• KSBB Journal
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• v.9 no.1
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• pp.1-7
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• 1994

A qualitative study was made on the mechanism of dextran synthesis by dextransucrase. Enzymatic synthesis of dextran was experimentally studied with initial sucrose concentration from 50g/$\ell$ to 150g/$\ell$. The molecular weight distribution of synthesized dextran was measured by using on-line gel Permeation chromatographic system Sucrose was observed not to work as a primer within the range of concentration tested. At the initial sucrose concentration of 50g/$\ell$, dextran with molecular weight of medium range ($10^4-2{\times}10^6$) was synthesized due to the mass transfer limitation of sucrose. The amount of the dextran of medium range decreased with the initial sucrose concentration. Dextran was likely to be synthesized by radical chain polymerization mechanism since the dextran of medium range was not produced at higher sucrose concentrations.

• Polymer(Korea)
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• v.30 no.1
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• pp.50-55
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• 2006

When the monodisperse polystyrene(PS)/HDDA polymer particles were synthesized via one-step polymerization using polystyrene seed particles by dispersion polymerization, the effects of 1) the molecular weight of seed polymer particles, 2) the ratio of the absorbed HDDA to the seed polymer particles (swelling ratio) and 3) seeded polymerization rate on the surface morphology of PS/HDDA polymer particles were investigated. It was observed that the creation of the crater shaped defect on the surface of PS/HDDA polymer particles was irrespective of the molecular weight of seed polymer ant swelling ratio. But its surface morphology could be controlled by the change of the seeded polymerization rate.

• Elastomers and Composites
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• v.39 no.4
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• pp.281-285
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• 2004

In this paper, the simple way to evaluate the value of the activation energy for the overall rate of free radical polymerization by using DSC thermograms was studied using free radical polymerization or butylacrylate as a model. Activation ehergies were determined at heating rates of 1, 2, 5, and $10^{\circ}C/min$ by applying the multiple scanning-rate methods of Kissinger, Osawa, and half-width methods as well as the single rate method of Barrett. The value of the overall activation energy measured was closely matched with the values calculated from individual data. This work also demonstrated that the use of the isoconversional method was a simple and effective way to estimate the activation energy for the overall free radical polymerization.

• Journal of Adhesion and Interface
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• v.3 no.4
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• pp.27-36
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• 2002

The organic/organic core-shell composite polymer for nonwomen binder were synthesized by stage polymerization of methyl methacrylate and styrene with ammonium persulfate after preparing monomer pre-emulsion in the presence of anionic surfactant. We study the effect of initiator concentration, $0.79{\times}10^{-3}{\sim}3.16{\times}10^{-3}mol/L$ for core polymer, $2.0{\times}10^{-4}{\sim}8.0{\times}10^{-4}mol/L$ for shell polymer, sulfactant concentration, $1.45{\times}10^{-5}{\sim}4.15{\times}10^{-5}mol/L$ for core polymer, $0.73{\times}10^{-5}{\sim}2.91{\times}10^{-5}mol/L$ for shell polymer on core-shell structure of polymethyl methacrylate/polystyrene and polystyrene/polymethyl methacrylate. Emulsion stability was major test method, particle size and particle size distribution were measured using particle size analyzer and the morphology of the core-shell composite polymer was determined using transmission electron microscope, glass temperature was also measured using differential scanning calorimeter.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.349-349
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• 2012

산화제를 이용 기상중합법을 통해 합성되는 고전도도 Poly (3,4-Ethylenedioxythiophene)(PEDOT) 박막은 OTFT, RFID tag, 또는 연성 디스플레이 같은 분야에 다양한 응용 가능성을 가지고 있으며 이로 인해 최근에 연구가 활발히 진행되고 있다. PEDOT박막의 전극소재로써 가능성은 박막의 중합 정도와 표면 형상에 크게 좌우된다. 특히, Si-웨이퍼 기판 위에 산화제의 균일한 도포 및 산화제 자체의 높은 산도 ($pH{\leq}2$)에 따른 부반응의 억제는 기상중합법을 이용한 PEDOT박막의 합성에 있어 매우 중요하다. PEDOT의 효율적인 중합과 균일한 성장을 위해 산화제에 DUDO 와 PEG-PPG-PEG를 첨가한 혼합 산화제 용액을 제조 기상중합 방법을 통해 PEDOT박막을 제작하였다. 그 결과 산화제만을 사용하여 제작된 박막에 비해 전도도가 최대 3,660 S/cm로 향상된 PEDOT 박막이 합성되었다. 이러한 결과는 PEG-PPG-PEG가 산화제 용액의 균일 도포를 향상시키고 Base Inhibitor로 작용하는 DUDO는 PEDOT 성장 시 중합속도를 조절하고 부반응을 최소화 하여 효율적인 공액 이중 결합의 생성을 촉진한데 주로 기인한다. 따라서 그로인해 조밀하며 마이크로 스케일의 기공이 최소화된 PEDOT박막의 합성이 가능하였다. PEDOT박막의 특성 평가에는 4-point probe, optical microscopy, Field Emission-Scanning Electron Microscope, 등이 사용되었으며 또한 전도도의 향상 원인을 분석하고자 ATR-IR Spectrophotometer를 이용하여 합성된 박막의 작용기를 분석하였다. 이러한 고전도도의 PEDOT 박막이 OTFT의 전극소재로 사용된다면 OTFT소자의 성능 향상에 크게 기여 할 것으로 기대된다.

• Polymer(Korea)
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• v.26 no.4
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• pp.422-430
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• 2002

The kinetics of polycondensation of bishydroxyethyl naphthalate has been studied in the range of 241 -$260^{\circ}C$ using antimony trioxide catalyst. The reaction was performed in a batch reactor and the concentration of reaction mixture was measured with HPLC. The activation energy values of forward and reverse reaction determined from molecular species model were found to be 19.7 and 31.4 kcal/mole, respectively, and the equilibrium constants were in the range of 1.4-2.0, which were larger than that of polycondensation of PET and varied to some degree with temperature. It was confirmed by applying the Flory's distribution function that the reaction rate of the hyroxyethyl group does not depend on the molecular size. By applying functional group model, we observed that there was few difference between the activation energy of the forward reaction and that of reverse reaction, therefore the equilibrium constant has almost constant value of 1.4. The rate constants obtained from functional group model was about 3-4 times larger than that from molecular species model, which showed that both model explains the reaction system well. Although the molecular species model should predict the concentration of as many as ten molecules, it fits for the experimental results well.

• Geophysics and Geophysical Exploration
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• v.1 no.3
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• pp.161-169
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• 1998

The Kunsan basin is a pull-apart basin which was formed during Tertiary. The pre-Tertiary section consists of various rock types, such as meta-sediments, igneous rocks, carbonates, clastics, and volcanics. Tertiary sections are the main targets for the petroleum exploration. In order to determine the optimum processing parameters of the basin, about 12 kinds of test processings were performed. The first main steps for the quality control is to determine the noisy or bad traces by examining the near trace section and shot gathers. The true amplitude recovery was applied to account for the amplitude losses due to spherical divergence and inelastic attenuation. Source designature and predictive deconvolution test were conducted to determine the optimum wavelet parameters and to remove the multiples. Velocity analysis was performed at 1km intervals. The optimum mute function was picked by locating the range of offsets which gives the best stacking response for any particular reflections. Post-stack deconvolution was tested to see if the quality of stacked data improved. The stacked data was migrated using a finite difference algorithm. The migration velocity was obtained from the stacking velocities using the time varying percentages. The AGC sections were provided for the structural interpretation. The RAP sections were used for DHI analysis and for the detection of volcanics.

• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.235-246
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• 1982

The free radical polymerization and copolymerization of N-acetyl ${\alpha}$-aminoacrylic acid were investigated. From the result of kinetic investigation of N-acetyl ${\alpha}$-aminoacrylic acid in DMF at $60^{\circ}C$, a rate equation of $R_p$ = $k_p[M]^{0.97}[I]^{0.59}$ was obtained. The overall activation energy for the polymerization was found to be 25.2 kcal/mole. Copolymerization of N-acetyl ${\alpha}$-aminoacrylic acid with acrylic acid and styrene was carried out for the determination of monomer reactivity ratios. The monomer reactivity ratios for the monomer pairs determined at 70.0{\pm}0.1^{\circ}C$ using benzoyl peroxide as an initiator are; $r_1$(N-acetyl ${\alpha}$-aminoacrylic acid) = 0.49, $r_2$(acrylic acid) = 1.41, $r_1$(N-acetyl ${\alpha}$-aminoacrylic acid) = 0.44, $r_2$(styrene) = 0.91. The values of Alfrey-Price's Q and e parameters for N-acetyl ${\alpha}$-aminoacrylic acid were calculated to be 0.51 and 0.16 for the both systems. Differential thermal analysis and thermogravimetry showed that acrylic acid copolymers have poorer thermal stability as compared with the homopolymer of N-acetyl ${\alpha}$-aminoacrylic acid.

• Proceedings of the Korean Fiber Society Conference
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• 1993.06a
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• pp.61-61
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• 1993

• Proceedings of the Korean Fiber Society Conference
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• 1991.06b
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• pp.32-32
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• 1991