• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.376-379
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• 2003

In this paper, a novel processing technique for fabrication of high-temperature MEMS based on polymer-derived SiCN microstructures is described. PDMS molds are fabricated on SU-8 photoresist using standard UV-photolithographic processes. Liquid precursors are injected into the PDMS mold. And then, the resulting solid polymer structures are crosslinked under isostatic pressure, and pyrolyzed to form a ceramic capable of withstanding over $1500^{\circ}C$. These fabricated SiCN structures would be applied for high-temperature applications, such as heat exchanger and combustion chamber.

• 폴리머
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• 제28권1호
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• pp.41-50
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• 2004

열방성 액정상을 형성하는 새로운 하이드록시프로필 키토산과 이의 2가지의 유도체, 즉 6-콜레스테릴옥시카보닐펜톡시프로필 키토산들과 이들의 아크릴산 에스터들을 합성하였다. 또한 액정상태에 있는 6-콜레스테릴옥시카보닐펜톡시프로필 키토산의 아크릴산 에스터들을 광가교시켜 액정질서를 지닌 가교필름들을 제조하였다. 모든 시료들의 액정특성과 아세톤 중에서의 가교필름의 팽윤거동을 검토하였다. 하이드록시프로필 키토산과 판이하게 콜레스테릴을 지닌 모든 미가교시료들은 좌측방향의 나선구조를 지닌 단방성 콜레스테릭 상들을 형성하며 콜레스테릭 상의 전 범위에서 반사색깔들을 나타내었다. 이것이 키토산유도체가 가시광 영역의 반사대를 지닌 열방성 콜레스테릭 상을 형성한다고 하는 최초의 보고이다. 6,콜레스테릴옥시카보닐펜톡시프로필 키토산과 이의 아크릴산 에스터의 광학 피치들 (λ$_{m}$ 'S)은 온도상승 혹은 주어진 온도에서는 콜레스테릴 함량의 증가에 의해 감소한다. 그러나 콜레스테릴 함량이 동일한 경우, 동일한 온도에서 나타내는 λ$_{m}$ 은 6-콜레스테릴옥시카보닐펜톡시프로필 키토산이 이의 아크릴산 에스터에 비해 크다. 모든 가교시료들은 반사색깔을 나타내지 않았으며, 이러한 사실은 6-콜레스테릴옥시카보닐펜톡시프로필 키토산의 아크릴산 에스터의 콜레스테릭 구조가 가교에 의해 현저하게 변화됨을 시사한다. 모든 가교시료들에 있어서 액정가교겔의 특징적인 2차원적 이방성 팽윤이 관찰되었다.

• 공업화학
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• 제10권3호
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• pp.374-381
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• 1999

스티렌-무수만레인산 공중합체 (PSMAn)를 이용하여 가교 폴리비닐알콜막을 제조하였고, 물-에탄올 혼합물 분리에 대한 투과증발 특성을 연구하였다. 제조된 폴리비닐알콜막은 92/8 wt. % 에탄올/물 조성에서 PSMAn 함량이 증가할수록 투과도와 선택도가 모두 증가된 특성을 나타내었다. 그러나 공급액에서 물의 함량이 증가하면 가교도가 증가했음에도 불구하고 2%>1%>0.5%순으로 총괄 투과도는 증가하였고, 선택도는 물에 대한 높은 흡착과 그로부터 생긴 가소화 작용 때문에 감소하였다. 또한, 온도에 대한 전반적인 투과도는 Arrhenius 형태를 따랐으며, 특히, 2.0% 가교 PVA막의 경우, 조업 온도가 $30^{\circ}C$에서 $50^{\circ}C$로 증가함에 따라 투과도와 선택도가 모두 증가되는 투과증발 특성을 보여주었다. 이러한 결과로부터, PSMAn에 의해 막내에 도입된 친수성 기들이 물질 투과에 크게 영향을 준다는 것을 알 수 있었다.

• Macromolecular Research
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• 제14권4호
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• pp.449-455
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• 2006

Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-${\beta}$-cyclodextrins (${\beta}-CDSO_3H$) or phosphated-${\beta}$-cyclodextrins (${\beta}-CDPO(OH)_2$). When Nafion, developed for a fuel cell using low temperature, polymer electrolyte membranes, is used in a direct methanol fuel cell, it has a methanol crossover problem. The ionic inverted micellar structure formed by micro-segregation in Nafion, known as ionic cluster, is distorted in methanol aqueous solution, resulting in the significant transport of methanol through the membrane. While the ionic structure formed by the ionic sites in either ${\beta}-CDSO_3H$ or ${\beta}-CDPO(OH)_2$ in this composite membrane is maintained in methanol solution, it is expected to reduce methanol transport. Proton conductivity was found to increase in PVA membranes upon addition of ionized cyclodextrins. Methanol permeability through the PVA composite membrane containing cyclodextrins was lower than that of Nafion. It is thus concluded that the structure and fixation of ionic clusters are significant barriers to methanol crossover in direct methanol fuel cells.

• Macromolecular Research
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• 제16권5호
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• pp.424-428
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• 2008

We prepared an ionic gel polymer electrolyte for dye-sensitized solar cells (DSSCs) without leakage problem. Triiodide compound (BTDI) was synthesized by the reaction of benzene tricarbonyl trichloride with diethylene glycol monotosylate and subsequent substitution of tosylate by iodide using NaI. Bisimidazole was prepared by the reaction of imidazole with the triethylene glycol ditosylate under strongly basic condition provided by NaH. BTDI and bisimidazole dissolved in an ionic liquid were injected into the cells and permeated into the $TiO_2$ nanopores. In situ crosslinking was then carried out by heating to form a network structure of poly(imidazolium iodide), thereby converting the ionic liquid electrolytes to a gel or a quasi-solid state. A monomer (BTDI and bisimidazole) concentration in the electrolytes of as low as 30 wt% was sufficient to form a stable gel type electrolyte. The DSSCs based on the gel polymer electrolytes showed a power conversion efficiency of as high as 1.15% with a short circuit current density of $5.69\;mAcm^{-2}$, an open circuit voltage of 0.525 V, and a fill factor of 0.43.

• 한국산업융합학회 논문집
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• 제6권1호
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• pp.17-21
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• 2003

5원환 고리아세탈 화합물인 4-methylenes(4,5)을 합성하고 저온조건 하에서 중합반응을 조사한 결과, 선택적인 개환중합이 일어났다. 보통의 양이온 개시제를 사용한 결과 $-78^{\circ}C$에서 가교체가 얻어졌으며, $CH_3SO_3H$를 개시제로 사용하면 같은 조건에서도 주사슬과 곁사슬에 이중결합을 가지는 개환중합체가 얻어진다. 이 중합체는 반응성을 가지는 불포화기를 포함하고 있으므로 prepolymer로써 널리 사용될 수 있다.

• 한국막학회:학술대회논문집
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• 한국막학회 1996년도 추계 총회 및 학술발표회
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• pp.92-93
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• 1996

PVA membrane was widely used in the dehydration pervaporation process. PVA membrane showed remakable selectivity towed water and an excellent film-forming polymer, with a good resistance to orgamic solvents but it has poor stability in aqueous mixtures. Generally the PVA is manufactured by the hydrolysis reaction from poly vinyl acetate(PVAc) and so the degree of PVA hydrolysis is a major parameter for properties of PVA membrane such as the crystallinity and polarity.

• 한국응용과학기술학회지
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• 제24권2호
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• pp.160-166
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• 2007

The rheological properties and surface tensions of polymer solutions and polymer-surfactant mixed solutions were investigated. The polymers used in this study were a homopolymer of acrylic acid crosslinked with an allyl ether of pentaerythritol, an allyl ether of sucrose, or an allyl ether of propylene (CARBOMER), acylate/C10-30 alkyl acylate crosspolymer (AAAC), and ammonium acryloydimethyltaurate/VP copolymer (ADTV). A solubilizing agent PEG-40 hydrogenated castor oil (HCO-40) and an emulsifying agent polyoxyethylene (20) sorbitan monostearate (POLYSORBATE 60) made the micelles intervening between AAAC polymers, resulting in the increase of viscosity. However, HCO-40 made this behavior over the wider range of surfactant concentration than POLYSORBATE 60. From the view point of surface tensions in the same range of surfactant concentration, AAAC/HCO-40 solution showed the area of increasing surface tension with surfactant concentration in contrast to the AAAC/POLYSORBATE 60 solution showing no increasing area.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.295-295
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• 2008

Water tree experiments were done for several types of cross-linked polyethylenes. Test method is followed by ASTM D6097. Polyethylene is divided for four subgroup. First One is chemically cross-linked general XLPE, and second one is chemically cross-linked tree-retardant XLPE, and the third one is silane cross-linked polyethylene made by monosil process, and the last one is silane cross-linked polythylene made by copolymer. Tree retardant XLPE shows the shortest water tree length. Cahemcally cross-linked general XLPE shows the longest water tree length. Silane cross-linked polyethylene by copolymer is similar to tree retardant XLPE and similar breakdown strength. So silane cross-linked XLPE by copolymer could be used for the the medium voltage cable which should have tree retardant characteristics.

• Macromolecular Research
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• 제13권6호
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• pp.483-490
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• 2005

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan ($_{k}C$), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for $_{k}C$­g-polymethacrylic acid ($_{k}C$-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of super absorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.