• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.169-173
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• 2010

• Analytical Science and Technology
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• v.8 no.4
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• pp.493-498
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• 1995

PAZO-6 is a new combined type liquid crystalline polymers (LCP) which has two types of mesogens combined non linearly. Ordering of branch mesogen azo group, in PAZO-6 is an important parameter to observe as well as the substitution effect on the backbone. The related small molecules sllch as monomers as well as the polymer itself are studied by solid state NMR techniques. Preliminary $^{13}C$ CP/MAS (cross polarization/ magic angle spinning) spectral results suggest that the azo groups in the monomers are not aligned with themselves. Azo groups in the monomers seem to be poorly ordered between well ordered p-phenylene terephthalate moeities. Similar disordering tendency of the azo group in PAZO-6 is deduced from the overall aromatic carbon peak positions which are not much different from those of the monomer.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.274-278
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• 2003

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C $(Sm\;C^*)$ phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable $(Sm\;C^*)$ phase in the melt. The smectic phases having the octenyloxy group such as $(CH_2)_6CH=CH_2$ showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm² (X=H) and 225 nC/ cm² (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.197-199
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• 2007

Four banana-shaped compounds have beene synthesized introducing ester linking group into mesogenic unit, varying the central core with 1,6-, 1,7-, 2,3-, and 2,7-naphthylene units, and introducing the dodecyloxy group as the terminal flexible unit. All obtained compounds except one with 1,7-naphthylene unit were reversibly thermotropically liquid crystalline. The compound with 1,7-naphthylene unit could not form the mesophase due to its asymmetrical and sharp substitution angle. The compounds with 1,6- and 2,3-naphthylene units showed an antiferroelectric switchable smectic phase, which has been designated B2 phase. Interestingly, the compound with the 2,3-naphthylene unit showed the two mesophases of B2 and nematic phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.424-425
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• 2007

We have studied the optically compensated splay mode using reactive mesogen (RM) monomer to reduce setting voltage and phase transition time from initial bend to splay state. When the OCS cell has low pretilt angle close to $45^{\circ}C$, OCS state can be formed easily. The low pretilt angle was formed through the polymerization of UV curable reactive RM monomer at the surfaces. In this way, reorientation of the LC is well defined and thus the device shows better performances in setting voltage and phase transition time.

• Polymer(Korea)
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• v.39 no.1
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• pp.185-190
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• 2015

Since a transition from liquid crystal to crystal state is slow for the large photo-reactive liquid crystal molecules, it needs a long time for recrystallization of LC242 molecules when lowering the temperature of the liquid crystal. Although liquid crystals usually align along one direction, the directions of individual liquid crystal molecules are little different from one another with increasing temperature, resulting in changes of birefringence of the liquid crystal films. When the photo-reactive liquid crystals are photo-cured, faster curing kinetics and much larger curing degrees are observed for the films cured at the liquid crystal phase.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.71-75
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• 1998

Liquid crystalline compounds with amine terminal group and related linear and cross-linked liquid crystal polymers with epoxy resin structure were synthesized and characterized to develope matrix materials for polymer dispersed liquid display applications. Both linear and crosslinked side chain type liquid crystal polymers made with aromatic amine mesogens and ethylene glycol diglycidyl ether exhibited nematic texture as shown by polarized optical microscope(POM) and their transition temperatures were determined both by DSC and POM. Liquid crystal polymer samples also showed even-odd effect as the spacer length of aromatic amine mesogens were varied, however, the effect was samller than that of low molecular weight mesogens. Changes of nematic-to-isotropic transition($T_{NI}$) of crosslinked type polymer liquid crystals were also disscussed in relation to the concentration change of crosslinking agent 1,10-diaminodecane.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.176-180
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• 2005

The liquid crystalline properties of a series of main chain liquid crystalline polymers and four series compounds consisting of aromatic type Schiff base mesogenic units and polymethylene flexible spacers were studied. The thermal and liquid crystalline properties were investigated by differential scanning calorimetry and on the hot stage of a polarizing microscope. The nature of the liquid crystalline phase of the polymers and compounds depended greatly on the length of the central polymethylene spacer and on the terminal alkoxy groups. Polymers I and Series III exhibited an even-odd effect in melting and isotropization temperatures but Series II and Series IV exhibited an even-odd effect in isotropization temperatures. They formed nematic and smectic mesophases in melts as judged by their optical textures observed through a polarizing microscope.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.661-667
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• 2008

In this study, cholesteric liquid crystal (CLC) was synthesized and applied as a polarizing component on the optical film of back light units (BLU) for LCDs. After mixing CLC with nematic liquid crystal, this mixture was fulfilled in the module consisting of two films and then its amplifying efficiency and polarizing ability for a planarly emitted light were examined to apply as a BLU polarizer film for increasing the brightness of light. The properties of CLC compound were tested by UV/Visible spectroscopy and polarizing optical microscopy (POM). Flexible spacer was made by linear carboxylic acid group of cholesteric derivatives between cholesterol mesogen units for one-axis orientation in each layer. The CLC containing film could be used as a module to increase the ability of polarization and to enhance brightness of BLU and to widen wavelength range by stacking the films.

• Journal of Adhesion and Interface
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• v.15 no.4
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• pp.161-168
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• 2014

New self-assembled discotic liquid crystals have been prepared through single hydrogen bonding between phenol and pyridine moieties, and their liquid crystalline properties were investigated. For the construction of discotic structure, we used phloroglucinol as a core molecule and trans-4-alkoxy-4'-stilbazoles with systematically varied alkyl chain lengths as peripheral units. FTIR results showed that the intermolecular hydrogen bonds between core and peripheral molecules are successfully formed, and the stability of the hydrogen bond is strongly influenced by molecular ordering. Discotic complexes exhibited different liquid crystalline phases depending on the length of alkyl chains around the discotic mesogen. The discotic complexes with longer alkyl chains showed hexagonal columnar mesophases, while the other complexes formed nematic columnar mesophases. These results indicated that the type of mesophase structure was strongly dependent on the alkyl chain length around the aromatic core.