• Polymer(Korea)
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• v.36 no.1
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• pp.29-33
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• 2012

Solution type pressure sensitive acrylic adhesives were synthesized from 2-ethylhexyl acrylate (2-EHA) as a base monomer and acrylic acid as a functional monomer. The surface energy and basic physical properties of synthesized PSA (pressure sensitive adhesives) were investigated as a function of contents of acrylic acid and crosslinking agent. The structures of adhesive were identified by FTIR. Viscosities and molecular weights of PSA were measured by a Brookfield viscometer and GPC, respectively. Consequently, molecular weight and viscosity increased as the contents of acrylic acid increased up to 6 wt% and then decreased at higher contents. Surface energy increased as the contents of acrylic acid increased owing to the increase of COOH groups, which yielded the enhancement of polarity of PSA. On the other hands, their peel strengths were inversely proportional to molecular weight and showed tendencies of decreasing as the contents of acrylic acid and crosslinking agent increased.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.285-295
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• 1999

Electroluminescent(EL) devices based on organic materials have been of great interest due to their possible applications for large-area flat-panel displays. They are attractive because of their capability of multi-color emission, and low operation voltage. An approach to realize such device characteristics is to use active layers of lanthanide complexes with their inherent extremely sharp emission bands in stead of commonly known organic dyes. In general, organic molecular compounds show emission due to their $\pi$-$\pi*$ transitions resulting in luminescence bandwidths of about 80 to 100nm. Spin statistic estimations lead to an internal quantum efficiency of dye-based EL devices limited to 25%. On the contrary, the fluorescence of lanthanide complexes is based on an intramolecular energy transfer from the triplet of the organic ligand to the 4f energy states of the ion. Therefore, theoretical internal quantum efficiency is principally not limited. In this study, Powders of TPD, $Eu(TTA)_3(phen) and AlQ_3$ in a boat were subsequently heated to their sublimation temperatures to obtain the growth rates of 0.2~0.3nm/s. Organic electrolumnescent devices(OELD) with a structure of $glass substrate/ITO/Eu(TTA)_3(phen)/AI, glass substrate/ITO/TPD/Eu(TTA)_3(phen)/AI and glass substrate/ITO/TPD/Eu(TTA)_3(phen)/AIQ_3AI$ structures were fabricated by vacuum evaporation method, where aromatic diamine(TPD) was used as a hole transporting material, $Eu(TTA)_3(phen)$ as an emitting material, and Tris(8-hydroxyquinoline)Aluminum$(AlQ_3)$ as an electron transporting layer. Electroluminescent(EL) and current density-voltage(J-V) characteristics of these OELDs with various thickness of $Eu(TTA)_3(phen)$ layer were investigated. The triple-layer structure devices show the red EL spectrum at the wavelength of 613nm, which is almost the same as the photoluminescent(PL) spectrum of $Eu(TTA)_3(phen)$.It was found from the J-V characteristics of these devices that the current density is not dependent on the applied field, but on the electric field.

• Journal of Microbiology and Biotechnology
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• v.24 no.2
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• pp.270-279
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• 2014

Microbial community shifts, associated with performance data, were investigated in an anaerobic batch digester treating high-solid food waste under mesophilic conditions using, a combination of molecular techniques and chemical analysis methods. The batch process was successfully operated with an organic removal efficiency of 44.5% associated with a biogas yield of 0.82 L/g $VS_{removal}$. Microbial community structures were examined by denaturing gel gradient electrophoresis. Clostridium and Symbiobacterium organisms were suggested to be mainly responsible for the organic matter catabolism in hydrolysis and acidogenesis reactions. The dynamics of archaeal and methanogenic populations were monitored using real-time PCR targeting 16S rRNA genes. Methanosarcina was the predominant methanogen, suggesting that the methanogenesis took place mainly via an aceticlastic pathway. Hydrogenotrophic methanogens were also supported in high-solid anaerobic digestion of food waste through syntrophism with syntrophic bacterium. Microbial community shifts showed good agreement with the performance parameters in anaerobic digestion, implying the possibility of diagnosing a high-solid anaerobic digestion process by monitoring microbial community shifts. On the other hand, the batch results could be relevant to the start-up period of a continuous system and could also provide useful information to set up a continuous operation.

• Environmental Analysis Health and Toxicology
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• v.16 no.4
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• pp.223-226
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• 2001

Acetanilide is a High Production Volume Chemical, which is produced about 2,300 tons/year in Korea as of 1998 survey. Most is used as an intermediate for synthesis of pharmaceuticals and dyes. The chemical is one of seven chemicals, which are under the frame of OECD SIDS program sponsored by National Institute of Environmental Research of Korea. Regarding the information on the environmental fate. bioconcentration is one of important factor to estimate the environmental tranfer. However, measurement of bioconcentration needs high expense and time. For this reason, OECD recommends to use BCFWIN model to estimate bioconcentration of organic chemicals, BCFWIN estimates the bioconcentration factor (BCF) of an organic compound using the log octanol-water partition coefficient (Kow) of the compound. Structures are entered into BCFWIN through SMITES (Simplified Molecular Input Line Entry System) notations. The BCFWIN method classifies a compound as either ionic or non-ionic. ionic compounds include carboxylic acids, sulfonic acids and salts of sulfonic acids, and charged nitrogen compounds (nitrogen with a + 5 valence such as quaternary ammonium compounds). All other compounds are classified as non-ionic. In this study, bioaccumulation of acetanilide was estimated using BCFWIN model based on SMIIES notation, chemical name data and partition coefficient as one of environmental fate/distribution of the chemical elements.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.2
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• pp.103-108
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• 1997

A series of batch tests were conducted to evaluate the design parameters for the application of soil washing techniques to the hydrophobic organic compounds (HOCs)-contaminated soil using mixed surfactants. Because the mixed surfactants form different structures of molecular aggregates from single surfactant, they were applied to improve the washing efficiency. Kinds of surfactants added, mixing ratio, and total concentration of mixed surfactants were evaluated. The uncontaminated soil was obtained from a country hill near Nock-Chun Station in Seoul. The portion of soil passing #4 (4.75 mm) sieve was used. The pH, organic contents and cation exchange capacity were 4.4, 1.6% and 4.08 meq/100 g, respectively The soil was artificially contaminated by n-dodecane. The 5% solution of OA-5 and OA-14 (1:1) showed 86% washing efficency. The 4% solution of SDS and OA-5 (1:1) showed 95% washing efficiency.

• Journal of the Korean Chemical Society
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• v.43 no.3
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• pp.315-320
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• 1999

Novel electroluminescent materials, polymer material, PU-BCN and low molar mass material, D-BCN with the same chromophores were designed and synthesized. A molecular structure of chromophore was composed of bisstyrylbenzene derivative with cyano groups as electron injection and transport and phenylamine groups as hole injection and transport. Device structures with PU-BCN and D-BCN as an emission layer were fa-bricated, which were a single-layer device(SL), Indium-tin oxide(ITO)/emission layer/MgAg, and two kinds of double-layer devices which were composed of ITO/emission layer/oxadiazole derivative/MgAg as a DL-E device and ITO/triphenylamine derivative/emission layer/MgAg as a DL-H device. The two emission materials, PU-BCN and D-BCN with the same emission-chromophore were evaluated as having excellent performance of charge injection and transport and revealed almost the same emission characteristics in high current density. EL emission maximum peaks of two material were detected at about 640 nm wavelength of red emission region.

• Applied Chemistry for Engineering
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• v.35 no.5
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• pp.399-403
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• 2024

Lecithin is one type of surfactant with amphiphilic properties, which forms spherical reverse micelles in various organic solvents. Salts with markedly low solubility in organic solvents can significantly increase their solubility through ionic interactions through the hydrophilic head of lecithin, leading to changes in the molecular morphology of lecithin. As a result, spherical reverse micelles can transform into cylindrical reverse micelles, which can cause abrupt rheological changes when these cylindrical reverse micelles form a transient network. This study precisely analyzes the formation of self-assembled structures and rheological changes by simultaneously adding two types of salts to a lecithin solution, using small-angle X-ray scattering analysis and rheometry.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1727-1734
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• 2013

Synthesis and characterization of some novel symmetric bis-azospiropyrans are reported in this study. These bis-azospiropyrans are bifunctional chromophores with two spiropyrans linked by a bis-azo extended aromatic system that produce more color strength (large molar absorption coefficient in mero forms) due to appending two azospiropyran chromophores on one molecule. Comparing to the molar absorption coefficients of the conventional spiropyran chromophores (${\varepsilon}=0.31{\times}10^4\;M^{-1}{\cdot}cm^{-1}$) and mono-azospiropyran chromophores ($1.35{\times}10^4\;M^{-1}{\cdot}cm^{-1}$), the novel synthesized photochromes showed astonishingly increased molar absorption coefficients ($2.3-3.8{\times}10^4\;M^{-1}{\cdot}cm^{-1}$) at the same conditions. Such high molar absorption coefficients confers high sensitivity to light and more color intensity of mero form, that leads to improvement of their light sensitivity and better discrimination of spiro (OFF) form from mero (ON) ones in molecular switches. The structures were deduced from their MS, FT-IR, and $^1H$-NMR spectroscopic data and CHN analysis. All the synthesized photochemically bifunctional compounds revealed fluorescent emission in their colorless form which was faded out after exposing to UV light. Fluorescence quantum yield values of the mero forms were 0.25-0.81 and two high fluorescence quantum yield values (0.60 and 0.81) were found in these series.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.167-168
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• 2008

Organic light emitting diodes (OLEDs) show a lot of advantages for display purposes. Because OLEDs provide white light emission with a high efficiency and stability, it is desirable to apply OLEDs as an illumination light source and back light in LCD displays. We synthesized new emissive materials, namely $Zn(HPB)_2$ and Zn(HPB)q, which have a low molecular compound and thermal stability. We studied white OLEDs using $Zn(HPB)_2$ and $Zn(PQ)_2$. The fundamental structures of the white OLEDs were ITO / NPB (40 nm) / $Zn(HPB)_2$ (40 nm) / $Zn(PQ)_2$ (20 nm) / LiAl (120 nm). As a result, we obtained a maximum luminance of $4200cd/m^2$ at a current density of $440mA/cm^2$. The CIE (Commission International de l'Eclairage) coordinates are (0.319, 0.338) at an applied voltage of 10 V.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.24-30
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• 2004

New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis($\alpha$-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd $m^{-2}$ at an applied voltage of 10 V and current density of 680 $mA/cm^2$. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.