• Polymer(Korea)
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• v.36 no.3
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• pp.364-371
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• 2012

Polystyrene/single-walled carbon nanotube (PS/SWCNT) nanocomposites were prepared by latex technology and the effect of surfactant (SDS) on nanotube dispersion, rheological and electrical properties was investigated. The nanocomposites were prepared through freeze-drying after mixing PS particles and aqueous SWCNT/SDS suspension. As the SDS content increased, the storage modulus and complex viscosity of the nanocomposites were increased due to enhanced dispersion of nanotubes, but if the content excessively increased, the modulus and viscosity began to decrease due to low molecular weight of SDS. The electrical conductivity sharply increased with the addition of SDS, and then did not show significant changes. This result is speculated to be the competition between the increased dispersion of nanotubes and the deterioration of electrical conductivity by SDS adsorption. An optimal ratio of SDS to SWCNT for improving electrical conductivity and end-use properties was 2. With this ratio, the electrical percolation threshold of SWCNT was less than 1 wt%.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• Polymer(Korea)
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• v.37 no.2
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• pp.162-166
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• 2013

Graphene-coated polymer particles have attracted research interests due to their emerging applications derived from their controlled structure and morphology. To control the properties of graphene oxide (GO)-polystyrene (PS) composite particles, the adsorption time and instantaneous adsorption conditions were investigated by varying their mixing method. Polystyrene particles prepared by emulsion polymerization were modified to have positive surface charge by adsorption of polyethylene imine (PEI) on the surface of PS particles. GO prepared by the chemical exfoliation method had negative surface charge from the oxygenated groups. The adsorption of the negatively charged GOs onto the positively charged PS particles was successfully completed, and it was found that a longer adsorption time and a greater difference in the instantaneous relative concentration led PS-GO particles to have more homogeneously coated surfaces without aggregation.

• Journal of Adhesion and Interface
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• v.9 no.4
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• pp.30-33
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• 2008

Two polymeric interfaces with single component homo-polymers were prepared to control the orientation of block copolymer thin-film nanostructures. Poly(4-acetoxy styrene) (OH-PAS) and poly(4-methoxy styrene) (OH-PMS) which have the average chemical composition of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) were precisely synthesized through nitroxide-mediated radical polymerization. After dehydration reactions between above polymers and SiOx layers of silicon wafers, the polymer-modified interface induced partial (30%) vertical orientation of PS-b-PMMA thin film in the case of OH-PMS and wholly parallel orientation in the case of OH-PAS. Chemical compositions of polymeric interface layers are regarded as the key parameter to control the orientation of nanostructures of block copolymer thin film.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.198-205
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• 2002

Isothermal pyrolysis of high density polyethylene(HDPE), polypropylene(PP) and polystyrene(PS) was performed at $450^{\circ}C$, respectively. The effect of pyrolysis time on yield and product composition was investigated. Conversion and liquid yield obtained during HDPE pyrolysis continuously increased with time up to 80minutes, but those of PP and PS did not largely change after 35minutes. Each liquid product formed during the pyrolysis was classified into gasoline, kerosene, light oil and wax according to the distillation temperature based on the petroleum product quality standard of Korea Petroleum Quality Inspection Institute. The major liquid product of HDPE pyrolysis was light oiH34 wt.% based on the amount of HDPE treated) and the amounts of the other liquid ingredients(gasoline, kerosene and wax) were almost the same. On the other hand, the pyrolysis of PP produced 27 wt.% gasoline, 22 wt.% kerosene, 24 wt.% light oil and 13wt.% wax, and the pyrolysis of PS produced 56 wt.% gasoline, 12 wt.% kerosene, 9 wt.% light oil and 13 wt.% wax.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.469-469
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• 2012

유기발광소자는 빠른 응답속도, 넓은 시야각, 얇은 두께의 특성으로 차세대 디스플레이 소자 기술로 많은 주목을 받고 있다. 백색 조명 광원 관련 기술은 친환경 에너지와 관련하여 연구가 활발하게 진행되고 있다. 청색과 황색의 유기물층을 적층하여 제작한 백색 유기발광소자는 서로 다른 두 유기물질의 계면 불균일로 인한 효율 저하와 형광 여기자의 수명과 유기물의 두께 상관관계에 따라 색안정성이 나빠지는 문제점이 있다. 본 연구에서는 고분자 poly (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV)와 polystyrene (PS) 혼합물을 스핀코팅 방법을 사용하여 박막을 형성한 후 열처리에 의한 상분리 현상을 이용하여 선택적으로 PS 물질을 제거하여 MEH-PPV 황색 고분자 발광층을 형성하여 황색 고분자 발광층의 표면 성질 변화를 관찰하였다. 고분자 MEH-PPV와 PS의 혼합 비율과 혼합층 두께에 따른 MEH-PPV 황색 고분자 박막의 변화를 원자힘 현미경을 통하여 관찰할 수 있었다. MEH-PPV 황색 고분자 발광층의 표면 특성은 MEH-PPV와 PS 혼합물의 PS 혼합비가 높아지면 표면거칠기가 작아지며, 혼합된 두 고분자 물질의 분자량의 차이에 의한 응집도의 차이로 인하여 MEH-PPV와 PS 혼합물 박막의 두께가 얇아지면 표면거칠기가 커진다. 이 연구 결과는 고분자-저분자 혼합 발광층 구조를 사용하는 백색 유기발광소자의 효율 향상에 대한 기초자료로 활용할 수 있다.

• Polymer(Korea)
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• v.32 no.2
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• pp.131-137
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• 2008

We have fabricated polystyrene (PS) nanofibrous scaffold for hepatocyte culture by electrospinning method and subsequently coated with specific ligand of Poly[N-p-vinylbenzyl-O-$\beta$-D-galactopyranocyl-($1{\rightarrow}4$)-D-gluconamide](PVLA) to enhance hepatocytes attachment. Rat hepatocytes behavior on the PVLA-coated and non-coated PS nanofibrous matrices have been investigated. Electrospun PS nanofiber structures revealed randomly aligned fibers with average diameter of 500 nm. It is observed that PS nanofibrous matrix could incorporate many cells into the interior of the matrix probably due to the suitable pore size. Cell viabilities cultured on PVLA-coated PS nanofibrous mats were maintained for 3 weeks, while it was decreased rapidly on PVLA-coated PS dishes. High hepatic functions especially for albumin secretion and ammonia removal were maintained at least for 2 weeks on nanofibrous mats but rapidly decreased on flat PS dishes. These results indicate that nanofibrous structure enabled 3-D culture with high level of cell-cell contact results in providing cell-cell communications and subsequent long-term maintenance of specific cell functions.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.1
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• pp.1-9
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• 2012

In this study, 5 solvent soluble polymers were treated on Hanji. Mechanical properties, morphology and oxidation index with thermal aging were measured on the aged Hanji, dewaxed Hanji and polymer treated Hanji. Synthetic polymers(such as polylactic acid, polybutylene succinate, polystyrene) treated Hanji had higher strength and thermal stability than cellulose derivatives(such as cellulose nitrate and cellulose acetate) treated Hanji. Polymer treated Hanji showed a little bit of color change. The oxidation index of PS treated Hanji did not increase with thermal aging because it did not have a carboxyl group in chemical structure. Finally, polystyrene was found to be the most efficient method for strengthening the dewaxed Hanji. The best aging safety and thermal stability were obtained at the polystyrene 3% solution.

• Membrane Journal
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• v.14 no.2
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• pp.173-184
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• 2004

For the application of direct methanol fuel cell (DMFC), sulfonated polystyrene/teflon (PS/PTFE) composite membranes were developed by changing monomer ratio of styrene and DVB. The composite membranes were prepared as follows: first, the monomer mixtures consisting of styrene, divinyl benzene and AIBN were impregnated in porous PTFE film and then, polymerized under 8$0^{\circ}C$ to give PS/PTFE membranes. Finally, the membranes were reacted with chlorosulfonic acid in 1,2-dichloroethane to give the sulfonated composite membranes. The measurements of ATR-FTIR, SEM, solvent uptake test and ion exchange capacity (IEC) were done for the resulting membranes before or after sulfonation, respectively, which showed the composite membranes with proper crosslinking degree and sulfonic acid content were prepared well as a function of styrene/DVB ratio. ion conductivity and methanol permeability were studied for the sulfonated membranes. It was found that with decreasing the ratio of styrene/DVB, methanol permeability decreased from $6.6{\times}10^{-7}∼1.3{\timas}10^{-7}$ $\textrm{cm}^2$/s, which are much lower values than that of Nafion$^{(R)}$117($1.02{\times}10^{-6}$ $\textrm{cm}^2$/s). Under the same monomer condition, ion conductivity decreased from 0.11 S/cm ($25^{\circ}C$) to 0.08 S/cm ($25^{\circ}C$), which are similar or a little higher values compared with $Nafion^{(R)}117 (1.02{\times}10^{-6}$ $\textrm{cm}^2$/s, 0.0824 S/cm). These two results confirmed the composite membranes prepared could be applied successfully to DMFC.C.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.617-617
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• 2013

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 박막(nanosheet) [1]이나 붕소 탄화질화물(boron caronitride; BCN) 박막 [2,3]과 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 박막으로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 폴리스틸렌(polystyrene, PS)과 보레인 암모니아(borane ammonia)를 고체 소스로 이용하여 열화학기상증착법으로 BCN 박막을 SiO2 기판 위에 직접 합성하였다. SEM과 AFM 관측을 통해 합성된 BCN 박막의 두께가 약 10 nm이며, RMS roughness가 0.5~2.6 nm로 매우 낮은 것을 확인하였다. 합성과정에서 PS의 양을 조절하여 BCN 박막의 탄소의 밀도를 성공적으로 제어하였으며, 이에 따라 전기적인 특성이 제어되는 양상을 확인하였다. 또한 합성온도 변화에 따른 BCN 박막의 전기적인 특성이 제어되는 양상을 확인하였다. 추가적으로 같은 방법을 이용하여 BCN 박막을 Cu 위에서 합성하여 SiO2 기판위에 전사하였다. 합성된 BCN 박막의 구조적 특징과 화학적 조성 및 결합 상태를 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy), 라만 분광법(Raman spectroscopy)을 통해 조사하였고, 이온성 용액법(ionic liquid) [4]을 이용하여 전계효과 특성을 측정하였다.