• Macromolecular Research
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• v.14 no.1
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• pp.34-37
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• 2006

Attaching the organosilyl groups to macromolecular chains of 2-hydroxyethyl methacrylate (HEMA) should lead to important modifications of polymer properties. t-$BuMe_{2}Si$ and cubane-l, 4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked HEMA is abbreviated as TSMA, while cubane-l ,4-dicarboxylic acid (CDA) linked to two HEMA groups is the cross-linking agent (CA). Free radical cross-linking copolymerization of TSMA and HEMA with various ratios of CA as the cross-linking agent was carried out at 60-70$^{circ}C$. The compositions of the cross-linked, three-dimensional polymers were determined by FTIR spectroscopy. The glass transition temperature ($T_{g}$) of the network polymers was determined calorimetrically. The $T_{g}$ of the network polymer increased with increasing cross-linking degree.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.37-42
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• 2006

The preparation and processing of PVP-gate insulators on the device performance have been studied in the fabrication of organic thin film transistors (OTFTs). One of polyvinyl series, poly-4-vinyl phenol(PVP) was used as a solute and propyleneglycol monomethyl etheracetate(PGMEA) as a solvent in the formation of organic gate solutions. The cross-linking of organic insulators was also attempted by adding the thermosetting material, poly (melamine-co-formaldehyde) as a hardener in the compounds. From the measurements of electrical insulating characteristics of metal-insulator-metal (MIM) samples, PVP-based insulating layers showed lower leakage current according to the increase of concentration of PVP and poly (melamine-co-formaldehyde) to PGMEA in the formation of organic solutions. The PVP(20 wt%) copolymer with composition of 20 wt% PVP to PGMEA and cross-linked PVPs in which 5 wt% and 10 wt% poly (melamine-co-formaldehyde) hardeners had been additional]y mixed into PVP(20 wt%) copolymers were used as gate dielectrics in the fabrication of OTFTs, respectively. In our experiments, the maximum field effect mobility of $0.31cm^2/Vs$ could be obtained in the 5 wt% cross-linked PVP(20 wt%) device and the highest on/off current ratio of $1.92{\times}10^5$ in the 10 wt% cross-linked PVP(20 wt%) device.

• Archives of Plastic Surgery
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• v.33 no.6
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• pp.723-731
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• 2006

Purpose: Collagen is the principal structural biomolecule in cartilage extracellular matrix, which makes it a logical target for cartilage engineering. In this study, porous type I collagen scaffolds were cross-linked using dehydrothermal(DHT) treatment and/or 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide(EDC), in the presence and absence of chondroitin-6-sulfate(CS) for cartilage regeneration. Methods: Cartilage defects were created in the proximal part of the ear of New Zealand rabbits. Four types of scaffolds(n=4) were inserted. The types included DHT cross-linked(Group 1), DHT and EDC cross- linked(Group 2), CS added DHT cross-linked(Group 3), and CS added DHT and EDC cross-linked(Group 4). Histomorphometric analysis and cartilage-specific gene expression of the reconstructed tissues were evaluated respectively 4, 8, and 12 weeks after implantation. Results: The largest quantity of regenerated cartilage was found in DHT cross-linked groups 1 and 3 in the 8th week and then decreased in the 12th week, while calcification increased. Calcification was observed from the 8th week and the area increased in the 12th week. Group 4 was treated with EDC cross-linking and CS, and the matrix did not degrade in the 12th week. Cartilage-specific type II collagen mRNA expression increased with time in all groups. Conclusion: CS did not increase chondrogenesis in all groups. EDC cross-linking may prevent chondrocyte infiltration from the perichondrium into the collagen scaffold.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.362-363
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• 2012

A new cross-linkable polymer, cross-linked d-PBAB, which has the triphenylamine as the hole transporting moiety and ethynyl group as the thermal cross-linker is firstly synthesized by the combination of anionic polymerization and deprotection process. The thermal cross-linking reaction was performed at $240^{\circ}C$ for 50 min and cross-linked d-PBAB layer showed smooth surface and is not soluble at organic solvent under spin-coating of emitting layer (EML). The solution-processed PLED which was fabricated with cross-linked d-PBAB as HTL showed approximately two times higher Lmax and four times higher LEmax than those obtained from PLED with PEDOT:PSS as the HTL. These result is ascribed to better ability of cross-linked d-PBAB to block electrons and to prevent exciton-quenching than those of PEDOT : PSS at the EML interface. This results strongly suggested that cross-linked d-PBAB can be a promising material to replace conventional PEDOT : PSS. It can be suspected that PLEDwith cross-linked d-PBAB would show longer lifetime compared with that of PLED with PEDOT : PSS, and thus further studies are under investigation.

• Macromolecular Research
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• v.12 no.4
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• pp.336-341
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• 2004

A new type of cross-linked methylaluminoxane (MAO)-supported cocatalyst has been prepared by the reaction of a soluble MAO and a cross-liking agent such as an aromatic diamine compound. The cross-linked MAO-supported cocatalyst was used for the polymerization of ethylene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride, (n-BuCp)$_2$ZrCl$_2$. The catalyst activity of (n-BuCp)$_2$ZrCl$_2$ cocatalyzed with the new supported cocatalyst was higher than that of the commercial silica-supported MAO (SMAO) cocatalyst. The molecular weight and the bulk density of the polyethylene produced by using the new supported cocatalyst were slightly higher than those of polyethylene synthesized using commercial SMAO. The resulting polyethylene particles possess spherical morphologies with very few fine particles.

• Journal of Marine Bioscience and Biotechnology
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• v.6 no.2
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• pp.53-61
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• 2014

This study was investigated the antimicrobial activity of glutaraldehyde cross-linked glucosamine. Glutaraldehyde was used as a cross-linker which specifically combines an amine-group of molecules. To optimize the mixing ratio of glutaraldehyde and glucosamine, mixing ratio was set up 1:1, 2:1, 3:1 and 0.5:1 in molarity, respectively. The optimum mixing ratio of glucosamine and glutaraldehyde was found to be 3:1 using thin layer chromatography based on the production of complex. Glucosamine-glutaraldehyde cross-linked complex (Ggcc) revealed significant antimicrobial activity toward PWG than F1, both microbial strains were isolated from porcine semen as antibiotics resistance bacteria (ARB). These results clearly demonstrate that Ggcc has potential bactericidal activity toward ARB in porcine semen.

• Macromolecular Research
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• v.16 no.4
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• pp.293-302
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• 2008

In our previous publication, the problem of particle deformation and coagulation at the nucleation stage in the presence of cross-linker was intensely studied by seeded batch dispersion polymerization of methyl methacrylate (MMA). In the present work, highly cross-linked, monodisperse PMMA particles were prepared under various reaction conditions by seeded semi-continuous process. Monodisperse, $6.5{\mu}m$-diameter PMMA particles containing up to 8 wt% of DVB or EGDMA were successfully made by seeded semi-continuous process and multi-semi-continuous addition process, respectively. Therefore, this study shows that seeded semi-continuous process is more effective and efficient to prepare highly cross-linked, monodisperse particles than non-seeded and seeded batch processes.

• Macromolecular Research
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• v.15 no.3
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• pp.244-255
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• 2007

Nucleation is the most sensitive stage in the preparation of highly cross-linked, monodisperse microspheres by dispersion polymerization, since the addition of a small amount of cross-linker results in particle deformation and coagulation. To overcome these problems, $5\;{\mu}m$ poly(methyl methacrylate) seed particles prepared by dispersion polymerization were used in the preparation of mono disperse, cross-linked PMMA particles containing up to 7 wt% divinylbenzene by seeded batch dispersion polymerization. Spherical particles with a narrow size distribution containing up to 8 wt% of EGDMA were prepared by seeded multi-batch dispersion polymerization processes. These particles were identified by scanning electron microscopy and DSC.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.224-231
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• 2006

agents used for enhancing mechanical properties of porous natural scaffolds, reduces biocompatability of the scaffolds, due to their inherent cytotoxicity. In this study, scaffolds which was composed of chitosan, alginate and gelatin were cross-linked by using heat treatment instead of cross-linking agent and mechanical properties of the cross-linked scaffold were investigated. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that cross-linking of heat-treated scaffold was formed via amide or ester linkage between the polymer chains. The heat-treated scaffold had interconnected pores with mean diameter of 100~200 m and showed more than two fold increase of water uptake in comparison with chemically cross-linked scaffold. Tensile strength of the heat-treated scaffold increased up to 130% compared to non cross-linked scaffold and average maximum elongation was 11.3%. The porous cross-linked scaffold with the improved mechanical property may be suitable as a biocompatable scaffold for tissue engineering.

• Membrane Journal
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• v.28 no.3
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• pp.205-213
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• 2018

In this study, cross-linked membrane were successfully prepared by using brominated PPO (Br-PPO) as the main polymer chain. Chitosan and quaternary ammonium modified chitosan (QA-chitosan) was used as the cross linking agents. The cross linked membranes were post-functionalized by using trimethylamine solution. The degree of cross linking was also controlled by varying the ratio of cross linking agent. The applicability of the cross-linked membrane (A-PPO + chitosan, A-PPO + QA-chitosan) as ion exchange membranes was verified through various characterization techniques. The cross-linked membrane using QA-chitosan as cross linking agent was found to be better in performance than the membrane using pristine chitosan cross linking agent. As the percentage of QA-chitosan increased, the ion exchange capacity from 1.18 meq/g to 1.53 meq/g and water uptake from 21.6% to 42.2% was improved.