• Macromolecular Research
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• v.11 no.5
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• pp.334-340
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• 2003

In order to fabricate new sustained delivery device of nerve growth factor (NGF), we developed NGF-loaded biodegradable poly(L-lactide-co-glycolide) (PLGA, the mole ratio of lactide to glycolide 75:25, molecular weight: 83,000 and 43,000 g/mole, respectively) film by novel and simple sandwich solvent casting method for the possibility of the application of neural tissue engineering. PLGA was copolymerized by direct condensation reaction and the molecular weight was controlled by reaction time. Released behavior of NGF from NGF-loaded films was characterized by enzyme linked immunosorbent assay (ELISA) and degradation characteristics were observed by scanning electron microscopy (SEM) and gel permeation chromatography (GPC). The bioactivity of released NGF was identified using a rat pheochromocytoma (PC-12) cell based bioassay. The release of NGF from the NGF-loaded PLGA films was prolonged over 35 days with zero-order rate of 0.5-0.8 ng NGF/day without initial burst and could be controlled by the variations of molecular weight and NGF loading amount. After 7 days NGF released in phosphate buffered saline and PC-12 cell cultured on the NGF-loaded PLGA film for 3 days. The released NGF stimulated neurite sprouting in cultured PC-12 cells, that is to say, the remained NGF in the NGF/PLGA film at 37 $^{\circ}C$ for 7 days was still bioactive. This study suggested that NGF-loaded PLGA sandwich film is released the desired period in delivery system and useful neuronal growth culture as nerve contact guidance tube for the application of neural tissue engineering.

• Journal of Adhesion and Interface
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• v.4 no.2
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• pp.10-20
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• 2003

This paper is relative to the electroless deposition of nickel or copper films on polyimide and polytetrafluoroethylene substrates. First, it is presented an original approach of the electroless process which consists in grafting nitrogenated functionalities on the polymer surfaces via plasma or VUV-assisted treatments operating in a nitrogen-based atmosphere ($NH_3$, $N_2$), and then in catalysing the grafted surfaces in an aqueous tin-free, Pd(+2)-based solution. Adhesion of the Pd(+2) catalytic species on polymer surfaces is explained by the formation of strong covalent bonds between these species and the grafted nitrogenated groups. Second, it is show how a fragmentation test performed in conjunction with electrical measurements can be used to characterize the practical adhesion of the electroless coatings deposited on flexible polymer substrates, and to evidence the influence of some experimental parameters (plasma treatment time and nature of the gas phase).

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.9-10
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• 2006

Recent work in our laboratory has focused on the molecular and supramolecular engineering of conjugated polymers and oligomers for device applications, including light emitting diodes for displays and lighting, photovoltaic cells, and thin film transistors. A central finding is that the supramolecular structure of conjugated polymers can have a dominant influence on their properties and the performance of devices. Some major results include: highly efficient RGB light-emitting diodes from polymers and oligomers; high mobility n-channel polymer field effect transistors; ambipolar thin film transistors from copolymer semiconductors; and self-assembly and ambipolar charge transport in polymer nanowires.

• Korea-Australia Rheology Journal
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• v.16 no.4
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• pp.213-218
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• 2004

Linear high-density polyethylene (PE) was controlled to induce strain-hardening behavior by introducing a small amount of second component with an anisotropic structure. In order to form an anisotropic structure in the PE matrix, the polymer was extruded through a twin-screw extruder, and the structure was controlled by varying the extrusion conditions. Depending on conditions, the second component formed a film, thread and droplet structure. If the second component was kept rigid, the morphology evolution could be delayed and the second component could maintain its film or thread structure without further relaxation. In par­ticular, the second component of the thread structure made a physical network and gave rise to remarkable strain hardening behavior under high extension. This study suggests a new method that induces strain hard­ening behavior by introducing a physically networked second component into the linear polymer melt. This result is anticipated to improve the processibility of linear polymers especially when extensional flow is dominant, and to contribute to our understanding of strain hardening behavior.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.18.1-18.1
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• 2010

Here, we introduce our R&D status and strategies for printed electronics containing the two types of aspects such as materials and process/architectures. Specially, in this talk, we focus on the high-performance polymer thin film transistors (PTFTs) backplanes fabricated by ink-jet printing using new polymer semiconductors for the applications of flexible display.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.30-33
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• 2002

We have shown that it is possible to form a fibrilar network of fibronectin on a polyelectrolyte polymer film whose dimensions are similar to those reported on the extra cellular matrix. The fibronectin network was observed to form only when the charge density of the polymer was in excess of the natural charge density of the cell wall. Furthermore, the self-organized fibronectin layer was much thicker than the polymer film, indicating that long ranged interaction may playa key role in the assembly process. It is therefore important to understand the structure of the polymer layer/protein interface. Here we report on a neutron reflectivity study where we explore the structure of the polyelectrolyte layer, in this case sulfonated polystyrene (PSSx,), with varying degree of sulfonation (x<30%), as a function of sulfur content and counter ion concentration. These results are then correlated with systemic study of the adsorption and the multilayer formation of fibronectin as a function of incubation time for various sulfonation levels of $PSSx.^1$

• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.137-140
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• 2006

In order to overcome the weak actuation and relaxation problems during the deformation of IPMC actuator, polymeric anion (polystyrenesulfonate)-doped polypyrrole(Ppy(PSS)) was electrodeposited onto IPMC actuator. Electrochemical quartz crystal microbalance study showed that hydrated cations were instilled into Ppy(PSS) film and polymeric-anion dopants introduced during polymerization were not expelled. Ppy(PSS)-coated IPMC actuator formed two electrode/electrolyte interfaces, Pt/nafion and Ppy(PSS)/bulk solution, and additive volume expansion phenomena at interfaces induced the large deformation compensating the relaxation of actuation by back diffusion of water.

• Applied Science and Convergence Technology
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• v.23 no.1
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• pp.44-47
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• 2014

In this study, we investigated the basic properties of N-doped ethylcyclohexene plasma polymer thin films that deposited by radio frequency (13.56 MHz) plasma-enhanced chemical vapor deposition (PECVD) method with controlled ammonia flow rate. Ethylcyclohexene was used as organic precursor with hydrogen gas as the precursor bubbler gas. Additionally, ammonia ($NH_3$) gas was used as nitrogen dopant. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared [FT-IR] spectroscopy, UV-Visible spectroscopy, and water contact angle measurement. We found that with increasing plasma power, film thickness is gradually increased while optical transmittance is drastically decreased. However, under the same plasma condition, water contact angle is decreased with increasing $NH_3$ flow rate. The FT-IR spectra showed that the N-doped ethylcyclohexene plasma polymer films were completely fragmented and polymerized from ethylcyclohexane.

• Journal of Photoscience
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• v.12 no.1
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• pp.41-46
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• 2005

We synthesized chiral choleseric liquid crystalline monomer p-phenylene bis-(p-3-acryloxy-2(S)-methylpropoxy)benzoate (1) and achiral nematic liquid crystalline monomer, p-phenylene p-acryloxy-6-hexyloxy-p-octyloxybenzoate (2) for the construction of cholesteric polymer network with a pitch gradient. In this research we attempted to synthesize cholesteric polymer film which have a wide reflection bandwidth in the region of visible wavelength with the synthesized chiral cholesteric monomer 1 and nematic monomer 2 under various photopoly merization conditions. We succeeded to construct cholesteric polymer film network with a pitch gradient covering more than 200 nm bandwidth in the visible wavelength by diffusion controlled photostructuring method.

• Journal of Photoscience
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• v.9 no.3
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• pp.57-63
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• 2002

A homopolymer containing anthracene groups, poly[6-(9-anthryloxy)hexyl methacrylate] (PAn) was prepared and the effect of oxygen on its photochemical reaction was studied by UV and IR absorption spectroscopy in order to understand its photochemical behavior. Photochemical reaction of the PAn in THF solution under an atmosphere of air resulted in the formation of endoperoxide at the beginning stage of reaction followed by photodimerization reaction after all the oxygen was consumed, whereas photodimerization and endoperoxide formation took place concomitantly in the film state. The photoreversible reaction of the anthracene photodimer groups in the polymer by photolysis with 254 nm UV light was not efficient. The IR absorption spectral changes of the PAn film upon irradiation indicate that various photooxidation products were produced in the atmosphere of air.