• Title/Summary/Keyword: mesomorphic behavior

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Polysiloxanes Containing Alkyl Side Groups: Synthesis and Mesomorphic Behavior

  • Kim, Byoung-Gak;Moon, Jin-Kyung;Sohn, Eun-Ho;Lee, Jong-Chan;Yeo, Jong-Kee
    • Macromolecular Research
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    • v.16 no.1
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    • pp.36-44
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    • 2008
  • A series of polysiloxanes containing alkylsulfonyl side groups were synthesized using a polymer analogous reaction beginning from poly(methylhydrosiloxane) and the corresponding olefins. These polymers showed a mesomorphic behavior with smectic liquid crystalline phases. The chemical and physical properties of these polymers were examined using nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction.

Effect of Molecular Weight on Thermal Behavior of Polyurthanes Containing Mesogen Unit (분자량이 메소겐기를 포함한 폴리우레탄의 열적거동에 미치는 영향)

  • Hong, Sung-Chul;Lee, Woo-Young;Nam, Byeong-Uk;Lee, Sang-Won
    • Elastomers and Composites
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    • v.40 no.3
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    • pp.212-221
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    • 2005
  • Polyurethanes containing mesogen unit (MPU-6) were prepared from 4,4'-diphenylmethane diisocyanate (MDI) and 4,4'-bis(6-hydroxy hexoxy)biphenyl (BP-6) having flexible chain composed of 6 carbons. Intrinsic viscosities of MPU-6s were in the range of $0.23{\sim}0.56 dL/g$. The mesomorphic behaviors of MPU-6 were observed in X-ray and polarizing microscopy analysis. However, MPU-6s demonstrated a 'virtual liquid crystal' behavior, which did not exhibit mesophase on slow heating and slow cooling. MPU-6 having lower molecular weight exhibited higher crystallization rate and melting crystallization temperature due to increased mobility of polymer chains. The increased mobility of polymer chains facilitate the orientation of mesogen units that may act as a nucleating agent.

Synthesis and Mesomorphic Behavior of Cholesteryl S-Alkoxybenzene Thiocarbonates. (Cholesteryl S -Alkoxybenzene Thiocarbonates의 합성과 액정 성질에 관한 연구)

  • Jeon, Young-Jai
    • Korean Journal of Materials Research
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    • v.2 no.6
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    • pp.398-407
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    • 1992
  • Cholesteryl S-alkoxybenzene thiocarbonates was synthesized and their liquid crystal transition temperature were determined. Those compounds exhibit enantiotropic cholesteric mesophases. The cholestric-isotropic transition temperatures decrease gradually with increasing alkoxy chain length and mesophase transition were investigated by differential scanning calorimetry.

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Synthesis and Mesomorphic Properties of Palladium(II) Complexes Based on 3,4,5-Trialkoxy Benzonitrile Ligands

  • 이명수;유용식;최문근
    • Bulletin of the Korean Chemical Society
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    • v.18 no.10
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    • pp.1067-1070
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    • 1997
  • The synthesis and characterization of the nitrile ligands 3,4,5-tridodecyloxy benzonitrile (7) and 3,4,5-trioctadecyloxy benzonitrile (8), and their corresponding palladium(Ⅱ) complexes are described. The nitrile ligands display only a crystalline phase and do not show liquid crystalline behavior, while their corresponding palladium(Ⅱ) complexes dispaly an enantiotropic columnar mesophase. The induction of the columnar mesophase is mainly due to dimerization through the palladium complexation of the half disk-like nitrile ligands giving rise to a trans square planar geometry.

Synthesis and Characterization of Liquid Crystalline Polyurethanes Containing Aromatic Ring Moiety (방향족 고리를 갖는 액정폴리우레탄의 합성 및 특성)

  • Lee, Jong-Baek
    • 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.

Synthesis, Molecular Structure and Mesomorphic Phase Behavior of${\eta}^1$-Benzylideneaniline Palladium(II) Complexes

  • Yu, Yong Sik;Im, Jun Hwan;Han, Bong Hwan;Lee, Myeong Su;Choe, Mun Geun
    • Bulletin of the Korean Chemical Society
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    • v.22 no.12
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    • pp.1350-1360
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    • 2001
  • The synthesis and characterization of very stable Pd(Ⅱ) η1-imine complexes of bis(3,4-dialkyloxybenzylidene-3', 4'-dialkyloxyaniline)dichloropalladium(Ⅱ) with alkyl chain of hexyl (8), octyl (9), decyl (10) and dodecyl (11) groups, a nd of bis(4-ethyloxybenzylidene-4'-ethyloxyaniline)dichloropalladium(Ⅱ) as a model complex are described. The molecular structure with twisted board-like geometry of the complex resulting from the coordination of Pd(Ⅱ) with η1-imine bonding was confirmed by X-ray crystallographic analysis of the model complex. In contrast to the imine ligands, all the complexes with an exception of 11 display a thermally stable monotropic smectic A mesophase without any decomposition of the complex. These results, characterized by a combination of differential scanning calorimetry, optical polarized microscopy, and powder X-ray scattering experiments, are discussed.

Analysis of Intermolecular Interaction in Thermotropic Aromatic Polyurethanes with Flexible Spacers (Spacer를 가지고 방향족 polyurethane의 분자간 상호 작용에 의한 액정성의 발견)

  • Lee, Jong Back;Song, Jin Cherl
    • Textile Coloration and Finishing
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    • v.7 no.4
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    • pp.8-15
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    • 1995
  • A series of thermotropic Polyurethanes mesogenic unit were synthesized by polyaddition of a para-type diisocyanate such as 2,5-tolylene diisocyanate(2,5-TDI) with 4-4'-bis($\omega$-hydroxyalkoxy) biphenls(BPm: $HOCmH_{2m}OC_{6}H_{4}OC_{m}H_{2m}OH$ : m is the carbon number of the hydroxyalkoxy group) in DMF. Intrinsic viscosities of the polymers were in the range of 0.41~0.99dL/g DSC thermograms for these polymers exhibited two endothermic peaks corresponding to phase transitions of melting and isotropization. For examplem polyurethane 2,5-TDI/BPll with [η]=0.99 prepared from 2.5-TDI and 4,4'-bis[11-hydroxyundecaoxy biphenyl(BP11) a liquid crystalline phase from 156 to 173$^{\circ}C$. The thermotropic properites of liquid crystalline polyurethanes have been investigated by wide-angle X-ray scatter(WAXS), infrared (IR) spectroscopy, and differential scanning calorimetry (DSC). The mesomorphic behavior of the polyurethanes was concluded to be greatly dependent on the intermolecular hydrogen bonds through the urethane.

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Synthesis and Characterization of New Thermotropic Liquid Crystalline Polyurethanes with Naphthalene Moiety (나프탈렌기를 갖는 새로운 액정폴리우레탄의 합성 및 특성)

  • Lee, Jong-Baek;Lee, Kwang-Hyun
    • 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.

Ferroelectric and Antiferroelectric Behavior in Chiral Bent-shaped Molecules with an Asymmetric Central Naphthalene Core

  • Lee, Seng-Kue;Tokita, Masatoshi;Shimbo, Yoshio;Kang, Kyung-Tae;Takezoe, Hideo;Watanabe, Junji
    • 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.

Thermotropic Polyurethanes Prepared from Diisocyanates and 4,4'-Bis(3-hydroxypropoxy)Biphenyl Containing Mesogenic Unit (4,4'-Bis(3-hydroxypropoxy)Biphenyl와 Diisocyanate 에 의한 열방성 액정폴리우레탄 합성)

  • Lee, Jong Baek
    • Korean Chemical Engineering Research
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    • v.48 no.5
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    • pp.615-620
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    • 2010
  • In this study, five series of novel polyurethanes was synthesized by the polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate(2,6-TDI), 2,5-tolylene diisocyanate(2,5-TDI), 2,4-tolylene diisocyanate(2,4-TDI), and 1,4-phenylene diisocyanate(1,4-PDI), hexamethylene diisocyanate(HDI) with 4,4'-Bis(3-hydroxypropoxy)biphenyl (BP3), 4,4'-bis(3-hydroxypropoxy)biphenyl exhibited a smectic type mesophase. Monotropic mesophase was found for all synthesized liquid crystalline polyurethanes except HDI/BP3. In contrast, 1,4-PDI/BP3 without a methyl substituent in the phenylene unit exhibited no explicit mesomorphic behavior, which was confirmed by DSC and polarizing microscopy experiments. Structures of the compound were identified by FT-IR and $^1H$-NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry(DSC), polarized optical microscopy(POM) and x-ray diffraction analysis.