• Applied Chemistry for Engineering
• /
• v.25 no.5
• /
• pp.526-530
• /
• 2014

Polystyrene-poly(etheramic acid) core-shell particles were prepared by dispersion polymerization of styrene using poly(etheramic acid) obtained by the reaction of 2,2'-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride and 3,5-diamniobenzoic acid as a stabilizer. 4-Vinylbenzyltrimethylammonium chloride was used as a comonomer to increase the binding efficiency of poly(etheramic acid). When the ethanol-water mixture (7 : 3) was used as a reaction medium, particles were stabilized well and the size distribution of particles was fairly narrow. The particle size increased with the amount of styrene. The particles polymerized in the dimethylformamide-water mixture had a broad size range. Polystyrene-poly(etheramic acid) core-shell particles were transformed to polystyrene-polyetherimide core-shell particles by the chemical imidization of shells.

• Journal of the Korean Chemical Society
• /
• v.36 no.1
• /
• pp.95-99
• /
• 1992

A spectrophotometric method for the determination of copper using N,N'-Oxalylbis(salicylaldehyde hydrazone) as a chromogenic reagent has been developed. Determination has been performed by measuring the absorbances of the copper complexes in solutions containing 60% dimethylformamide (pH 2) at 422 nm. The method allows the determination of 0.4${\sim}$1.8 ${\mu}$g/ml of copper and has been applied to its determination in synthetic mixtures and alloy samples.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.12
• /
• pp.1751-1756
• /
• 2003

An electrochemical study related to the electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazin-5-one(I), 6-methyl-3-thio-1,2,4-triazin-5-one(II), and 2,4-dimetoxy-6-methyl-1,3,5-triazine(III) in dimethylformamide at glassy carbon electrode has been performed. A variety of electrochemical techniques, such as differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry, and coulometry were employed to clarify the mechanism of the electrode process. The compounds I and II with thiol group exhibited similar redox behavior. Both displayed two cathodic peaks, whereas the third compound, III, without thiol group showed only one cathodic peak in the same potential range of the second peak of I and II. The results of this study suggest that in the first step the one electron reduction of thiol produced a disulfide derivative and in the second reduction step the azomethane in the triazine ring was reduced in two electron processes. A reduction mechanism for all three compounds is proposed on this basis. In addition, some numerical constants, such as diffusion constant, transfer coefficient, and rate constant of coupled chemical reaction in the first reduction peak were also reported.

• Journal of the Korean Chemical Society
• /
• v.31 no.6
• /
• pp.486-490
• /
• 1987

The effect of the hydrogen-bonding between thioacetamide (TA) and amides (N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and N,N-dimethylpropionamide (DMP)) on the hindered rotation of N-C(S) bond of TA was investigated by the nmr spectroscopy. The $^1H$-nmr spectrum of $NH_2$ group in TA was distinctly separated into two peaks with increasing the amount of $CCl_4$ and the effect of amides on the peak separation was in the order of DMF < DMA < DMP. Those phenomena were interpreted in terms of hydrogen-bonding between TA and amide.

• Journal of the Korean Chemical Society
• /
• v.37 no.7
• /
• pp.672-676
• /
• 1993

The complexation of bilirubin with zinc(II) and copper(II) ions was studied spectrophotometrically. In the zinc(II)-bilirubin (Zn-BR) system, complex is formed, but the copper(II) ion oxidizes bilirubin to biliverdin and then to the further oxidation products. The electrochemical reduction behavior of ZN-BR complex has been investigated with DC polarography and cyclic voltammetry. The three polarographic waves were obtained for the reduction of ZN-BR complex in DMF solution. Thde reduction current of the third wave was diffusion current, but that of the first and the second waves contained a little kinetic current.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.185-185
• /
• 2010

유기물과 무기물이 혼합된 나노 복합재료는 저전력 동작을 요구하는 휘어짐이 가능한 차세대 전자소자 응용에 대단히 유용한 소재이다. 간단하고 저렴한 제조 공정과 휘어짐이 가능한 유기물과 무기물이 혼합된 나노 복합재료를 사용한 비휘발성 메모리 소자의 제작과 전기적 특성은 연구되었다. 최근에 간단한 방법으로 고집적화된 휘어짐이 가능한 유기 쌍안정성 소자의 제작에 대한 연구가 진행되고 있다. 그러나 유기 쌍안정 소자의 기억 메커니즘에 대한 연구는 비교적 적게 연구되었다. 유기 쌍안정성 소자의 기억 메커니즘에 대한 연구는 효율과 신뢰성을 증진하기 위하여 대단히 중요하다. 본 연구에서는 polymethyl methacrylate (PMMA) 층에 콜로이드 ZnO 양자점을 혼합하여 제작한 유기 쌍안정성 소자의 전기적 성질과 기억 메커니즘에 대한 것을 연구하였다. 본 연구에 사용된 콜로이드 ZnO 양자점은 dimethylformamide를 사용한 환원법을 이용하여 제작하였다. 소자를 제작하기 위하여 PMMA에 대한 콜로이드 ZnO 양자점의 조성비가 1.5 wt% 가 되도록 dimethylformamide에 녹여 혼합한 용액을 하부 전극인 ITO가 증착된 유리기판위에 스핀코팅 방법을 이용하여 박막을 형성하였다. 콜로이드 ZnO 양자점을 포함한 PMMA 박막위에 상부전극으로 Al을 증착하였다. 복합 소재에 대한 투과 전자 현미경 상은 콜로이드 ZnO 양자점이 PMMA 층 안에 형성되어 있음을 보여주었다. 측정된 전류-전압(I-V) 특성은 쌍안정성 특성을 나타내었으며 이 결과는 콜로이드 ZnO 양자점에서 전하 포획, 저장과 방출 과정에 의한 것이다. 콜로이드 ZnO 양자점을 포함한 PMMA 박막을 저장 영역으로 사용한 유기 쌍안정성 소자의 I-V 측정결과를 바탕으로 전하 수송 모델과 전자적 구조를 사용하여 기억 메커니즘을 논하였다.

• Toxicological Research
• /
• v.30 no.3
• /
• pp.199-204
• /
• 2014

The aim of this research was to improve our understanding of human toxicity due to exposure to DMF, MEK, or TOL individually as compared to exposure to DMF-MEK or DMF-TOL mixtures, by comparing $EC_{50}$ values as well as the morphological changes in HepG2 cells treated with these substances. We found that there was marked cell necrosis in the groups treated with mixtures than in those treated with the compounds alone, and that the amount of cell death and the $EC_{50}$ value were more dependent on MEK and TOL than on DMF. Moreover, analysis of the changes in effective concentration curves revealed that MEK had an antagonistic effect on the human toxicity of DMF, whereas TOL had a synergistic effect. Accordingly, these results suggest that in workplaces involved in the manufacture of synthetic leather, mixtures of DMF and TOL should be avoided as much as possible in order to minimize environmental toxicity and protect the health of the workers.

• Membrane Journal
• /
• v.31 no.4
• /
• pp.282-292
• /
• 2021

In this work, we tested commercial organic solvent nanofiltration (OSN) membranes using both in-house dead-end and crossflow systems. Four different crosslinked polyimide Duramem (DM) OSN membranes with various MWCO (molecular weight cut off) values were tested in organic solvents such as ethanol, N,N-dimethylformamide, acetone and acetonitrile. The membranes exhibited more reliable and reproducible performance in the crossflow system, and the performance changed significantly depending in the physical properties of the testing solvent. This is due to the initial stabilization period via pressure-induced compaction phenomenon, which can be vastly different between membrane samples. Hence, to obtain reliable and reproducible results, crossflow system is the preferred choice.

• Korean Chemical Engineering Research
• /
• v.61 no.2
• /
• pp.322-327
• /
• 2023

A design of experiments was evaluated in optimizing MOF-5 synthesis for acetylene adsorption. At first, mixture design was used to optimize precursor concentration, terephthalic acid, zinc acetate dihydrate and N,N-dimethylformamide. More specifically, 13 conditions with various molar ratios were designed by extreme vertices design method. After preparing the samples, XRD, N₂ physisorption and SEM analysis were performed for their characterization. Moreover, acetylene adsorption experiments were carried out over the samples under identical conditions. The optimal precursor composition for MOF-5 synthesis was predicted on a molar basis as follows: terephthalic acid : acetate dihydrate : dimethylformamide = 0.1 : 0.4 : 0.5. Thereafter, multi-level factorial design was designated to investigate the effect of synthesis reaction conditions such as temperature, time and stirring speed. By the statistical analysis of 18 samples designed, 4 reaction parameters were determined for additional adsorption experiments. Therefore, MOF-5 prepared under the synthesis time and temperature of 100 ℃ and 12 h, respectively, showed the maximum adsorption capacity of 15.1 mmol/g.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.20 no.4
• /
• pp.225-235
• /
• 2010

This study was aimed to assess the status of working environment, health care management status and cause of exposure in manufactories using dimethylformamide (DMF). For the purpose, airborne concentration of DMF in the workplaces and N-methylformamide (NMF) in worker's urine were measured with job type and process. In addition, management of local exhaust ventilation system (LEV) and personal protective equipment (PPE) was evaluated at 35 work places (107 workers) located in Busan and Gimhae area. Mean DMF concentrations in work places by job type and process were of high level measured in printing and record media reproduction (5.23 ppm) and flaking process (2.48 ppm). Workers in adhesive job were measured a large amount of urine NMF (21.59 mg/${\ell}$). 98.1% of DMF handling workers were provided respirators, but 67.3% of those workers used them. The main reasons for not using respirators were inconvenience and difficulty of breathing. Airborne concentrations of DMF were higher in the workplaces in which LEVs were working abnormally, but there was not statistically significant. In addition, the urine NMF levels were correlated with management of LEV within the workers who did not use the respirators (p<0.048). These results implied that LEV should be installed and maintained properly to protect the workers from the exposure to DMF. Management of PPE should be also necessary to protect the workers from chemical hazards.