• Title/Summary/Keyword: mesogenic

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Synthesis and Properties of Thermotropic Compounds with Two Terminal Mesogenic Units and a Central Spacer Ⅲ. Homologous Series of $\alpha,\omega$-Bis[4-(p-nitrobenzoyloxy)phenoxy]alkanes

  • Jin, Jung-Il;Kang, Joo-Sam;Jo, Byung-Wook;Lenz, Robert W.
    • Bulletin of the Korean Chemical Society
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    • v.4 no.4
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    • pp.176-180
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    • 1983
  • A series of new liquid crystalline compounds having two identical mesogenic terminal units, the 4-(p-nitrobenzoyloxy)phenoxy group, attached to both ends of a central polymethylene spacer of various lengths was prepared. The mesomorphic properties of the compounds were investigated by differential scanning calorimetry (DSC) and by polarizing microscopy. Almost all of the compounds formed monotropic nematic mesophases. The trimethylene spacer compound was found to be non-liquid crystalline, while the one with the hexamethylene central spacer was enantiotropic. A thermodynamic analysis was performed for the phase transitions of the compounds and the results are discussed in relation to their liquid crystal properties.

Liquid Crystal Polymers (X). Synthesis and Properties of New Thermotropic Main Chain Copolyesters with Either Mixed Polymethylene Spacers or Mixed Mesogenic Units (액정 중합체 (제10보). 혼합폴리에틸렌 격자나 메소젠 단위를 갖고 있는 새로운 주사슬 혼성폴리에스테르의 합성 및 성질)

  • Jung-Il Jin;Robert W. Lenz;S. Antoun
    • 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.

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High Out-of-Plane Alignment of Liquid Crystalline Methacrylate Copolymer Bearing Photoreactive 4-Styrylpyridine Moiety

  • Kwak, Gi-Seop;Kong, Jong-Yun;Kim, Min-Woo;Hyun, Seok-Hee;Kim, Woo-Sik
    • Macromolecular Research
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    • v.17 no.4
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    • pp.271-275
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    • 2009
  • This paper describes the out-of-plane order of a liquid crystalline(LC) methacrylate copolymer(3) comprised of a methacrylate(1) with a 4-styrylpyridine moiety as the photo-cyclodimerizable group and a benzoate moiety as the mesogenic group in the side chain, and another methacrylate(2) with a 4-(4-methoxyphenyl)benzoate moiety as the mesogenic group. The composition of 1 and 2 units in 3 was estimated to have a molar ratio of 54.2:45.8 by $^{1}H$ NMR spectroscopy. The X-ray diffraction study revealed that the copolymer forms a partial bilayer smectic structure. The copolymer gave rise to a high out-of-plane order parameter of about 0.74 in a wide LC temperature range of $110{\sim}160^{\circ}C$ after linearly polarized, UV light irradiation and subsequent annealing. Moreover, the external reflection IR analysis indicated that excess UV-light irradiation makes the out-of-plane LC structure of the copolymer appear in a higher and wider temperature range.

Raman and Fluorescence Studies of Thermotropic Liquid-Crystalline Oligomers with Different Type of Coils

  • Chae, Jong-Bok;Yu, Soo-Chang;Lee, Youn-Sik
    • Bulletin of the Korean Chemical Society
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    • v.28 no.2
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    • pp.193-199
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    • 2007
  • Raman and fluorescence spectroscopies were employed to study the coil effects on the intermolecular structure of a rod-coil liquid crystalline (LC) oligomer, the esterification products of ethyl 4-[4'-oxy-4-biphenylcarbonyloxy]- 4'-biphenylcarboxylate with poly(propylene)oxides (PPO) (DP=12) and poly(ethylene oxide)s (PEO) (DP=12). Three different vibrational modes (carbonyl, aromatic C-H, and aromatic C=C) obtained from the Raman experiment at variable temperature indicate that PPO and PEO coils induce the hydrogen bonding in a different manner. Further information about the micro-environment around the mesogenic unit obtained by fluorescence excitation spectra of P12-4 (LC with PPO coil) and 12-4 (LC with PEO coil) suggests that the mesogenic unit of P12-4 is quite different from that of 12-4 in intermolecular structure. This study supports the results obtained only from Raman spectroscopy, providing more accurate information about the intermolecular structural changes of liquid crystalline polymers at a molecular level during the phase transitions.

Synthesis and Properties of Combined Main-Chain/Side-Chain Liquid Crystalline Polymers with Cholesteryl and Azobenzene Groups

  • Gu, Su-Jin;Lee, Eung-Jae;Bang, Moon-Soo
    • 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.

Synthesis and Properties of Polyesters with Bent-Shaped Mesogens Containing Naphthalene Central Unit

  • Seo, Young-Ho;Choi, E-Joon
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.633-636
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    • 2009
  • New polyesters with bent-shaped mesogens were synthesized varying the central unit with 1,6- and 2,3- naphthylenes, and introducing the dodecamethylene flexible spacer. The mesogenic properties of the polymers were characterized by FT-IR spectroscopy, DSC, polarizing optical microscopy.

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Synthesis and Characterization of a Novel TTF Derivative

  • Wang, Lei;Lee, Myong-Hoon
    • 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.

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Photoresponsive Liquid Crystalline Copolymers Bearing a p-Methoxyazobenzene Moiety

  • 최동훈;강석훈;이준열;Asit Baran Samui
    • Bulletin of the Korean Chemical Society
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    • v.19 no.11
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    • pp.1179-1184
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    • 1998
  • Mesogenic and azo monomers were synthesized and copolymerized to obtain two copolymers composed of methacrylate and itaconate backbone. Glass transition temperatures of the copolymers were found to be slightly higher than ambient temperature. Both the copolymers showed liquid crystalline properties. Trans-cis isomerization in film state was observed under UV-irradiation with a light of 365 nm. Regarding the photochemical phase transition behavior, the transition rate of nematic-to-isotropic state was slightly faster in the methacrylate copolymer during irradiation at 365 nm and the rate of the reverse transition was much faster in itaconate copolymer under thermal effect.