• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.1-4
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• 1995

The microstructure of polymer membranes produced via thermally induced phase separation (TIPS) of polymer solutions is a strong function of both the early-stage (by spinodal decomposition or nucleation & growth) and the late-stage phase separation (referred to in general as coarsening). In the case of early stage effects, the membrane morphology resulting from a nucleation & growth mechanism is either a poorly interconnecsed, stringy, beady structure which is mechanically fragile or a well interconnected structure with highly nonuniform pore sizes. In contrast, spinodal decomposition results in a well interconnected, mechanically strong membrane with highly uniform pore sizes. Here I describe recent quantitative studies of the coarsening effects on the microstructure of membranes produced via TIPS process. The dependence of microstructure on coarsening time, quench depth, solution viscosity, and polymer molecular weight was investigated in order to distinguish among three possible coarsening mechanisms, Ostwald ripening, coalescence, and hydrodynamic flow, which may be responsible for structural evolution after the early-stage phase Separation (spinodal decomposition or nucleation & growth).

• Proceedings of the Membrane Society of Korea Conference
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• 1993.10a
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• pp.13-20
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• 1993

The sorption equilibria and permeation rates for carbon dioxide in such glassy polymer membranes with high glass-transition temperature as polyimide, polyetherimide, polysulfone and polyethersulfone membranes, were measured. The sorption isotherms for these systems can be described well by the dual-mode sorption model, whereas the pressure dependences of the mean permeability coefficients are simulated better by a modified dual-mode mobility model than the conventional dual-mode mobility model in which the Henry's law and Langmuir populations execute four kinds of diffusive movement.

• Membrane Journal
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• v.8 no.1
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• pp.11-21
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• 1998

The study on penetrant transport in glassy polymers has been actively pursued for decades because of its growing significance in polymer processing and related applications such as not only membranes, but corrosion protective coatings, microlithography, microelectronic fabrication, etc. In membranes application of polymeric materials, successful utilization requires understanding of how solvents penetrate, swell, and sometimes dissolve polymeric materials under various environmental conditions, as their permselecdve performance is significantly affected by it. The expose of polymer membranes to solvents may result in the structural failure due to mechanical softening, embrittlement or crazing.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.03a
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• pp.13-35
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• 2004

Metal Complexes in Macromolecules Applications of Polymer Electrolyte Membranes Facilitated Transport in Solid State Roles of Electrolytes in Solar Cells - Electrolytes :ㆍI- and $I_3$-conductor ㆍelectron barrier or hole conductor ㆍelectrochemical redox reaction media ㆍinterfacial contactor for dye, $TiO_2$ and electrode ㆍmechanical separator (omitted)

• Membrane Journal
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• v.22 no.3
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• pp.208-215
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• 2012

Gel polymer electrolyte membranes were prepared from blends of polyvinyl alcohol (PVA) and poly (acrylic acid) (PAA), by solution-cast technique. The PAA content in the blend varied from 30 to 80 wt%. With the gel polymer electrolyte membranes, Zn air batteries were fabricated. The gel polymer electrolyte membranes were characterized by means of stress-strain test, impedance test. The Zn air batteries were tested by current interrupt method and galvanostatic discharge method. The tensile strength and tensile modulus decreased with increasing PAA content in the gel polymer electrolyte membrane. On the other hand, the ionic conductivity increased with increasing PAA content. The effect of ionic conductivity trend of the gel polymer electrolyte membrane in the Zn air battery was confirmed through current interrupt method and galvanostatic discharge method experiments. The battery with higher PAA content gel polymer electrolyte membrane showed lower IR drop and higher discharge capacity.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.51-54
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• 2003

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.281-283
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• 2005

Water management in polymer electrolyte membrane fuel cells(PEMFCs) is one of the most challenging issues. Freeze start-up in the automotive applications is also important research topic in the PEMFC field. Transportation of proton and separation of reactant gases are main roles of polymer electrolyte membranes. It has been known that water in the membrane conducts as a vehicle for the proton transportation. At sub-zero temperature, the frozen water blocks the access of reactant gases to the active sites of electrode as well as occurs the physical destruction of fuel cell structures. In this study, property changes of electrolyte membranes in the freeze conditions $(at\;-25^{\circ}C)$ were investigated. For the various amount of water contained membranes, the property changes, especially for the proton conductivity, were observed after several times of freeze/thaw$(-25\~80^{\circ}C)$ cycle.

• Membrane and Water Treatment
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• v.7 no.4
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• pp.355-365
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• 2016

The improvement of fouling resistance of porous polymeric membrane is one of the most important targets in membrane preparation for water purification in many process like wastewater treatment. Membranes can be modified by various techniques, including the treatment of polymer material, blending of hydrophilic polymer into polymer solution, and post treatment of fabricated membrane. This research proposed the modifications of morphology and surface property of hydrophobic membrane by blending polyethersulfone (PES) with three polymeric additives, polyvinylpyrrolidone (PVP), Pluronic F127 (Plu), and Tetronic 1307 (Tet). PES hollow fiber membranes were fabricated via dry-wet spinning process by using a spinneret with inner and outer diameter of 0.7 and 1.0 mm, respectively. The morphology changes of PES blend membrane by those additives, as well as the change of performance in ultrafiltration module were comparatively observed. The surface structure of membranes was characterized by atomic force microscopy and Fourier transform infra red spectroscopy. The cross section morphology of PES blend hollow fiber membranes was investigated by scanning electron microscopy. The results showed that all polymeric additives blended in this system affected to improve the performances of PES membrane. The ultra-filtration experiment confirmed that PES-PVP membrane showed the best performance among the three membranes on the basis of filtration stability.

• Membrane and Water Treatment
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• v.5 no.3
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• pp.171-182
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• 2014

Organic compounds are adsorbed on RO/NF membranes, and the adsorption may influence the rejection of organic compounds by the membranes. Because almost RO/NF membranes are composite membranes, the results obtained by adsorption experiment with using membrane pieces are unable to avoid the influence by the support membrane. In this work, the interaction between membrane polymer and organic solutes was examined by an inverse HPLC methodology. Poly (m-phenylenetrimesoylate), the constituent of skin layer of RO/NF membranes, was coated on silica gel particles and used as a stationary phase for HPLC. When water was used as a mobile phase, almost hydrophilic aliphatic compounds were not effectively adsorbed on the stationary phase, although hydrophobic compounds were slightly adsorbed. The results indicated that the hydrophilic aliphatic compounds are useful probe solutes to examine the molecular sieving effect of a membrane. When water was used as a mobile phase, the aromatic compounds were strongly retained, and therefore $CH_3CN/H_2O$ (30/70) was used as a mobile phase. It was revealed that the adsorption of aromatic compounds was controlled by stacking between solute and polymer and was hindered by non-planar structure and substituents.

• Macromolecular Research
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• v.9 no.5
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• pp.285-291
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• 2001

The polysulfone(PSf)/polyethersulfone(PES) blend membranes were prepared by an immersion precipitation method. N-methyl-2-pyrrolidone(NMP) was used as a solvent and water as a nonsolvent. The composition of the coagulation bath and the dope polymer concentration as well as the blend ratio of two polymers were varied. The membrane morphologies were interpreted on the basis of the phase diagram of the PSf/PES/NMP/water system. As the solvent content in the coagulation bath increased in the single polymer system, the number of macrovoids decreased and the morphology was changed from finger-like to cellular structure. In the given bath condition phase separation occurs earlier for the solutions of PSf/PES blend than for those of single polymer. A horizontally layered structure and horizontal protuberances inside the macrovoid were observed for the membranes formed from PSf/PES blend solutions. This peculiar structure formation can be interpreted by a PSf-rich/PES-rich phase separation followed by a polymer-rich/polymer-lean phase separation during the exchange of solvent and nonsolvent.