Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Light (2)
- Morphology (2)
- Systems (2)
- Achiral molecules (1)
- Chain (1)
-
- Crystal Violet (1)
- Defects (1)
- Diffraction gratings (1)
- Electro-optical devices (1)
- Films (1)
- Gratings (1)
- Layers (1)
- Liquid crystal devices (1)
- Materials (1)
- Melt (1)
- Molecular Media (1)
- Network (1)
- Orientation (1)
- Phases (1)
- Polarization (1)
- Polyethylene (1)
- Smectic liquid-crystal (1)
- Smectic phases (1)
- Spherulites (1)
- Symmetry (1)
- X-ray (1)
Articles 1 - 17 of 17
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
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
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. The two polymers exhibit similar …
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
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.
A Polymer-Stabilized Single-Layer Color Cholesteric Liquid Crystal Display With Anisotropic Reflection, Shin-Ying Lu, Liang-Chy Chien
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
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 …
A Novel Polymer Patterning Method Based On Pattern Forming States Of Liquid Crystals As Templates, Liang-Chy Chien, Samuel N. Sprunt, Shin-Woong Kang
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 of …
Electro-Optical Study Of Nematic Elastomer Gels, C.C. Chang, Liang-Chy Chien, R. B. Meyer
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
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
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. The …
Polymer-Stabilized Diffraction Gratings From Cholesteric Liquid Crystals, S. N. Lee, Liang-Chy Chien, Samuel N. Sprunt
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
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 N phase …
Electrically Reconfigurable And Thermally Sensitive Optical Properties Of Gold Nanorods Dispersed Liquid Crystal Blue Phase, Jenny-Marie Wong, Jeoung-Yeon Hwang, Liang-Chy Chien
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
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
Carbon Nanotube Doped Liquid Crystal Ocb Cells: Physical And Electro-Optical Properties, Shin-Ying Lu, Liang-Chy Chien
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.
Measurements Of The Hyperpolarizability Tensor By Means Of Hyper-Rayleigh Scattering, Liang-Chy Chien, V. Ostroverkhova, R. G. Petschek, K. D. Singer, L. Sukhomlinova, R. J. Twieg, S.-X. Wang
Measurements Of The Hyperpolarizability Tensor By Means Of Hyper-Rayleigh Scattering, Liang-Chy Chien, V. Ostroverkhova, R. G. Petschek, K. D. Singer, L. Sukhomlinova, R. J. Twieg, S.-X. Wang
Liang-Chy Chien
We describe improvements to a previously reported hyper-Rayleigh scattering technique [J. Opt. Sec. Am. B 15, 289 (1998)], for measuring all rotational invariants of the first hyperpolarizability tensor. The full hyper-Rayleigh scattering tensor is expressed in terms of its rotationally invariant components leading to a figures of merit corresponding to each of the rotationally invariant tensors. With elliptically polarized incident light, the polarization state and the intensity of the harmonic light are measured at a scattering angle of 45 degrees. A new analytical fitting method is applied to the signal for two polarization measurements to yield the invariants. We have …
Measurements Of Kleinman-Disallowed Hyperpolarizability In Conjugated Chiral Molecules, S. Hubbard, R. Petschek, K. Singer, N. D'Sidocky, C. Hudson, Liang-Chy Chien, C. Henderson, P. Cahill
Measurements Of Kleinman-Disallowed Hyperpolarizability In Conjugated Chiral Molecules, S. Hubbard, R. Petschek, K. Singer, N. D'Sidocky, C. Hudson, Liang-Chy Chien, C. Henderson, P. Cahill
Liang-Chy Chien
We have designed a hyper-Rayleigh scattering scheme to measure six scalar invariants of the squared hyperpolarizability tensor beta(2). OUT theoretical approach expresses the rotational invariants of the irreducible beta components as scalars, which eliminates the need for difficult frame transformations. We applied our scheme to several conjugated chiral molecules and found that there are significant Kleinman-disallowed pseudotensor contributions to their hyperpolarizability. These components, along with a large optical rotation and the results of quantum-chemical calculations, indicate a handed nonplanar delocalization of the charge-transfer system in such molecules as predicted by quantum-chemical calculations and are expected to lead to macroscopic second-harmonic …
Effects Of Low Polymer Content In A Liquid-Crystal Microlens, Toshiaki Nose, Shin Masuda, Susumu Sato, Jianlin Li, Liang-Chy Chien, Philip Bos
Effects Of Low Polymer Content In A Liquid-Crystal Microlens, Toshiaki Nose, Shin Masuda, Susumu Sato, Jianlin Li, Liang-Chy Chien, Philip Bos
Liang-Chy Chien
A small number of bifunctional monomers are mixed with a nematic liquid crystal (LC) and cured with a distributed electric field, which is produced by a circular-hole-patterned electrode structure. A gradient type of lens, that is, a LC microlens, is investigated for various polymer concentrations. Addition of 3% polymer is enough to freeze the gradient-index properties of the structure in the form of a convex lens, and a polymer-stabilized LC microlens is demonstrated. Although a lower concentration of polymer cannot hold the distribution properties in a curing process, it can maintain the variable focus as a nematic material can. The …