• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.274-279
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• 2011

In this study, we investigated the analytical methods for bromine (Br) and chloride (Cl) with oxygen combustion bomb, using a halogen-containing polymer materials. On measuring Cl content, it showed less reproducibility of the results applying Mohr method or potentiometric titration method than those applying acid-base titration method. In both Br and Cl tests with an oxygen combustion bomb, their concentrations in the absorption and cleaning solution with distilled water were much higher than those in the combustion gas. On the other hand, the concentration level of Br measured by the oxygen combustion bomb method were a little bit lower than those measured by XRF or combustionion chromatography.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.1-5
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• 1999

The dispersing performance of oligomer-type anionic surfactants ($C_mD-Na$), cooligomers of diethylester maleate and alkylvinylether of different alkyl chain lengths or polymerization degree were studied on the aqueous suspension of iron dxide or titanium dioxide particles which are hydrophilic pigments. The dispersion behavior of oligomer-type surfactants for these dispersoids, although anion charges on the surface of pigments particles showed different dispersing properties, was dependent upon the side alkyl chain length. Oligomer-type surfactants having more than $C_8$ side alkyl chain exhibited large dispersing action for relatively hydrophobic ${\alpha}-Fe_2O_3$ and Anatase $TiO_2$ in the concentration range of more than 0.1% oligomer-type surfactant solutions.

• Membrane Journal
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• v.26 no.6
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• pp.463-469
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• 2016

In this research, a new expectation in enhancing the PES (polyethersulfone) polymer phase inversion membrane performances with nanoparticles is proposed by using ZnO. This paper investigated the synthesis of PES phase inversion membranes including ZnO nanoparticles and evaluates the performance of these mixed matrix membranes. The PES-ZnO mixed matrix membranes were fabricated by phase inversion method using the PES-ZnO-NMP(N-methyl-1-pyrrolidone) casting solutions with low ZnO nanoparticles content of 0.375 wt%. The influence of ZnO nanoparticles on the characteristics of PES-ZnO mixed matrix membranes was investigated with scanning electron microscope observations of membrane cross-sections, contact angle measurements, tensile strength measurements, pure water flux measurements and ultrafiltration experiments of BSA solution. Those results showed that the performance advancements in comparison with the pure PES membrane without ZnO in terms of increasing hydrophilicity as well as reducing membrane fouling by adding ZnO nanoparticles even in low concentration.

• Journal of the Korean Society of Combustion
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• v.7 no.4
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• pp.36-44
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• 2002

Carbon molecules with closed-cage structures are called fullerenes $(C_{60},\;C_{70})$, whose applications include super-conductors, sensors, catalysts, optical and electronic device, polymer composites, and biological and medical materials. The synthesis of fullerenes has been recently studied with low-pressure benzene/argon/oxygen flames. The formation of fullerene is known as molecular weight growth processes of PAHs (polycyclic aromatic hydrocarbon). This study presents results of PAHs and fullerene measurements performed in a low-pressure benzene/argon/oxygen normal co-flow laminar diffusion flame. Through the central tube of the burner, benzene vapors carried by argon are injected. The benzene vapors are made in a temperature-controlled bubbler. The burner is located in a chamber, equipped with a sampling system for direct collection of condensable species from the flame, and exhausted to a vacuum pump. Samples of the condensable are analyzed by HPLC (High Performance Liquid Chromatography) to determine the yields of PAHs and fullerene. Also, we computed mole fraction of fullerene and PAHs in a nearly sooting low pressure premixed, one-dimensional benzene/argon/oxygen flame (equivalence ratio ${\Phi}=2.4$, pressure=5.33kPa). The object of computation was to investigate the formation mechanism of fullerenes and PAHs. The computations were performed with CHEMKIN/PREMIX. As a result of this study, fullerenes were synthesized in a low pressure (20torr) $C_6H_6/Ar/O_2$ flames and the highest concentration of fullerene was detected just above the visible surface of a flame.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.137-137
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• 2003

Conducting PPy/PVA composite and pure PPy gas sensors were prepared by in-situ vaporstate polymerization method in a vaporization chamber under N2 condition, by exposing the pre-coated electrode with PVA/FeC13 to distilled pyrrole monomer. The various electrical sensing behaviors of both types of sensors were systematically investigated by a flow measuring system including mass flow controller (MFC) and bubbling bottle. The FT-Raman spectroscopy of vapor state polymerized PPy was identical to that of chemically polymerized PPy, confirming the same chemical structure. Both types of sensors had positive sensitivity when exposed to methanol gas. The sensitivity varied linearly with gas concentration in the range of 50ppm to 1059ppm. The detection limit of PPy/PVA sensor was believed to be as low as 10ppm. The sensitivity of PPy/PVA composite sensor was higher than that of pure PPy sensor. Both the response time and recovery time of PPy/PVA composite sensors were longer than those of pure PPy sensors. The thickness of the sensing film affected the sensitivity this way that the sensor having thinner film had higher sensitivity, indicating that the resistance of polymer film involved in the sensing behavior was bulk resistance rather than surface resistance. The reproducibility of PPy/PVA composite sensor was excellent during eight on-off cycles by switching between N2 and 3000ppm methanol gas. The sensitivity of PPy/PVA composite sensor was only maintained for two weeks, while the sensitivity of pure PPy sensor was maintained over two months.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.135-135
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• 2003

The fast evolution in the fold of optical communication systems demands powerful optical information treatment. These functions can be performed by integrated optical systems. A key component of such systems is erbium doped waveguide amplifier(EDWA). The intra 4f radiative transition of Er at 1.5 $\mu\textrm{m}$ is particularly interesting because this wavelength is standard in optical telecommunications. The fabrication of waveguide amplifier for integrated optics using sol-gel process has received an increasing attention. Potential advantage of lower cost by less capital equipment and easy processing makes this process an attractive alternatives to conventional technologies like flame hydrolysis deposition, ion exchange and chemical vapor deposition, etc. In addition, sol-gel process has been found to be extremely suitable for the control of composition and refractive index related directly with optical properties. The main drawback of such an amplifier with respect to the EDWA is the need for a much higher Er3+ concentration to compensate for the smaller interaction length. However, the high doping of Er might be resulted in the non-radiative relaxation by clustering of Er ions End co-operative upconversion. In order to solve this problem, we investigate the possibility of avoiding short Er-Er distances by encapsulation of Er3+ ions in hosts such as organic-inorganic hybrid materials. For inorganic-organic hybrid sols, methacryloxypropyltrimethoxysilane (MPTS), zirconyl chloride octahydrate and erbium(III) chloride hexahydrate were used as starting materials, followed by conventional sol-gel process. It was observed by TEM that nano sols having core/shell toplology were formed, depending on the mole ratio of Zr/Er. The surface roughness for the coatings on Si substrate was investigated by AFM as a function of Zr/Er ratio. The local environment and vibrational Properties of Er3+ ions were studied using Near-IR, FT-IR, and UV/Vis spectroscopy. Nano hybrid coatings derived from polymer and Er doped encapsulation Eave the good luminescence at 1.55$\mu\textrm{m}$.

• Analytical Science and Technology
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• v.7 no.2
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• pp.205-211
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• 1994

Acetic acid and succinic acid bonded polyamine-polyurea(CPPI and SAPPI) resins were synthesized from the reaction of polyethylenimine-polymethylenepolyphenylene isocyanate(PPI) resin as matrix polymer and chloroacetic acid and chlorosuccinic acid respectively. These resins were confirmed with infrared spectrometry and elemental analysis. The adsorption characteristics of the chromium(III) and dichromate(or chromate) ions on the resins were studied by measuring distribution coefficients($K_d$) with changing pH of the solution. It was thought that these ions were adsorbed by ion exchange mechanism. Chromium(III) and dichromate ion could be separated with stepwise elution method by changing pH of the eluent using SAPPI resin packed column($0.6cm(i.\;d.){\times}10cm(L.)$). Also, dichromate ion could be preconecntrated with CPPI resin column by a concentration factor of 50.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.273-277
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• 1998

The synthesis of hydroxy-terminated poly(propylene carbonate)(HTPPC) was performed by the reaction of propylene carbonate(PC) with alcohol initiator using metal alkoxides, crown ethers and quaternary onium salts as catalysts. The effects of catalyst structure, types and concentration of alcohol, and solvent were investigated. Among the alkoxide catalysts tested, the ones with higher Lewis acidity and with more nucleophilic alkoxide anion showed higher catalytic activity. Mixed catalysts of metal alkoxied and crown ether showed higher conversion of PC than metal alkoxide alone. Quaternary onium salts of bulky cation exhibited higher catalytic activity. High polar solvent showed higher yield of HTPPC and the yield increased with the decrease of [PC]/[Initiator] ratio.

• Journal of Pharmaceutical Investigation
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• v.34 no.5
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• pp.401-406
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• 2004

To develop an intravenous delivery system of all-trans retinoic acid (ATRA) for the cancer therapy, poly(L-lactic acid) nanoparticles were prepared and characterized. Emulsification-solvent evaporation method was chosen to prepare submicron sized nanoparticles. Spherical nanoparticles less than 200 nm in diameter with narrow size distribution were prepared, and the entrapment efficiency of drug was more than 95%. The endothermic peak at $183^{\circ}C$ and X-ray crystallographic peak of ATRA appeared in the nanoparticle system, suggesting the inhibition of crystallization of ATRA by polymer adsorption during the precipitation process. ATRA was released at $37^{\circ}C$ for 60 days and the release rate was dependent on the concentration of drug incorporated in the nanoparticles. While ATRA was unstable in the light, it was very stable at $4^{\circ}C$. These results suggest the usefulness of PLA nanoparticles as a sustained and prolonged release carrier for ATRA.

• Journal of the Korean Applied Science and Technology
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• v.15 no.2
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• pp.77-81
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• 1998

Surface active properties of these aqueous Gemini surfactant solutions including surface tension, critical micelle concentration(cmc), foaming power, foam stability, emulsifying power and Krafft point were measured at given conditions. They showed excellent properties, being compared with conventional single-chain surfactants such as sodium dodecyl sulfonate(SDS). Their surface tensions in the aqueous solutions were decreased to $30{\sim}38$ mN/m, which is lower than 39 mN/m of SDS, and their cmc values evaluated by surface tension method were $2.8{\times}10^{-5}{\sim}3.3{\times}10^{-4}$ mol/L. These values were also much lower than that of SDS, $9.8{\times}10^{-3}$ mol/L. The foaming power and foam stability, especially decyl and dodecyl compounds, were good and the emulsifying power in benzene or soybean oil was also excellent. All of the synthesized Gemini surfactants possessed good water solubility and their Krafft points were all below $0^{\circ}C$. As results, DDED and DDOD, Gemini surfactants which were synthesized are expected to be applied as foamers, emulsifiers and so on.