• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.228-228
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• 2006

Conjugated oligomers, used as models for fluorene-thiophene copolymers, are compared in terms of the microscopic morphology of thin deposits and the optical properties. The AFM images and the solid-state absorption and emission spectra are interpreted in line with the structural data, in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long strip-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates. The difference in behavior between the two compounds most probably originates from their different capability of forming densely-packed assemblies of ${\pi-pi}$ interacting molecules. These assemblies are used as active elements in organic field effect transistors designed by using soft lithography technique.

• ALGAE
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• 제24권4호
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• pp.239-248
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• 2009

Fluorescence and electron microscopy were used to examine epidermal shedding in the fucoid alga, Ascophyllum nodosum. Mature meristoderm cells are ca. 50-100 x 30-40 ${\mu}m$ and highly polarized, with a single nucleus and chloroplasts near the base of the cell. Nuclei in these cells undergo mitosis when they are dividing to form a new cortical cell towards the middle of the frond, or anticlinal divisions as part of frond elongation. However, cytokinesis also occurs regularly in these cells when a new periclinal wall is deposited at about 30% of the cell length from the apical end. The newly formed distal cells are anucleate and without chloroplasts. Following cytokinesis the tangential walls then break at the thinnest point. The whole process is synchronous in adjoining epidermal cells across large areas of the frond surface, and this layer dehisces from the thallus. This is the only known plant or algal system in which cytokinesis regularly occurs in the absence of mitosis. We consider this process a novel form of programmed cell death.

• 공업화학
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• 제18권2호
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• pp.130-135
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• 2007

EGCG의 안정성을 향상시키기 위해 ethosome에 포집을 시도하였다. 물에 에탄올을 첨가해서 EGCG의 용해도를 높임으로써 ethosome에 적정량의 EGCG이 포집될 수 있도록 하였다. EGCG 수용액의 농도와 ethosome 막을 구성하는 지질의 조성은 ethosome 입자크기와 포집효율에 상당한 영향을 미치는 것을 확인하고 ethosome의 액정상 형성은 편광 현미경을 사용하여 관측하였다. EGCG가 수용액 상태로 있을 때와 ethosome에 포집되어 있을 때, UV 또는 고온의 상태에서의 안정성을 비교한 결과 ethosome에 포집된 EGCG의 안정화 효과를 확인하였다. Ethosome에 토코페롤의 첨가는 UV에 의한 EGCG의 분해를 지연시켰다.

• 한국표면공학회지
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• 제40권1호
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• pp.16-22
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• 2007

Recently, mesoporous metallic materials are becoming more and more important in various applications like catalysts, electrochemical detectors, batteries, and fuel cells because of their high surface area. Among the various methods for manufacturing mesoporous structure, surfactant templating method followed by electroplating has been tried in this study. A mesoporous metallic film was prepared by electrodeposition from electroplating solution mixed with surfactant template. Nonionic type lyotropic liquid crystalline surfactant, Brij56, and nickel acetate based solution were selected as a template material and electroplating solution, respectively. To determine the content of surfactant forming a hexagonal column structure, the phase diagram of electroplating solution and surfactant mixture has been exploited by polarized optical microscopy equipped with heating and cooling stage. Nickel films were electroplated on Cu foil by stepwise potential input method to alleviate the concentration polarization occurred during the electroplating process. TEM and XRD analyses were performed to characterize the size and shape of mesostructures in manufactured nickel films, and electrochemical characterization was also carried out using cyclic voltammetry.

• 공업화학
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• 제3권2호
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• pp.280-287
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• 1992

테레프탈산, 비페닐 디카르복시산과 히드로퀴논을 용액중합하여 전방향족 액정 폴리에스테르를 합성하고 테레프탈산과 비페닐 디카복시산의 몰비가 액정중합체의 열적성질, 열안정성 및 메소상의 구조에 미치는 영향을 DSC, TGA, 편광현미경 및 X선회절기로 조사하였다. 본 연구에서 합성한 중합체는 모두 열방성 액정중합체였고 네마틱 액정상을 나타내었으며, 용융온도 및 등방화온도는 중합체중의 비페닐렌구조가 증가함에 따라 약간씩 증가하였다. 또한 중합체의 열안정성은 중합체중의 비페닐렌구조가 증가함에 따라 개선되었으며, 비페닐렌구조를 가지는 중합체의 결정도는 상당히 높아서 약 33%정도로 나타났다.

• 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

• 폴리머
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• 제31권5호
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• pp.385-392
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• 2007

Poly (N-vinylpyrrolidone) (PVP) groups were grafted onto a poly(3-hydroxybutyrate-co-3-hydroryvalerate) (PHBV) backbone in order to modify its properties and synthesize a novel biocompatible copolymer. The crystallization behavior of PHBV and grafted PHBV was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). During the cooling-induced crystallization process, the crystallization temperature and the crystallization rate of the grafted PHBV decreased with increasing PVP weight fraction. On the heating scans of all grafted PHBV samples, a new crystallization exothermic peak appeared at almost the same temperature, suggesting the operation of a recrystallization process, while the melting temperature ($T_m$) and the apparent enthalpy of fusion (${\Delta}H_f$) were not affected by graft modification. During the isothermal crystallization process at the same temperature, the presence of side PVP groups decreased the spherulitic growth rate and the spherulitic band spacing with increasing PVP weight fraction in samples.

• Macromolecular Research
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• 제10권4호
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• pp.230-235
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• 2002

Alternating polyols of oxymethylene and oxyalkylene were synthesized and used as precursors for thermoplastic poly(ether-ester) elastomers (TPEs). The polyols were synthesized by reacting diols having different methylene units with dichloromethane in the presence of a phase transfer catalyst. The number of methylene units in the alkylene oxides was varied from 3 to 6. TPEs were prepared using the polyols as soft segments and poly(butylene terephthalate) units as hard segments. The polyols and TPEs synthesized were characterized using FTIR, NMR, GPC, DSC, and polarized optical microscopy. The polyols showed a profound odd-even effect on the melting (T$_{m}$) and glass transition temperatures (T$_{g}$). Polyols with odd numbers of methylene groups in the alkylene units have higher transition temperatures than polyols with odd number of methylene groups. The tendency is still kept in TPEs, even though the T$_{g}$ of soft segment in TPEs are slightly higher than those of corresponding neat polyols. The T$_{m}$ and T$_{g}$ of soft segments are almost constant in the range of 20 to 60 wt % contents of soft segments. On the other hand, the normalized heat of fusion of hard segment decreased with increasing the content of loft segment.ent.t.ent.

• 한국식품조리과학회지
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• 제10권1호
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• pp.76-79
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• 1994

본 연구는 청포묵의 제조과정에서 일어나는 동부전분의 형태변화와 결정성의 변화를 조사하기 위하여 수행하였다. 동부전분은 70~75$^{\circ}C$에서 결정성이 상실되는 것을 편광현미경과 X-선 회절도로부터 알 수 있었다. 가열에 따른 동부전분의 변화를 SEM관찰했을 때, 65~75$^{\circ}C$에서는 팽윤이 일어나면서도 입자의 형태는 보전되었으나 85$^{\circ}C$ 이상에서는 용출물이 많이 빠져나온 후 입자의 중첩이 일어나는 것을 볼 수 있었다. 묵의 형성, 즉 호화전분의 겔화는 한 그룹의 약한 수소결합에 의하여 안정화되는 junction zone이 형성되어 망상조직이 이루어지는 것임이 저장했던 전분겔을 재가열할 때의 DSC thermogram을 통하여 나타났고, 재가열한 전분의 X-선 회절도 분석한 결과 결정화는 아닌 것이 밝혀졌다.

• 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.