• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.188-193
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• 1982

Four new thermotropic copolyesters were prepared and their liquid crystal properties were investigated by differential scanning calorimetry and on a hot-stage of a polarizing microscope. Three copolyesters had same mesogenic unit, triad aromatic ester structure, interconnected through a random combination of either odd-even, or odd-odd, or even-even number of methylene groups in the polymethylene flexible spacers. Another random copolyester consisted of mesogenic units of 1 : 1 mixture of central methyl-and bromohydroquinone moieties with two flanking p-oxybenzoate units connected by decamethylene spacer. All of the polyesters formed nematic liquid crystal phase upon melting. The transitions for melting and nematic ${\to}$ isotropic transformations could be reversibly observed by DSC as well as by microscopic study. The thermodynamic properties for their liquid crystal ${\to}$ isotropic phase transitions were discussed in relation to their chemical structures.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.890-892
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• 2007

We report the syntheses and characterizations of a novel TTF derivative. To extend the mesogenic core, alkoxy naphthalenic group and short alkyl chains were introduced on either side of TTF unit, which results in asymmetric planar structure. TTF molecule is expected to show many interesting properties.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.933-935
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• 2002

In this paper, new non-chiral molecules with semi-fluorinated alkyl chains were synthesized varying the structure of central bent core unit. Their mesomorphic properties were investigated by DSC and polarized microscopy. The compound with 1,3-dihydroxy phenylene unit could form an enantiomeric smectic phase, but the remaining compounds with bent-core mesogenic unit were not liquid crystalline. In this presentation, their x-ray measurement and electro-optical property will be also described.

• Elastomers and Composites
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• v.54 no.1
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• pp.14-21
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• 2019

Main-chain/side-chain liquid crystalline polymers (MCSCLCPs) combined with an azobenzene group and a cholesteryl group were synthesized to impart light and temperature sensitivity to the polymer. The polymers were designed with the azobenzene unit as the mesogenic group of the main-chain and various compositions of the azobenzene and cholesteryl units as the mesogenic group of the side-chain. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and ultraviolet-visible (UV-Vis) spectroscopy. All the MCSCLCPs were amorphous and exhibited enantiotropic liquid crystal phases; these polymers achieved the nematic phase with increasing content of the azobenzene group and exhibited the cholesteric phase with weak liquid crystallinity as the content of the cholesteryl group was increased. Furthermore, the polymers containing the azobenzene group showed photoisomerization when exposed to UV-Vis light, and the CP-A3C7 and CP-A5C5 polymers exhibited thermochromism in the temperature range of the liquid crystal phase.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.339-346
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• 1997

Liquid crystalline polyurethanes were prepared from 1,4-bis(6-hydroxyhexoxy)benzene (BHB6) and 2,5-tolylene diisocyanate (2,5-TDI) solution polymerization in dimethylformamide produced intrinsic viscosities in the range 0.26 and $0.42d{\ell}/g$. The polyurethanes were investigated by DSC, Polarizing microscopy, X-ray, $^1H$-NMR and IR spectroscopy. Polyurethanes of two different molecular weights were studied in detail and these will be referred to as low molecular weight and high molecular weight. Polyurethane 2,5-TDI/BHB6 with $[{\eta}]=0.26d{\ell}/g$ prepared from BHB6 and 2,5-TDI, exhibited monotropic liquid crystallinity, although these polyurethanes contained no mesogenic core unit. For example, LCPU-L(low molecular weight) exhibited $T_{I-LC}$ of $122^{\circ}C$ $T_{LC-K}$ $89^{\circ}C$.

• Elastomers and Composites
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• v.48 no.2
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• pp.141-147
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• 2013

Polyurethanes containing no mesogenic unit were prepared by polyaddition reaction of homo- and copolyurethanes based on para-type 1,4-phenylene diisocyanate (1,4-PDI), 2,6-bis($\omega$-hydroxypentoxy)naphthalene (BHN5) with 1,4-bis($\omega$-hydroxypentoxy)benzene (BHB5). All copolyurethanes showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane Poly(50/50, mol%) with $[\eta]$=0.32 dL/g exhibited liquid crystallinity in the temperature range from $223^{\circ}C$ to $211^{\circ}C$ in the cooling stage. In contrast, two homopolyurethanes exhibited no explicit mesomorphic behavior, which was observed by DSC (Differental Scanning calorimeter) and measurement and polarized microscopic observation. The mesomorphic behavior of synthesized polyurethane was identified and characterized by differential scanning calorimetry, polarized optical microscope and X-ray.

• 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.

• Journal of Information Display
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• v.2 no.3
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• pp.6-12
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• 2001

Formation of intensity gratings was studied with two s-polarized (s+s) configuration in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) by photoinduced alignment of PLCs. Remarkable differences were observed between the two PLCs. T-AB showed a faster response to the change in the diffraction intensity than CB-AB. In T-AB, alignment change took place faster than that of CB-AB. By introducing the tolane unit at the side chain, we obtained a diffraction efficiency of 30 % in the Raman-Nath regime

• Elastomers and Composites
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• v.40 no.1
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• pp.37-44
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• 2005

Novel polyurethanes containing no mesogenic unit were synthesized by the polyaddition reaction of para-type diisocyanates such as 2,5-tolylene diisocyanate (2,5-TDI) or 1,4-phenylene diisocyanate (1,4-PDI) with 2,6-bis(${\omega}$-hydroxyalkoxy)naphthalene (BHNm; m= 5, 6, 8, 11). Intrinsic viscosities of the polymers were in the range of 0.28-0.43 dL/g. The thermal properties of these polymers were studied by differential scanning calorimetry and polarizing microscopy. Polyurethanes prepared from BHNm and 2,5-TDI haying methyl substituent on the phenylene unit exhibited monotropic liquid crystallinity. However, in the series of polyurethanes prepared from 1,4-PDI and BHNm, no explicit mesomorphic behavior was observed by differential scanning calorimetry and polarizing microscopy.

• Journal of the Korean Chemical Society
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• v.52 no.5
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• pp.583-587
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• 2008