• Title/Summary/Keyword: dimethyl acetamide

Search Result 22, Processing Time 0.022 seconds

MO Studies on the Conformational Stabilities and the Rotational Barriers about C-N Bond in Amides (Amide류에서 형태안정화와 C-N결합의 회전장벽에 관한 분자궤도론적 연구)

  • Wang Ki Kim;Chang Kook Sohn;Ikchoon Lee
    • Journal of the Korean Chemical Society
    • /
    • v.32 no.3
    • /
    • pp.163-170
    • /
    • 1988
  • The MNDO calculations were performed on the various rotamers of N-methyl formamide, N,N-dimethyl formamide, N-methyl acetamide, and N,N-dimethylacetamide in order to investigate the contribution of the one-electron and the steric effect on their rotational barriers about the C-N bond. Results show that while the conformational stabilities of formamides depend mainly on the one-electron factor, those of acetamides depend mainly on the steric factor. According to results obtained by calculations on the rotational barriers about C-N bond, for N-monosubstituted amides the steric effect is larger in the rotational ground state than in the transition state and for N,N-disubstituted amides the steric effect is larger in the rotational transition state.

  • PDF

The rheological properties of poly(vinylidene fluoride-co-hexafluoropropylene) solutions in dimethyl acetamide

  • Lee, Ki-Hyun;Song, In-Kyu;Kim, Byoung-Chul
    • Korea-Australia Rheology Journal
    • /
    • v.20 no.4
    • /
    • pp.213-220
    • /
    • 2008
  • The effects of temperature on the rheological properties of the solutions of poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) in dimethyl acetamide (DMAc) were investigated in terms of frequency and concentration. The effects of temperature on the intrinsic viscosity of the solutions were discussed. In dynamic rheological measurement, the concentrated solutions showed a little unexpected rheological response; as temperature was increased dynamic viscosity was increased and the solutions exhibited more noticeable Bingham body character over the temperature range, 30 to $70^{\circ}C$. In addition, the solution gave longer relaxation time, lower value of loss tangent and higher value of yield stress at higher temperature and at higher concentration. On the other hand, the dilute solutions revealed that intrinsic viscosity was decreased and its Huggins constant was increased with increasing temperature. These physical parameters suggested that the increase of viscosity with increasing temperature resulted from the localized gelation of PVDF-HFP due to reduced solubility to the solvent.

Preparation and Permeation Characteristics of Finely Porous Ultrafiltration Membranes by Phase Inversion Method (상전환법에 의한 미세다공성 한외여과막의 제조 및 투과특성)

  • 홍영기;배기서
    • Textile Coloration and Finishing
    • /
    • v.15 no.2
    • /
    • pp.68-75
    • /
    • 2003
  • In this work, ultrafiltration(UF) membranes were prepared using polyethersulfone(PES). The polymer was dissolved in various solvent, such as N, N-dimethyl formamide(DMF), N,-dimethyl acetamide (DMAc), N,N-dimethyl sulfoxide(DMSO) and N-methyl-2- pynolidone(NMP). Each polymer solution was casted on the glass plate, and immersed into non-solvent bath. In this way finely porous UF membranes were prepared by phase inversion method. The cross sectional structure of PES membrane was asymmetric which was consist of sponge-like sublayer, finger-like toplayer, and active skin layer. From the solute rejection experiments, the molecular weight cut off of the prepared membrane in various solvent was evaluated 10,000 for DMF, 30,000 for DMAc, 50,000 for DMSO, and 10,000 for NMP respectively.

Methylation Methods on Identification of Phenolics in Chebulae Fructus (Chebulae Fructus중 페놀 물질 확인시의 Methylation법 비교)

  • 김정숙
    • Journal of the East Asian Society of Dietary Life
    • /
    • v.4 no.1
    • /
    • pp.79-86
    • /
    • 1994
  • Food quality in food processing and storage were affected by the kinds of phenolics involved. To analyze phenolics of Chebulae Fructus by the way of GC-MSm methylation and trimethylsilyation(TMS) are necessary. The methods of methylation were dimethyl sulfate method and diazomethane method. so this study was undertaken to research the better methylation method before measuring GC-MS. But dimethyl sulfate method of methylation was not sufficient to analyze phenolics. So the phenolics of Chebulae Fructus were analyzed by the diazomethane methylation method and TMS with the pyridine, N-O-bis-trimethylsilyl-acetamide(BSTFA) and trimethylchlorosilane(TMCS). With the exception of pyrogallol and phloroglucinol in insoluble phenolics of Chebulae Fructus, the greater part of phenolics. analysis could be analyzed by GC-MS in company with diazomethane methylation method and TMS.

  • PDF

Dry-jet Wet Spinning of Polyhydroxyamide Fibers

  • Park, Seung-Koo;Cho, Seo-Hyun;Farris, Richard-John
    • Fibers and Polymers
    • /
    • v.1 no.2
    • /
    • pp.92-96
    • /
    • 2000
  • A high molecular weight polyhydroxyamide (PHA) solution in N, N-dimethyl acetamide (DMAc) was prepared from 3, 3'-dihydroxybenzidine and isophthalic chloride (IPC), which was used for spinning PHA fiber. Before spinning, the diffusion property of DMAc into various coagulants was examined. The fiber was well formed in coagulants such as water/ethanol with a composition of 5/5, ethanol, and ethanol/isopropanol with a composition of 7/3 and 5/5. However, the PHA fiber spun in the water/ethanol mixture contained voids. After the fiber spun in ethanol was annealed at over $350^{\circ}C$, the ultimate stress and initial modulus of the fiber increased from 75.5 MPa and 3.22 GPa to 369 MPa and 29.5 GPa, respectively. These properties of the PHA fiber spun by the dry spinning method were also enhanced, attaining 154 MPa and 5.56 Gpa, respectivel.

  • PDF

The Behavior of Solutes in Nonaqueous Solutions (Ⅱ). Relative Viscosities and Osmotic Coefficients of Urea, 1,3-Dimethylurea, Acetamide, and Propionamide (물아닌 용액에서의 용질의 행동에 관한 연구 (제2보). 요소, 1,3-디메틸요소, 아세트아미드와 프로피온아미드의 상대점도와 삼투계수)

  • Si-Joong Kim;Young-Kook Shin
    • Journal of the Korean Chemical Society
    • /
    • v.24 no.3
    • /
    • pp.209-217
    • /
    • 1980
  • The relative viscosities and osmotic coefficients of solutions of urea, 1,3-dimethyl-urea(DMU), acetamide(AA), and propionamide (PA) in dimethylsulfoxide(DMSO), water, methanol, and in ethanol have been measured at 25 and $45^{\circ}$C by viscometry and osmometry. Viscosity increment in nonaqueous solutions decreased with increasing of the partial molal volumes of the solutes, but in aqueous solution the result was inversed. Viscosity increment of aqueous solution was smaller than that of aqueous DMU solution, but that of nonaqueous urea solution was larger than that of DMU. Amides, however, showed similar viscosity increment in any solvent.Osmotic coefficients of aqueous solution of urea were larger than those of DMU. In the nonaqueous solutions urea exhibited larger deviation from Raoult's law than DMU. The results indicated that urea molecules break water-structure in water, self-associate in DMSO, and showed larger solute-solvent interaction in alcohols than DMU. It can be also confirmed that amides break alcohol structure to a greater extent than any other solutes.

  • PDF

Charge-Discharge Characteristics of Lithium Metal Polymer Battery Adopting PVdF-HFP/(SiO2, TiO2) Polymer Electrolytes Prepared by Phase Inversion Technique (상반전 기법으로 제조한 PVdF-HFP/(SiO2, TiO2) 고분자 전해질을 채용한 리튬금속 고분자 2차전지의 충방전 특성)

  • Kim, Jin-Chul;Kim, Kwang-Man
    • Korean Chemical Engineering Research
    • /
    • v.46 no.1
    • /
    • pp.131-136
    • /
    • 2008
  • Silica- or titania-filled poly (vinylidene fluoride-co-hexafluoropropylene)-based polymer electrolytes were prepared by phase inversion technique using N-methyl-2-pyrrolidone and dimethyl acetamide as solvent and water as non-solvent. The polymer electrolytes were adopted to the lithium metal polymer battery using high-capacity cathode $Li[Ni_{0.15}Co_{0.10}Li_{0.20}Mn_{0.55}]O_2$ and lithium metal anode. After the repeated charge-discharge test for the cell, it was proved that the cell adopting the polymer electrolyte based on the phase-inversion membrane containing 40~50 wt% silica showed the highest discharge capacity (180 mAh/g) until 80th cycle and then abrupt capacity fade was just followed. The capacity fade might be due to the deposition of lithium dendrite on the polymer electrolyte, in which the capacity retention was no longer sustainable.

Effects of Acetamide and Lactamide on the Viability of Frozen-thawed Mammalian Cells (포유류배양세포 동결보존에 있어 Lactamide의 효과)

  • Kim, Hyun;Cho, Young Moo;Ko, Yeoung-Gyu;Seong, Hwan-Hoo
    • Journal of Life Science
    • /
    • v.24 no.11
    • /
    • pp.1252-1257
    • /
    • 2014
  • While dimethyl sulfoxide (DMSO) is the most commonly used cryoprotectant agent in the cryopreservation of cultured mammalian cells, it has been reported to cause differentiation of some cell lines by DNA methylation and associated histone modifications. To avoid the side effects of DMSO in cryopreservation, other agents might be more appropriate for maintaining the stable differentiation of cultured cell phenotypes through cryopreservation. All cryoprotectants should be highly soluble in water and display low cell toxicity. Cryoprotective agents have been shown to be effective in animal sperm preservation, and eight types of amides were examined in the cryopreservation of cultured mouse endothelial cells. Among the amides examined, acetamide and lactamide were effective cryoprotectants for cultured mammalian cells. The most effective concentration of lactamide, 1.5 M, had an even lower cryoprotective ability than 1M DMSO. Because successful cryopreservation of cultured cells is hampered by osmotic stress, the adequate ionic concentration was determined by diluting phosphate-buffered saline (PBS) in the 1.5M lactamide solution. The most effective concentration was $0.4{\times}PBS$, which minimized osmotic stress during the cryopreservation of cultured cells. As the addition of high molecular weight materials in cryopreservation media improves the viability of cells, the effects of bovine serum albumin (BSA), hydroxyethyl-starch (HES), and dextran were examined. The best combination of lactamide-based media for cryopreservation was found to be 1.5 M lactamide in $0.4{\times}PBS$ with 1% BSA.

Mechanical Property of Clay-polymer Nanofiber Composite Membrane (Clay를 함유한 Polysulfone 나노섬유 복합막의 제조 및 물리적 특성 연구)

  • Park, Yeji;Yun, Jaehan;Byun, Hongsik
    • Membrane Journal
    • /
    • v.27 no.3
    • /
    • pp.284-289
    • /
    • 2017
  • In this study, natural clay as a filler was systematically integrated into polysulfone nanofibers to prepare polysulfone/clay composite membranes with mechanical properties. The composite nanofibers were formed by electrospinning of a mixed precursor of polysulfone and clay. The pore size of the composite membranes was adjusted by simply controlling the number of layers of nanofibers. The overall membrane properties were examined by SEM, contact angle, pore characteristics, tensile strength and water flux. In particular, the presence of clay within the nanofibers was confirmed with SEM images and the mechanical property of the composite nanofiber membranes was examined by tensile strength measurements. Thus, the prepared composite membranes were expected to be utilized for water treatment system.

Synthesis and Properties of Copolyterephthalamides Containing Biphenyl-2,2'-diyl Structure (Biphenyl-2,2'-diyl 구조를 함유하는 Copolyterephthalamides의 합성과 성질)

  • Jeong, Hwa-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.11 no.6
    • /
    • pp.2311-2316
    • /
    • 2010
  • Three series of copolyterephthalamides having biphenyl-2,2'-diyl structure in the main chain, were synthesized from p-phenylene-containing diamines such as p-phenylene diamine, 4,4'-oxydianiline or 1,4-bis(4-aminophenoxy)benzene, with mixed diacids of terephthalic acid and 2,2'-bibenzoic acid by the direct polycondensation method. The resulting copolymers had inherent viscosities ranging from 0.46 to 0.93dL/g, and most of them could be readily dissolved in polar aprotic solvents including N,N-dimethyl acetamide and N-methyl-2-pyrrolidone. These copolymers had glass transition temperatures between 239 and $326^{\circ}C$, and their 10% weight loss temperatures were recorded in the range of $410{\sim}485^{\circ}C$ in nitrogen atmosphere.