• Polymer(Korea)
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• v.25 no.1
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• pp.6-14
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• 2001

The monomer N,N'-bis(3-pyrrol-1-yl-propyl)-4,4'-bipyridinium$(PF_6)_2$ was electrochemically polymerized on glassy carbon electrode surface. This polymer film electrode has electroactive sites on its bipyridinium ions distributed at the polymer strands. The formal potentials of the electrodes were -0.41V and -0.81V(vs. SSCE) for each step at phosphate buffer(pH=5.70). The diffusion coefficients of the dopants ions into the polymer matrix were $1.57{\times}10^{-4}$ and $4.35{\times}10^{-5}cm^2s^{-1}$ for first and second redox couple, respectively. The rate constants of electron transfer at $V^{2+/+}$ of the first step was a $57.53s^{-1}$, which was 22 times higher than $V^{+/0}$ one having $2.63s^{-1}$ in the solution. The charge transfer resistance of the polymer film was influenced by the dopant ion of the electrolyte. Thus the resistances were 22.63, 16.81, 12.44 and $11.36k{\Omega}$ for $LiClO_4,\;NaClO_4,\;KClO_4$, and phosphate buffer, respectively. The reaction order of the electropolymerization was first order and the rate constant of the polymerization was $1.31{\times}10^{-1}s^{-1}$ as determined by EQCM method. The G.C./p-BPB type electrode doped with phosphate ions showed a stability and reproducibility in CV procedure over 20 cycles.

• Polymer(Korea)
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• v.25 no.1
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• pp.115-121
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• 2001

High molecular weight syndiotactic poly(vinyl alcohol)(HMW s-PVA) with number-average degree of polymerization of 10000 and syndiotactic diad content of 61.5%/iodine complex film was prepared. Its adsorption and desorption behaviors of iodine in hot water were investigated. In comparison with atactic PVA film or low molecular weight s-PVA film, the degree of solubility of s-PVA film and the iodine desorption of HMW s-PVA/iodine film in hot water were limited to an extremely lower level. As the soaking time increased, the iodine desorption in hot water was increased. This reason might be explained by the fact that as the soaking time increased, so the iodine adsorption increased not by the stable molecular complex between PVA and iodine but by the simple physical adsorption of iodine.

• Polymer(Korea)
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• v.24 no.6
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• pp.737-743
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• 2000

Polyquinonediimines (PQDI) which have stable structure on heat and contains mono-azobenzene in the side chain were synthesized by means of condensation polymerization under TiCl$_4$. The synthesized monomers and polymers were identified by FT-IR, $^1$H-NMR, and elementary analysis. Especially, PQDI was comfirmed by the double-bonding peak of >C=N appeared near 1625 $cm^{-1}$ / by means of FT-IR spectrum. PQDI containing mono-azobenzene group in both side chains wat not soluble in non-polar solvents at all but partially soluble in the polar solvents having small dielectric constant, and dissolved in the strong acid such as sulfuric acid and $CH_3$SO$_3$H. Molecular weight distribution of PQDI measured by GPC showed 1.74. It was confirmed through X-ray diffraction analysis that the polymer was partially crystalline at the low angle region, but amorphous after heat treatment at 1$25^{\circ}C$. The glass transition temperature (T$_{g}$ ) of synthesized polymer was measured as 1$25^{\circ}C$ by differential scanning calorimetry. The SHG value for $\chi$$^{(2)}$ after poling at 1$25^{\circ}C$ was 8.6 pm/V (λ=1.542 ${\mu}{\textrm}{m}$). The SHG value slowly decreased with time from the start but appeared temporal stability after 100 hours.

• Membrane Journal
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• v.29 no.6
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• pp.348-354
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• 2019

Recently, the application range of organic solvent nanofiltration (OSN) technology has been expanding, requiring membranes with better performance. In this work, thin film composite (TFC) OSN membrane was fabricated. First, ultrafiltration support membrane was prepared via nonsolvent-induced phase separation (NIPS) technique using polysulfone (PSf) and polyethersulfone (PES). Then, the effect of pore forming additives such as polyvinylpyrrolidone (PVP) and pluronic F-127 were employed to improve the membrane permeance. The well-known interfacial polymerization technique was employed using MPD-TMC chemistry to form a thin film on top of the fabricated support, and its solvent permeance and nanofiltration performance was characterized. It was found that polyethersulfone support exhibited more reliable performance compared to polysulfone, and PVP additive was more effective compared to Pluronic F-127. As for the oSN performance, polar aprotic solvents like acetonitrile show significantly higher flux (986.5 L·m^-2·h^-1·bar^-1) compared to water and EtOH (9.5 L·m^-2·h^-1·bar^-1).

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.437-442
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• 2016

A new route for PBT (Poly butylene terephthalate) production from recycled PET (Poly ethylene terephthalate) has been explored. The route consists of glycolysis of PET (Poly ethylene terephthalate) wastes using 1,4-butandiol into BHBT oligomers and polycondensation of the oligomers into PBT oligomer. This process uses post-consumer or post-industrial recycled PET and converts it into high-end PBT type engineering thermoplastic via a chemical recycling process. Zink acetate was used as a catalyst for both glycolysis and polycondensation. Two types of reactor for the glycolysis, batch and semi-batch reactor, were investigated and their performances were compared. Semi-batch reactor removes ethylene glycol (EG) and THF (tetrahydrofuran) during the reaction. Amounts of EG and THF generated during the glycolysis reaction were measured and used as criteria for the reactor performance. Performance of semi-batch reactor was shown to be better than that of batch reactor. Optimum reaction condition for the semi-batch reactor was BD/PET ratio of 4, and reaction temperature of $220^{\circ}C$, giving high EG yield (max 91%) and low production of THF. In addition, it was confirmed that the molecular weight of PBT oligomer increases in accordance with the progress of the polycondensation reaction.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.62-68
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• 2011

In the study, acrylate copolymer as MMA-co-GMA-co-AA with a high hardness and flexibility was synthesized for applying to the clear protection film, where GMA was used as a mediator to enhance polymerization-efficiency between MMA and AA. With an increase of GMA content, molecular weight and hardness of acrylate copolymer increased, however, flexibility decreased. With an increase of AA content, its molecular weight and hardness decreased, however, flexibility increased. Molar ratio of GMA/MMA and AA/GMA were optimized as 1.6 and 1.8, respectively, at 30 g of MMA to enhance hardness and flexibility of acrylate copolymer film. Molecular weight and Tg of the acrylate copoylmer were 13,300 g/mol and 136.5 $^{\circ}C$, respectively. Hardness of the coated film at 1.4 g/$m^2$ of spread was 1 H and no crack was observed at expansion ratio of 5% and 15%, respectively. Hardness of film was improved to 3 H by increasing spread of 4.1-4.6 g/$m^2$.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.575-586
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• 2000

In this study, adaptation of compomer to saliva contaminated dentin was evaluated with scanning electron microscope(SEM) and confocal laser scanning microscope(CLSM). For the SEM study, the occulusal surfaces of thirty two molar teeth were grounded to exposure dentin surfaces. The specimen were randomly assigned to control and three experimental groups with four samples in each group. In control group, Dyract and F-2000 compomer were bonded on the specimens according to the manufactures direction. Experimental groups were subdivided into three groups. They were contaminated with saliva on dentin surfaces ; Experimental group 1 : Saliva was dried with compressed air. Experimental group 2 : Saliva was rinsed with air-water spray and dried. Experimental group 3 : After polymerization of an adhesive, they were contaminated with saliva, and then saliva was rinsed with air-water spray and dried. Dyract and F-2000 compomer were bonded on saliva-treated dentin surfaces. The interfaces between dentin and compomer were observed with SEM. For the CLSM study, Class V cavities were prepared in buccal and ligual surfacess of thirty two molars. The specimens were divided into control and experimental groups. Class V cavities in experimental group were contaminated with saliva and those surfaces in each experimental groups received the same treatments as for the SEM study. Cavities were applied Prime & Bond 2.1 and F-2000 compomer primer/adhesive that were mixed with fluorescein, and then were filled with Dyract and F-2000 compomer. Specimens were embedded in transparent acrylic resin and sectioned buccolingual1y with diamond wheel saw, and then mounted on cover slide for CLSM study. The interface between cavity and compomer was observed by fluoresence imaging with a CLSM. The results were as follows : 1. In SEM exammination of Dyract group, control group, experimental group 2, 3 showed close adaptation to dentin and hybrid layer of $3{\sim}4{\mu}m$ diameter. Interfacial gap between compomer and dentin in experimental group 1 was wider than in control group. 2. In SEM examination of F-2000 group, adaptation to dentin of control group was closer than Dytact control group, but hybrid-like layer was not observed. Interfacial gap between compomer and dentin in experimental group 1 was wider than in Dyract experimental group 1. 3. In dissolution specimens of Dyract and F-2000 group, resin tags penetrated through dentinal tubules in control group and experimental group 1 and 3, but the penetration of resin tag was irregular and partial in experimental group 1. 4. In CLSM exammination of Dyract and F-2000 group, adhesive patterns of control and experimental groups showed same as in SEM. This result suggests the treatment methods, rinsing & drying, repeating all adhesive procedures, will produce good effect on adaptation of compomer to dentin if the dentin surface or polymerized adhesive is contaminated by saliva.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.60-68
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• 2012

In this study, the manufacturing process of micro capsulized PCM (phase changing material) for thermal storage performance of latent heat was investigated to save energy during the use of buildings: i.e. use of melamine-type resin as the micro-capsule material and paraffin wax as the inner material that are together used in concrete walls. For the manufacturing process of the micro-capsulized PCM, the amount of SDS addition as surfactant was the key variable and the resulting thermal storage performance depended on the SDS amount. With increasing amount of SDS, the micro capsulation became much easier while the capsule surface became harder. The micro capsules became uniform at an optimum SDS addition. The addition of SDS also affected the thermal capacity: with increasing SDS amount, the heat storage and release tendency at melting point was more clearly manifested. The current investigation is part of a study under progress to explore the use of PCM in concrete walls to save building maintenance cost and energy.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.173-180
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• 2009

In order to develop a novel polymer electrolyte membrane for direct methanol fuel cell (DMFC), styrene monomer was graft-polymerized into poly(tetrafluoroethylene perfluoropropyl vinyl ether) (PFA) film followed by a sulfonation reaction. The graft polymerization was prepared by the $\Upsilon$-ray radiation-grafting method. Subsequently, sulfonation of the radiation-grafted film was carried out in a chlorosulfonic acid/1,2-dichloroethane (2 v/v%) solution. The chemical, physical, electrochemical and morphological properties of the radiation-grafted membranes (PFA-g-PSSA) were characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The water uptake, ionic conductivity, and methanol permeability of the PFA-g-PSSA membrane were also measured. The cell performances of MEA prepared with the PFA-g-PSSA membranes were evaluated and the cell resistances were measured by an impedance analyzer. The MEA using PFA-g-PSSA membranes showed superior performance for DMFCs in comparison with the commercial Nafion 112 membrane.

• Environmental Analysis Health and Toxicology
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• v.19 no.1
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• pp.33-40
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• 2004

Benzoyl peroxide is a High Production Volume Chemical, which is produced about 1,371 tons/year in Korea as of 2001 survey. The substance is mainly used as initiators in polymerization, catalysts in the plastics industry, bleaching agents for flour and medication for acne vulgaris. In this study, Quantitative Structure-Activity Relationships (QSAR) are used for getting adequate information on the physical -chemical properties of this chemical. And hydrolysis in water, acute toxicity to aquatic and terrestrial organisms for benzoyl peroxide were studied. The physical -chemical properties of benzoyl peroxide were estimated as followed; vapor pressure=0.00929 Pa, Log $K_{ow}$ = 3.43, Henry's Law constant=3.54${\times}$10$^{-6}$ atm-㎥/mole at $25^{\circ}C$, the half-life of photodegradation=3 days and bioconcentration factor (BCF)=92. Hydrolysis half-life of benzoyl peroxide in water was 5.2 hr at pH 7 at $25^{\circ}C$ and according to the structure of this substance hydrolysis product was expected to benzoic acid. Benzoyl peroxide has toxic effects on the aquatic organisms. 72 hr-Er $C_{50}$ (growth rate) for algae was 0.44 mg/1.,48 hr-E $C_{50}$ for daphnia was 0.07mg/L and the 96hr-L $C_{50}$ of acute toxicity to fish was 0.24mg/L. Acute toxicity to terrestrial organisms (earth worm) of benzoyl peroxide was low (14 day-L $C_{50}$ = > 1,000 mg/kg). Although benzoyl peroxide is high toxic to aquatic organisms, the substance if not bioaccumulated because of the rapid removal by hydrolysis (half-life=5.2 hr at pH 7 at $25^{\circ}C$) and biodegradation (83% by BOD after 21 days). The toxicity observed is assumed to be due to benzoyl peroxide rather than benzoic acid, which shows much lower toxicity to aquatic organisms. One can assume that effects occur before hydrolysis takes place. From the acute toxicity value of algae, daphnia and fish, an assessment factor of 100 was used to determine the predicted no effect concentration (PNEC). The PNEC was calculated to be 0.7$\mu\textrm{g}$/L based on the 48 hr-E $C_{50}$ daphnia (0.07 mg/L). The substance shows high acute toxicity to aquatic organisms and some information indicates wide-dispersive ore of this substance. So this substance is, a candidate for further work, even if it hydrolysis rapidly and has a low bioaccumulation potential. This could lead to local concern for the aquatic environment and therefore environmental exposure assessment is recommended.