• Textile Coloration and Finishing
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• v.7 no.4
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• pp.54-60
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• 1995

Cellulose(cell)/dimethylacetamide(DMAc)/lithium chloride(LiCl) solutions were prepared and spun to fibers in coagulants. Then, obtained fibers were annealed in appropriate chemicals. The fibers from cell/DMAc/LiCl showed cell III morophology prior to annealing without differenciating the kind of coagulants. Morphology of crystallite, however, was affected by annealing. Annealed fibers at 17$0^{\circ}C$ showed cell IV morphology and had better mechanical properties than others.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.977-982
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• 2013

Cellulose mixed esters (CME), substituted by various fatty acyl chains, are renewable bio-based polyesters. It has lots of potential due to the biodegradable property. In this study, Alpha cellulose was activated for 2h at $40^{\circ}C$ in deionized water prior to synthesis. Homogeneous esterification of CME was accomplished with water-activated alpha cellulose, various saturated fatty acids and acetic anhydride in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) medium. CME was obtained after 5 hr at $120^{\circ}C$. The filtrated products were characterized using TGA, FT-IR, 1H-NMR and FE-SEM, and the influence of water activation on the total degree of substitution was investigated.

• Polymer(Korea)
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• v.34 no.5
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• pp.391-397
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• 2010

Poly(amic acid)(PAA) was prepared by reaction of bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylicdianhydride(BTDA) containing double bond for crosslinking and bis[4-(3-aminophenoxy) phenyl] sulfone(BAPS) in N,N-dimethylacetamide(DMAc). The cast film of PAA was heat-treated at different temperatures to create polyimide(PI) films. With increasing thermal crosslinking temperatures from 250 to $350^{\circ}C$, the thermo-mechanical properties, degree of crosslinking, and optical transparency of the cross-linked PI were investigated. The maximum enhancement in the thermo-mechanical properties was observed at a heat treatment condition of $350^{\circ}C$. However, the optical transparency was found to be optimal for $250^{\circ}C$ heat treatment. The degree of crosslinking in NMR was determined to be 85% to 93% with increasing annealing temperature conditions from 250 to $350^{\circ}C$.

• Polymer(Korea)
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• v.34 no.5
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• pp.480-484
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• 2010

A series of poly(amic acid)s(PAAs) was prepared by reacting 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride)(BPADA) as the anhydride monomer and 2,2'-bis(trifluoromethyl) benzidine (TFB), bis(3-aminophenyl)sulfone (APS), 4,4'-methylenebis-(2-methylcyclohexylamine) (MMCA), or bis[4-(3-aminophenoxy) phenyl] sulfone (BAPS) as the amine monomer with 5 mol% melamine in N,N-dimethylacetamide (DMAc). Colorless and transparent polyimide (PI) films were obtained by casting the PAAs at various heat treatment temperatures. The thermo-mechanical properties and optical transparency of the PI films were investigated. The thermal properties of the PI films were examined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA), and their optical transparency were measured by spectrophotometry. The coefficient of thermal expansion (CTE) and yellow index (YI) values of all samples were in the range of $48.53-64.24ppm/^{\circ}C$ and < 3.0, respectively.

• Membrane Journal
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• v.23 no.3
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• pp.204-210
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• 2013

Recently, many applications with grapheneoxide (GO) have been reported. But GO membrane for water treatment has not been developed. In this study we prepared polyvinylidene difluoride (PVdF) nanofiber/GO hybrid membrane (FG) for the microfiltration application. The PVdF substrate membrane was prepared by using the electrospinning method with a solution of PVdF in N,N-dimethylacetamide (DMAc) and acetone. GO sheets used in this study were prepared by modified Hummer's method. The PVdF/GO hybrid membrane was finally prepared by spraying the GO solution dispersed in ethanol on the PVdF nanofiber. The successfully prepared FG was thoroughly examined by SEM, Raman, contact angle, porometer and UTM, and water-flux was measured with designed cell (Dead-End Cell). From the contact angle results, it was found that the surface of FG membrane was reformed by hydrophilic property and the water permeability was increased about 2.5 times than that of the nascent PVdF membrane, indicating the possible alternative of the commercial MF membrane.

• Journal of the Korean Magnetics Society
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• v.20 no.6
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• pp.216-221
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• 2010

Magnetic nanocomposites contained iron oxide were synthesized by through cross-linking polymerization of dimethylacetamide (DMAc) solution and toluen solution on the amphiphilic polymer networks based on urethan acrylate nonionomer (UAN) precursor chains. For the study on microscopic structures and magnetic properties of the magnetic nanoparticles, FESEM and XRD and Mossbauer spectroscopy were used. The results investigated show that there are magnetic nanoparticles of $Fe_2O_3$ in samples and the magnetic nanocomposites contained iron oxide in polymer networks of UAN using DMAc solution are more smaller than using toluen solution. All of the Fe ions in the samples present $Fe^{3+}$ and the magnetic property of samples are paramagnetic by superparamagnetic effect at room temperature.

• Polymer(Korea)
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• v.26 no.4
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• pp.535-542
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• 2002

We have prepared the surfactant-free nanoparticles of poly(DL-lactide-co-glycolide) (PLGA) by dialysis method and their physicochemical properties such as particle size and drug contents were investigated against various solvent. The size of PLGA nanoparticles prepared by using dimethylacetamide (DMAc), dimethylformamide (DMF), and dimethylsulfoxide (DMSO) was smaller than that from acetone. Also, the order of drug contents was DMAc>DMF>DMSO=acetone. These phenomena could be expected from the fact that solvent affects the size of nanoparticles and drug contents. The PLGA nanoparticles have a good spherical shapes as observed from scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also, surfactant-free nanoparticles entrapping norfloxacin (NFx) have a good drug loading capacity without free-drug on the surface of nanoparticles confirmed by the analysis of X-ray powder diffraction. Release kinetics of NFx used as a model drug was governed not only by drug contents but also by particle size. Also, the biodegradation rate of PLGA nanoparticles prepared from DMF was faster than that prepared from acetone, indicating that the biodegradation of PLGA nanoparticles is size-dependent.

• Membrane Journal
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• v.26 no.3
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• pp.212-219
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• 2016

The alumina hollow fiber membranes were prepared by spinning and sintering a polymer solution containing suspended alumina powders. For determine pore structure of hollow fiber membranes formed by different solvent-nonsolvent interaction rate, dimethylsulfoxide (DMSO), dimethylacetamide (DMAc), triethylphosphite (TEP) were prepared in dope solution by solvent, polyethersulfone (PESf) and polyvinylpyrrolidone (PVP) were used as a polymer binder and additive. The pore structure of hollow fiber membranes was characterized using scanning electron microscope (SEM). The alumina hollow fiber membranes prepared by DMSO, DMAc were had the asymmetric structure mixed sponge-like and finger-like morphology, while TEP solvent were had single sponge-like structure. The prepared hollow fiber membranes were analyzed gas permeation and mechanical strength experiment also. The hollow fiber membrane having single sponge-like structure was had high gas permeation performance. On the contrary to this, more finger-like morphology was less gas permeation performance.

• Journal of the Korean Chemical Society
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• v.30 no.6
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• pp.510-515
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• 1986

Spectra for the $v_3$+ Amide II combination band of thioacetamide(TA) were obtained in carbon tetrachloride solutions and in very dilute solutions of TA-N,N-dimethlylacetamide (DMA) in carbon tetrachloride in the range of 5~55$^{\circ}$C. The combination band in the three component system can be resolved into components due to monomeric TA, 1 : 1 TA-DMA complex and 1 : 2 TA-DMA complex. In the dilute solutions the experimental spectrum was resolved by using the computer into its two Lorentzian-Gaussian product components which have been identified with the monomeric TA and the 1 : 1 complex. The equilibrium constants and thermodynamic parameters of 1 : 1 complex were determined by analysis of concentration and temperature dependent spectra. The ${\Delta}H^{\circ}$ and ${\Delta}S^{\circ}$ for the 1 : 1 complex were -14.4 KJ mol$^{-1}$ and -15.6 J mol$^{-1}deg^{-1}$, respectively.

• Polymer(Korea)
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• v.36 no.4
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• pp.448-454
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• 2012

A poly(amic acid) (PAA) was prepared by reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluropropane (BAPP) in N,N-dimethylacetamide (DMAc). The cast films of the synthesized PAA were thermally treated at different temperatures to create polyimide (PI) films. The heat treatment temperature varied between 80 and $230^{\circ}C$ to investigate the imidization index in relation with the solvent evaporation rates. The progress of PAA imidization was examined using a thermogravimetric analyzer (TGA) and a Fourier transform infrared spectroscope (FTIR) at various time and temperature. The experimental results showed that the imidization index was fast at the initial stage in the presence of solvent, DMAc, reaching the final imidization. When the imidization temperature is high over $200^{\circ}C$, the imidization index decreased because the solvent was evaporated too fast.