• Prospectives of Industrial Chemistry
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• v.23 no.6
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• pp.14-24
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• 2020

최근 우수한 발광 특성을 갖는 양자점을 고해상도 디스플레이의 발광 소재로 도입하고자 하는 노력이 활발하다. 양자점을 활용한 디스플레이의 실현을 위해서는 콜로이드 상태인 다색의 양자점을 고해상도로 패터닝하는 기술의 확립이 필요하다. 본 연구에서는 ethane-1,2-diyl bis(4-azido-2,3,5,6-tetrafluorobenzoate)를 양자점용 가교제로 활용하여 용액공정을 기반으로 형성된 양자점 박막을 고해상도로 패터닝한 기술을 소개하고자 한다. 위 양자점용 가교제의 양 말단에는 아지드 그룹을 포함한 작용기가 존재한다. 아지드 기는 자외선에 의해 광 활성화되어 양자점 표면의 알킬 리간드와 가교 결합을 형성함으로써, 양자점 박막에 화학적 내구성을 부여한다. 본 기술을 기반으로, 적색, 녹색, 청색의 카드뮴 기반 양자점을 고해상도로 패터닝하고 정밀하게 배열하여 인치 당 화소 수 1400 이상의 픽셀 형성에 성공하였다. 또한 가교 반응 후에도 성능 저하가 없는 양자점 박막 및 자발광 양자점 다이오드를 개발하였다.

• Journal of Adhesion and Interface
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• v.12 no.2
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• pp.73-80
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• 2011

In order to develop the environmental-friendly new materials based on soybean protein which is plantable macromolecule, thermal characteristics of the soybean protein resin (SPI) modified by plasticizers (1,3-propandiol, glycerol) and cross linking agents (glutaraldehyde, epichlorohydrin, glyoxal, urea) were analyzed by TGA. Mechanical properties of modified SPI were investigated and fracture was observed by SEM. As the result, flexibility of SPI film was increased by adding plasticizers; 1,3-propandiol and glycerol. Plasticization effect of glycerol was relatively greater than that of 1,3-propandiol. With the application of crosslinking agents (glycerol, epichlorohydrin and glyoxal), strength and thermal stability of SPI increased with their content. On the other hand, in case of addition of urea, thermal stability of SPI decreased and its strength was reduced because cross-linking between urea and SPI was somewhat difficult. Fracture surfaces and domain interfaces of the modified SPI resins were observed with SEM.

• Polymer(Korea)
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• v.29 no.6
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• pp.599-604
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• 2005

The hyaluronic acid (HA) with excellent biocompatibility has been combined with lactide, the ester dimer of polylactide, with good biodegradability to produce biocompatible materials which can control the period of degradation in a human body. By freeze frying method, HA and lactide were crosslinked with crosslinking agent, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). Degree of lactide and EDC reaction was determined by the analysis of nuclear magnetic resonance spectroscopy. Both lactyl group and EDC conversion increased as the mole ratio of lactide to HA increased from 5 to 13. The membrane swelled less and became more brittle with the more addition of lactyl group resulting from the higher mole ratio of lactide to HA. Swelling ratio decreased and tensile modulus increased due to the more addition of lactyl group as the EDC concentration increased or reaction temperature decreased. Drug release experiment from various membranes with different degree of crosslinking showed that permeability decreased with increasing degree of crosslinking. The degradation became slower with the more addition of lactyl group. Mechanical property and degradation rate of the synthesized membrane were shown to be controlled through adjusting operation parameters such as mole ratio, temperature, and crosslinking agent concentration.

• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.24-31
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• 2008

In this work, calcium hydroxide and magnesium carbonate as metal ionic crosslinking agents were used to introduce ionic crosslinking points to the ethylene vinylacetate (EVA) emulsions for the enhancement of water resistance and mechanical properties of emulsion films. The properties of EVA emulsion film were investigated in crosslinking density, thermal features, surface energy, and mechanical properties, such as tensile strength, elongation at break and tear strength. With the increasing content of metal ionic crosslinking agent, the crosslinking density of the EVA emulsion film increases, resulting into the improvement of water resistance. The surface energy and mechanical properties of the EVA emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.4% for calcium hydroxide and 0.5% for magnesium carbonate was added respectively, because the EVA emulsion containing carboxylic acid forms strong carboxylate-metal bond of ionically-crosslinked system. Therefore, it can be concluded that metal ionic crosslinking agents, such as magnesium carbonate and calcium hydroxide are considered to improve water resistance and mechanical properties of the EVA emulsion.

• Polymer(Korea)
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• v.26 no.6
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• pp.778-784
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• 2002

Chemical modification of a dextran film to improve its physical properties was carried out by addition of plasticizers and crosslinking agents. Moreover, low-temperature plasma treatment with acetylene gas was done. The dextran film showed high mechanical strength but was brittle and vulnerable to moisture. When plasticizer was added, it became very soft but with large reduction of mechanical strength. However, a flexible film with fairly high mechanical strength and water resistance was prepared when the film was crosslinked by adding crosslinking agent with or after the addition of plasticizer. Treatment with an acetylene plasma changed the dextran film surface from hydrophilic to hydrophobic with little influence on the bulk properties of the film.

• Polymer(Korea)
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• v.32 no.4
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• pp.390-396
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• 2008

The hyaluronic acid (HA) polymers cross-linked with lactide (LA) using the crosslinking agent, 1,3-butadiene diepoxide (BD), were prepared in order to develop a biomedical material for tissue engineering. The degree of lactide and BD reaction of the crosslinked polymer was determined by the analysis of nuclear magnetic resonance spectroscopy. Both degree of reaction and swelling ratio increased with BD concentration or LA/HA mole ratio. Tensile modulus decreased with increasing BD concentration or decreasing LA/HA mole ratio. Degradation was shown to be progressed at two different stages and became slow with increasing BD concentration. It was shown that the first stage degradation was mainly due to the decomposition of ester linkage in the crosslinked structure. The cell growth inhibition increased with BD concentration. Although cytotoxicity was slightly observed in the high BD concentration, the value was very low (below 6%) enough not to affect the cell growth.

• Membrane Journal
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• v.24 no.4
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• pp.311-316
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• 2014

The polyacrylonitrile (PAN) hollow fiber composite membranes were prepared and their pervaporation performance was tested to concentrate the acetic acid aqueous solution. The coating of the composite membranes were confirmed by SEM images and the coating thickness was averagely $3.85{\mu}m$. As the crosslinking agent and the crosslinking temperature increase, the permeability decreases while the separation factor increases. Typically, the permeability $250g/m^2{\cdot}hr$ and the separation factor 13 were obtained for glutaraldehyde 13 wt% as the crosslinking agent and crosslinking temperature $140^{\circ}C$. And for the use of another crosslinking agent, poly (acrylic acid) 9 wt% and crosslinking temperature $140^{\circ}C$, the permeability $330g/m^2{\cdot}hr$ and separation factor 9 were obtained.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.182-189
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• 1990

Various crosslinked poly(4-vinylpyridines) having different degrees of crosslinking were prepared by radical copolymerizations of 4-vinylpyridine with N, N'-2, 6-pyridinebisacrylamide as a crosslinker. The abilities of these crosslinked polymers to bind methyl orange and butyl orange were investigated at various temperatures in a buffer solution of pH 7. The first binding constants were evaluated from the equilibrium binding amounts. The first binding constants against the temperatures showed bell-shaped curves. Also, the first binding constants against the degree of crosslinking showed bell-shaped curves. When the temperature and the degree of crosslinking of maximum binding in the curves of these binding systems were compared with those of previous systems containing crosslinked poly(4-vinylpyridines) prepared by using N, N'-methylenebisacrylamide, N, N'-tetramethy-lenebisacryamide and divinylbenzene as crosslinkers, respectively, they were varied with the crosslinked poly(4-vinyl pyridines) containing different crosslinkers. These results were discussed in terms of the properties of the crosslinkers.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.802-807
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• 2015

In this study, we synthesized a new biocatalyst consisting of glucose oxidase (GOx), polyethyleneimine (PEI) and carbon nanotube (CNT) with addition of terephthalaldehyde (TPA) (TPA/GOx/PEI/CNT) for fabrication of glucose sensor that shows improved sensing ability and stability compared with that using other biocatalysts. Main bonding of the new TPA/GOx/PEI/CNT catalyst is formed by Aldol condensation reaction of functional end groups between GOx/PEI and TPA. Such formed bonding structure promotes oxidation reaction of glucose. Catalytic activity of TPA/GOx/PEI/CNT is evaluated quantitatively by electrochemical measurements. As a result of that, large sensitivity value of $41{\mu}Acm^{-2}mM^{-1}$ is gained. Regarding biosensor stability of TPA/GOx/PEI/CNT catalyst, covalent bonding formed between GOx/PEI and TPA prevents GOx molecules from becoming leaching-out and contributes improvement in biosensor stability. With estimation of the biosensor stability, it is found that the TPA/GOx/PEI/CNT catalyst keeps 94.6% of its initial activity even after three weeks.

• KSBB Journal
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• v.5 no.2
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• pp.141-149
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• 1990

$\beta$-glucosidase derived from Aspergillus niger was immobilized by (1) covalent linkage on chitin and chitosan with glutaraldehyde, (2) adsorption on DEAE-cellulose and Amberite IRA93 after succinylation, and (3) entrapment on alginate and polyacrylamide gels with various cross linking agents. The retention yield of $\beta$-glucosidase immobilized on chitosan was 31.5% and operational stability was 69% after continuous operation at column reactor(5$0^{\circ}C$ at pH 4.8) for 15 days. The retention yield and operational stability were 24.7% and 60% respectively, in adsorption on Amberite IRA 93. On the other hand, the entrapment method by alginate and polyacrylamide gel was identified to be not appropriate due to the continuous elution of inlmobilized $\beta$-glucosidase. Optimum conditions for the immobilization on chitosan were also studied with optimum pH of 4.8 and glutaraldehyde concentration of 0.4%(w/v). The properties and stability of immobilized $\beta$-glucosidase are also investigted. The conversion yield of cellobiose to glucose was also analyzed using the column type enzyme reactor to evaluate the effectiveness of immobilized enzyme.