• Elastomers and Composites
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• v.46 no.2
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• pp.94-101
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• 2011

The conventional radiation barriers may show some disadvantages such as heavy weight and possibility of poisoning human bodies because they are composed of lead plates or resin plates containing large amounts of lead powders. Another disadvantage may be direct penetration of radiation through small pin holes. In this article, technologies of multi-layered polymer barriers against radiation, which has been extensively focused recently, will be introduced. A new concept of radiation protection as well as improving endurance with employing nano-layered inorganic particles is introduced.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.108-108
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• 2006

The role of conformational entropy of polymer chains in polymer crystallization is investigated by molecular modeling and theory. The entropy of folded loops dominates at experimentally relevant temperatures to dictate short equilibrium lamellar thicknesses, which are much smaller than the extended chain thickness. Also the entropic barriers control the kinetics of polymer crystallization. These results based on chain entropy are different from the classical views of how polymer chains crystallize.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.165-167
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• 2007

The performance of polymer light emitting diode can be improved significantly by interfacial engineering on anode and/or cathode through adjusting the charge injection barriers for holes and electrons. Studies involve CFx and SAM modifications on ITO, thickness and delay time to baking of PEDOT:PSS, and electron injection/hole blocking layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.457-457
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• 2010

Flexible organic light emitting diodes (F-OLEDs) requires excellent moisture permeation barriers to minimize the degradation of the F-OLEDs device. Specifically, F-OLEDs device need a barrier layer that transmits less than $10^{-6}g/m^2/day$ of water and $10^{-5}g/m^2/day$ of oxygen. To increase the life time of F-OLEDs, therefore, it is indispensable to protect the organic materials from water and oxygen. Severe groups have reported on multi-layerd barriers consisting inorganic thin films deposited by plasma enhenced chemical deposition (PECVD) or sputtering. However, it is difficult to control the formation of granular-type morphology and microscopic pinholes in PECVD and sputtering. On the contrary, atomic layer deoposition (ALD) is free of pinhole, highly uniform, conformal films and show good step coverage. Thus, $Al_2O_3/TiO_2$ multi-layer was deposited onto the polyethersulfon (PES) substrate by electron cyclotron resonance atomic layer deposition (ECR-ALD), and the water vapor transmission rates (WVTR) were measured. WVTR of moisture permeation barriers is dependent upon density of films and initial state of polymer surface. A significant reduction of WVTR was achieved by increasing density of films and by applying low plasma induced interlayer on the PES substrate. In order to minimize damage of polymer surface, a 10 nm thick $TiO_2$ was deposited on PES prior to a $Al_2O_3$ ECR-ALD process. High quality barriers were developed from $Al_2O_3$ barriers on the $TiO_2$ interlayer. WVTR of $Al_2O_3$ by introducing $TiO_2$ interlayer was recorded in the range of $10^{-3}g/m^2.day$ at $38^{\circ}C$ and 100% relative humidity using a MOCON instrument. The WVTR was two orders of magnitude smaller than $Al_2O_3$ barriers directly grown on PES substrate without the $TiO_2$ interlayer. Thus, we can consider that the $Al_2O_3/TiO_2$ multi-layer passivation can be one of the most suitable F-OLEDs passivation films.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.27-30
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• 1997

1. Introduction : Molecular diffusion of small molecules in polymers plays an important role in many areas where polymers are acting as barriers, and in separation processes, such as selective diffusion. Different applications of polymers have different requirements on their transport properties. Therefore, reliable predictions of diffusion coefficients for small molecules in polymeric materials could be a useful tool to design appropriate materials. For many years, the theories based on free-volume concepts have been widely used to correlate and predict diffusion behavior in polymer/solvent systems. In the theory derived by Vrentas and Duda, the empty space between molecules that is available for molecular transport, referred to as hole free-volume, is being redistributed. Molecular transport will occur only when a free-volume of sufficient size appears adjacent to a molecule and the molecule has enough energy to jump into this void. The diffusive jump is considered complete when the void left behind is closed before the molecule returns to its original position. In this paper, the Vrentas-Duda free-volume theory is presented and the methods to estimate free-volume parameters for predicting polymer/ solvent diffusion coefficients are described in detail.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1209-1213
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• 2005

Nuclear membrane is one of the main barriers in intracellular delivery of genetic materials. The previous report showed that glucocorticoid receptor dilated the nuclear pore to 60 nm in the presence of a ligand. It was also suggested that the transport of genetic material to nucleus might be facilitated by glucocorticoid. In this study, the effect of glucocorticoid preincubation in the polymeric gene delivery was investigated. The cells were preincubated with dexamethasone, a potent glucocorticoid, and transfection assays were performed with polyethylenimine (PEI) and polyamidoamine (PAMAM) dendrimer. As a result, the transfection efficiency of PEI or PAMAM to the cells in the presence of dexamethasone was enhanced, compared to the cells without dexamethasone. This effect was not observed in the cells preincubated with cholesterol. The polymer/DNA complex was stable in the presence of dexamethasone. In addition, the cytotoxicities of the polymeric carriers to the cells were observed in the presence of dexamethasone. In conclusion, dexamethasone enhances the transfection efficiency of polymeric carriers and may be useful in the development of polymeric gene carriers.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.138-146
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• 2007

Some biodegradable polymers and other materials such as hydrogels have shown the promising potential for surgical applications. Post surgical adhesion caused by the natural consequence of surgical wound healing results in repeated surgery and harmful effects. Recently, scientists have developed absorbable anti-adhesion barriers that can protect a tissue from adhesion in case they are in use; however, they are dissolved when no longer needed. Although these approaches have been attempted to fulfill the criteria for adhesion prevention, none can perfectly prevent adhesions in all situations. Overall, we developed a new method to fabricate an anti-adhesion membrane using biodegradable polymer and hydrogel. It employed a highly accurate three-dimensional positioning system with pressure-controlled syringe to deposit biopolymer solution. The pressure-activated microsyringe was equipped with fine-bore nozzles of various inner-diameters. This process allowed that inner and outer shapes could be controlled arbitrarily when it was applied to a surgical region with arbitrary shapes. In order to fulfill the properties of the ideal barriers f3r preventing postoperative adhesion, we adopted the pre-mentioned method combined with surface modification with the hydrogel coating by which anti-adhesion property was improved.

• Macromolecular Research
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• v.14 no.4
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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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.126-126
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• 2009

알루미나와 실리카로 대표되는 투명 산화물 박막은 폴리머 기판상의 투습 방지막으로 응용되고 있으며, 플라즈마와 이온빔을 이용한 폴리머 기판 전처리를 통해 산화물 박막의 투습 특성을 향상시켰다. 기상 증착된 산화물 박막의 성장 거동에 대한 전처리 후 폴리머 기판의 wettability와 morphology의 효과를 확인하였으며, 그 폴리머 기판상에 증착되는 산화물 박막의 성장 메카니즘을 제안하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.7-10
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• 2003

Blue-light-emitting peiymer/dielectric nanolayer nanocomposites were prepared by the solution intercalation method and employed in electroluminescent device. Their photoluminescence and electroluminescence characteristics suggested that the nanolayers isolate the polymer chains and hinder the formation of excimers and aggregates. By reducing the excimer formation and its deleterious effects on emission efficiency, both the color purity and the luminescence stability were improved. Furthermore, the dielectric nanolayers have an aspect ratio of about 500 and therefore act as efficient barriers to oxygen and moisture diffusion, which produced a dramatic increase in the device stability.