• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.1-6
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• 2008

Block copolymers spontaneously assemble into various nanoscale structures such as spheres, cylinders, and lamellar structures according to the relative volumn ratio of each macromolecular block and their overall molecular weights. The self-assembled structures of block copolymer have been extensively investigated for the applications such as nanocomposites, photonic crystals, nanowires, magnetic-storage media, flash memory devices. However, the naturally formed nanostructures of block copolymers contain a high density of defects such that the practical applications for nanoscale devices have been limited. For the practical application of block copolymer nanostructures, a robust process to direct the assembly of block copolymers in thin film geometry is required to be established. To exploit self-assembly of block copolymer for the nanotechnology, it is indispensible to fabricate defect-free self-assembled nanostructure over an arbitrarily large area.

• Elastomers and Composites
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• v.48 no.1
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• pp.30-38
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• 2013

Polyolefin is one of the most important commodity polymers having excellent physical properties and cost competitiveness, which has continuously broadened their market in response to a heavy demand from industry. However, the lack of polarity in polyolefin has limited its applications, especially where interactions with other materials are important. In view of the above, the incorporation of polar functional groups in polyolefin has been widely attempted. Especially, the preparations of segmented modified polyolefin copolymers, such as block and graft copolymers have been extensively investigated, since the loss of the original properties of polyolefin can be minimized while the polar segments can endow interactions with other materials. Living radical polymerization (LRP) method can be one of the most attractive synthetic tools for the preparation of the modified polyolefin block or graft copolymers. In this review, progress on the preparation of the polyolefin based block or graft copolymers through LRP technique is briefly summarized.

• Nuclear Engineering and Technology
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• v.16 no.3
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• pp.155-160
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• 1984

Analyzed is the thermal margin of the Korea Nuclear Unit 1 (KNU-1) reactor core consisting of either 14 x 14 standard fuel assemblies (SFA) or optimized fuel assemblies (OFA). Employed for the analysis are two different thermal design methods; traditional and statistical thermal design method. Compared to the traditional design thermal method, the statistical thermal design method improves the core thermal margin utilizing best-estimate values for the core operating parameters combining their uncertainties in a statistical manner. Calculations are performed using a steady state and transient thermal-hydraulic analysis computer program, COBRA-IV-i. Calculated results show that the statistical thermal design method significantly improves the thermal margin and satisfies the core thermal design base of the KNU-1 SFA and OFA core. However, the thermal design base can not be met, if the traditional thermal design method is employed for the OFA role analysis.

• Polymer(Korea)
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• v.30 no.1
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• pp.28-34
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• 2006

A series of methoxypoly(ethylene glycol) $(MPEG)-poly(\varepsilon-co-L-lactide)$ (PCLA) diblock copolymers were synthesized by ring-opening polymerization of a mixture of $\varepsilon-caprolactone$ and L-lactide with different ratios in the presence of $Sn(Oct)_2$. The characterization of MPEG-PCLA diblock copolymers were examined by $^1H-NMR$, GPC, DSC, and XRD. Kinetic study on ring-opening polymerization of monomer mixtures was carried out in various conditions such as a variation with polymerization time, amount of catalyst, and temperature. The highest conversion obtained in 1.2 ratic of initiator venn catalyst at $110\;^{\circ}C$. The biodegradable characterization of MPEG-PCLA diblock copolymers in aqueous solution was carried out by using GPC for $1\~14$ weeks. The biodegradability of MPEG-PCLA diblock copolymers increased as the L-lactide content of diblock copolymers increased. In conclusion, we confirmed the dependence of polymerization rate according to various conditions. In addition, we can control the biodegradability of MPEC-PCLA diblock copolymers by changing the ratio of PCL and PLA block segment.

• Polymer(Korea)
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• v.30 no.6
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• pp.464-470
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• 2006

Diblock copolymers consisting of methoxy Poly (ethylene glycol) (MPEG) and poly (${\epsilon}-ca$ prolactone) (PCL), poly(${\delta}-valerolactone$) (PVL), poly(L-lactide) (PLLA), or poly(L-lactide-co-glycolide) (PLGA) were prepared to compare the characterization of diblock copolymers as a drug carrier. MPEG-PCL, MPEG-PVL, MPEG-PLLA, and MPEG-PLGA diblock copolymers were synthesized by the ring-opening polymerization of ${\epsilon}$-caprolactone or ${\delta}$-valerolactone in the presence of $HCl{\cdot}Et_2O$ as a monomer activator at room temperature and by the ring-opening polymerization of L-lactide or a mixture of L-lactide and glycolide in the presence of stannous octoate at $130^{\circ}C$, respectively. The synthesized diblock copolymers were characterized with $^1H-NMR$, GPC, DSC, and XRD. The micellar characterization of MPEG-polyester diblock copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AFM, and fluorescence techniques. Most micelles exhibited a spherical shape in AFM. Thus, ore confirmed that the micelles formed with MPEG-polyester diblock copolymers have possibility as a potential hydrophobic drug delivery vehicle because a hydrophobic drug could be preferentially distributed in the micelle core.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.21-27
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• 2003

The copolymers with various composition of methyl methacrylate (MMA), ethyl methacrylate (EMA), methacrylic acid (MA) and hydroxyethyl methacrylate (HEMA) were synthesized for capacitive humidity sensitive materials. The capacitive humidity sensor consisted of a polymethacrylate film coated on both sides with gold electrode. Capacitance versus relative humidity increased with HEMA content in the copolymer. In the case of self-crosslinkable MMA/MA/HEHA= 40/10/10, the average capacitance at 30%RH, 60%RH and 90%RH are 102, 134 and 166 pF, respectively. And also, the hysteresis, temperature cycle and long-term stability were evaluated as a capacitance humidity sensor.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.329-331
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• 2006

연료전지용으로 많이 사용되는 전불소계 고분자인 Nafion은 좋은 기계적, 화학적 안정성 및 높은 이온전도도에도 불구하고 고가의 생산단가, 높은 메탄올 투과도, 그리고 MEA 재활용 문제 등으로 인해 상업적 응용에 제한이 있다. 본 연구는 불소그룹을 함유한 술폰화된 아릴렌이서계 블록 공중합체 고분자 전해질막의 제조 및 연료전지 특성에 관한 것이다. 이러한 고분자를 제조하기 위하여 양말단에 불소계 비닐기를 가지면서, 상온에서 술폰화 가능한 biphenyl계 단량체와 술폰화가 불가능한 sulfonyl계 단량체를 각각 합성하였으며, 이들로부터 다양한 몰조성과 분자량을 갖는 올리고머를 포함한 일련의 perfluorocyclobutane기를 포함하는 블록 공중합체를 열적 고리화 부가중합을 사용하여 합성하였다. 제조된 블록 공중합체를 상온에서 술폰화제인 chlorosulfonic acid를 이용하여 선택적으로 후술폰화시켜 강산 이온기인 sulfonic acid를 블록 올리고머에 도입하였다. 합성된 고분자들의 연료전지 특성을 Nafion-115와 비교하였다. 술폰화가 되는 올리고머 블록의 비율 증가에 따라 이온교환능력이 증가하였고, 그에 따라 높은 함수율과 이온 전도도를 나타내었으며 건조 및 습윤 상태에서도 기계적 강도가 우수하였다. 최적화된 블록공중합체를 대상으로 MEA를 제조하여 연료전지 초기성능을 측정한 결과 Nafion과 유사한 전기화학적 성능을 나타내었다.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.287-291
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• 1987

The composite mole fraction of monomers in PVA-PVFAc copolymer could be calculated from the analysis of trifluoroacetyl group by the pyrolysis gas chromatography without breaking of C-F bonds in polymer. A linearity between trifluoroacetyl peak areas in pyrogram and sample weights was obtained within the range below 3mg. The data of trifluoroacetyl contents derived from gas chromatogram of copolymers with various D.S. were in good agreement with results by the Specific Ionmeter.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.121-125
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• 2007

Siloxane monomer and oligomer were introduced to n-butyl acrylate and methyl methacrylate copolymer for improvement of water resistance and tactile sensation of acryl-type emulsion. Terpolymerimerization of n-butylacrylate, methyl methacrylate and siloxane monomer or oligomer was carried out in aqueous solution. The glass transition temperature (Tg) of terpolymer decreased with increasing siloxane monomer, however, the Tg of terpolymer increased with increasing siloxane oligomer due to the crosslinking of acrylated end group. The adhesion property and surface energy of the obtained terpolymer decreased with introducing siloxane monomer or oligomer in terpolymer. Decrement of tack and surface energy means the enhancement of water resistance and tactile sensation of the emulsion.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.221-223
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• 2007

고분자전해질연료전지의 효율과 수명은 고분자 전해질 막과 밀접하게 관련되어있다. 연료전지 상용화를 위해 내구성과 안정성은 반드시 확보되어야 한다. 본 연구에서는 고분자전해질연료전지용 막전극접합체에 대해서 제작과정, 체결과정 및 운전 중에 발생할 수 있는 물리적 손상이 연료전지에 미치는 영향을 알아보고자 하였다. 실제 고분자전해질연료전지 조건에서 구멍이 생기는 경우를 모사하기 위해 막전극접합체에 다양한 크기 및 형상의 물리적 손상을 형성시켰다. 또한 여러 위치에서의 손상도 비교하였다. 손상시킨 막전극접합체에 대해 단위전지 성능평가와 순환전압전류 실험을 비교 분석하였다. 막전극접합체의 결함이 커질수록 수소기체투과도는 증가하고, OCV와 성능은 감소하였다. 또한 성능과 수소기체투과도는 서로 관련이 있음을 알 수 있었다.