• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.494-497
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• 2002

The influence of isomeric state of doped azo dye on the $B_7$ phase of bent-shaped liquid crystal (LC) is studied. It was found that modulating the isomeric trans-cis state of azo dye can change the molecular arrangement of the bent-shaped LCs. To identify these phenomena the observations of microscopic texture, electro-optic response, second harmonic wave generation (SHG) and switching current were carried out..

• 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.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2241-2247
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• 2007

A new series of chiral bent-shaped liquid crystals with an asymmetric central core based on 1,6- dihydroxynaphthalene and chiral terminal chain prepared from (S)-(?)-2-methyl-1-butanol, 1,6-naphthalene bis[4-(4-alkoxyphenyliminomethyl)]benzoates [N(1,6)-n-O-PIMB(n-2)*-(n-4)O (n = 8-11)] were synthesized. Their mesomorphic properties and phase structures were investigated by means of electro-optical, polarization reversal current, and second harmonic generation measurements in order to confirm the relationship between the molecular structure and phase structure. All odd n (n = 9 and 11) compounds, N(1,6)-9-O-PIMB7*-5O and N(1,6)-11-O-PIMB9*-7O exhibit antiferroelectric phase, whereas even n (n = 8 and 10) compounds was flexible, N(1,6)-10-O-PIMB8*-6O exhibits the ferroelectric phase but N(1,6)-8-O-PIMB6*-4O exhibits the antiferroelectric phase. These results come from the decrease of the closed packing efficiency within a layer and the lack of uniform interlayer interaction between adjacent layers, which were caused by the asymmetrical naphthalene central core. Thus, we concluded that the structure of central core as well as the terminal chain plays an important role for the emergence of particular polar ordering in phase structures.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1647-1652
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• 2012

With the objective to design and synthesis of Schiff's base symmetrical liquid crystal dimmers and to study the effect of molecular structure variation ($o-ortho$, $m-meta$, $p-para$) and change in alkoxy terminal chain length on mesomorphic properties of liquid crystals, We have synthesized Schiff base dimers from dialdehyde derivative containing 2-hydroxy-1,3-dioxypropylene as short spacer with aniline derivatives having different lengths of terminal alkoxy chains ($n$ = 5, 7, 9). The chemical structure of the final products was characterized by proton nuclear magnetic resonance ($^1H$ NMR) spectroscopy and fourier transform infrared (FT-IR) spectroscopy. The mesomorphic properties and optical textures of the resultant dimers were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The existence of smectic A phase transition was confirmed by the observation of batonnets and fan shaped textures in optical microscopy when compound were heated from crystalline phase. All of the dimers of this series, with the exception of $\mathbf{2S_5}$ -ortho, -meta, -para, were thermotropic liquid crystal. The compound $\mathbf{2S_9}$ -meta was monotropic, while the rest were enantiotropic. It was found that the change in terminal alkoxy chain length has pronounced effect on the mesomorphic properties. The temperature range of smectic A phase window widens with increasing alkoxy chain length.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.445-448
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• 2002

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(7-octenyloxy)phenyliminomethyl}benzoate](PBOEB), 1,3-phenylene bis [4-{3-fluoro-4-(7-octenyloxy)phenyliminomethyl}benzoate] (PBFOEB), 1,3-phenylene bis [4-{4-(10-undecyloxy)phenyliminomethyl}benzoate](PBEUB), and 1,3phenylene bis [4-{3-fluoro-4-(10-undecyloxy)phenyliminomethyl}benzoate](PBFEUB) were obtained by general synthetic methods. PBOEB and PBFOEB having the octenyloxy groups such as $-(CH_2)_6CH=CH_2$ showed ferroelectric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/$cm^2$ and 225 nC/$cm^2$, respectively. PBEUB and PBFEUB having the undecyloxy groups such as $-{CH_2)_9CH=CH_2$ showed antiferroelectric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/$cm^2$ and 140 nC/$cm^2$, respectively. We could obtain ferroelectric and antiferroelectric phases by controlling the number of carbon atom in alkenyloxy chains of bent-core molecules.