAXD), it was realized that PLCP formed a nematic (N) phase below the isotropization temperature (T-NI = 145 degrees C) and the N phase turned to the glassy N phase below the glass transition temperature (T-g = 24 degrees C). Especially, two-dimensional (2D) WAXD of the uniaxially oriented PLCP fibre indicated that the ...


Electrically Reconfigurable And Thermally Sensitive Optical Properties Of Gold Nanorods Dispersed Liquid Crystal Blue Phase, Jenny-Marie Wong, Jeoung-Yeon Hwang, Liang-Chy Chien Aug 2011

Electrically Reconfigurable And Thermally Sensitive Optical Properties Of Gold Nanorods Dispersed Liquid Crystal Blue Phase, Jenny-Marie Wong, Jeoung-Yeon Hwang, Liang-Chy Chien

Liang-Chy Chien

We report the electrically reconfigurable optical properties of gold nanorods (AuNRs) dispersed liquid crystal blue phase (BP). In principle, dispersing gold nanorods in a BP should not possess a critical concentration of the dispersant at the nanoscale, because the free-energy cost of disclination is negligible. Yet, the experimental results indicate that BP range reaches a plateau at a critical concentration of AuNRs. The mesophase range of the pure BP studied by polarizing optical microscopy is theoretically validated. The optical property of an AuNRs dispersed BP system is electrically and thermally reconfigurable.


Electrically Switched Color With Polymer-Stabilized Blue-Phase Liquid Crystals, Shin-Ying Lu, Liang-Chy Chien Feb 2010

Electrically Switched Color With Polymer-Stabilized Blue-Phase Liquid Crystals, Shin-Ying Lu, Liang-Chy Chien

Liang-Chy Chien

We report an electrical-field switched color device using a polymer-stabilized blue-phase ( PSBP) liquid crystal in which the Bragg-reflected color of the blue phase ( BP) can be switched to reflect a second color. The phase-separated three-dimensional polymer network transcribes the cubic structure of a BP liquid crystal and restrains the deformation of cubic lattice by the external electric field. The new wide-range electric-field switched colors with PSBP may be an important step toward ecofriendly color reflective displays. (C) 2010 Optical Society of America


Photochromic 3-Dimensional Actuator Based On An Uncrosslinked Liquid Crystal Elastomer, Hyong Choi, Kwang-Un Jeong, Liang-Chy Chien, Myong-Hoon Lee Dec 2008

Photochromic 3-Dimensional Actuator Based On An Uncrosslinked Liquid Crystal Elastomer, Hyong Choi, Kwang-Un Jeong, Liang-Chy Chien, Myong-Hoon Lee

Liang-Chy Chien

A chemically programmed photochromic liquid crystal (LC) polymer was newly synthesized and used to fabricate an actuator exhibiting reversible photo-activated bending behavior at ambient temperature. Due to the lack of chemical crosslinking in this photochromic LC elastomer, it was possible to fabricate an actuator in the form of fiber or film by melt or solution processing, respectively. The three-dimensional (3D) bending of the film actuator can be precisely controlled in various directions by polarized ultraviolet (UV) light. The novel photochromic LC elastomer, exhibiting reversible photomechanical bending with controlled directions at room temperature, is beneficial for the realization of wireless remote-controlled ...


Carbon Nanotube Doped Liquid Crystal Ocb Cells: Physical And Electro-Optical Properties, Shin-Ying Lu, Liang-Chy Chien Aug 2008

Carbon Nanotube Doped Liquid Crystal Ocb Cells: Physical And Electro-Optical Properties, Shin-Ying Lu, Liang-Chy Chien

Liang-Chy Chien

We report single-wall carbon nanotube (CNT) doped liquid crystal materials which show significant improvement in the response time for optical controlled birefringence (OCB) cells. Four different types of liquid crystals (LCs) were chosen to mix with CNTs and they demonstrated similar results in improving the response time. Experimental results show that the anchoring energy at alignment layers has been changed by CNT doping. CNTs were attracted to the alignment layer and modified the property of the surface. The anchoring enhancement is due to the pi-pi electron stacking between the CNTs, LC molecules and alignment layers.


Liquid Crystal Blazed Gratings Formed In A Single-Step Through Photo-Induced Localization Of Polymer Into A Prismatic Structure, Sang Hwa Kim, Liang-Chy Chien Apr 2004

Liquid Crystal Blazed Gratings Formed In A Single-Step Through Photo-Induced Localization Of Polymer Into A Prismatic Structure, Sang Hwa Kim, Liang-Chy Chien

Liang-Chy Chien

A liquid crystal blazed grating having a prismatic polymer microstructure has been developed. The polymer structure is fabricated by photo-induced localization and polymerization of a small concentration of monomer onto one substrate of an electro-optical cell by using ultraviolet light irradiation at 45degrees direction from normal incident. Using this method a periodical one-dimensional pattern with a prismatic shape of polymer can be formed on a one-dimensional pattern-forming state of a cholesteric host. The optical diffraction properties of the grating are evaluated by the application of electric field and light incident angles.