• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 춘계 총회 및 학술발표회
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• pp.13-16
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• 1997

The permeation, solution and diffusion of simple gases ($He, H_2, O_2, N_2$ and CH$_4$) and condensible vapers($CO_2, SO_2, C_2H_4$ and $C_3H_8$), and the mixed gases ($O_2/N_2$ mixtures and $CO_2/CH_4$ mixtures) through composite membrane was studied. Composit membranes were made by deposition of aromatic fluorocarbons onto polymer substrams of porous Celgard in a microwave discharge. In the both cases of simple gases and condensible vapors, as the kinetic molecular diameter of the permeant molecules increased, the permeability decreased. However, when the kinetic molecular dimemr are similar, the condensible vapors showed higher permeabilities than that of permanent gases. The vapor solubility increased with increasing critical temperature of the vapors. However, in the case of propane, despite its high critical temperature, it showed lower solubility than other vapors. The vapor diffusivity decreased with increasing kinetic diameter of the molecule. Compared to conventional polymers, the plasma polymers showed much lower values for vapor diffusivities. The pressure of the permeant did not affect the permeability. The permeability was also not affected by the composition in cases of mixed gases.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.319-320
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• 2003

압전성과 초전성을 나타내는 고분자인 poly(vinylidene fluoride)(PVDF)는 poly(methyl methacrylate), poly(vinyl acetate), 및 Poly(vinyl methyl ketone)(PVMK) 등과 블렌딩하면 혼화성(miscibility)이 있다. 이들 블렌드물들을 용융온도 이상으로 승온시키면 낮은 온도에서는 균일상으로 존재하지만, 온도가 계속 증가하면 상분리되어 LCST(lower critical solution temperature)를 나타낸다[1]. 이러한 승온에 의한 상분리 거동에서 외부전장을 가하면 전기활성 고분자인 PVDF에 영향을 주어 상분리 거동이 변화될 것으로 예산된다. (중략)

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 가을 학술발표회 논문집
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• pp.193-194
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• 2003

전기활성 고분자인 poly(vinylidene fluoride)(PVDF)를 전기 비활성 고분자와 블렌드시키는 경우 어떤 블렌드계에서는 용융 온도 이상에서 LCST(lower critical solution temperature) 상분리 거동을 나타내는데[1,2], 이때 외부 전장을 가해주면 이들의 상분리 거동에 영향을 미칠 수 있다[3]. PVDF와 블렌딩시켰을 때 LCST 상분리 거동을 나타내는 고분자로는 poly(methyl methacrylate), poly(ethyl methacrylate), poly(1,4-butylene adipate) (PBA) 등이 있다[l,3]. (중략)

• Biomaterials and Biomechanics in Bioengineering
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• 제2권2호
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• pp.97-109
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• 2015

A series of amphiphilic graft copolymers were synthesized by varying the number of graft chains and graft chain lengths. The polarity of the hydrophobic graft chain on the copolymers was varied their solution properties. The glass transition temperature of the copolymers was in the low-temperature region, because of the amorphous nature of poly (trimethylene carbonate) (PTMC). The surface morphology of the lyophilized colloid gel had a bundle structure, which was derived from the combination of poly(N-hydroxyethylacrylamide)( poly(HEAA)) and PTMC. The solution properties were evaluated using dynamic light scattering and fluorescence measurements. The particle size of the graft copolymers was about 30-300 nm. The graft copolymers with a higher number of repeating units attributed to the TMC (trimethylene carbonate) component and with a lower macromonomer ratio showed high thermal stability. The critical association concentration was estimated to be between $2.2{\times}10^{-3}$ and $8.9{\times}10^{-2}mg/mL$, using the pyrene-based fluorescence probe technique. These results showed that the hydrophobic chain of the graft copolymer having a long PTMC segment had a low polarity, dependent on the number of repeating units of TMC and the macromonomer composition ratio. These results demonstrated that a higher number of repeating units of TMC, with a lower macromonomer composition, was preferable for molecular encapsulation.

• KSBB Journal
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• 제14권1호
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• pp.58-65
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• 1999

온도 및 pH에 동시에 민감한 하이드로젤 Poly(N-isopropy-lacrylamide-co-N,N'-dmerhylaminopropyl methacrylamide)을 합성하고, 그 팽윤 특성을 연구하였다. pH 민감성분인 N,N'-dmerhylaminopropyl methacrylamide (DMAPMAAn)의 물분율이 5%인 하이드로젤이 팽윤정도는 lower critucal solution temperature(LCST) 이상의 온도($37^{\circ}C$ 및 $40^{\circ}C$)에서 pH가 낮은 범위(pH 1-8)일 때 크게 증가하였다. 이는 온도민감성 하이드로젤이 같은 pH범위에서 전혀 팽윤이 일어나지 않는 것과 대조되었다. DMAPMAAm의 물분울이 20%인 경우에는 높은 pH(pH 12)에서도 젤이 상당히 팽창하였다. $40^{\circ}C$에서 pH가 12에서 2로 감소할 때 젤의 수분함량은 5mol%젤의 경우 38.8 wt%에서 84.7wt%로 증가하였고, 20mol%젤의 경우 60.6 wt%에서 90.8wt%로 증가하였다. 온도 및 pH에 동시에 민감한 하이드로젤의 부피 변화에 대해 이와 같이 pH는 온도 및 젤 조성의 영향을 받아 $37^{\circ}C$에서 pH 8보다 $40^\circC$에서 (pH 7) 더 낮아졌고, 5 mol%에서 (pH 7)보다 20 mol%일때 (pH 9) 증가하였다 LCST 이하의 온도 ($25^{\circ}C$)에서는 젤의 팽윤정도가 pH에 의해 크게 영향받지 않았다. 젤의 투명도와 LCST는 DMAPMAAm의 물분율에 따라 증가하였다.

• 폴리머
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• 제25권2호
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• pp.186-198
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• 2001

pH와 온도에 민감한 N-isopropylacrylamide (NIPAAm)계 공중합체인 poly(NIPAAm-co-AAc), Poly(NIPAAm-co-AAm-GAc), 및 poly(NIPAAm-co-AMPS)를 산성 공단량체의 조성비를 달리하여 자유라디칼 중합법에 의해 제조하였다. 합성된 공중합체들의 하한임계용액온도 거동(LCST)에 대한 pH와 공단량체의 구조 및 함량변화 효과를 열광학분석기 (TOA)를 이용하여 측정한 흐림점으로부터 결정하였다. Poly(NIPA.Am-co-AAc) 수용액의 상전이온도(T$^{p}$ )는 공중합체내 AAc의 카르복실기가 이온화될수록, 보다 높은 값을 나타내었는데, 이와 같은 현상은 이온화된 상태에서 공중합체내 이온기들간의 정전기적 반발력이 보다 친수성을 나타나게 한 원인이 되었다. 반면에, 2-acrylamido glycolic acid (AAmGAc)가 공중합체에 도입된 경우, pH 3보다 낮은 pH에서는 T$^{p}$ 의 변화가 거의 없었지만, pH 3에서 5까지는 T$^{p}$ 가 매우 급격히 증가하였다가 pH 6이상에서는 공중합체의 T$^{p}$ 가 ionic screen effect에 의해 pH 3에서 pH 5일 때보다 오히려 더 낮아졌다. 또한 이 같은 ionic screen effect는 강산성 공단량체로 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)가 도입된 공중합체 의 경우에서도 관찰되었다.

• Macromolecular Research
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• 제10권6호
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• pp.359-364
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• 2002

A series of PLA-PEO-PLA triblock stereo-copolymers with varying PLA/PEO and L-DL-LA ratios were synthesized via ring opening pelymerizations. Aqueous solutions of these copolymers undergo thermo-responsive phase transitions as the temperature monotonically increases. Further study shows that there is a critical gel concentration (CGC), and also lower and upper critical gel temperatures (CGTs), at which the thermo-responsive phase transition occurs. The CGC and CGTs are affected by various factors such as block length, as well as the compositions of the PLA blocks and of the additives. In particular, the changes in the phase diagram produced by varying the L-/DL-LA ratio in the PLA blocks were determined to be mainly due to consequent stereo-regularity changes in the PLA blocks.

• Bulletin of the Korean Chemical Society
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• 제23권4호
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• pp.549-554
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• 2002

Thermosensitive poly(organophosphazenes) bearing methoxy-poly(ethylene glycol) (MPEG) and alkylamines as substituents have been synthesized and characterized by elemental analysis, NMR spectroscopy, GPC, and DSC. All the polymers exhibited crystallinity, which was probably induced by the MPEG side chain of the polymers. All the polymers exhibited the lower critical solution temperature (LCSTs) in the range of 28 to $94^{\circ}C$ depending on several factors such as mole ratio of the substituents, kinds of PEG and alkylamines. The higher content of MPEG and shorter chain length of alkylamines of the polymers afforded the higher LCST. The LCSTs of the polymers exhibited almost concentration-independent behavior in the range of 3-30 wt % of the polymers in aqueous solutions. The polymers showed the higher LCSTs in the acidic solutions than in the neutral and basic solutions. The ionic strength of the polymer solution affected the LCST, which decreased with increased NaCl concentration. The polymer bearing almost equimolar substitutuents with the -N-P-N- unit has shown the LCST more sensitive to NaCl and pH than that with the -N-P-O- unit. The polymers were found to degrade in acidic solution but be very stable in alkali solution as well as in the buffer solution of pH 7.4.

• 대한화학회지
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• 제32권4호
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• pp.311-317
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• 1988

임계점 이상의 여러 온도와 압력에서 암모니아내의 나프탈렌의 용해도를 측정함으로써 용해도와 암모니아의 밀도 사이의 관계를 간단한 식으로 나타낼 수 있었다. 이 식을 이용하여 더 높은 압력이나 더 낮은 압력에서의 용해도를 계산할 수가 있으며, 이로부터 용해에 수반되는 에너지 변화와 엔트로피변화를 구하고, 초임계 이산화탄소내의 나프탈렌의 용해도 자료로부터 얻어진 결과와 비교하였다. 또한 나프탈렌과 암모니아 사이의 상호작용 비리알 계수를 결정하여 나프탈렌과 이산화탄소 사이의 경우와 비교 검토하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.274-278
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• 2001

Polymer membranes composed of N, N-dimethylaminoethyl methaccrylate(DMAEMA) and acrylamide(AAm)(or ethyl acrylamide(EAAm) were prepared to demonstrated the thermo-control of solute permeation. Poly DMEMA has a lower critical solution temperature(LCST) at around 50$\^{C}$ in water, With the copolymerization of DMAEMA with AAm (or EAAm) a shift in the LCST to a lowere temperature was observed, probably due to the formation of hydrogen bonds between the amide and N-N-dimethylamino groups. However, the temperature-induced phase transition of poly(DMAEMA-co-EAAm) did not show a similar trend to that of poly(DMAEMA- co-AAm) in the gel state. The hydrogen bonds in poly(DMAEMA-co-EAAm) were significantly disrupted with the formation a gel network, which led to a difference in the swilling behavior of polymer gels in response to temperature. To apply these polymers to temperature-sensitive sol-ute permeation, polymer membranes were prepared. The permeation pattern of hydrocortisone, used as the model solute, was explained based on the temperature-sensitive swelling behavior of the polymer membranes.