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용매와 용매 첨가제가 고분자 막 구조에 미치는 영향 연구
원종옥,박철민,강용수,박현채,김은영 한국막학회 1997 멤브레인 Vol.7 No.4
기체 투과도 및 기계적 강도가 높은 고분자 비대칭막을 상분리법으로 제조하기 위해 막 제조 메카니즘을 규명하는 연구를 수행하였다. 기본적인 연구가 많이 이루어진 폴리스티렌, 이에 비해 용매와의 관계가 덜 알려져 있는 폴리아미드이미드인 Torlon과 3,3'4,4'-benzophenontetracarboxylic diahmydride와 1,4-phenylene diarnine로 이루어진 폴리이미드를 여러 용매에 녹여 얻어진 캐스팅 용액으로부터 비대칭막을 제조하였다. 용매와 비용매와의 혼합열과 막 구조의 관계로부터, 막의 구조를 결정하는 데에는 용매와 비용매의 혼합열이 크게 영향을 미침을 알 수 있었다. 이 결과로부터 폴리술폰 막의 구조를 용매 첨가제를 사용하여 조절하였다. 캐스팅 고분자 용액이 비용매를 만날 때 용매와 비용매와의 혼합열이 두 물질의 교환 속도에 영향을 미쳐 결국에는 막의 구조에 영향을 미치는 데에 대한 이론적인 고찰도 아울러 수행하였다. Membrane formation mechanism by the phase inversion has been investigated in order to control the membrane morphology. It was found that finger-like structures were obtained when the heat of mixing between the solvent and non-solvent is exothermic, while sponge-like structures were obtained when they are endothermic in polystyrenes as well as in polyimides (Torlon and polyimide made frorn 3,3'4,4'-benzophenontetracarboxylic diahmydride and 1,4-phenylene diarnine) membranes. This concept was applied to control the morphology of polysulfone membranes simply by adding a solvent additive by adjusting the heat of mixing. A crude, but simple, relationship between the heat of mixing and the exchange rate of the solvent with non-solvent has been also developed.
Ionic Cluster Mimic Membranes Using Ionized Cyclodextrin
원종옥,강용수,유지영,강문성 한국고분자학회 2006 Macromolecular Research Vol.14 No.4
Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-β-cyclodextrins (-CDSO3H) or phosphated-β-cyclodextrins (-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 β-CDSO3H or β-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 cross over in direct methanol fuel cells.
The Effect of Annealing on sSEBS/Polyrotaxanes Electrolyte Membranes for Direct Methanol Fuel Cells
원종옥,조현동,강용수 한국고분자학회 2009 Macromolecular Research Vol.17 No.10
Solution casting films of sulfonated poly[styrene-b-(ethylene-r-butylene)-b-styrene] copolymer (sSEBS)- based composite membranes that contained different amounts of organic, nanorod-shaped polyrotaxane were annealed at various temperatures for 1 h. The films’ properties were characterized with respect to their use as polymer electrolyte membranes in direct methanol fuel cells (DMFCs). Different aspect ratios of polyrotaxane were prepared using the inclusion-complex reaction between α-cyclodextrin and poly(ethylene glycol). The presence of the organic polyrotaxane inside the membrane changed the morphology during the membrane preparation and reduced the transport of methanol. The conductivity and methanol permeability of the composite membranes decreased with increasing polyrotaxane content, while the annealing temperature increased. All of the sSEBS-based, polyrotaxane composite membranes annealed at 140 oC showed a higher selectivity parameter, suggesting their potential usage for DMFCs.