• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.454-458
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• 2009

Polypyrrole (PPy) nanotubes have been synthesized by chemical oxidative polymerization of pyrrole within the pores of polycarbonate membrane using the technology of diffusion of solutes. The nanotubes array prepared by the proposed method can be considered as nanoelectrode ensembles (NEEs). An amperometric uric acid sensor based on PPy NEEs has been developed and used for determination of uric acid in human serum samples. The electrode can direct response to uric acid at potential of 0.60V vs. SCE with wide linear range of $1.52{\times}10^{-6}\;to\;1.54{\times}10^{-3}\;M.\;The\;detection\;limit\;is \;3.02{\times}10^{-7}$ M. This sensor has been used to determine uric acid in real serum samples. PPy NEEs is thought of as a good application in the foreground.

• 폴리머
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• 제35권4호
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• pp.356-362
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• 2011

폴리카보네이트(polycarbonate, PC)에 화학적 구조가 다른 두 가지의 분지제를 첨가하여 용융중합으로 분지형 폴리카보네이트(branched PC, B-PC)를 합성하였다. 분지제의 함량은 0.001~0.005 mol% 내에서 조절하였다. 합성된 PC의 화학구조는 FTIR, $^1H$ NMR파 $^{13}C$ NMR 스펙트럼을 이용하여 확인하였으며, 분자량, 유리전이온도 및 분해온도는 GPC, DSC와 TGA를 이용하여 측정하였다. Phloro type의 분지제를 가지는 B-PC의 분자량에 낮은 값을 보여주었으며, 유리전이온도는 분자량에 따라 증가하였다. 두 형태의 B-PC 모두 선형 PC와 비교하였을 때 낮은 주파수(frequency) 영역에서 복합점도(complex viscosity)가 높게 나타났고, shear thinning 현상이 크게 나타났다. Shear thinning의 정도를 표시하는 power law index(n)는 선형회귀분석에 의해 계산되었고 0.483~0.996 범위의 값을 보여주었다. Phloro 타입의 B-PC가 높은 shear thinning 경향을 보였으며 이들 B-PC의 유변학적 특성은 동적유변측정기를 이용하여 측정하였다.

• 소성∙가공
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• 제18권8호
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• pp.616-624
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• 2009

In this work we demonstrate the hot-embossing process under different forming conditions such as forming temperature, load, and holding time in pressing, in order to determine the suitable conditions required for linear patterning on polymer plates (PC). Results showed that the replicated pattern depth increased in proportion to an increase in the forming temperature, load, and time. The reduction of the workpiece thickness increased according to the holding time in the pressing process. In the process of time, the reduction ratio of the workpiece thickness decreased due to the surface area increment of the workpiece, while the pressure on the workpiece declined. In order to reduce the bulging ratio we introduced a temperature difference between the upper and the lower punch.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.277-280
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• 2008

Recently, a demand of nano/micro patterned polymer for display or biochip has been rising. Then many studies have been carried out. Nano/micro-embossing is a deformation process where the workpiece materials is heated to permit easier material flow and then forced over a planar patterned tool. In this work, the hot-emboss process is performed with different forming conditions; forming temperature, load, press hold time, to get the proper condition for linear pattern fabrication on plated-type polymers (PC). Replicated pattern depth increases in proportion to the forming temperature, load and time. Reduction of the workpiece thickness increases according to press hold time. In process of time, reduction ratio of workpiece thickness decreases because of surface area increment of the workpiece and pressure decline on it.

• Carbon letters
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• 제23권
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• pp.55-62
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• 2017

We report on the dispersion state of partially reduced graphene oxide (PRGO) in organic solvents, namely methyl ethyl ketone, ethyl acetate, methylene chloride, toluene, and xylene, by controlling the carbon to oxygen (C/O) atomic ratio of the PRGOs. A two-phase solvent exchange method is also proposed to transfer PRGO from water to an aprotic solvent, such as methyl ethyl ketone. We achieve relatively good dispersion in aprotic and non-polar solvents by controlling the C/O atomic ratio of the PRGOs and applying the two-phase solvent exchange method. There is an increase in the glass transition temperatures with the dispersion of PRGOs into amorphous polymers, in particular a $4.4^{\circ}C$ increase for poly(methyl methacrylate) and $3.0^{\circ}C$ increase for polycarbonate. Good dispersion of PRGO in a nonpolar polymer, such as linear low density polyethylene, is also obtained.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1968-1972
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• 2010

Pt-Co alloy nanowire array was directly synthesized by electrochemical deposition with polycarbonate template at -1.0V and subsequent chemical etching of the template. The use of Pt-Co alloy nanowire array-modified electrode (Pt-Co NAE) for the determination of morphine (MO) is described. The morphology of the Pt-Co alloy nanowire array has been investigated by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS) analysis), respectively. The resulting Pt-Co NAE offered a linear amperometric response for morphine ranging from $2.35\times10^{-5}$ to $2.39\times10^{-3}$ M with a detection limit of $7.83\times10^{-6}$ M at optimum conditions. This sensor displayed high sensitivity and long-term stability.

• 대한기계학회논문집A
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• 제27권5호
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• pp.840-847
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• 2003

The bonding of adhesive joints of adhesive joints is influenced by the surface roughness of the joining Parts. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, it is shown that surface treatment affects adhesive strength and durability of alumina/polycarbonate single-lap .joints, and leading speed affects tensile-shea strength of adhesive Joints. To evaluate effect of surface treatments on the adhesive strength, several surface treatment methods are used, that is, cleaning, grinding, SiC polishing and sand blasting. It is shown that an optimum value of the surface roughness exists with respect to the tensile-shea strength of adhesive joints. The adhesive strength shows linear relationship with the surface roughness and loading speed. And the mechanical removal of disturbing films of lubricants, impurities and oxides make adhesive strength increase significantly.

• Tribology and Lubricants
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• 제30권5호
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• pp.278-283
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• 2014

Carbon nanotubes (CNTs) are used in various composite materials to enhance electrical, thermal and mechanical properties of composite materials. In this study, we investigate the wear characteristics of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends containing multi-walled carbon nanotubes (MWCNTs). PC/ABS blends are commonly used in many industrial applications such as cellular phones and display cases and MWCNTs have been added to the PC/ABS blends to improve their electromagnetic interference shielding (EMS). We performed wear tests on PC/ABS blends containing MWCNTs under reciprocating linear sliding conditions with chrome steel balls as a counterpart material. The normal loads were 10, 30, 50, 70, 100 N, the sliding speed was 10 mm/s, the stroke length was 15 mm, and the tests lasted 900 s. The MWCNTs included in the PC/ABS blends lower the wear volume and friction coefficient of the composites. We analyzed the wear debris collected from the composites during the tests in terms of the MWCNT concentration using inductively coupled plasma optical emission spectroscopy. The results show that the quantity of MWCNTs in the debris is proportional to the concentration of MWCNTs in the composite, indicating that the exposure of the MWCNTs to environments by wear could be increased with their concentration in the composite.

• Journal of Pharmaceutical Investigation
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• 제22권2호
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• pp.155-161
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• 1992

Although glycosylated liposomes have attracted much attention as targeting delivery systems (DDS) of drugs to specific organs which have glycoside receptors, physical instability of liposomes greatly limits their practical application. In this case, proliposomes might be a potential answer to solve this problem. Utilizing the proliposomes as tageting DDS has been a goal of our series of works; we have tried to develop DDS which form liposomes uppon adding water and can deliver drugs to specific target organs/cells such as hepatocytes. In this paper, preparation of glycosylated liposomes and binding of the liposomes with lectin (agglutinin RCA 120) was studied. Asialoletuin (AF) was selected as a model compound which has galactose terminal and is favorable for binding with galactose receptor on the surface of hepatocytes. AF was obtained by splitting the terminal N-acetylneuraminic acid (NANA) of fetuin. Small unilamellar AF-liposomes were prepared by mixing aqueous solution of AF-palmitate with thin film of phosphatidyl choline and cholesterol (30:10 w/w) formed on the innersurface of the round bottomed flask. They were successively extruded through polycarbonate membranes (0.45 mm). Palmitoyl-AF not incorporated into the liposomal bilayer was separated from liposomes by a Sepharose 4B column equilibrated with 10 mM Tris-HCI buffered saline. Lectin (agglutinin RCA 120) was added to the suspension of AF-liposomes and incubated at $37^{\circ}C$ for 2 hr. After centrifugation, the unbound lectin in the supernatant was assayed for protein. The binding of the lectin to AF-liposomes (AF content 2.8 nmole) at $37^{\circ}C$ was linear at least upto 35 mg of lectin indicating high affinity association of the lectin to AF molecules of the liposomes.

• Toxicological Research
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• 제30권1호
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• pp.39-44
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• 2014

Bisphenol A (BPA) is widely used in the production of polycarbonate plastics, epoxy resins, and food and beverage containers. In the present study, we aimed to investigate the relationship between urinary concentrations of BPA and waist circumference in Korean adults. A total of 1,030 Korean adults (mean age, $44.3{\pm}14.6$ years) were enrolled in the study on the integrated exposure to hazardous materials for safety control, conducted by the Ministry of Food and Drug Safety from 2010 to 2012. Abdominal obesity was defined as having a waist circumference of at least 90 cm and 85 cm for men and women, respectively. The participants were divided into 4 groups according to the urinary BPA concentration quartile. Waist circumference was significantly higher among subjects with a urinary BPA concentration in the highest quartile relative to those in the lowest quartile (p = 0.0071). Linear regression analysis revealed a significant positive association between urinary BPA concentrations and body mass index, body fat, after adjusting for potential confounders. Moreover, subjects with urinary BPA concentrations in the fourth quartile were more likely to be obese compared to those with urinary BPA concentrations in the first quartile (odds ratio, 1.938; 95% CI: 1.314~2.857; p for trend = 0.0106). These findings provide evidence for a positive association between urinary BPA concentration and waist circumference in Korean adults.