• Elastomers and Composites
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• 제52권3호
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• pp.173-179
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• 2017

Side-chain liquid crystalline polymers having polysiloxane skeletons were synthesized by a thiol-ene reaction, using two kinds of mesogenic groups: a cholesteryl group for induction into a cholesteric liquid crystal phase and a triazomesogenic group for imparting light-sensitivity. All the synthesized polymers were crystalline, except the one with a single cholesteryl group. Crystallinity, glass transition temperature, and melt transition temperature increased with increasing content of the azomesogenic group. The polymer (P-C10A0) with a single cholesteryl group has a cholesteric phase, the one (P-C0A10) with a single azomesogenic group has a smectic phase, and those with both types of mesogenic groups showed both smectic and cholesteric phases. The temperature ranges of the two liquid crystalline phases in the co-polymers were independent of the contents of the two types of mesogenic groups. The rate of photoisomerization of the light-sensitive azobenzene group in the polymer decreased with increasing azobenzene content due to steric hindrance between the azomesogenic groups.

• 한국염색가공학회지
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• 제8권1호
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• pp.56-63
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• 1996

A number of thermotropic liquid crystalline polyurethanes with mesogenic unit were synthesized by polyaddition of a para-type diisocyanate such as 1, 4-phenylene diisocyanate(1,4-PDI) with 4, 4'-bis($\omega$-hydorxyalkoxy) biphenyls($BP{m}$) in DMF. The thermal and liquid crystab line properties were examined by differential scanning calorimetry(DSC), polarized optical microscopy, and wide-angle X-ray scattering(WAXS). Intrinsic viscosities of the polymers exbibited two endothermic peaks correspondinding to phase transitions of melting and isotropization. For example, polyurethane(1,4-PDI/($BP{11}$) ) was found to display a liquid crystalline phase between 177 to 205$^{\circ}C$. In order to know how the hydrogen bonding interaction affects the formation of mesophases in polyurethane 1, 4-PDI/($BP{8}$) / thermal processing FT-IR measurements were carried out. It was found that the stretches regarded as shift to higher frequency region with increasing temperature which showed grdually their liquid crystalline phase

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1266-1267
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• 2008

Liquid crystalline polymer BB-3(1-methyl) takes two kinds of glass phases which are liquid crystalline glass and liquid glass below the glass temperature. This study is aimed to analyze the phase transitions of those samples with variation of temperature. For the analyzing temperature dispersion of dielectric constants was measured and the results were analyzed.

• 공업화학
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• 제28권2호
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• pp.230-236
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• 2017

본 연구에서는 콜레스테릭 액정상 유도를 위하여 아이소소바이드기를 가지고 있으며, 액정상 전이온도의 조절을 위하여 메틸렌기를 포함하고 있는 액정고분자들을 합성하였고, 합성된 액정고분자 내의 아이소소바이드기의 함량과 메틸렌기의 위치가 액정고분자의 물성에 미치는 영향이 조사되었다. 합성된 모든 고분자들 중, 주사슬에 메틸렌 유연격자를 가진 고분자(MnHI-x)가 곁사슬에 메틸렌 유연격자를 가진 고분자(SnBI-x)들보다 더 높은 용융전이온도와 열안정성을 나타내었다. 합성된 모든 고분자들은 양방성 액정상을 나타냈으며, 콜레스테릭 액정상 유도체로써 아이소소바이드 함량이 10몰%인 고분자는 네마틱상을, 20몰% 이상의 고분자들은 콜레스테릭 액정상 또는 카이랄 스멕틱상을 형성하였다. 이로써, 아이소소바이드기가 콜레스테릭 액정상 유도체로써의 역할을 하였음을 알 수 있다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.542-544
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• 2007

New liquid crystalline Y-shaped molecules containing 1,3,4-oxadizoles have been synthesized with variation of terminal groups (R = H, $OCH_3$ or $OC_8H_{17}$). The structures of obtained compounds were identified by FT/IR and NMR spectrometry, and their thermal and liquid crystalline properties were investigated by DSC and polarizing optical microscope.

• Journal of Magnetics
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• 제15권2호
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• pp.61-63
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• 2010

We used $^1H$ nuclear magnetic resonance (NMR) to study the phase transitions and molecular dynamics in a characteristic ferroelectric liquid crystal with a carbon number n = 7, S-2-methylbutyl 4-n-heptyloxybiphenyl-4'-carboxylate (C7). The results were compared with those of our recent work on S-2-methylbutyl 4-n-octanoyloxybiphenyl-4'-carboxylate (C8), with a carbon number n = 8. While the recrystallization and isotropic phase transitions exhibited a first-order nature in the $^1H$ NMR spin-lattice and spin-spin relaxation measurements, a second-order nature was shown at the Sm-A - Sm-$C^*$ liquid crystalline phase transition. A soft-mode anomaly arising from the tilt angle amplitude fluctuation of the director, of which only a hint had been noticed in the C8 system, was manifested in the C7 system at this transition.

• Bulletin of the Korean Chemical Society
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• 제21권3호
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• pp.310-316
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• 2000

Molecular dynamics simulation studies for thermotropic liquid crystalline systems conposed of rodlike molecules with 6 Lennard-Jones interaction sites wre performed in NPT ensemble. Within the range of temperature studied, the system exhibited isotropic and smectic phase. For the characterization of the smectic phase, we examined the structure of the liquid crystalline phase via the radial distribution function, its longitudinal and transverse components to the director, and other orientational correlation function, its longitudinal and transverse components to the director, and other orientational correlation functions. In the smectic A phase, our results showed a large anisotropy in translational motion (i.e.,$D_⊥ >> D_∥$), and the decay of the collective orientational correlation function of rank two became slower than that of the single particle orientational correlation function of rank one. Comments on the spontaneous growth of orientational order directly from the isotropic phase are given.

• Applied Microscopy
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• 제45권2호
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• pp.58-62
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• 2015

Formation of an icosahedral phase in the bulk glass forming $Ti_{40}Zr_{29}Be_{14}Cu_9Ni_8$ alloy during crystallization from amorphous phase and solidification from melt is investigated. The icosahedral phase with a size of 10 to 15 nm forms as a thermodynamically stable phase at intermediate temperature during the transformation from amorphous to crystalline phases such as Laves and ${\beta}$-(Ti-Zr) phases, indicating that the existence of the icosahedral cluster in the undercooled liquid. On the other hand, the icosahedral phase forms as a primary solidification phase even though the Laves phase is stable at high temperature, which is can be explained based on the high nucleation rate of icosahedral phase relative to that of competing crystalline Laves phase due to lower interfacial energy between icosahedral and liquid phases.

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.110-117
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• 2000

A series of new liquid crystalline dimesogenic compounds with chiral tails was synthesized, and their thermal and liquid crystalline properties were studied. The chain length of the central polymethylene spacers (x) was varied from dimethylene (2) to decamethylene (12). These compounds were characterized by elemental analysis, IR and NMR spectroscopy, differential scanning calorimetry (DSC), and cross-polarizing microscopy. All compounds were found to be enantiotropically liquid crystalline, and the values of melting ($T_m$) and isotropization temperature ($T_i$) as well as enthalpy change (Δ$H_i$) and entropy change for isotropization (Δ$S_i$) decreased in a zig-zag fashion revealing the so-called odd-even effect as x increases. Their mesomorphic properties fall into three categories depending upon x; (a) compounds with x=2 and 4 formed two different mesophases, smectic and cholesteric phases in that order on heating, and vice versa on cooling, (b) compounds with x=3, 7, 8, 10 and 11 reversibly formed only the cholesteric phase, and (c) compounds with x=5, 6, 9 and 12 exhibited only a cholesteric phase on heating, whereas on cooling they formed two different mesophases, cholesteric and smectic phases, sequentially.

• 한국자기공명학회논문지
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• 제15권1호
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• pp.14-24
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• 2011

We have performed Liquid Chromatography-Solid Phase Extraction-NMR (LC-SPE-NMR) analysis for liquid crystalline mixture and elucidated the structures of selected components by NMR spectra. Combining the results of one-dimensional 1H experiments as well as homonuclear and heteronuclear two-dimensional experiments, we could analyze the molecular structure of the liquid crystal singles whose structure had not been interpretable by mass spectrometry alone.