• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.345-345
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• 2006

It is well known that poly(glutamate)s with long n-alkyl side chains form thermotropic liquid crystalline state by melting of the side-chain crystallites and also poly(glutamate)s such as poly(${\gamma}-benzyl\;L-glutamate$ )(PBLG), poly(${\gamma}-n-alkyl\;L-glutamate$), etc. in solvent form the isotropic, biphasic and liquid crystalline phases which contains cholesteric and columnar liquid crystalline forms depending on the polypeptide concentration. Although there is no diffusion study for PBLG in liquid crystalline state, because it is difficult to observed $^{1}H$ spectrum of PBLG in liquid crystalline state for its very short $^{1}H\;T_{2}$. In this study, the diffusional behavior of rodlike PBLG in concentrated solution is successfully elucidated as studied by the field-gradient $^{1}H$ NMR methods.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.677-680
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• 1999

Rapid developing automation technology enhances the need of sensors. Among many materials, silicon has the advantages of electrical and mechanical property, Single-crystalline silicon has different piezoresistivity on 야fferent directions and a current leakage at elevated temperature, but poly-crystalline silicon has the possibility of controling resistivity using dopping ions, and operation at high temperature, which is grown on insulating layers. Each wafer has slightly different thicknesses that make difficult to obtain the precisely same thickness of a diaphragm. This paper deals with the fabrication process to make poly-crystalline silicon based pressure sensors which includes diaphragm thickness and wet-etching techniques for each layer. Diaphragms of the same thickness can be fabricated consisting of deposited layers by silicon bulk etching. HF etches silicon nitride, HNO$_3$+HF does poly -crystalline silicon at room temperature very fast. Whereas ethylenediamice based etchant is used to etch silicon at 11$0^{\circ}C$ slowly.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.94-97
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• 2005

For the fabrication of poly-crystalline silicon ingot, CCCC (Cold Crucible Continuous Casting) method under a high frequency alternating magnetic field, was utilized in order to prevent crucible consumption and ingot contamination and to increase production rate. In order to effectively and continuously melt and cast silicon, which has a high radiation heat loss due to the high melting temperature and a low induction heating efficiency due to a low electric conductivity, Joule and pinch effects were optimized. Throughout the present investigation, poly-crystalline Si ingot was successfully produced at the casting speed of above 1.5 mm/min under a non-contact condition.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.4027-4034
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• 2011

$CaCO_3$ crystalline structures having novel assemblies were in situ fabricated as analogs of naturally occurring proteins and polysaccharides for biomineralization. The calcite crystal was mineralized in a poly(vinyl alcohol)-$Ca^{2+}$ complex film immersed in a $Na_2CO_3$ solution containing poly(aspartic acid). The morphology and size of the $CaCO_3$ crystals were tuned by varying the concentration of poly(aspartic acid). The mechanisms of their nucleation orientation and formation were investigated experimentally and through molecular dynamics (MD) simulations in order to obtain a better understanding of the interactions between the polymers and the crystal at the molecular level. Both the MD results and experimental results indicate that the interaction between PVA and calcite mainly depends on the concentration of the polymer. The novel approach proposed herein for the fabrication of inorganic crystalline assembly structures can be used to fabricate precise crystalline structures.

• Fibers and Polymers
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• 제1권1호
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• pp.18-24
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• 2000

The phase transformation of poly(trimethylene terephthalate) in crystalline state was simulated by atomistic modeling using molecular mechanics technique. The crystalline structure of PTT was successfully prepared using the well-defined unit cell structure of PTT and was satisfactorily verified by comparing that with the structure obtained from the x-ray diffraction experiments. The basic elastic properties were predicted in this study, showing that the crystalline structure of PTT is very pliable to the deformation at small strain. When the crystalline structure of PTT was stepwise deformed up to 50% of strain in chain direction under uniaxial extension condition, the change in dihedral angle of trimethylene unit from gg to tt conformation was accompanied with a large increase of stress, indicating that the phase transformation of PTT in crystalline state is difficult to occur.

• 폴리머
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• 제37권2호
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• pp.177-183
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• 2013

본 연구에서는 poly(ethylene terephthalate)(PET) 필름을 기재로 하여 분산코팅에 의해 형성된 poly(vinylidene fluoride)(PVDF)와 poly(methyl methacrylate)(PMMA) 블렌드 코팅의 표면 특성을 관찰하였다. 분산코팅의 특성상 저온에서 형성된 블렌드 코팅은 PVDF 입자의 형태와 결정구조가 그대로 유지되었으나 $120^{\circ}C$ 이상의 코팅온도에서 형성된 코팅의 경우 블렌드에 포함되어 있는 PVDF의 양에 따라 다양한 표면 특성을 나타내었다. 블렌드 중 PVDF의 양이 80 wt% 이상인 경우 PVDF의 ${\alpha}$-결정구조에 의한 특성이 확실히 관찰되는 반면에 PMMA의 양이 증가하면 표면 형태와 결정구조의 변화가 변화하는 것을 관찰하였다. 또한 코팅층의 최외각 표면에 대한 XPS 분석결과는 분산코팅에서도 PVDF의 표면 이행성이 나타남을 보여준다.

• 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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• 제6권3호
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• pp.206-218
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• 2005

Structural studies of series of 'as spun' and drawn PEEK fibers have been carried out using X-ray diffraction and optical microscopy techniques. The analysis of results suggest that fibers produced at a constant draw ratio with increasing draw temperatures show enhanced orientation and crystalline behaviour. The resolved equatorial and meridional traces provide additional structural parameters in terms of crystallinity, crystallite size, and crystallite thickness. It is concluded that drawing at a temperature below $T_g(i.e.,\;144^{\circ}C)$ results in poorly oriented non-crystalline materials, whereas drawing above $T_g$ results in highly oriented semi crystalline materials. Additional drawing proved to increase the overall orientation with slight improvements in lateral order of the chain molecules. Quantitative analysis revealed that the crystallite size increases with increasing drawing temperature. The results also revealed the increased crystallite size upon additional drawing. Crystalline orientation parameter, $_c$, suggests almost perfect orientation. In all cases, the amorphous orientation is found to be lower than the overall orientation parameter obtained from the optical birefringence. As a result of additional drawing, crystalline orientation was found to increase slightly but the increase in the orientation of non-crystalline material was found to be substantial. An average crystalline density was determined from the orthorhombic unit cell dimensions. It was found to vary as a result of processing conditions. It was also found that the value of the maximum birefringence shows heavy dependence on the chain conformation.

• 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.

• Macromolecular Research
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• 제11권1호
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• pp.62-68
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• 2003

Thermotropic liquid crystalline polymer (TLCP)/poly(ethylene 2,6-naphthalate) (PEN)/poly(ethylene terephthalate) (PET) ternary blends were prepared by melt blending, and were melt-spun to fibers at various spinning speeds in an effort to improve fiber performance and processability. Structure and property relationship of TLCP/PEN/PET ternary blend fibers and effects of annealing on those were investigated. The mechanical properties of ternary blend fibers could be significantly improved by annealing, which were attributed to the development of more ordered crystallites and the formation of more perfect crystalline structures. TLCP/PEN/PET ternary blend fibers that annealed at 18$0^{\circ}C$ for 2 h, exhibited the highest values of tensile strength and modulus. The double melting behaviors observed in the annealed ternary blend fibers depended on annealing temperature and time, which might be caused by different lamellae thickness distribution as a result of the melting-reorganization process during the DSC scans.