• Polymer(Korea)
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• v.39 no.1
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• pp.165-168
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• 2015

Thermoresponsive polymers were successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). Poly(2-hydroxyethyl methacrylate) (PHEMA) was synthesized by ATRP, followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-alkyne. Homopolymers having secondary amine groups, tertiary amines with hydroxyethyl and hydroxypropyl groups were synthesized by adding 2-azido-N-ethyl-ethanamine, 2-[(2-azidoethyl)amino]ethanol, and 2-[(2-azidoethyl)amino]propanol, respectively, to the PHEMA-alkyne backbone using click chemistry. Molecular weight (MW), molecular weight distribution (MWD), and click reaction efficiency were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The transmission spectra of the 1.0 wt% aqueous solutions of the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) could be easily controlled by the length of the hydroxyalkyl groups.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.1-11
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• 1997

The soot and OH radical distributions have been experimentally studied in ethylene and propane laminar diffusion flames. The integrated soot volume fraction was measured along the centerline of a flame using a laser light extinction method. Planar laser light scattering and PLIF techniques are employed for the soot and OH radical distribution measurements utilizing Nd:YAG laser and OPO, FDO system. The concentration of OH radical is rapidly decreased at the edge of sooting region, which implies the importance of OH radical species on the soot oxidation process. For ethylene flames, the addition of air in fuel moves the OH radical distribution towards the center line of a flame at the soot oxidation region, while the concentration of OH radical remains relatively high at the soot formation region. The interaction between soot particles and OH radicals becomes more active with fuel-air at the soot oxidation region. For propane flames, however, any indication of the increased interaction between soot particles and OH radicals with fuel-air was not noticed.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.20-24
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• 1980

The frontier electron densities and pK values for benzologous pyridine ligands are calculated using the HMO. Linear regression formula for pK in protonation of ligands is derived from the electron densities and observed pK values. The calculated pK values are in agreement with those of experimental values and a parallelism is shown between pK and qN. The reactivities for electrophilic, nucleophilic and radical reactions have also been calculated respectively by frontier electron densities.

• Journal of the Korean Vacuum Society
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• v.7 no.1
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• pp.72-76
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• 1998

A new gas-flow type reactor for plasma polymerization was developed to synthesize functional polymers, which enhances reaction of radicals activated in the discharge. Styrene was used for the plasma polymerization and molecular strucure and molecular weight distribution of the plasma -polymerized styrene were studies. The ploymer was evaluated to be an efficient electron beam resist. The sensitivity of the plasma-polymerized styrene film formed by this new reactor was better than that of the reported values of conventional polystyrene, Fine resist patterns could be successfully developed by a wet process.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.352-356
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• 2011

In this paper, we prepared new type of hydrophilic block copolymers that exhibit the long-ranged lateral ordering in thin film. It was previously demonstrated that poly(ethyleneoxide-b-styrene) and poly(ethyleneoxide-b-metharylate-b-styrene) block copolymer thin films have a high degree of lateral ordering after solvent annealing process. In these cases, the relative humidity plays an important role in long-ranged lateral ordering. However, the origin of the humidity effect on the orders of these hydrophilic block copolymers is not fully understood. To investigate the effect of the humidity further, we prepared other hydrophilic poly(N,N-dimethylacrylamide-b-styrene)(PDMA-b-PS) block copolymers via RAFT polymerization. As with PEO-containing block copolymers, PDMA-b-PS block copolymers exhibit the long-ranged lateral ordering after solvent annealing process.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.136-141
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• 2007

The decomposition of chlorinated methanes including $CCl_4$, $CCl_3H$, and $CCl_2H_2$ was carried out using a thermal plasma process and the characteristics of the process were investigated. The thermal equilibrium composition was analyzed with temperature by Fcatsage program. The decomposition rates at various process parameters including the concentration of reactants, flow rate of carrier gas, and quenching rate, were evaluated, where sufficiently high conversion over 92% was achieved. The generation of main products was strongly influenced by the reaction atmosphere; carbon, chlorine, and hydrogen chloride at neutral condition; carbon dioxide, chlorine, and hydrogen chloride at oxidative condition. The decomposition mechanism was speculated considering the results from Factsage and the identification of generated radicals and ionic species. The main decomposition pathways were found to be dissociative electron attachment and oxidative by radicals formed in a plasma state.

• Korean Journal of Food Science and Technology
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• v.49 no.3
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• pp.331-337
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• 2017

To evaluate the antioxidant activity of hexane, ethyl acetate, and butanol fractions obtained from Agastache rugosa extract, we measured the total polyphenol levels, DPPH radical scavenging activity, and reducing power. The ethyl acetate fraction of A. rugosa (AREA) displayed high phenolic levels, potent DPPH radical scavenging effect, and powerful reducing power. In addition, we examined the ability of AREA to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 microglia. AREA suppressed NO production and inducible nitric oxide synthase (iNOS) expression and downregulated interleukin-6 (IL-6) mRNA level in LPS-stimulated BV-2 microglia. Furthermore, we detected rosmarinic acid in AREA by HPLC, which suggested that rosmarinic acid could be one of the bioactive materials responsible for the antioxidant and anti-inflammatory activities of AREA. These results suggested that AREA may be a good source of functional foods with antioxidant and anti-inflammatory activities.

• Journal of Radiation Protection and Research
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• v.17 no.1
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• pp.1-10
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• 1992

A number of investigators have reported the formation of the radiolytic ultrafine particles produced by the interaction of ionizing radiation with water vapor. Previous studies have suggested that a very high localized concentration of the OH radical produced by the radiolysis of water can react with trace gas like organic vapors and produce lower vapor pressure compounds that can then nucleate. In order to determine water vapor dependence of the active, positively charged, first radon daughter(Po-218), an experiment was conducted using a well-controlled radon chamber. The activity size distribution of the radon daughter in the range of 0.5-100nm was measured using the parallel graded wire screens system. Measurements were taken for different relative humidity. The resultant activity size distributions were analyzed. The addition of water vapor to the radon carrier gases resulted in the formation of ultrafine particles by OH radicals formed by radon radiolysis. It may be due to the neutralization of charged Po-218 ion with water vapor through the radio lysis.

• The Journal of the Convergence on Culture Technology
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• v.5 no.4
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• pp.467-472
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• 2019

Seaweeds are rich in in minerals, vitamins, proteins, and fiber, and are classified as green algae, and they are distributed on the coasts of Korea, East Asia, Oceania, etc. and are used as a health function material as well as food ingredients in our countries and countries. In this study, Codium fragile was extracted from ethanol and concentrated to confirm DPPH radical scavenging activity, SOD activity, FRAP and ABTS cation radical scavenging ability. As a result, DPPH scavenging activity was 0.83, 22.83, 38.27, 40.93, 45.60% at 6.25, 12.50, 25, 50 and $100{\mu}g/mL$, SOD-like activity were 23.13, 33.63, 33.93, 44.07 and 59.07%. FRAP and ABTS showed antioxidant activity in a concentration-dependent manner, as in the previous experiment. Therefore, this study confirmed that it can be used as a cosmetic material using Codium fragile, a natural material.

• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.57-66
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• 2000

OH radical and NO distributions have been measured in methane/air partially premixed counterflow flames(${\alpha}$=1.0, 0.8, 0.6) using PLIF technique. The results are discussed and compared with the numerical analysis results obtained under the same flame conditions. Measured OH and NO LIF signals agree with the computed concentration distributions. Both numerical and experimental results indicate that the structural change in a flame alters the NO formation characteristics of a partially premixed counterflow flame. The nitrogen dilution also changes flame structure, temperature and OH radical distributions and results in the decreased NO concentrations in a flame. The levels of decrease in NO concentrations, however, depends on the premixedness(${\alpha}$) of a flame. The larger change in the flame structure and NO concentrations have been observed in a premixed flame($\alpha$=1.0), which implies that the premixedness is likely to be a factor in the dilution effect on NO formation of a flame.