• Title/Summary/Keyword: Polymeric effect

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Effect of Annealing on Carbon Nitride Films Prepared by High Voltage Discharge Plasma (고전압 방전 플라즈마에 의해 합성한 질화탄소 박막의 열처리 효과)

  • 김종일
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.5
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    • pp.455-459
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    • 2002
  • I have investigated the effects of annealing on a polymeric $\alpha-C_3N_{4.2}$ at high pressure and temperature in the presence of seeds of crystalline carbon nitride films prepared by a high voltage discharge plasma. The samples were evaluated by x-ray photoelectron spectroscopy (XPS), infrared spectroscopy, Auger electron spectroscopy and x-ray diffraction(XRD). Notably, XPS studies of the film composition before and after annealing demonstrate that the nitrogen composition in $\alpha-C_3N_{4.2}$ material initially containing more than 58% nitrogen decreases during the annealing process and reaches a common, stable composition of ~43%. XPS analysis also shows that the nitrogen composition in the annealed films without polymeric $\alpha-C_3N_{4.2}$ was reduced from 35% to 17%. Furthermore the concentration of the sp$^3$bonded phase increased with the increment of the annealing temperature.

Biodistribution and Hemolysis Study of Terplex Gene Delivery System in Mice

  • Oh, Eun-Jung;Shim, Jin-young;Kim, Jin-Seok
    • Macromolecular Research
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    • v.11 no.1
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    • pp.19-24
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    • 2003
  • Polymeric gene delivery system attracts profound attention as it shows less toxicity, versatility, and reasonable gene expression efficiency. Terplex system, a synthetic biopolymeric gene delivery system consisting of stearyl poly-L-lysine (stearyl-PLL) and low density lipoprotein (LDL) was evaluated for its body distribution of gene expression of exogenously administered pDNA after tail-vein injection in mice. Kidney and spleen are two major organs with highest gene expression, whereas liver and heart showed marginal gene expression among the organs examined. Hemolytic effect of the terplex system was evaluated using human red blood cells, where terplex system did not cause significant hemolysis at the concentrations above the experimental ranges, although unmodified PLL or stearyl-PLL without LDL did. Serum stability of terplex system against enzymatic degradation was also significantly enhanced, presumably due to the steric stabilization from the polymers. Based on these findings and along with its high in vitro transfection efficiency, terplex system could serve as a safe and efficient polymeric gene delivery system with many applications for the in vivo gene therapy.

Chemiluminescence Properties of Polymeric Fluorophores Containing Distyrylarylene Unit

  • Lee, Hui U;Kim, Cheol Hui;Gong, Myeong Seon
    • Bulletin of the Korean Chemical Society
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    • v.22 no.7
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    • pp.727-731
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    • 2001
  • Conjugated-non-conjugated alternating block copolymers containing distyrylarylene units were synthesized via Wittig reaction for chemiluminescent fluorophores. The polymers were differentiated from others by the presence of aromatic unit in the chromophoric block. When UV-VIS, photoluminescence and chemiluminescence spectra of these materials were compared with copolymers, a strong bathochromic effect was observed. A more pronounced red shift and higher chemiluminscence efficiency were observed in the polymer with anthracene ring. Sodium salicylate-catalyzed reaction of bis(2-carbopentyloxy-3,5,6-trichlorophenyl) oxalate with hydrogen peroxide produced a strong chemiluminescence from blue to yellow-green light emission with wavelength of 450-537 nm in the presence of the fluorophore. The chemiluminescent intensity decayed exponentially. The glow of chemiluminescence maintained more than l2 hr and was visible with the naked eye.

Synthesis of $La_{1-x}Sr_xCoO_3$ (x≤0.2) at Low Temperature from PVA-polymeric Gel Precursors

  • 권호진;박동곤;국승태;박휴범;김건
    • Bulletin of the Korean Chemical Society
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    • v.18 no.12
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    • pp.1249-1256
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    • 1997
  • Single phase La1-xSrxCoO3 (x≤0.2) was synthesized as a uniform sized 100 nm particulates with relatively high surface area of 20-30 m2/g, at low temperature (≥600 ℃), from a polymeric gel precursors prepared by using poly(vinyl alcohol) as homogenizer. No minor phase developed during the crystallization when polymer/metal mole ratio was higher than 3. As the polymer/metal mole ratio was raised in the gel, the amount of carbonaceous residues in the amorphous solid precursor prepared by heating the gel at 300 ℃ increased. Most of the residues were eliminated by exothermic thermal decomposition around 400 ℃. The amount of residual carbon (less than 1%) left in the crystalline La1-xSrxCoO3 decreased as more polymer was used, eliminating detrimental effect which might be posed by using large amount of organic homogenizer. The crystal structure of La1-xSrxCoO3 synthesized at temperature lower than 800 ℃ was observed to be shifted from rhombohedral to more symmetric cubic. The structure shifted back to rhombohedral as the cubic sample was annealed at 1000 ℃.

Simulation of injection-compression molding for thin and large battery housing

  • Kwon, Young Il;Lim, Eunju;Song, Young Seok
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1451-1457
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    • 2018
  • Injection compression molding (ICM) is an advantageous processing method for producing thin and large polymeric parts in a robust manner. In the current study, we employed the ICM process for an energy-related application, i.e., thin and large polymeric battery case. A mold for manufacturing the battery case was fabricated using injection molding. The filling behavior of molten polymer in the mold cavity was investigated experimentally. To provide an in-depth understanding of the ICM process, ICM and normal injection molding processes were compared numerically. It was found that the ICM had a relatively low filling pressure, which resulted in reduced shrinkage and warpage of the final products. Effect of the parting line gap on the ICM characteristics, such as filling pressure, clamping force, filling time, volumetric shrinkage, and warpage, was analyzed via numerical simulation. The smaller gap in the ICM parting line led to the better dimensional stability in the finished product. The ICM sample using a 0.1 mm gap showed a 76% reduction in the dimensional deflection compared with the normal injection molded part.

Fabrication of a 1*4 Polymeric Optical Power Divider Based on the Multi-Mode Interference Effect (다중모드간섭 현상에 입각한 1*4 폴리머 광파워분할기의 제작)

  • 김기홍;송현채;오태원;신상영;이운영
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.11
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    • pp.85-90
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    • 1998
  • A 1 4 polymeric optical power divider based on the multimode interference effect is designed and fabricated. The two dimensional finite difference beam propagation method has been utilized in designing the device. Polymers used for the core layer and the cladding layer are Cyclotene-3022 and UV-15, respectively. The device is fabricated by the reactive ion etching method. The splitting ratio of the fabricated device is 0.93 : 1.00 : 0.93 : 0.90 for TE mode and 0.84 : 0.94 : 1.00 : 0.83 for TM mode. The advantages of this device are small size and low polarization-dependence.

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The Effect of BSA on the Release of Cefadroxil from a Polycaprolactone Matrix (폴리카프로락톤 매트릭스로부터 세파드록실의 방출에 미치는 BSA의 영향)

  • Kim, Seung-Ryul;Jung, Yun-Jin;Kim, Young-Mi;Lee, Chi-Ho;Kim, Dae-Duk
    • Journal of Pharmaceutical Investigation
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    • v.34 no.5
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    • pp.363-368
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    • 2004
  • In order to investigate the effect of bovine serum albumin (BSA), as a pore former, on the controlled release of an antibiotic from a biodegradable polymeric device, polycaprolactone (PCL)-cefadroxil matrices were prepared by the solvent casting method. The amount of cefadroxil released from various formulations at $37^{\circ}C$ was measured by HPLC. The duration of antimicrobial activity of matrices against S. aureus was evaluated by measuring the diameters of the inhibition zone. The morphology of the matrices was investigated by scanning electron microscopy (SEM). The release rate and extent of cefadroxil from PCL matrix increased as the loading dose and particle size of BSA/cefadroxil mixture powder increased. Cefadroxil released from the matrix exhibited antibacterial activity for up to 4 days. SEM of the cross-section of matrix showed the typical channel formation after 3 days of release study. Thus, a biodegradable polymeric matrix loaded with antibiotic/BSA mixture can effectively prevent bacterial infection on its surface, thereby bringing about an enhancement of biocompatibility of biomaterials.

The Effect of the Molecular Weight of Poly(ethylene glycol) on Diffusion through Cellulose (폴리에틸렌글리콜의 분자량에 따른 셀룰로스에서의 확산 거동)

  • 윤기종;우종형;서영삼
    • Textile Coloration and Finishing
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    • v.16 no.1
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    • pp.48-52
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    • 2004
  • Diffusion/penetration rates of finishing agents are not a major criterion in the design of low molecular weight finishing agents. However, in the case of polymeric finishing agents, high molecular weights result in large hydrodynamic volumes and diffusion/penetration of the finishing agent into the substrate may become a critical factor in the design of textile finishing agents. Thus the effect of the molecular weight of a model compound, polyethylene glycol, on its diffusion through a cellulose membrane or cotton fabric is studied. Diffusion experiments of polyethylene glycol of molecular weight 400, 1000, 2000, 4600, 8000, and 10000 through cellulose membrane or fabric was carried out in a glass U-tube diffusion apparatus and the half penetration times and the penetration coefficients were determined. Both the half penetration times and the penetration coefficients exhibited a significant change between molecular weight 2000 and 2500 as the molecular weight of polyethylene glycol increased, suggesting that there is a critical molecular weight above which diffusion/penetration becomes difficult. Based on this study on a model compound, it is suggested that polymeric textile finishing agents can be expected to exhibit similar behavior.

Preparation of Ferroelectric PZT Thin Film by Sol-Gel Processing; (II) Effect of Catalysts on Densification and Crystallization (솔-젤법에 의한 강유전성 PZT 박막의 제조;(II) 치밀화 및 결정화에 미치는 촉매의 영향)

  • 김병호;박성호;김병호
    • Journal of the Korean Ceramic Society
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    • v.32 no.7
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    • pp.783-792
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    • 1995
  • Sol-Gel derived ferroelectric PZT thin films were fabricated on ITO/Glass and Si/SiO2 substrates. In order to investigate the effect of catalysts on the densification and crystallization of PZT thin films, a nitric acid or ammonium hydroxide was added to the PZT stock solution at the state of partial hydrolysis reaction. The measured pH for a stable PZT sol was 5.2~9.3. In case of an acid-catalyzed PZT sol, a highly condensed particulate PZT sol was formed by accelerating the hydrolysis reaction. But weakly branched polymeric PZT sol was formed with a base-catalyzed condition. The difference in densification behavior was not found in the pH range of added catalyst, but the refractive index of PZT thin film was increased rapidly as the annealing temperature increased. The PZT thin film annealed at 54$0^{\circ}C$ for 10 min was fully densified and its refractive index was above 2.4. When the annealing temperature increased, the transition from the pyrochlore phase to perovskite appeared at 54$0^{\circ}C$. The base-catalyzed PZT thin film suppressed to form the pyrochlore phase and proceeded effectively to convert the perovskite phase. This was due to the formation of polymeric molecular structure by controlling the hydrolysis and condensation reaction through the additiion of the ammonium hydroxide.

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Study on the separation of large ionic-molecules by electrofiltration (전기여과에 의한 거대이온성 분자체 분리현상연구)

  • Park Young-Gyu
    • Journal of the Korean Electrochemical Society
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    • v.1 no.1
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    • pp.18-23
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    • 1998
  • Theoretical model has been derived in the electrophoretic separation system where an electric potential is applied to the system in the axial direction. The effect of electrophoretic convection in the polymeric media is significantly contributed to separate large ionic-molecules because the conformation of large ionic-molecule quickly orients in the field direction. The dependence of the transport in the polymeric media upon field intensity and molecular size aids in understanding the transport of large ionic-molecule in the system, since the convective velocity of large ionic-molecule is accelerated inside a porous material. The separation of two different large ionic-molecules is predicted with a value of $(Pe_t/Pe_g)$ of individual large ionic-molecule using an operator and the reptation theories.