• Polymer(Korea)
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• v.24 no.3
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• pp.287-298
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• 2000

In preparing micron-sized monodisperse polystyrene beads by dispersion polymerization, the conversion, and the particle size and its distribution were affected by the reaction temperature, concentration of the monomer, solvent and initiator, molecular weight and concentration of the steric stabilizer, amount of oxygen existing in the reactor, and an appropriate combination of these starting materials. Ethanol as a dispersing agent, styrene as a monomer, PVP as a steric stabilizer, AIBN as an initiator, DVB as a cross-linking agent and toluene as a co-solvent were the basic materials for the synthesis. The reaction rate and the conversion were increased with the reaction temperature and the amount of DVB from 1 to 4%, and the conversion was saturated after 10 hours of the reaction time. The optimum reaction recipe for the preparation of the monodisperse PS beads was 25% styrene monomer, 0.5% DVB, 25% toluene, 10-15% PVP, and 2 and 4% AIBN, thereby, 3.9~4 ${\mu}{\textrm}{m}$ and 3.4~9.3 ${\mu}{\textrm}{m}$ of polystyrene beads, respectively, were successfully synthesized.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.29-32
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• 2009

Dense and periodic arrays of nano-sized holes were patterned in oxide thin film on GaAs substrate. To obtain the nano-size patterns, self-assembling diblock copolymer was used to produce thin film of uniformly distributed parallel cylinders of polymethylmethacrylate (PMMA) in polystyrene (PS) matrix. The PMMA cylinders were removed with UV expose and acetic acid rinse to produce PS nanotemplate. By reactive ion etching, pattern of the PS template was transferred to under laid silicon oxide layer. Transferred patterns were reached to the GaAs substrate by controlling the dry etching time. We confirmed the achievement of etching through the removing oxide layer and observation of GaAs substrate surface. Optimized etching time was 90 to 100 sec. Pore sizes of the nanopattern in the silicon oxide layer were 20~22 nm.

• Korean Journal of Food Science and Technology
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• v.46 no.6
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• pp.739-742
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• 2014

This study investigated the effect of perforation by the Indian meal moth (Plodia interpunctella) larvae on various flexible food-packaging films, in relation to their thickness and type. Among the various flexible packaging films, polyethylene (PE), aluminum foil (AF), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were selected for this study due to their wide usage in food packaging. Based on their thickness, film penetration by P. interpunctella larvae was measured as in following order: PP, $20{\mu}m$; AF, $9{\mu}m$; PET, $12{\mu}m$; PP, $30{\mu}m$; PS, $30{\mu}m$; PE, $40{\mu}m$; PE, $35{\mu}m$; PS, $60{\mu}m$; and PET, $16{\mu}m$. P. interpunctella larvae rapidly penetrated through the packaging films regardless of their thickness and type. In particular, it was observed that PP of $20{\mu}m$ and PS of $30{\mu}m$ were completely penetrated by P. interpunctella larvae within 72 h, rendering thin PP and PS films less valuable as anti-insect packaging films. Our results show that the perforations by P. interpunctella larvae were observed in the thin films. These results imply that each packaging film has a marginal thickness against the perforations by P. interpunctella larvae.

• Macromolecular Research
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• v.17 no.5
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• pp.301-306
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• 2009

This work has demonstrated that a novel amphiphilic poly(epichlorohydrine)-graft-polystyrene (PECH-g-PS) copolymer at 34:66 wt% was synthesized via atom transfer radical polymerization (ATRP) of styrene using PECH as a macroinitiator. The structure of the graft copolymer was characterized by nuclear magnetic resonance ($^1H$ NMR) and FTIR spectroscopy, demonstrating that the "grafting from" method using ATRP was successful. The self-assembled graft copolymer was used as a template film for the in-situ growth of silver nanoparticles from $AgCF_3SO_3$ precursor under UV irradiation. The in situ formation of silver nanoparticles with 6-8 nm in average size in the solid state template film was confirmed by transmission electron microscopy (TEM), UV-visible spectroscopy and wide angle X-ray scattering (WAXS). Differential scanning calorimetry (DSC) also displayed the selective incorporation and the in situ formation of silver nanoparticles within the hydrophilic PECH domains, probably due to stronger interaction of the silvers with the ether oxygens of PECH backbone than that with hydrophobic PS side chains.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.47-50
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• 1997

We synthesized N-Hydroxysuccinimidyl (NHS) azidobenzoate as a cross-linking reagent for immobilization of peptide onto the solid surface. Thin polystyrene(PS) films spin-coated with a NHS azidobenzoate solution were exposed with ultraviolet light at 245nm$(3.3mW/cm^2)$ for 5 min. The NHS active ester groups became covalently attached to the polymer via photogenerated, highly reactive nitrene intermediates derived from NHS azidobenzoate. Using this technique, it is demonstrated that well-defined surface regions can be functionalized with a minimum observable feature size of 1mm for UV exposure. Through reaction of this functionalized PS surface with primary amine-containing biomolecules, biological molecule had been immobilized on the polymer surface.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.742-745
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• 2001

Plastics are one of difficult materials for recycling due to their characteristics in use. Recycling ratio of waste plastics was around 40% in last year in Japan, which includes energy recovery. Feed stock recycling and mechanical recycling are not easy because of additives in commercial plastics. Then, pyrolysis treatments have been done to recovery energy. Although plastics are easy to fire, complete combustion of them is not easy if anti-firing agents are added especially. Therefore, researches on pyrolysis or combustion behaviors of plastics containing additives are important from a view point recycling of plastics. Direct observation of popular plastics like polystyrene (PS), polycarbonate (PC), polyphenyle ether (PPE) and polyvinyl chloride (PVC) to investigate their pyrolysis behaviors in the present study. In case of PS, melting and gas evolution started at 9$0^{\circ}C$ and 39$0^{\circ}C$ respectively. And combustion finished at 445$^{\circ}C$. On the other hand, more than $600^{\circ}C$ and sufficient oxygen are required for complete combustion of PC and PPE.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.196.2-196.2
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• 2014

Nanostructuring the electrode surface is an emerging technology to improve the performance of supercapacitors since it can facilitate charge transfer, ion diffusion and electron propagation during electrochemical process. Fabrication of the electrode consisting of two or more materials together has also been focused on since it can provide synergetic effect such as broader working potential range and enhanced capacitance. In this work, we have used polyaniline (PANi) and manganese oxide (MnO2) as electrode materials. PANi is one of the promising electrode materials due to its high electrochemical activity, high doping level and stability. MnO2 is also widely studied material for supercapacitors since it is relatively cheap and environmentally friendly. Firstly, we synthesized polystyrene nanospheres on MnO2 nanoparticles. MnO2-incorporated PANi hollow nanospheres were then fabricated by polymerizing aniline monomers on these PS nanospheres and dissolving the inner PS spheres. The surface morphology, electronic absorption and electrical conductivity of the electrode were analyzed using field-emission scanning electron microscope (FE-SEM), UV-visible spectrometer, and sheet resistivity meter, respectively. The electrochemical properties such as capacitance of the supercapacitors were also estimated using cyclic voltammetry.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.248.1-248.1
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• 2014

We present results from an experimental study of conductivity change of poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) film according to the surface structuring. We demonstrate that the patterned structure was enhanced with approximately five times conductivity in comparison with non structure of PEDOT:PSS film. In order to patterning, we have fabricated polystyrene (PS) colloidal monolayer as a template with sphere diameter of 780nm and 1.8um. Structure has honeycomb shape and it provide shorter path way to flowing of electron. Pattern size was controlled by PS diameter and varied by Transformer Coupled Plasma (TCP) etching system. Conductivity was converted from sheet resistance which measured by 4-point prove. Film thickness was derived using Field Emission Scanning Electron Microscopy (FE-SEM) images.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.384.1-384.1
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• 2014

대면적 그래핀을 합성하는 방법으로 주로 화학기상증작법, SiC 기판을 고온 열처리하는 방법 그리고 최근에는 고체소스를 활용하여 그래핀을 합성하는 방법 등이 보고되고 있다. 이에, 본 연구에서는 폴리머 용액들을 원하는 기판에 스핀코팅하여 건조시킨 후, 후 열처리 공정을 통해 그래핀을 합성하고 물성을 평가해보았다. 그래핀 합성을 위해서 사용된 폴리머 탄소원은 Vinyl계 폴리머 용액으로, polystyrene (PS), polyacrylonitrile (PAN), 그리고 polymethylmetacrylate (PMMA) 등으로 2wt%의 폴리머 용액을 $SiO_2$기판에 스핀 코팅을 하고, 그 위에 Nickel이나 Copper와 같은 catalytic metal을 capping layer로 증착하고, 고진공에서 후열처리 공정에 의해 그래핀을 성장하였다. 이때, 탄소원으로 쓰인 PS, PMMA 폴리머는 pristine graphene 합성을 위해, PAN 폴리머는 질소가 도핑된(n-type) 그래핀 합성을 위해 사용되었다. 그래핀의 물성은 폴리머 종류, 코팅된 두께, 촉매 금속층 종류와 두께, 그리고 후열처리 공정 온도와 시간에 따라서 조절이 가능하였다. 우리는 Raman spectroscopy, AFM, SEM 등을 활용하여 그래핀의 층수, 결함, 표면양상 등을 평가하였고, 또한 전사된 그래핀을 기반으로 제작된 FET의 게이트 전압에 따른 I-V 곡선을 측정하여 캐리어 종류 및 전하 이동도 등을 평가하였다. 더욱 상세한 내용은 프레젠테이션에서 논하겠다.

• Macromolecular Research
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• v.8 no.3
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• pp.103-115
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• 2000

The structural changes viewed from the molecular level have been investigated for the isothermal crystallization phenomena of polyethylene (PE) and the solvent-induced crystallization phenomenon of syndiotactic polystyrene (sPS) glassy sample. The data, which were collected by the time-resolved measurements of Fourier-transform infrared spectra, Raman spectra, synchrotron-sourced small-angle X-ray scattering, wide-angle X-ray scattering, and so on, were combined together to extract the detailed structural information in these phase transition phenomena. In the case of PE, the isothermal crystallization from the melt to the orthorhombic form was found to occur via the conformationally-disordered trans chain form, followed by the formation of the lamellar stacking structure of regular orthorhombic-type crystals. In the case of sPS, the amorphous chains in the glassy sample were found to enhance the mobility through the interaction with the injected solvent molecules, which act as a trigger to cause the conformational ordering from the random coil to the regular T$_2$G$_2$-type helical form. The thus created short helical segments were found to grow into longer helices, which gathered together to form the crystallites, as revealed by the organized coupling of the infrared, Raman and X-ray scattering data.