• Macromolecular Research
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• 제13권1호
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• pp.19-29
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• 2005

Polymer composites based on a thermotropic liquid-crystalline polymer (TLCP) and poly(butylene terephthalate) (PBT) were prepared using a melt blending process. Polymer composites consisting of bulk cheap polyester with a small quantity of expensive TLCP are of interest from a commercial perspective. The interactions between the PBT chains and the flexible poly(ethylene terephthalate) (PET) units in the TLCP phase resulted in an improvement in the compatibility of PBT/TLCP composites. TLCP droplets deformed and fragmented into smaller droplets in the PBT/TLCP composites, which resulted in TLCP fibrillation through the effective deformation of the TLCP droplets. The nucleation activities of the PBT/TLCP composites increased by adding even a small amount of the TLCP component.

• 대한화학회지
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• 제48권3호
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• pp.261-265
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• 2004

12-4라는 액정올리고머가 액정이 되는 과정에서 일어나는 동력학을 2차원 라만상관분광법을 이용하여 연구하였다. 분광법의 결과로부터 에틸그룹 옆에 붙어있는 자유 카보닐 그룹이 먼저 움직이고, 수소결합을 이룬 카보닐 그룹이 나중에 움직인다는 것을 알아내었다. 반면에 바이페닐그룹사이에 존재하는 자유 카보닐 그룹은 좀처럼 움직이지 않는 것으로 나타났다. 샘플-샘플상관분광법의 결과로부터는 액정이 되는 온도 135$^{\circ}C$보다 훨씬 낮은 온도인 50$^{\circ}C$에서 이미 카보닐 그룹의 움직임이 있음을 알 수 있었다.

• Elastomers and Composites
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• 제41권2호
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• pp.108-115
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• 2006

비페닐기를 함유하는 새로운 형태의 액정성 폴리우레탄을 신규로 합성한 4,4'-Bis(9-hydroxynonoxy)biphenyl (BP9)와 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, 1,4-phenylene diisocyanate 및 hexamethylene diisocyanate의 중부가 반응에 의해 합성하였다. 단량체 BP9은 스멕틱상을 형성하였으며 1,4-PDI/BP9을 제외한 나머지 폴리우레탄에서는 모두 액정성을 나타내었다. 합성된 단량체와 중합체들의 구조는 적외선분광분석기 및 핵자기공명분석기를 사용하여 확인하였으며, 그들의 열적 상전이 온도 및 안정성들은 시차주사 열량분석기와 편광현미경으로 조사하였다.

• Bulletin of the Korean Chemical Society
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• 제27권1호
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• pp.39-43
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• 2006

The relaxed torsional potential of a liquid crystalline polymer containing an ester functional group in a mesogenic unit (hereafter 12-4 oligomer) has been calculated with the ab initio self-consistent-field using 6-31G$^*$ basis set. GIAO^{13}C NMR chemical shifts also have been calculated at the B3LYP/6-31G$^*$ level of theory for each conformational structure obtained from torsional potential calculation. The results show that the phenyl ring-ester linkages are coplanar with the dihedral angle of about 0$^{\circ}$ and the ring-ring linkages in the biphenyl groups are tilted with the dihedral angle of around 43-44$^{\circ}$ in the lowest energy conformer. The biphenyl ring has a comparatively lower energy barrier of internal rotation potential in the ring-ring than that of phenyl ring-ester. The ^{13}C chemical shifts of carbonyl carbons were found to move to upfield due to $\pi$ -conjugation with phenyl ring and slightly affected about 0.5 ppm by dihedral angle of the ring-ring linkage.

• Macromolecular Research
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• 제14권3호
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• pp.261-266
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• 2006

Blends of silicone rubber (VMQ) and liquid crystalline polymer (LCP) were prepared using a melt blending technique in the presence and absence of glass fiber and coupling agents. The effect of glass fiber and coupling agents on the thermal, dynamic mechanical, morphological pro-perties and cure characteristics of VMQ/LCP blends were studied. The vinyl silane coupling agent showed a significant effect on the above mentioned properties of VMQ/LCP blends by reacting at the interface between VMQ and LCP. The viscosity of the VMQ/LCP blends decreased with the addition of a coupling agent. A substantial improvement in storage modulus of VMQ/LCP blends was observed in the presence of glass fiber and coupling agents. However, as a coupling agent vinyl silane proved to be better than amine for the VMQ/LCP-glass-containing blends. The thermal stability of the pure silicone rubber was higher than those of the blends. This high thermal stability of silicone rubber was attributed to the Si-O-Si bonds. However, the thermal stability of the blends decreased further in the presence of a coupling agent, possibly due to a decrease in blend crystallinity.

• 한국산학기술학회논문지
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• 제8권5호
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• pp.1215-1219
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• 2007

이 논문에서는 폴리프로필렌/열방성 액정고분자 블렌드에 관한 연구 결과를 나타냈다. 기존의 연구에서 주로 쓰인 액정고분자 (Thermotropic Liquid Crystalline Polymer, TLCP)는 용융점이 대부분 270o0 이상으로 가공은 적어도 300oC 이상에서 가능하기 때문에, PP와의 블렌드 시 PP의 열분해를 피할 수 없다. 이 때문에 원하는 정도의 물성을 얻기 위해서는 과량의 TLCP를 첨가하여야 한다. 이 연구에서 고온용 TLCP 대신 융점이 220oC 정도 되는 새로운 TLCP를 사용하여 블렌드를 제조하였고, 그 특성을 관찰하였다. 연구 결과 기존 PP/TLCP 블렌드와 비교해 동등 이상의 물성을 보임을 관찰할 수 있었고, 이로서 새로운 저온용 TLCP가 PP의 강화제로 사용될 수 있음을 알 수 있었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.279-282
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• 2005

Composites comprising various volume fractions of crystalline nickel and bulk amorphous (BA) were produced by means of electroless coating of nickel on BA powder of $Cu_{54}Ni_6Zr_{22}Ti_{18}$ and subsequent spark plasma sintering (SPS) of coated BA powder. The flow curves of composites at various temperatures in the supercooled liquid region were determined by the uniaxial compression test with various strain rates. During compression at $450^{\circ}C$ with $\dot{\varepsilon}=2\times10^{-3}$, the monolithic BA sample and crystalline-BA composites displayed the superplastic deformation with $\varepsilon>1.4$. At temperatures above $460^{\circ}C$, the stress-strain curve of the monolithic BA sample depicted a sharp peak stress and a fellowing stress drop due to cracking, while those of the crystalline-BA composites displayed work-hardening up to the imposed strain. FEM analysis indicated that a fairly homogeneous strain state prevailed throughout the composite, while a higher level of stress was obtained in a harder BA.

• Composites Research
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• 제34권3호
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• pp.180-185
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• 2021

기존 아민계 경화제를 사용해 액정 에폭시를 경화할 경우, 랜덤 한 3차원 네트워크 구조의 생성으로 인해 phonon의 산란이 많이 발생하기 때문에 열전도도가 낮게 나타났다. 이러한 문제를 mesogen그룹을 적층된 구조로 형성하는 양이온 개시제를 이용하여 해결하기 위해 본 연구에서는 아민계 경화제와 양이온 개시제를 사용한 에폭시의 TGA분석(Thermogravimetric Analysis)을 통해 등온 열분해 활성화에너지를 조사하여 열적안정성을 비교하였다. 양이온 개시제를 이용한 에폭시의 경우 활성화가 에너지가 높았으며 기존 실험과 비교했을 때, 열적안정성은 열전도도와 비슷한 양상을 보인다.

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.199-206
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• 1991

A statistical thermodynamic theory of thermotropic main-chain polymeric liquid crystalline melts is developed within the framework of the lattice model by a generalization of the well-known procedure of Flory and DiMarzio. According to the results of Vasilenko et al., the theory of orientational ordering in melts of polymers containing rigid and flexible segments in the main chain is taken into account. When the ordering of flexible segments in the nematic melt is correlated with that of rigid mesogenic groups, the former is assumed to be given as a function of the ordering of rigid mesogenic cores. A free energy density that includes short-range packing contributions is formulated. The properties of the liquid-crystalline transiton are investigated for various cases of the system. The results calculated in this paper show not only the order-parameter values but also the first-order phase transition phenomena that are similar to those observed experimentally for the thermotropic liquid-crystalline polymers and show the transitional entropy terms which actually increase upon orientational ordering. In the orientational ordering values, it is shown that mesogenic groups, flexible segments, and gauche energy (temperature) may be quite substantial. Finally, by using the flexibility term, we predict the highly anisotropic mesophase which was shown by Vasilenko et al.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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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.