• Proceedings of the Membrane Society of Korea Conference
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• 1998.04a
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• pp.1-6
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• 1998

To change permselectivity between anions through the anion exchange membrane in electrodialysis, the various modified anion exchange membranes were prepared: highly crosslinked anion exchange membranes, anion exchange membranes having benzyl trialkylammonium groups with different carbon number of alkyl chain as anion exchange groups and anion exchange membranes having pyridinium groups with a hydrophilic or hydrophobic substituent at a different position as anion exchange groups. It became clear from the evaluation of these membranes that the degree of the hydrophilicity of the anion exchange membranes greatly affects the permselectivity between two artions. To increase the hydrophiticity of the anion exchange membranes further, electrodialysis was carried out in the presence of ethylene glycols and the permeation of strongly hydrated anions increased and that of less-hydrated anions decreased. It became clear that the change in the permselectivity between two artions is due to the change in the affinity of anions to the membranes, not the change in mobility ratio of the anions in the membranes phase.

• Macromolecular Research
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• v.12 no.1
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• pp.94-99
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• 2004

We have performed Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies on blends of poly(vinyl phenol) (PVPh) with poly(n-alkylene 2,6-naphthalates) containing alkylene units of different lengths. The results indicate that each poly(ethylene 2,6-naphthalate) (PEN) and poly(trimethylene 2,6-naphthalate) (PTN) blend with PVPh is immiscible or partially miscible, but blends of poly(butylene 2,6-naphthalate) (PBN) with PVPh are miscible over the whole range of compositions in the amorphous state. FTIR spectroscopic analysis confirmed that significant degree of intermolecular hydrogen bonding occurs between the PBN ester carbonyl groups and the PVPh hydroxyl groups. The large difference in the degree of mixing in these blend systems is described in terms of the effect that chain mobility has on the accessibility of the ester carbonyl functional groups toward the hydroxyl groups of PVPh, which in turn impacts the miscibility of these blends.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.3
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• pp.228-238
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• 2005

Purpose: Several cryoprotectants are in use to help the survival of cells during cryopreservation of bone in maxillofacial region. Among them, $Me_2SO$(dimethyl sulfoxide), EG(ethylene glycol), sucrose were used for experimentally created defects with accompanying cryopreserved bone graft in the rabbit model. The aim of this study is to analyze the effect of above mentioned agents on bone formation using histologic and histomorphometrical methods, thus to provide experimental support for clinical application of these agents. Materials and methods: Nine rabbits were used as experimental animals. Surgical defects were created on the distal femoral heads and mesial tibial heads of each animal using trephine drill(5mm diameter and 5mm length). The harvested bones were cryopreserved in $-80^{\circ}C$ refrigerator for one week. The defects were filled with cryopreserved bone with cryoprotectants as experimental groups and cryopreserved bone without cryoprotectant as control. Then, the animals were sacrificed at 1, 2, and 3 weeks after surgery. With Goldner's modified Masson trichrome staining and semiautomatic image analysis system, we observed the change of the cells and bone formation. Results: After bone graft, bone formation and active remodeling process were examined in all experimental groups and the control. But the intensity of such activities of the control were somewhat weaker than that of the experiments. Especially $Me_2SO$+sucrose group was the best in bone formation and bone remodeling. $Me_2SO$ group was more than that of EG group in bone fomation. Sucrose seems to be helpful in survival of the bone cell. Histologic findings showed superior bony quantity and quality in experimental groups than that in control. Conclusions: The data from this study provides the basis for future studies for evaluating the effect of cryoprotectants in the cryopreservation of bone and clinical study for predictable use of these agents.

• Journal of the Korean Applied Science and Technology
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• v.15 no.1
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• pp.99-108
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• 1998

Novel type surfactants containing two long-chain hydrophobic alkyl groups and two hydrophilic sulfonate groups were successfully synthesized by reactions of ethylene glycol diglycidyl ether with long-chain fatty alcohols, after then by reactions with 1,3-propane sultone and sodium hydride under THF solvent. All these compounds, so called Gemini surfactants, were purified by thin layer chromatography and column chromatography. Their structures were identified by FT-IR and $^{1}H$-NMR.

• Macromolecular Research
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• v.9 no.2
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• pp.71-83
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• 2001

The metallocene compounds had been applied to the polymerizations of olefins and vinyl monomers with methylaluminoxane (MAO) cocatalyst, and they have usually one transition metal atom per molecule, i.e., mononuclear metallocene. Recently it has been found that the dinuclear metallocene compounds containing two transition metal atoms exhibit the peculiar polymerization behaviors for olefins and vinyl monomers. In this article, the dinuclear metallocenes are classified into four groups of dinuclear bent-metallocene, dinuclear ansa-metallocene, dinuclear constrained geometry catalyst and dinuclear half-metallocene, and then the synthesis of dinuclear metallocene of each group as well as the polymerization behaviors for ethylene, propylene, and styrene are described.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.592-599
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• 2011

Plum is a climacteric fruit and softening is a serious problem for storage and transportation. Thus $1{\mu}L{\cdot}L^{-1}$ of 1-methylcyclopropene (1-MCP) was applied to plums to prolong their shelf life and maintain quality. Japanese plums (Prunus salicina cv. Formosa) were stored at $20^{\circ}C$ and $0^{\circ}C$ for 14 days and 46 days respectively, with or without 1-MCP treatment. Fruits were treated with $1{\mu}L{\cdot}L^{-1}$ 1-MCP at $10^{\circ}C$ for 24 h. Ethylene production and respiration rate were strongly inhibited in 1-MCP-treated fruits at $20^{\circ}C$. It was also observed that there was less ethanol and acetaldehyde evaporation in 1-MCP-treated fruits stored at $20^{\circ}C$ compared to those in control fruits not treated with 1-MCP. Fruit qualities, such as firmness, titratable acidity (TA), skin color, and decay, changed more slowly in 1-MCP-treated fruits stored at $20^{\circ}C$ than in untreated fruits. There were no differences in the ethylene production or respiration rate between the groups of fruits stored at $0^{\circ}C$ throughout the experiment. Chilling injury was also inhibited by the application of 1-MCP during storage at $0^{\circ}C$. When the fruits stored at $0^{\circ}C$ with or without 1-MCP were transferred to $20^{\circ}C$ after 25 days, the differences in ethylene production and respiration rate, firmness, TA, TSS, and acetaldehyde and ethanol evaporation between the initial (after being stored at $0^{\circ}C$ for 25 days) and the final measurements (after being stored at $0^{\circ}C$ for 25 days and then transferred to $20^{\circ}C$ for three days) were lower in 1-MCP treated fruits than in non-treated fruits. The postharvest application of 1-MCP in Formosa plums showed positive effects at both $0^{\circ}C$ and $20^{\circ}C$ storage conditions with regard to quality, such as low ethylene production and low respiration rates, firmness, TA, ethanol, and acetaldehyde evaporation, chilling injury, and decay.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.55-61
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• 2013

Heterogeneous metallocene catalysts supported on montmorillonite (MMT), [$Cp_2ZrCl_2$/MMT, $Cp_2ZrCl_2$/MAO/MMT, and $Cp_2ZrCl_2$ + MAO/MMT], were prepared with three different methods of immobilization and tested for ethylene polymerization. The heterogeneous catalysts immobilized on organo clay (30B-MMT) showed the higher metal loading and polymerization activity than those immobilized on natural clay $Na^+-MMT$. These results suggest that the hydroxyl groups of organo clay interlayers react with the MAO and catalyst through the chemical bond. The metallocene catalyst supported directly on MMT showed lower activity for ethylene polymerization compared to the homogeneous systems, while MMT/MAO/$Cp_2ZrCl_2$, catalysts treated with MAO before impregnation, showed a higher activity. The polymers obtained from MMT-supported catalysts have higher melting point, molecular weight and molecular weight distributions than those of homogeneous catalysts. The polymer particles with increasing significant size. Ethylene polymerization over 30B-MMT/MAO/$Cp_2ZrCl_2$ catalyst was also performed varying the process variables to optimize the process conditions.

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.482-486
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• 2005

The biodegradable poly(${\varepsilon}$-caprolactone)(PCL)/poly(ethylene imine)(PEI) microcapsules containing $Al_2O_3$ and fragrant oil were prepared with different PEI contents. The effects of stirring rate and concentration of the surfactant on the diameter and morphologies of microcapsules were investigated by using scanning electron microscope (SEM). Thermal behaviors were studied by using a differential scanning calorimetry(DSC), and the release behaviors of fragrant oil from microcapsule were characterized by UV/vis. spectrophotometer. As a result, the average particle size of the microcapsules decreased with increasing the stirring rate or concentration of the surfactant. The surface morphologies of the microcapsules were changed from smooth surfaces to skin-like rough surfaces as increasing the PEI content. These results were mainly due to the increased hydrophilic groups at the microcapsule surfaces, resulting in increasing the release rate of fragrant oil in the microcapsules studied.

• Polymer(Korea)
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• v.27 no.5
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• pp.449-457
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• 2003

The purposes of this work were the producing of a biodegradable poly($\varepsilon$-caprolactone) (PCL) / poly(ethylene oxide) (PEO) microcapsule and the analyzing of form and features for the manufacturing conditions which could be observed in a prospective drug delivery systems through drug release. The effects of emulsifier, emulsifier concentration, and stirring rate for the diameter and form of the microcapsules were observed using image analyzer and scanning electron microscope. The role of interfacial adhesion between PCL/PEO and drug was determined by contact angle measurements, and the drug release test of the microcapsules was characterized by UV/vis. spectra. As a result, the microcapsules were made in spherical fonns with a mean particle size of 170 nm∼68 $\mu$m. And the work of adhesion between water and PCL/PEO increased with increasing the content of PEO, probably due to the increased the hydrophilicity. It was also found that the drug release rate from the microcapsules significantly increased with increasing the content of PEO, which could be also attributed to the increasing of the hydrophilic groups or the degree of adhesion force at interfaces.

• Membrane Journal
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• v.19 no.4
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• pp.333-340
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• 2009

This paper is designed with the purpose of improving the efficiency of the sulfonic acid ion exchange membranes by radiation induced graft polymerization. It has been shown that the porous hollow fiber membranes could cause permeability blocking between pores and ion exchanged graft chains. Addition of crosslinker such as N-ethylene glycol dimethacrylate will permit to increase the permeation flux. In this research, the ethylene glycol dimethacrylate (EDMA) and diethylene glycol dimethacrylate (DDMA) with different length are used as crosslinkers. The ion exchanged cross-linked membrane (EDMA, DDMA) containing sulfonic acid group by radiation induced grafted polymerization are sn died for adsorb metal ions (Pb). It has been shown that adsorbed metal ions ($Pb^{2+}$) for the EDMA and DDMA membranes with the density of sulfonic acid groups, 1.40 mmol/g and 2.14 mmol/g, respectively are 13.82 mg/g, 17.37 mg/g, accordingly.