• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.90-90
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• 2006

Mesogen-Jacketed Liquid Crystalline Polymers, MJLCPs, are polymers with mesogenic side groups directly attached to main-chains without using flexible connecting spacers and are able to form liquid crystalline structures. Later work on structure-property of the polymers revealed that the side groups are not necessarily mesogenic for the polymers to form a mesophase so long as that the side groups are directly attached to the backbones and the side groups are large enough. Because of its inherent chain stiffness and that the monomers of MJLCPs are readily polymerizable by "living" free radical polymerizations, MJLCP offered a unique handy tool for making block copolymers. In addition, MJLCP offered also new opportunities for novel functional materials.

• 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.

• Korea-Australia Rheology Journal
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• 제15권3호
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• pp.109-115
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• 2003

Rheometry testing and the DSC measurement of five thermotropic liquid crystalline polymers (TLCP) have been carried out. The dynamic viscosities of the five TLCPs show a typical shear-thinning behaviour obeying the power-law with the power indices from 0.2 to 0.3. When these TLCPs are heated above the melting temperatures determined by the DSC measurements, the dynamic viscosities first rapidly decrease by 2～3 orders of magnitude then level off, finally increase gradually with the further increasing of temperature. The steady shearing exhibited the same behaviour as the dynamic shearing, but serious edge fracture of material slippage out of the plates occurred. The abnormal temperature dependence of the viscosities can be explained by the nematic-isotropic transition. By using the concept of activation energy, we propose a simple model which can fit the shear-thinning behaviour quite well and predict qualitatively correct temperature effects.

• Fibers and Polymers
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• 제1권2호
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• pp.83-91
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• 2000

Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate)(PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=$15.5^{\circ}C$ appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of blends increased with blending time but sequential length of both PEN and PET segment decreased.

• Fibers and Polymers
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• 제2권3호
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• pp.117-121
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• 2001

Liquid crystalline spiroxazine derivatives have been synthesized. The spiroxazines obtained were characterized by H-NMR, IR spectroscopy, UV and GC-MS.

• Elastomers and Composites
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• 제54권1호
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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.

• 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.

• Korean Chemical Engineering Research
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• 제43권1호
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• pp.176-180
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• 2005

방향족 Schiff base 메소제닉 단위와 폴리메틸렌 유연격자로 이루어진 한 계열의 주사슬 액정중합체와 네 계열 화합물의 액정성을 살펴보았다. 이들의 열적 성질과 액정성은 시차 주사 열분석기와 가열판이 부착된 편광현미경에 의하여 조사하였다. 중합체와 화합물 액정상의 성질은 중앙 폴리메틸렌 유연격자와 말단 알콕시기의 길이에 크게 의존하였다. 중합체 I과 계열 III 화합물은 녹는점과 등방성액체화 전이온도에서 짝수-홀수 효과를 보여 주었으나 계열 II와 IV 화합물은 등방성액체화 전이온도에서만 짝수-홀수 효과를 나타내었다. 편광현미경을 통하여 이들의 광학구조를 관찰하였을 때 네마틱과 스멕틱 액정상을 형성하였다.

• 공업화학
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• 제26권4호
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• pp.445-451
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• 2015

주사슬에 메소젠기와 유연격자로써 옥타메틸렌기를 포함하고 있는 반 유연성 액정중합체가 용액 중축합반응에 의하여 합성되었다. 중합체의 메소젠기는 에스터와 케톤, 에터, 설파이드, 메틸렌, 설폰, 또는 아이소프로필리덴기들에 의해 결합된 4개의 방향족고리로 되어 있다. 본 논문에서는, 메소젠기의 가운데 연결기가 중합체의 물성에 미치는 영향에 대하여 고찰하였다. 합성된 중합체의 구조와 성질은 $^1H$-NMR, FT-IR, DSC, TGA, XRD, POM에 의하여 조사되었으며, 그 결과에 의하면, 굽은 구조의 연결기를 가지고 있는 중합체들은 낮은 열전이온도, 좁은 액정상 온도구간, 약한 액정성, 그리고 유기용매에 대한 좋은 용해성을 보여 주었고, 벌크한 연결기를 갖는 중합체들은 무정형 중합체로서 높은 유리전이온도($T_g$)를 나타내었다.

• 공업화학
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• 제25권1호
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• pp.47-52
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• 2014

주사슬에 X-모양의 메소젠기를 갖는 액정폴리에스터 시리즈가 단위체인 2,5-디(4-치환된 벤조에이트)하이드로퀴논과 4,4'-디카르복시-1,8-디페녹시옥테인으로부터 용액중합에 의해 합성되었다. 합성된 중합체의 구조와 물성들은 $^1H$-NMR, FT-IR, DSC, TGA, POM, WXRD를 이용하여 조사되었다. 1,1,2,2-테트라클로로에탄 내에서 측정된 중합체의 고유점성도(${\eta}_{inh}$)는 0.35~0.66 dL/g로 측정되었으며, 본 실험에서 용해도 조사에 사용된 대부분의 유기용매에 잘 용해되었다. 모든 중합체들은 비교적 낮은 용융전이온도($T_m$)와 결정성을 나타내었으며, $T_m$ 이상으로 가열했을 때 열방성 네마틱 액정성을 보였다. 중합체의 이러한 특성은 주사슬에 결합되어 있는 벌키한 4-치환된 벤조에이트기에 때문인 것으로 보인다.