• Korean Journal of Materials Research
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• v.33 no.1
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• pp.1-7
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• 2023

The physical and antibacterial properties of ophthalmic lenses fabricated by copolymerization with hydrogel monomers using two types of graphene were measured, and their usability as contact lens materials was analyzed. For polymerization, silicone monomers, including SID-OH, 3-(methacryloxy)propyl tris(trimethylsiloxy)silane, and decamethylcyclopentasiloxane, were used, and N,N-dimethylacetamide, ethylene glycol dimethacrylate as a crosslinking agent, and azobisisobutyronitrile as an initiator were added. Also, graphene oxide nanoparticle (GON) and graphene nanoplate (GNP) were used as an additive, and the physical properties of the lenses fabricated after copolymerization were evaluated. The fabricated lenses satisfied the basic physical properties of general hydrogel contact lenses and showed the characteristics of lenses with high water content, and the disadvantage of very weak durability, due to low tensile strength. However, it was confirmed that the tensile strength and antibacterial properties were greatly improved by adding GON and GNP. With GON, the oxygen permeability and refractive index of the fabricated lenses were slightly improved. Therefore, it was determined that the graphene materials used in this study can be used in various ways as a contact lens material.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.1
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• pp.105-113
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• 1995

Procedures for isolatin of chitin have been developed from crab(Chionoecetes opilio) shell waste with 26. 65% chitin on a dry basis. Optimal conditions for demineralization of crab shell were 1N HCl at ambient temperature for 30min with a solids to solbent ratio of 1 : 15(w/v). Optimal deproteinization involved treatment with 5% NaOH at $65^{\circ}C$ for 1 hr with a solids to solvent ratio of 1 : 15(w/v). Effective decoloration was achieved by bleaching with 0.32% sodium hypochlorite solution for 3min with a solids to solvent ratio of 1 : 10(w/v). Particular attentin was given to characterization of the physicochemical properties of the crab chitin. Chitins, from four different mesh sizes of crab shell, did not show significant differences in nitrogen and ash compositions. Bleaching decreased the viscosity of chitin but did not affect its solubility.

• Elastomers and Composites
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• v.55 no.3
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• pp.205-214
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• 2020

A series of wholly aromatic polyhyroxyamide (PHA) copolymers were prepared by direct polycondensation reaction of isophthalic acid and diacids containing bulky units with 3,3'-dihydroxybenzidine. The inherent viscosities of the PHAs measured at 35℃ in DMAc solution were in the range of 0.31-0.56 dL/g. The solubility study revealed that the PHAs were readily soluble in aprotic solvents such as, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP) at room temperature and in less polar solvent such as pyridine. However, the polybenzoxazole (PBO) copoymers were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid and partially soluble in NMP containing LiCl. The PBO copolymers showed maximum weight loss temperature in the range of 593-632℃ and high char yields in the range of 65.0-71.2% at 900℃ in a nitrogen atmosphere.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.266-270
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• 2012

A series of polyimide was prepared by reacting 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as the anhydride monomer and 2,2'-bis(trifluoromethyl)benzidine (TFB), 2,2'-bis(3-aminophenyl)hexafluoropropane (BAFP), 2,2'-bis(3- amino- 4-methylphenyl) hexafluoropropane (BAMF), bis(3-aminophenyl)sulfone (APS), p-xylyenediamine (p-XDA), or m-xylyenediamine (m-XDA) as the amine monomer in N,N-dimethylacetamide (DMAc). Colorless and transparent polyimide (PI) films were obtained by casting the poly(amic acid)s (PAAs) solution at various heat treatment temperatures. The thermal properties of the PI films were examined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA) and the mechanical properties were investigated using universal tensile machine (UTM), Their optical transparencies were also investigated using ultraviolet-visible (UV-vis.) spectrophotometry and colorimetry. The yellow index (YI) and coefficient of thermal expansion (CTE) values of all PIs were in the range 0.98~2.76 and 25.73~55.23 $ppm/^{\circ}C$, respectively.

• Membrane and Water Treatment
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• v.6 no.5
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• pp.423-437
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• 2015

Polyvinylidene fluoride/fullerene nanoparticle (PVDF/$C_{60}$) composite microfiltration (MF) membranes were fabricated by a non-solvent induced phase separation (NIPS) using N, N-dimethylacetamide (DMAc) as solvent and deionized water (DI) as coagulation solution. Polyvinylpyrrolidone (PVP) was added to the casting solution to form membrane pores. $C_{60}$ was added in increments of 0.2% from 0.0% to 1.0% to produce six different membrane types: one pristine PVDF membrane type with no $C_{60}$ added as control, and five composite membrane types with varying $C_{60}$ concentrations of 0.2, 0.4, 0.6, 0.8 and 1.0%, respectively. The mechanical strength, morphology, pore size and distribution, hydrophilicity, surface property, permeation performance, and fouling resistance of the six membranes types were characterized using respective analytical methods. The results indicate that membranes containing $C_{60}$ have higher surface porosity and pore density than the pristine membrane. The presence of numerous pores on the membrane caused weaker mechanical strength, but the water flux of the composite membranes increased in spite of their smaller size. Initial flux and surface roughness reached the maximum point among the composite membranes when the $C_{60}$ concentration was 0.6 wt.%.

• Polymer(Korea)
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• v.35 no.2
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• pp.130-135
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• 2011

Along with the fast development of electronics, the demands of portable electronics and wireless sensors are growing rapidly. The need for self-powering materials capable of powering the electrical devices attached to them is increasing, The piezoelectric effect of polyvinylidene fluoride (PVDF) can be used for this purpose. PVDF has a special crystal structure consisting of a ${\beta}$-phase that can produce piezoelectricity. In this paper, multilayer PVDF films were fabricated to increase the ${\beta}$-phase content. A solution of 10% concentration N;N-dimethylacetamide (DMAc) in PVDF (PVDF/DMAc) was used to fabricate the films via spin coating technique with the following optimum process parameters: a spin rate of 850 rpm, spin time of 60 s, drying temperature of $60^{\circ}C$, and drying time of 30 min, Compared with single-layer PVDF films, the multilayer films exhibited higher ${\beta}$-phase content. The ${\beta}$-phase content of the films increased gradually with increasing number of layers until 4, Maximum ratio of ${\beta}$-phase content was 7.72.

• Membrane Journal
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• v.27 no.1
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• pp.53-59
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• 2017

In this study, the composite membranes prepared by sulfonated graphene oxide (sGO) and Nafion were developed as proton exchange membranes (PEMs) for polymer electrolyte membrane fuel cells (PEMFCs). The sGO/Nafion composite membranes were prepared by mixing Nafion solution with the sGO dispersed in a binary solvent system to improve dispersity of sGO. The composite membranes were investigated in terms of ionic conductivity, ion exchange capacity (IEC), FT-IR, TGA and SEM, etc. As a result, the binary solvent system, i.e., ortho-dichlorobenzene (ODB) and N,N-dimethylacetamide (DMAc), were used to obtain high dispersion of sGO particles in Nafion solution, and the ionic conductivity of the sGO/Nafion composite membrane showed $0.06Scm^{-1}$ similar to other research results at lower water uptake, 11 wt%.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.129-136
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• 2010

A series of noble poly(amide-imide)s and copoly(amide-imide)s bearing 1,2-bis(4-phenoxy)benzene units were synthesized by the direct polycondensation of 1,2-bis(4-trimellitimidophenoxy)benzene[1,2-PTPB] with a combination of commercially available aromatic diamines and diacids such as m-phenylene diamine, p-phenylene diamine(PPD), isophthalic acid and terephthalic acid(TA) in N-methyl-2-pyrrolidone(NMP) using triphenyl phosphite and pyridine as a condensing agent in the presence of dehydrating agent ($CaCl_2$). The resulting polymers had inherent viscosities in the range of 0.37~0.78 dL/g and most of them were soluble m common organic solvents including NMP, dimethylacetamide, dimethylsulfoxide, dimethylformamide, and m-cresol. Wide-angle X-ray diffractograms revealed that the copoly(amide-imide) derived from PPD with mixed acids of 1,2-BTPB and TA, showed crystalline nature, whereas all of the other polymers were found to be amorphous. The glass transition temperatures of the polymers occurred over the temperature range of $270{\sim}323^{\circ}C$ in their differential scanning calorimetry curves and their 10% weight loss temperature, determined by thermogravimetric analysis in air and nitrogen atmosphere, were in the range $465{\sim}535^{\circ}C$, $500{\sim}550^{\circ}C$, respectively, indicating their good thermal stability.

• Membrane Journal
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• v.18 no.4
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• pp.282-293
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• 2008

Partially sulfonated poly(aryl ether sulfone) membranes were prepared from the sulfonated sulfone monomer, which was synthesized by a nucleophilic substitution, non-sulfonated monomers and potassium carbonate by a direct polymerization method and a subsequent solution casting technique with mixed solvents of N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). To investigate the effect of mixed solvent, the volume ratios of NMP and DMAc were varied in the range of $0{\sim}100%$ and the degrees of sulfonation of the copolymers were fixed as 50%. The surface properties of the resulting membranes were examined by scanning electron microscope (SEM) and atomic force microscope (AFM), and a comparative study of the morphology changes and the physicochemical properties such as proton conductivity and methanol permeability was achieved. It was found that proton conductivities depend on the volume ratio of NMP-DMAc mixed solvents, and the proton conductivity determined at the condition of $25^{\circ}C$ and 100% relative humidity was $1.38{\times}10^{-1}\;S/cm$ for the membrane prepared in the 50:50 v/v-% of NMP : DMAc mixed solvent.

• Korean Journal of Poultry Science
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• v.41 no.1
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• pp.21-27
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• 2014

To preserve chicken genetic materials like cryopreserved spermatozoa, various kinds of freezing agents like glycerol, dimethylsuloxide, dimethylformamide or dimethylacetamide have been used for rooster semen preparation. Recently, the usage of N-methylacetamide (MA) for Ogye rooster semen preservation resulted in hatched chicken successfully. In this study, we investigated the effects of 7, 9 and 11% of MA on the viability, fertility and hatchability of frozen-thawed rooster semen using artificial insemination. The results of viability, fertility and hatchability in frozen semen with 7%, 9% or 11% MA were $35.16{\pm}6.12%$, $67.83{\pm}15.3%$ and $66.2{\pm}16.3%$ of motile sperm rate, 21.5%, 34.7% and 25% of fertility rate, and 100%, 89.5% and 87.5% of hatchability rate. The results of control group with frozen semen were 96.0% of fertility rate and 92.2% of hatchability rate. With these results, the concentration range of MA as a freezing agent of rooster semen could be 7~9% of media. The higher concentration of 9 % MA could decrease the fertility rate of thawed semen not the rate of hatchability rate. So the use of MA without affecting fertility rate would be a key point of freezing method of rooster semen for poultry genetic resource preservation.