• Polymer(Korea)
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• v.24 no.2
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• pp.252-258
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• 2000

Various crosslinked poly(4-vinylpyridines) (CHP4VP) having different degrees of crosslinking were synthesized by radical copolymerization of 4-vinylpyridine with if N,N' -1, 6-hexamethylenebisacrylamide, and CHP4VP- Cu(II) complexes were prepared by the method of adsorption equilibrium. The catalytic activity of the complexes for the oxidation of ascorbic acid (AA) was investigated. The oxidation of AA by these complexes showed a kinetic behavior of the Michaelis-Menten type. The catalytic activity of CHP4VP-Cu(I ) catalytic system was increased with increasing the degree of crosslinking of CHP4VP, and its activity was scarcely decreased even after repeated use. However, the tendency of the catalytic activity of CHP4VP-Cu(II) complexes was decreased for the oxidation of AA when compared with that of the previously reported catalytic system containing crosslinked poly(4-vinylpyridine) prepared using N,N'-methylenebisacrylamide as a crosslinker. These results indicate that the degree of crosslinking of CHP4VP and the hydrophobicity of the crosslinker play an important role in the catalytic system of the oxidation of AA.

• Analytical Science and Technology
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• v.17 no.6
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• pp.496-513
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• 2004

This study was carried out to evaluate the performance of sampling and analytical methodology used for the measurement of toxic volatile organic compounds (VOCs) in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/MSD analysis. Target analytes were 33 compounds including major aromatic compounds such as BTEX, and halogenated compounds. The methodology was investigated with a wide range of different adsorbents which are commercially available and have been frequently adopted for the VOC measurement. A total of 10 adsorbents were tested in this study: 6 carbon-based adsorbents such as Carbotrap, Carbopack B, Carbosieve S-III, Carboxen 1000, Carbotrap C, Activated Charcoal; and 4 polymer-based adsorbents including Tenax, Porapak Q, Chromosorb 102, and Chromosorb 106. The sampling performance was evaluated with respect to the sampling capacity of VOCs with single-adsorbent and multiple-adsorbents methods for standard samples and field samples. As a result, the best adsorbents for single-adsorbent method in the sampling of toxic organic compounds (including benzene, toluene, xylenes etc.) appeared to be Carbotrap, Carbopack B and Tenax TA. On the other hand, Chromosorb 102, Chromosorb 106 and Porapak Q were found to be unsuitable adsorbents for VOC measurement based on thermal desorption method. Multi-adsorbent packings were evaluated with 4 carbon-based adsorbents, which classified by 3 combination sets of double adsorbents and 2 combination sets of triple adsorbents. The results indicated that the most suitable combination for toixc VOC measurements is Carbotrap C with Carbotrap. Multi-sorbents tubes packed with a strong adsorbent such as Carbosieve S-III or Carboxen 1000 were found to be relatively unsuitable for several compounds, not only owing to the effect of migration of adsorbed compounds from weaker adsorbent to stronger adsorbent, but to hydrophobic nature of the adsorbents. Therefore, it should be addressed that selection of a proper adsorbent (or combination of multi sorbents) is extremely important to obtain reliable data for the concentrations of toxic VOCs in indoor and outdoor environments.

• Polymer(Korea)
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• v.27 no.5
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• pp.464-469
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• 2003

In this work, the fragrant oil release behavior of poly($\varepsilon$-caprolactone) (PCL) microcapsules containing SiO$_2$ was investigated. The SiO$_2$ was chemically treated in 10, 20, and 30 wt% hydrochloric acid and sodium hydroxide. The acid and base values were determined by Boehm's titration technique and $N_2$/77 K adsorption isotherm characteristics, the specific surface area and total pore volume were studied by BET. The PCL microcapsules containing SiO$_2$ and fragrant oil were prepared by oil-in-water (o/w) emulsion solvent evaporation method. The shape and surface of PCL microcapsules were observed using image analyzer and scanning electron microscope (SEM). The fragrant oil release behavior of PCL microcapsules was characterized using UV/vis. spectra. The average diameters of PCL microcapsules were decreased from 35 to 21 $\mu$m with increasing stirring rate. It was found that in the case of acidic treatment the fragrant oil adsorption capacity and release rate were increased due to the increase of specific surface area and acid value. In the case of basic treatment, the fragrant oil adsorption capacity and release rate were decreased due to the decrease of sp ecific surface area and the increase of acid-base interactions between SiO$_2$-NaOH and fragrant oil with increasing base value of SiO$_2$.

• Polymer(Korea)
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• v.27 no.5
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• pp.397-404
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• 2003

The interaction of cell adhesive protein and polypeptide with bone marrow stromal stem cells (BMSCs) grown in tissue engineered films and scaffolds were examined. Several proteins or polypeptide known as cell-adhesive were coated adsorption on poly(lactide-co-glycolide) (PLGA) films and scaffolds and adhesion and proliferation behavior of BMSC on those surfaces were compared. The protein and polypeptide used include collagen IV, fibrinogen, laminin, gelatin, fibronectin, and poly(L-lysine). The protein and polypeptide were adsorbed on the PLGA film surfaces with almost monolayer coverage except poly(L-lysine). BMSCs were cultured for 1, 2, and 4 days on the protein- or polypeptide-adsorbed PLGA films and scaffolds. The cell adhesion and proliferation behaviors were assessed by sulforho damine B assay. It was observed that the protein- or polypeptide-adsorbed surfaces showed better cell adhesion and proliferation than the control.

• Polymer(Korea)
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• v.28 no.5
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• pp.397-403
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• 2004

The sulfonated PET-g-GMA ion-exchange fine fibers were synthesized by UV radiation-induced graft copolymerization using a photoinitiator, and their chemical structure and adsorption properties were investigated. The optimum values for synthetic conditions - UV intensity, reaction time, and reaction temperature were 450 W, 60 min, and $40^{\circ}C$, respectively. Maximum values of the degree of sulfonation and ion exchange capacity were 8.12 mmol/g and 3.25 meq/g, respectively. Tensile strength of sulfonated PET-g-GMA fine ion exchange fibers was lower than that of PET trunk polymer as the grafting reaction rates increased. It was shown that as for the adsorption rate of $Ca^{2+}$ and $Mg^{2+}$ by the sulfonated PET-g-GMA fine ion exchange fibers, magnesium ion is slower than calcium ion in the solution. However, in the mixture of the calcium and magnesium ions, the adsorption rate of calcium ion was much slower than that of magnesium ion.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.819-824
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• 1994

A membrane-like $H_3PMo_{12}O_{40}$-polysulfone film was prepared by blending $H_3PMo_{12}O_{40}$ with polysulfone using dimethylformamide as a common solvent. SEM and EDX analysis showed that $H_3PMo_{12}O_{40}$ was uniformly and finely distributed in the film catalyst. The ESCA measurement also revealed that the oxidation state of Mo was not changed. The $H_3PMo_{12}O_{40}$-polysulfone catalyst showed lower activity for acid-catalyzed reaction and higher activity for oxidation reaction than $H_3PMo_{12}O_{40}$ in ethanol conversion reaction. The oxidation activity of the film catalyst was about 10 times higher than $H_3PMo_{12}O_{40}$. The decrease of acidic activity was due to DMF strongly adsorbed in acid sites of $H_3PMo_{12}O_{40}$, whereas the increase of oxidation activity was mainly due to uniform distribution of $H_3PMo_{12}O_{40}$. Adsorption results showed that the surface character of $H_3PMo_{12}O_{40}$ was drastically increased, while the bulk property of that was almost same after blending. It is suggested that the control of surface/bulk property as well as acid/redox property of heteropoly acid would be possible by blending it with a polymer.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1321-1326
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• 2005

As a results of this research, the Nakdong River consisted of 43% of hydrophobic fraction, 39% of hydrophilic fraction, and 18% of transphilic fraction. The hydrophobic fraction in this raw water was mostly fulvic acid. Fulvic acid comprised of 62% and the rest was humic acid(38%). There was more carboxylic acid functional roup(64%) than phenolic group(36%). HPI-N and HPI-C comprised of 17% and 22% in the hydrophilic portion, respectively. The results of the membrane fouling test using UF membrane according to NOM fractions. HPI-N caused more fouling than HPI-C. Humic acid caused more fouling than fulvic acid probably due to higher adsorption capacity. Since humic acid has higher adsorption capacity than fulvic acid, it would be more adsorbed onto the membrane pores. The carboxylic acid functional group caused more fouling than the phenolic group.

• Journal of the Korean earth science society
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• v.26 no.7
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• pp.668-673
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• 2005

To collect or transfer samples of gaseous pollutants, various types of tubing are used. Hence, to analyze the uncertainties associated with the use of tubings, a series of comparative test were designed and conducted using the RSC standards with different concentration ranges. For the purpose of this study, we prepared tubings made of six different types of material which include: [1] silco-steel (S1), [2] stainless steel (S2), [3] silicone (S3), [4] PTFE Teflon (T1), [5] tygon (T2), and [6] brass (B). The patterns of RSC loss on to tubing walls, when compared on the basis of the least reactive material S1, exhibited that the extent of RSC loss varied dynamically. It was found that Teflon is highly stable. However, other materials tend to exhibit contrasting patterns of loss. S2 and B show significant loss of light RSC $(H_2S\;and\;CH_3SH)$, while S3 and T2 experience notable loss of heavy RSC (DMS and DMDS).

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.102-107
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• 2012

The recovery of a Pt anode in a PEMFC through 30 ppm $H_2S/H_2$ exposure was evaluated by using a cyclic voltametry(CV) scan. First, the PEMFC unit cell performanc loss was measured three times under an anode feeding with 30 ppm $H_2S/H_2$ for 1hr at $0.5A/cm^2$ of current density. The initial cell performance was $1.16A/cm^2$ at 0.6 V without $H_2S$ poisoning. After first poisoning step for 1hr the cell performance was decrease to $0.77A/cm^2$, and the further poisoning steps decreased up 0.57 V. Finally, the recovery of the cell performance of $H_2S$ poisoned PEMFC was achieved up to 90.3% by applying CV scan. Moreover, we also found out that another possible approach for over 80% recovery of the cell performance of $H_2S$ poisoned anode Pt catalyst layer was to just inject fresh hydrogen into the anode feeding stream.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.210-210
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• 2013

그래핀은 뛰어난 기계적, 화학적, 광학적, 전기적 특성을 가지고 있는 2차원 물질로, 대면적 합성법과 전사 공정을 통해 다양한 기판에서의 사용이 가능해지면서 차세대 전자 소자로 활용하기위한 활발한 연구가 이루어지고 있다. 디스플레이, 태양전지의 전극과 전계 효과 트랜지스터의 채널로 적용한 연구에서 우수한 결과들을 보이고 있다. 특히, 금속/금속 산화물 전극은 염료 감응형 태양전지와 유기 발광 다이오드 구조에서 화학적으로 불안정할 뿐 아니라 일함수가 고정되어 쇼트키 접촉이 형성되면 저항을 낮추기 어렵지만, 그래핀은 금속/금속 산화물 전극보다 화학적으로 안정하고 일함수의 조절이 가능해 옴 접촉 형성에 용이하다. 그래핀의 일함수를 조절하는 연구는 크게 공유결합과 비공유 결합을 이용한 방법이 시도된다. 공유 결합을 이용한 방법은 합성과정에서 그래핀의 구조에 내재된 결함 혹은 새로운 결함을 형성하여 다른 원소를 첨가하는 방법이다. 이러한 방법은 그래핀의 결함 영역에서 작용하기 때문에 그래핀 전자 구조의 높은 수준 조절을 위해선 그래핀 구조의 파괴가 동반된다. 반면, 비공유 결합을 이용한 방법은 전하 이동 도핑 효과를 이용해 그래핀의 전자 구조를 제어하는 방법으로, 금속/금속산화물/기능기와 그래핀의 적층으로 복합 구조를 형성하는 방법이다. 금속/금속 산화물과의 복합구조는 안정적인 p-형 도핑이 보고되었지만, n-형 도핑은 대기중의 수분, 산소 그리고 기판과의 상호작용에 의해 대기중에서 불안정해 추가적인 피막공정이 요구된다. 기능기를 이용한 적층 구조는 그래핀과 기판사이의 상호작용 혹은 그래핀 전자 구조를 다양한 기능기를 이용해 제어하는 것으로, 이극성을 가진 자기정렬 단일층(self-assembled monolayers)이 대표적인 방법이다. 공간기(spacer)의 길이나 말단기(end group)의 종류로 p-형과 n-형의 도핑 수준을 제어할 수 있지만, 흡착기(chemisorbing groups)의 반응성이 기판의 화학적, 물리적 표면상태에 의존하기때문에 기판 선택이 제약되며 전처리 공정이 요구될 수 있는 한계가 있다. 본 연구에서는 다양한 기판에 적용가능한 용액 공정을 이용해 그래핀과 고분자를 적층하였고, 안정적이고 효과적으로 일함수를 낮추는 구조를 확인하였다.