Browsing by Author "Wang, Ling-Yung"

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Configuration Effects of H-Bonded Sites and Rigid Core Lengths on H-Bonded Banana-Shaped Liquid Crystalline Supramolecules Consisting of Symmetric Trimers and Asymmetric Heterodimers
(2009-11-05)
Wang, Ling-Yung
;
Chiang, I-Hung
;
Yang, Po-Jen
;
Li, Wan-Sheung
;
Chao, I-To
Several series of novel banana-shaped H-bonded symmetric trimers (with two H-bonds) and asymmetric heterodimers (with one H-bond) were self-assembled by appropriate molar ratios of proton donors (H-donors) and acceptors (H-acceptors). The influences of H-bonded linking positions and aromatic ring numbers (4-8 aromatic rings in the rigid cores) as well as the chain lengths (n, m = 12 or 16, respectively, in the flexible parts) on the mesomorphism and the switching behavior of the bent-core supramolecules were evaluated and theoretically analyzed. Except for the supramolecular structures with longer rigid cores or shorter flexible chains possessing the rectangular columnar (Col(r) or Bl) phase, the SmC(A)P(A) phase was revealed in most supramolecular asymmetric heterodimers and switched to the SmC(S)P(F) phase by applying electric fields. The polar smectic C phase was dominated for those with H-bonded sites apart from the core center. Interestingly, the SmA and nematic phases were observed in H-bonded asymmetric dimers with H-bonded sites close to the core center, which theoretically proved that the polar smectic C phase was disfavored due to an unfavorable bend angle (smaller than the lower limit of 110 degrees) in the lowest-energy H-bonded conformer. Compared with the fully covalently bonded analogue, lower transition temperatures and lower threshold voltages were developed in the H-bonded asymmetric dimers with the polar smectic C phase. On the basis of the theoretical calculations of molecular modeling, the existence of polar switching behavior in the polar smectic C phase of asymmetric heterodimers; was proven to be associated with their configurations with higher dipole moments and suitable bend angles. Furthermore, the lack of polar switching behavior in supramolecular symmetric trimers, which exhibited the regular SmC phase with weak electrical stabilities, was related to their configurations with smaller dipole moments and confirmed by theoretical calculations.
DOPANT EFFECTS OF PHOTOREACTIVE ZnO NANOPARTICLES ON FAST RESPONSE LC MATERIALS IN OPTICAL COMPENSATED BEND (OCB) MODE LIQUID CRYSTAL DISPLAYS
(2010-11-01)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Chen, Wei-Hong
;
Chen, Szu-Fen
Photoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V-th) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V-th, is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) -> bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.
DOPANT EFFECTS OF PHOTOREACTIVE ZnO NANOPARTICLES ON FAST RESPONSE LC MATERIALS IN OPTICAL COMPENSATED BEND (OCB) MODE LIQUID CRYSTAL DISPLAYS
(2010-11-01)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Chen, Wei-Hong
;
Chen, Szu-Fen
Photoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V(th)) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V(th), is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) -> bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.
Effects of Liquid Crystal Compositions on Polymer Stabilized Blue Phase Liquid Crystals
(2010)
Wang, Ling-Yung
;
Huang, Tai-Hsiang
;
Sugiura, Norio
;
Liau, Wei-Lung
;
Han, Chun-Chieh
The compositions of polymer stabilized blue phase liquid crystals (PS-BPLCs) relating to the thermal properties and electro-optical ones which are important for both display performance and productivity were investigated in this paper. By optimizing quantity of chiral-dopants and new monomers, temperature range of the BPLCs could successfully be enlarged.
Improvement of fast response LC materials by bent-core dopants in optical compensated bend (OCB) mode liquid crystal displays
(2008)
Wang, Ling-Yung
;
Tsai, Shin-Yi
;
Lin, Hong-Cheu
;
Chen, Szu-Fen Fenny
;
Lyu, Robert
The stabilization of bend configuration in optical compensated bend (OCB) mode cells by doping bent-core molecules was developed in this study. The values of response time (tau) and threshold voltage (V-th) in OCB cells were dependent on not only the concentration but also the shape, dipole direction, and flexible chain length of the doping molecules. Experimental results showed that the total response time (tau(total)) and threshold voltage (V-th) of OCB cells could be reduced by doping bent-core molecules, and smaller tau values by reducing flexible chain lengths as well as smaller V-th values by reducing polarization of bent-core molecules were normally obtained. In general, higher concentrations of dopants normally induced shorter field-on response time (tau(on)) and a minimum field-off response time (tau(off)) occurred at 0.5% of doping concentration, where the fastest total response time (tau(total)) values were achieved.
Improvement of fast responsive LC materials by bent-core dopants in optical compensated bend mode liquid crystal displays
(2011-03-01)
Lin, Hong-Cheu
;
Wang, Ling-Yung
;
Jiang, Meng-Dan
;
Tsai, Shin-Yi
;
Chen, Szu-Fen Fenny
Stabilization of bend configuration in optical compensated bend (OCB) mode cells by doping bent-core molecules was developed in this study. The values of response time (t) and threshold voltage (V(th)) in OCB cells were dependent not only on the concentration but also on the shape, dipole direction, and flexible chain length of the doping molecules. Experimental results showed that the total response time (t(total)) and threshold voltage (V(th)) of OCB cells could be reduced by doping bent-core molecules, and smaller t values produced by reducing flexible chain lengths. In addition, attaining smaller V(th) values could be achieved by reducing polarization of bent-core molecules. In general, higher concentrations of dopants normally induced shorter field-on response time (t(on)) and a minimum field-off response time (t(off)) occurred at 0.5% of doping concentration, where the fastest total response time (t(total)) values were achieved.
Novel Supramolecular Side-Chain Banana-Shaped Liquid Crystalline Polymers Containing Covalent- and Hydrogen-Bonded Bent bores
(2010-02-09)
Wang, Ling-Yung
;
Tsai, Hsin-Yi
;
Lin, Hong-Cheu
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材料科學與工程學系
;
Department of Materials Science and Engineering
Novel supramolecular side-chain banana-shaped liquid crystalline (LC) polymer complexes AmBn-N bearing various (m/n) molar ratios of hydrogen- and covalent-bonded bent-core components were acquired by the free radical polymerization, where the hydrogen-bonded (H-bonded) structures were executed via mixing equimolar portions of proton donor (H-donor) polymers AmBn (homopolymers/copolymers) and pyridyl proton acceptor (H-acceptor) bent cores (small molecules). The influences of the molar ratios of bent-core H-bonded components in side-chain banana-shaped LC polymers and their corresponding polymer complexes on mesomorphic and electro-optical properties were first investigated. The voltage-dependent antiferroelectric properties of spontaneous polarization (Ps) values in the polar smectic phase of the supramolecular side-chain banana-shaped copolymers were also reported. The nematic and tilted smectic phases were verified by XRD measurements, and the SmCp phase was further confirmed by the triangular wave method. Suprinsingly, a novel enantiotropic polar smectic (SmCP(A)) phase was generated in some bent-core side-chain polymer complexes AmBn-N. Therefore, a special approach to constructing (or stabilizing) the SmCP phase was first developed in this study by copolymerization of bent-core covalent - and H-bonded units in side-chain polymer complexes (with proper m/n molar ratios of 16/1 and 10/1 from both bent-core covalent- and H-bonded monomers (i.e., B and A-N units, respectively) without the SmCP phase.
Polymeric Dopant Effects of Bent-Core Covalent-Bonded and Hydrogen-Bonded Structures on Banana-Shaped Liquid Crystalline Complexes
(2010-02-15)
Yang, Po-Jen
;
Wang, Ling-Yung
;
Tang, Chieh-Yin
;
Lin, Hong-Cheu
;
材料科學與工程學系
Two series of banana-shaped liquid crystalline (LC) H-bonded complexes HP(m)/CB(n) (i.e., bent-core H-bonded side-chain homopolymer HP mixed with bent-core covalent-bonded small molecule CB) and CP(m)/HB(n) (i.e., bent-core covalent-bonded side-chain homopolymer CP mixed with bent-core H-bonded small molecular complex HB) with various m/n molar ratios were developed. The bent-core covalent- and H-bonded structural moieties were homopolymerized in the banana-shaped LC H-bonded complexes HP(m)/CB(n) and CP(m)/HB(n), respectively. The influences of m/n molar ratios (polymeric moieties vs. small molecular moieties) on the mesomorphic and electro-optical properties of both banana-shaped LC H-bonded complexes HP(m)/CB(n) and CP(m)/HB(n) were investigated. The polar smectic phases could be achieved and stabilized by smaller contents of polymeric dopants in banana-shaped LC H-bonded complexes, such as HP1/CB10, HP1/CB15, CP1/HB10, and CP1/HB15, which possessed tunable spontaneous polarization (Ps) values according to the molar ratios of m/n, that is, lower Ps values obtained in H-bonded complexes HP(m)/CB(n), and CP(m)/HB(n) with higher ratios of H-bonded moieties (larger m/n molar ratios), respectively. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 764-774, 2010
Synthesis and characterization of side-chain liquid-crystalline block-copolymers containing laterally attached photoluminescent quinquephenyl units via ATRP
(2010-01-06)
Wang, Ling-Yung
;
Li, Kuang-Chieh
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of novel side-chain liquid-crystalline polymers (SCLCPs) consisting of laterally attached photoluminescent p-quinquephenyl (QQP) pendants with different flexible terminal- and/or side-alkoxy chains were synthesized via atom transfer radical polymerization (ATRP). Homopolymers (HP1-HP3) and block-copolymers (PSP1-PSP3 and PEOP1-PEOP3), where QQP units were copolymerized with styrene or ethylene oxide monomers, possessed the number average molecular weights (M(n)) of 8.7-26.0 x 10(3) with narrow PDI values of 1.08-1.26. Various characterization techniques of polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate their mesomorphic properties, and all homopolymers and block-copolymers exhibited the nematic phase affected by the flexible terminal- and/or side-alkoxy chains of the conjugated rod-like pendants. In addition, the photophysical properties of these polymers were measured by UV-vis and photoluminescence (PL) spectroscopies, which showed blue PL emissions with rather high fluorescence quantum yields in solutions. (C) 2009 Elsevier Ltd. All rights reserved.
THE INFLUENCE OF PROCESS PARAMETERS ON THE STRUCTURE AND MORPHOLOGY OF PULSED PLASMA-POLYMERIZED OCTAFLUOROTOLUENE FILMS
(2010-11-01)
Jiang, Meng-Dan
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Wang, Ling-Yung
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Lin, Hong-Cheu
;
Wei, Ta-Chin
;
Yang, Shih-Hsien
This work describes amorphous fluorinated polymer films deposited by pulsed plasma polymerizations of octafluorotoluene (PPP-OFT) monomers on ITO glass as the hole-injection layer of organic electroluminescent (EL) devices, in order to study the influence of sample position and duty cycle on PPP-OFT film characteristics, and also to find a good process to yield a higher retention degree of monomers and lower roughness of PPP-OFT fluorocarbon films. Experimental results revealed that PPP-OFT films deposited at positions far away from the RF coil and close to the monomer inlet showed less roughness than films deposited near the high RF-flux regions. In addition, the retention of the monomers in the PPP-OFT layer will be high if the deposition is conducted near the monomer inlet but some distance away from the RF electrode. Moreover, amorphous fluorinated polymer films can be deposited with higher fluorine to carbon (F/C) ratios and CF(2) contents at proper substrate positions by means of different sticking coefficients of free radicals dissociated by octafluorotoluene monomers.