• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.853-858
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• 2014

We propose a fabrication method for polydiacetylene (PDA)-embedded hydrogel microfibers on a microfluidic chip. These fibers can be applied to the detection of cyclodextrines (CDs), which are a family of sugar and aluminum ions. PDA, a family of conjugated polymers, has unique characteristics when used for a sensor, because it undergoes a blue-to-red color transition and nonfluorescence-to-fluorescence transition in response to environmental stimulation. PDAs have different sensing characteristics depending on the head group of PCDA. By taking advantage of ionic crosslinking-induced hydrogel formation and the 3D hydrodynamic focusing effect on a microfluidic chip, PCDA-EDEA-derived diacetylene (DA) monomer-embedded microfibers were successfully fabricated. UV irradiation of the fibers afforded blue-colored PDA, and the resulting blue PDA fibers underwent a phase transition to red and emitted red fluorescence upon exposure to CDs and aluminum ions. Their fluorescence intensity varied depending on the CDs and aluminum ion concentrations. This phase transition was also observed when the fibers were dried.

• Polymer(Korea)
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• v.34 no.1
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• pp.74-78
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• 2010

In this paper, crosslinked polyethylene (PE) separators for lithium secondary batteries were prepared by an electron beam irradiation under various beam currents and dose rates. The crosslinking degree increased up to maximum 71% with an increasing absorption dose and with a decreasing beam current. The PE separators irradiated at lower beam currents showed better thermal shrinkage (51%) and mechanical properties than the original PE separator and PE separators irradiated at higher beam current. The ionic conductivity ($1.01{\times}10^{-3}\;S/cm$) and electrolyte uptake (275%) of the crosslinked PE separators were comparable to the original PE separator.

• Nuclear Engineering and Technology
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• v.15 no.1
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• pp.1-10
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• 1983

By controlling both the means of grafting and the cast-solution components, no degradation and dimensional change of radiation-induced graft polymerization were found. The electric resistance of styrene-cellulose acetate grafts increases with increasing styrene content, while those for the hydrophilic monomers show no marked effect. In comparison with the grafted cellulose acetate membrane by simultaneous irradiation method, the appearance of the grafted membrane by post-polymerization method was not markedly changed irrespective of the percent of grafting and radiation dose of electron beam or ${\gamma}$-ray. The combination of crosslinking agents such as divinyl benzene (OB) or trimethyl propane triacrylate (TMPT) in the VP:St:BPO system leads to gradual increase of the percent of grafting. The activation energy for grafting of St:VP:BPO solution onto cellulose acetate membrane was determined to be about 21.8 Kcal/mole over the range of 55$^{\circ}$-8$0^{\circ}C$. The initial rate of grafting (in %/hr) is proportional to the power 0.76 for dose intensities.

• Polymer(Korea)
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• v.32 no.1
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• pp.56-62
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• 2008

Three types of network polyesters have been newly synthesized by a two-step condensation reaction by the various combination of several diols and diacids. When these polymer films were thermally treated at $240^{\circ}C$, they exhibited absorptions in a visible range despite the forbidden transition of carbonyl group. When excited at wavelengths above 330 nm, the polymers showed fluorescences in a wide visible range from blue to near yellow. These fluorescence phenomena are due to the formation of certain conjugated structures by the Knoevenagel type self-condensation under the high-temperature thermal treatment. These polymers showed significant difference in the thermal properties as a function of the degrees of chemical crosslinking. They also underwent photodegradation. Highly resolved, fluorescent image patterns were successfully obtained by the photodegradation of malonate group under a strong UV-light irradiation.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.88-93
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• 2013

In order to construct a controlled release system of drugs and to reduce toxic side effects of 5-fluorouracil, the novel ramose chitosan-based-5-fluorouracil microspheres (CS-FU-MS) were prepared. Firstly, using chitosan (CS) as carriers and 5-fluorouracil (5-FU) as a model drug, ramose chitosan-based-5-fluorouracil (CS-FU) was efciently synthesized by chemical crosslinking method through microwave irradiation, drug loading was 10.6%; Secondly, CS-FU-MS were prepared by CS-FU self-assembled under the dialysis conditions and the free 5-FU was encapsulated further at the same time. The size dispersivity of particles is uniform, and the average diameter of the CS-FU-MS was $4{\mu}m$. The drug encapsulation efficiency was 76.1%, and the drug loading was increased to 26.22%. CS-FU-MS maintain the zero-order release time in PBS (pH = 7.4) and HCl/KCl (pH = 1.2) dialysis medium was 40h and 34h respectively, and the cumulative release were 58.89% and 79.33% in 182 h. The results showed that CS-FU-MS have excellent sustained release properties.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4514-4521
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• 2022

In this study, the effects of heat and radiation on the degradation behaviour of fluoroelastomer under simulated normal operation and a severe accident environment were investigated using sequential testing of gamma irradiation and thermal degradation. Tensile properties and Shore A hardness were measured, and thermogravimetric analysis was used to evaluate the degradation behaviour of fluoroelastomer. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the structural changes of the fluoroelastomer. Heat and radiation generated in nuclear power plant break and deform the chemical bonds, and fluoroelastomer exposed to these environments have decreased C-H and functional groups that contain oxygen and double bonds such as C-O, C=O and C=C were generated. These functional groups were formed by auto oxidation by reacting free radicals generated from the cleaved bond with oxygen in the atmosphere. In this auto oxidation reaction, crosslinks were generated where bonded to each other, and the mobility of molecules was decreased, and as a result, the fluoroelastomer was hardened. This hardening behaviour occurred more significantly in the severe accident environment than in the normal operation condition, and it was found that thermal stability decreased with the generation of unstable structures by crosslinking.

• Polymer(Korea)
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• v.36 no.1
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• pp.47-52
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• 2012

Abstract: In this study, PAN/$TiO_2$ fiber mats were fabricated from polyacrylonitrile (PAN) and titanium(IV) butoxide ($Ti(OBu)_4$) by an electrospinning method with various solution concentrations, applied voltages and solution flow rates. The fiber mats were irradiated with an electron beam to induce structural crosslinking and enhance photocatalytic activity. As a result, uniform and bead-free fibers without pits or cracks on surface were obtained at 5 wt% of $Ti(OBu)_4$ solution with 15 kV and 0.02 mL/min flow rate. The PAN/$TiO_2$ fiber mats were irradiated with an electron beam of 1.14 MeV acceleration voltage, 4 mA of current and $1{\times}10^4kGy$. Electron beam irradiation was enhanced the photocatalytic activity of PAN/$TiO_2$ nano fiber mat. The photocatalytic activity of the PAN/$TiO_2$ fiber mat was analyzed by degradation of methylene blue and volatile organic compounds.

• Polymer(Korea)
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• v.38 no.1
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• pp.69-73
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• 2014

In this study, polysaccharide-poly(vinyl alcohol) (PVA) hydrogels were prepared by using ${\gamma}$-ray and evaluated for potential application as an anti-inflammation patch. Ulmus davidiana var. japonica (UD), one of polysaccharides has been particularly used as an oriental remedy for the treatment of inflammation and ulcers. PVA as a biocompatible polymer and glycerin as a moisturizer were blended with the UD, and its hydrogels were prepared by radiation crosslinking. Characterizations for UD hydrogels were performed by using cytotoxicity assay, antioxidant activity test, and physicochemical test such as gel fraction ratio, and swelling behavior. The results showed that these UD hydrogels had excellent physical properties, anti-inflammation activity, and non-cytotoxicity on the cells. Therefore, these polysaccharide based-UD hydrogels can be effectively used as an inflammation patch.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.299-304
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• 2021

This study focuses on the preparation of acetaminophen (AP) imprinted functional biomaterials for a transdermal drug delivery using mung bean starch (MBS), polyvinyl alcohol (PVA), sodium benzoate (S) as a crosslinking agent, glycerol (GL) as a plasticizer, and melanin (MEL) as a photothermal agent. The prepared AP imprinted biomaterials were characterized using FE-SEM and their physical properties were evaluated. The photothermal effect and AP release property for functional biomaterials were examined with the irradiation of near infrared (NIR) laser (1.5 W/cm²). When the NIR laser was irradiated on functional biomaterials with/without the addition of MEL, the temperature of MEL added biomaterial increased from 25 ℃ to 41 ℃, whereas the biomaterial without MEL increased from 25 ℃ to 28 ℃. Results indicate that there is the photothermal effect of prepared biomaterial with the addition of MEL. Based on the results, AP release properties were evaluated using standard buffer solutions and artificial skin. It was found that AP release rates of MEL added AP loaded biomaterials were 1.2 times faster than those of MEL non-added AP loaded biomaterials when irradiating with NIR laser. We envision that the developed functional biomaterials can be utilized for an acute pain-killing treatment.