• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.979-984
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• 1999

Aromatic soluble polyimides were synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and various dianhydrides such as pyromelltic dianhydride(PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride(BTDA), and 4,4'-(hexafluoroisopropylidene)-bis(phthalic anhydride)(6FDA). Polyimides prepared by thermal imidization were insoluble in common organic solvents (acetone, MNP, DMAc, DMSO, THF, and DMF) but those prepared by chemical imidization were soluble. The difference of solubility was explained by esterification between hydroxyl group and $CH_3COO^-$ from acetic anhydride used as a dehydration agent in chemical imidization. Glass transition temperatures of polyimides by thermal method were higher than those by chemical method. All of the polyimides are stable up to $300^{\circ}C$ regardless of the sample preparation. The x-ray diffraction patterns showed that all polyimides were amorphrous.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2384-2393
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• 2018

Porous alginate-based hydrogel beads (porous ABH) have been prepared through a facile and sustainable template-assisted method using nano-calcium carbonate and nano-$CaCO_3$ as pore-directing agent for the efficient capture of methylene blue (MB). The materials were characterized by various techniques. The sorption capacities of ABH towards MB were compared with pure sodium alginate (ABH-1:0) in batch and fixed-bed column adsorption studies. The obtained adsorbent (ABH-1:3) has a higher BET surface area and a smaller average pore diameter. The maximum adsorption capacity of ABH-1:3 obtained from Langmuir model was as high as $1,426.0mg\;g^{-1}$. The kinetics strictly followed pseudo-second order rate equation and the adsorption reaction was effectively facilitated, approximately 50 minutes to achieve adsorption equilibrium, which was significantly shorter than that of ABH-1:0. The thermodynamic parameters revealed that the adsorption was spontaneous and exothermic. Thomas model fitted well with the breakthrough curves and could describe the dynamic behavior of the column. More significantly, the uptake capacity of ABH-1:3 was still higher than 75% of the maximum adsorption capacity even after ten cycles, indicating that this novel adsorbent can be a promising adsorptive material for removal of MB from aqueous solution under batch and continuous systems.

• Journal of agriculture & life science
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• v.50 no.4
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• pp.27-34
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• 2016

Sclerotium rolfsii is a well known broad host range soil borne plant pathogenic fungus and caused serious damage to various vegetable crops. To develop an effective biological control agent for S. rolfsii, an isolate which showed strong inhibitory effect on the mycelial growth of S. rolfsii was selected among the antagonistic bacterial isolates collected from vinyl-house soil. The bacterial isolate was identified as Bacillus amyloliquefaciens KBC1009 based on the morphological, physiological characteristics and by 16S rRNA sequence analysis. The growth conditions for B. amyloliquefaciens KBC1009 were optimized in LB media(pH7) by culturing at 30℃ for 72 hrs. Glucose and yeast extract were confirmed as the best carbon and nitrogen sources, respectively. In order to test the inhibitory effect of B. amyloliquefaciens KBC1009 to stem rot of pepper, green house experiment was conducted. Drench of 1/500 diluted bacterial suspension of B. amyloliquefaciens KBC1009(5×108 cfu/ml) to each pepper plant 3 times with 10 days interval showed 66.7% control effectiveness. These results suggest that B. amyloliquefaciens KBC1009 is one of promising biocontrol agent to control stem rot caused by Sclerotium rolfsii.

• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.678-682
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• 2010

A doubly tethered chiral stationary phase (CSP) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid were applied to the liquid chromatographic resolution of racemic tocainide, an antiarrhythmic agent, and its analogues. The chiral recognition efficiency of the doubly tethered CSP for tocainide and its analogues was generally greater than that of the corresponding singly tethered CSP especially in terms of the resolution ($R_S$). The resolution of tocainide and its analogues on the doubly tethered CSP were dependent on the content and the type of the organic and acidic modifiers in aqueous mobile phase and the column temperature. Especially, the retention behaviors of analytes on the doubly tethered CSP with the variation of the content of organic modifier in aqueous mobile phase were opposite to those on the corresponding singly tethered CSP and these opposite retention behaviors were rationalized by the lipophilicity differences of the two CSPs.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2978-2982
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• 2013

A doubly tethered $N-CH_3$ amide chiral stationary phase (CSP 4) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of an antiarrythmic agent, tocainide, and its analogues and the chromatographic resolution results were compared with those on a singly tethered N-H amide CSP (CSP 1), a singly tethered $N-CH_3$ amide CSP (CSP 2) and a doubly tethered N-H amide CSP (CSP 3) under an identical aqueous mobile phase condition. CSP 4 was found to be generally better than other CSPs in terms of the separation factors (${\alpha}$) and resolutions (RS). The retention times of analytes denoted by the retention factors ($k_1$) on CSP 4 were quite long compared to those on other CSPs because of the improved lipophilicity of CSP 4. The long retention times of analytes on CSP 4 were successfully controlled by the addition of a small amount of ammonium acetate to aqueous mobile phase without hurting the chiral recognition efficiency. The variation of the content and type of organic and acidic modifier in aqueous mobile phase was found not to change the chiral recognition efficiency significantly.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.361-372
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• 2019

Effect of different alkane based solvents on the stability of emulsion liquid membrane was investigated using normal alkanes (n-hexane, n-heptane, n-octane and n-decane) under various operating parameters of surfactant concentration, emulsification time, internal phase concentration, volume ratio of internal phase to organic phase, volume ratio of emulsion phase to external phase and stirring speed. Results of stability revealed that emulsion liquid membrane containing n-octane as solvent and span-80 (5 % (w/w)) as emulsifying agent presented the highest amount of emulsion stability (the lowest breakage) compared with other solvents; however, operating parameters (surfactant concentration (5% (w/w)), emulsification time (6 min), internal phase concentration (0.05 M), volume ratio of internal phase to organic phase (1/1), volume ratio of emulsion phase to external phase (1/5) and stirring speed (300 rpm)) were also influential on improving the stability (about 0.2% breakage) and on achieving the most stable emulsion. The membrane with the highest stability was employed to extract acridine orange with various concentrations (10, 20 and 40 ppm) from water. The emulsion liquid membrane prepared with n-octane as the best solvent almost removed 99.5% of acridine orange from water. Also, the prepared liquid membrane eliminated completely (100%) other cationic dyes (methylene blue, methyl violet and crystal violet) from water demonstrating the efficacy of prepared emulsion liquid membrane in treatment of dye polluted waters.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1252-1256
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• 2010

A polyvinylpyrrolidone (PVP)/Ag nanocomposites was prepared by the simultaneous thermal reduction and radical polymerization route. The in situ synthesis of the Ag/PVP nanocomposites is based on the finding that the silver n-propylcarbamate (Ag-PCB) complex can be directly dissolved in the NVP monomer, and decomposed by only heat treatment in the range of 110 to $130^{\circ}C$ to form silver metal. Silver nanoparticles with a narrow size distribution (5 - 40 nm) were obtained, which were well dispersed in the PVP matrix. A successful synthesis of Ag/PVP nanocomposites then proceeded upon heat treatment as low as $110^{\circ}C$. Moreover, important advantages of the in situ synthesis of Ag/PVP composites include that no additives (e.g. solvent, surface-active agent, or reductant of metallic ions) are used, and that the stable silver nanocolloid solution can be directly prepared in high concentration simply by dissolving the Ag/PVP nanocomposites in water or organic solvent.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.117-124
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• 2007

Focused on the material-related aspect for enhancing the durability of concrete, the present study analyzed the effect of glycol ether admixture, which is a chemical admixture that can compact the structure of concrete by entraining air inside the concrete, on the basic physical properties and durability characteristic of the concrete. In analyzing the results of experiment, we examined the basic physical properties and durability characteristic of concrete according to addition rate based on OPC and selected the optimal addition rate. In addition, with the optimal addition rate, we added glycol ether admixture to concrete, which contained fly ash used as binder and high-performance water reducing agent for reducing the unit quantity, and examined changes in the characteristics of the concrete. According to the result, the optimal addition rate of glycol ether admixture was 3% of the unit quantity of cement, and the addition of binder and chemical admixture did not have a significant effect on unhardened concrete but reduced the air content. In addition, concrete showed resistance performance of around 30% to carbonation and around 40% to drying shrinkage. In addition, as for resistance to freezing and thawing, the relative dynamic modulus of elasticity was over around 85% through atmospheric curing. These performances prove the effect.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.265-268
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• 2002

In this work, the blend system of epoxy and PMR-15 polyimide is investigated in terms of the cure behaviors and thermal stabilities. The cure behaviors are studied in DSC measurements and thermal stabilities are also carried out by TGA analysis. DDM (4, 4'-diamino diphenyl methane) is used as curing agent for EP and the content of PMR-15 is varied within 0, 5, 10, 35, and 20 phr to neat EP. As a result, the cure activation energy ($E_a$) is increased at 10 phr of PMR-15, compared with that of neat EP. From the TGA results of EP/PMR-15 blend system, the thermal stabilities based in the initial decomposed temperature (IDT) and integral procedural decomposition temperature (IPDT) are increased with increasing the PMR-15 content. The fracture toughness, measured in the context of critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$), shows a similar behavior with $E_a$. This result is probably due to the crosslinking developed by the interactions between intermolecules in the polymer chains.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.569-573
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• 2013

In this study, activated carbon fabric was prepared from a cellulose-based polymer (viscose rayon) via a combination of physical and chemical activation (mixed activation) processes by means of $CO_2$ as a gasifying agent and surface and adsorption properties were evaluated. Experiments were performed to investigate the consequence of activation temperature (750, 800, 850 and $925^{\circ}C$), activation time (15, 30, 45 and 60 minutes) and $CO_2$ flow rate (100, 200, 300 and 400 mL/min) on the surface and adsorption properties of ACF. The nitrogen adsorption isotherm at 77 K was measured and used for the determination of surface area, total pore volume, micropore volume, mesopore volume and pore size distribution using BET, t-plot, DR, BJH and DFT methods, respectively. It was observed that BET surface area and TPV increase with rising activation temperature and time due to the formation of new pores and the alteration of micropores into mesopores. It was also found that activation temperature dominantly affects the surface properties of ACF. The adsorption of iodine and $CCl_4$ onto ACF was investigated and both were found to correlate with surface area.