• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.961-966
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• 2003

A quantum-chemical study of conformations and electronic structures of polyheterocyclic derivatives with vinylenediheteroatom substituents at the 3- and 4-positions was performed to search for novel blue-lightemitting conjugated polymers. Conformational potential energy curves of the polymers were constructed as a function of the helical angle (a) through semiempirical Hartree-Fock band calculations at the Austin model 1 level. It is found that poly(3,4-vinylenedioxythiophene) possesses a quite flat curve in the range of α = 51.4°- 120°. Replacing S atoms for O atoms greatly increases repulsion between the neighboring units, and thereby the units become perpendicular to one another. Because of the hydrogen bonding between O and NH, poly(3,4- vinylenedioxypyrrole) is predicted to be anti-coplanar and poly(3,4-vinylenediaminofuran) to be nearly anticoplanar. According to the modified extended Huckel band calculations, the HOMO-LUMO gaps (HLGs) of the polymers, unless the polymer chains are twisted, are close to or slightly smaller than those of their respective mother polymers. Among the polymers, poly(3,4-vinylenedioxythiophene) is presumed to be the most probable candidate for a blue-light emitter because its HLG is within the range of the electronic requirement for blue-light emitters.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.10.2-10.2
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• 2011

The design and synthesis of protein-like polymers is a fundamental challenge in materials science. A biomimetic approach is to explore the impact of monomer sequence on non-natural polymer structure and function. We present the aqueous self-assembly of two peptoid polymers into extremely thin two-dimensional (2D) crystalline sheets directed by periodic amphiphilicity, electrostatic recognition and aromatic interactions. Peptoids are sequence-specific, oligo-N-substituted glycine polymers designed to mimic the structure and functionality of proteins. Mixing a 1:1 ratio of two oppositely charged peptoid 36 mers of a specific sequence in aqueous solution results in the formation of giant, free-floating sheets with only 2.7 nm thickness. Direct visualization of aligned individual peptoid chains in the sheet structure was achieved using aberration-corrected transmission electron microscopy. Specific binding of a protein to ligand-functionalized sheets was also demonstrated. The synthetic flexibility and biocompatibility of peptoids provide a flexible and robust platform for integrating functionality into defined 2D nanostructures. In the later part of my talk, we describe the use of metal ions to construct two-dimensional hybrid films that have the ability to self-heal. Incubation of biomimetic peptoid polymers with specific divalent metal ions results in the spontaneous formation of uniform multilayers at the air-water interface. We anticipate that ease of synthesis and transfer of these two-dimensional materials may have many potential applications in catalysis, gas storage and sensing, optics, nanomaterial synthesis, and environmentally responsive scaffolds.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.784-788
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• 1999

The effects of pH, moisture content, and the relative amount of a polymer sample on the biodegradation of degradable polymers in soil were studied using various polymer materials such as cellulose, poly-(butylene succinate-co-adipate) (SG) polycaprolactone (PCL), a blend of PCL and starch (PCL-starch), and a poly-lactic acid (PLA). As with other materials, the polymers degraded faster at a neutral pH than at either acidic or basic conditions. Moisture contents of 60 and 100% water holding capacity exhibited a similar biodegradability for various polymers, although the effects differed depending on the polymer. For synthetic polymers, biodegradation was faster at 60%, while the natural polymer (cellulose) degraded faster at 100%. Fungal hypae was observed at a 60% water holding capacity which may have affected the biodegradation of the polymers. A polymer amount of 0.25% to soil revealed the highest biodegradability among the ratios of 0.25, 0.5, and 1%. With a higher sample amount, the residual polymer could be recovered after the biodegradation test. It was confirmed that a test for general biodegradation condition can be applied to plastic biodegradation in soil.

• Journal of the Korean Applied Science and Technology
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• v.16 no.1
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• pp.67-73
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• 1999

Chitosan and Algin are known as a natural polymers. Biodegradable films were prepared by solution blend method in the weight ratio of natural polymer(low, medium, high-Chitosan, Algin) for the purpose of useful bioimplants. The possibility of bioimplants, which were prepared from natural polymers as a skin substitute and food wrapping materials were evaluated by measuring biodegradability. This biodegradable films were inserted in the back of rats and their biodegradability was investigated by hematological change evaluation as a function of time to biotransformation. It was found that these values of biodegradable films give some good results with short period test.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.939-943
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• 1999

Recently there has been an explosion of interest in the topic of biodegradable polymers for medical applications. In this study, films were prepared by solution casting method using natural polymers (xanthan, locust bean, guar gum, chitosan and algin) as biomaterials. Biocompatibility of films prepared from natural polymer as a skin implant was evaluated. These biodegradable films were subcutaneously implanted in the back of rats and their biodegradability was investigated by the evaluation of changes in structure, film weight and hematology as a function of time for the biotransformation. The result of rats test showed that locust bean and guar gum induced some suspects of non-biocompatibility in the tissue by foreign body reaction 24 and 48 hrs after implantation. These results showed the potential of partial biodegradable films prepared from natural polymer for ideal skin biomaterials at short period.

• Biomedical Science Letters
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• v.19 no.1
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• pp.25-31
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• 2013

Electrospun nanofibers are being widely used as a substratum for mammalian cell culture owing to their structural similarity to collagen fibers found in extracellular matrices of mammalian cells and tissues. Especially, development of diverse synthetic polymers has expanded use of electrospun nanofibers for constructing cell culture substrata. Synthetic polymers have several benefits comparing to natural polymer for their structural consistency, low cost, and capability for blending with other polymers or small molecules to enhance their structural integrity or add biological functions. PMGI (polymethylglutarimide) is one of the synthetic polymers that produced a rigid nanofiber that enables incorporation of small molecules, peptides, and gold nanoparticles through co-electrospinning process, during which the materials are fixed without any chemical modifications in the PMGI nanofibers by maintaining their activities. Using the phenomenon of PMGI nanofiber, here I introduce a construction method of a nanofiber substratum having cell-affinity function towards a pluripotent stem cell by incorporating a small molecule in the PMGI nanofiber.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1915-1918
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• 2006

• Journal of Environmental Science International
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• v.24 no.1
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• pp.9-15
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• 2015

Sustainable and eco-friendly polymers, natural polymers, bio-based polymers, and degradable polyesters, are of growing interest because of environmental concerns associated with waste plastics and emissions of carbon dioxide from preparation of petroleum-based polymers. Degradable polymers, poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC), and poly(L-lactic acid) (PLLA), are related to reduction of carbon dioxide in processing. To improve a weak mechanical property of a degradable polymer, a blending method is widely used. This study was forced on the component separation of degradable polymer blends for effective recycling. The melt-mixed blend films in a specific solvent were separated by two layers. Each layer was analysed by FT-IR, DSC, and contact angle measurements. The results showed that each component in the PPC/PLLA and PPC/PBAT blends was successfully separated by a solvent.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3208-3212
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• 2012

Controlled drug delivery systems employing microparticles offer lots of advantages over conventional drug dosage formulations. Microencapsulation technique have been conducted with biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) for its adjustable biodegradability and biocompatibility. In this study, we evaluated two techniques, oil-in-water (o/w) emulsion solvent evaporation and spray drying, for preparation of polymeric microparticles encapsulating a newly synthesized drug, SS-AG20, for the long-term drug delivery of this low-molecular-weight drug with a very short half-life. Drug-loaded microparticles prepared by the solvent evaporation method showed a smoother morphology; however, relatively poor encapsulation efficiency and drastic initial burst were discovered as drawbacks. Spray-dried drug-loaded microparticles had an imperfect surface with pores and distorted portions so that its initial burst was critical (70.05-87.16%) when the preparation was carried out with a 5% polymeric solution. By increasing the concentration of the polymer, the morphology was refined and undesirable initial burst was circumvented (burst was reduced to 35.93-74.85%) while retaining high encapsulation efficiency. Moreover, by encapsulating the drug with various biodegradable polymers using the spray drying method, gradual and sustained drug release, for up to 2 weeks, was achieved.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2668-2671
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• 2010