• Transactions of the Korean hydrogen and new energy society
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• v.17 no.3
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• pp.331-337
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• 2006

높은 이온전도도와 충분한 기계적 강도, 전해질 누수가 적은 새로운 형태의 고분자 전해질막(pore-gel SPE)을 연구 개발하였다. 다공성 PVDF-HFP 고분자막의 기공 내에 전해질 용액을 흡수시킨 후 막 내에서 젤화를 진행시켰다. 전해질 용액은 2:2:1의 비를 갖는 PC/EC/DMA에 1M SA(Salicylic acid)를 용해하고 여기에 고분자막을 용해시킬 수 있는 아세톤을 첨가하였다. 초음파를 이용함으로써 고분자막의 용액 흡수율을 증가시키고 또 고분자막에서 젤화를 촉진 시킬 수 있었다. 이렇게 젤화한 막의 이온전도도는 젤화 전 막보다 $1{\sim}2.2$ 배 향상되었고, 인장강도는 gel-type SPE 보다 40 배 증가하였으며, 전해질 누수실험결과 hybrid-type SPE는 13%의 누수를 보였으나 본 연구의 막(pore-gel SPE)은 6%로 감소함을 보였다.

• Polymer(Korea)
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• v.26 no.4
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• pp.508-515
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• 2002

The effects of the crosslinking caused by irradiation dose, molecular weights of the foaming materials, and various foaming processes on the foam structure of the polypropylene (PP) were investigated. The maximum gel content of the PP was 48% when the sheet was irradiated with 3.2 Mrad. This high gel content improved the cell structures by providing high thermal stability. The increase of both the gel content and structural development were stopped at the irradiation dose exceeding 3.2 Mrad. The increase of the molecular weights served to help produce a foam with particularly fine and even cell structures, along with improved thermal stability as well.

• Advances in nano research
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• v.14 no.4
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• pp.355-362
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• 2023

Physical exercise, especially intense exercise and high intensity interval training (HIIT) by trampoline, can lead to muscle injuries. These effects can be reduced with intelligent products made of nanocomposite materials. Most of these nanocomposites are polymers reinforced with silicon dioxide, alumina, and titanium dioxide nanoparticles. This study presents a polymer nanocomposite reinforced with silica. As a result of the rapid reaction between tetraethyl orthosilicate and ammonia in the presence of citric acid and other agents, silica nanostructures were synthesized. By substituting bis (4-amino phenoxy) phenyl-triptycene in N, N-dimethylformamide with potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C, the diamine monomer bis (4-amino phenoxy) phenyl-triptycene is prepared. We synthesized a new polyaromatic (imide) with triptycene unit by sol-gel method from aromatic diamines and dianhydride using pyridine as a condensation reagent in NMP. PI readily dissolves in solvents and forms robust and tough polymer films in situ. The FTIR and NMR techniques were used to determine the effects of SiO₂ on the sol-gel process and the structure of the synthesized nanocomposites. By using a simultaneous thermal analysis (DTA-TG) method, the appropriate thermal operation temperature was also determined. Through SEM analysis, the structure, shape, size, and specific surface area of pores were determined. Analysis of XRD results is used to determine how SiO₂ affects the crystallization of phases and the activation energy of crystallization.

• Polymer(Korea)
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• v.27 no.4
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• pp.349-357
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• 2003

Hydrogels for wound dressing from a mixture of poly(vinyl alcohol) (PVAL), poly(N-vinyl pyrrolidone) (PVP), hexylene glycol (HG) and chitosan were made. The hydrogels were obtained by physical crosslinking of freezing and thawing, chemical crosslinking of irradiation, and irradiation after freezing and thawing of mixture solutions. The solid concentration of PVAL/PVP/HG/chitosan was 15 wt%. The concentration of chitosan was 0.3 wt%, and the ratio of PVAL/PVP was 6:4. The concentration of HG was in the range of 1∼5 wt%. The number of repeated freezing and thawing was in the range of 1∼3 times, and gamma irradiation doses were 25, 35 and 50 kGy. The physical properties such as gelation, water absorption and gel strength of hydrogels were examined. Gel content and gel strength decreased as HG concentration increased, whereas degree of swelling increased. Gel content and gel strength increased as irradiation dose and the number of freezing and thawing increased, whereas degree of swelling decreased. The hydrogels were evaluated for the healing effect for animals and for the antibacterial effect.

• Polymer(Korea)
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• v.34 no.5
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• pp.405-409
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• 2010

New sol-gel precursors having the ability to protect iron against corrosion were synthesized and used to prepare organic-inorganic hybrid coatings based on epoxy. Bisphenol A epoxy was modified with 3-isocyanatopropyltriethoxysilane to improve the compatibility, and water and HCl were used as catalysts for sol-gel process. Various coating formulations were prepared depending on the type of sol-gel precursors and the amount of each ingredient, and cast on iron substrates by dip-coating and thermally cured. Corrosion protection properties of coated iron were studied by a salt spray test and electrochemical impedance spectroscopy under 0.1 M NaCl electrolyte. Hybrid coatings containing anticorrosive functional group exhibited excellent corrosion protection on iron, compared to that of typical hybrid coatings. From electrochemical impedance spectroscopy, the hybrid coatings containing anticorrosive functional group could maintaine the initial impedance after 500 h, while the impedance of hybrid coatings without them started to decrease after 24 h.

• Polymer(Korea)
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• v.37 no.3
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• pp.387-392
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• 2013

The aim of this study was to investigate the effect of trasdermal delivery of the curcumin gel on healing of the rats' dorsum wounds. Carbopol 934 and propylene glycol were used to prepare gels containing 1% curcumin. Curcumin gel was evaluated for various properties such as antioxidant, cell viability, anti-inflammatory, in vivo wound healing. The free radical scavenging activity using 1,1-diphenyl-2-picryl hydrazyl (DPPH) was 50% at 12.5 ppm concentration. Inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells by curcumin gel. In the curcumin gel-treated group, the re-epithelialization in wounds was significantly increased compared to the control group throughout the experimental period. These results suggested that curcumin may be helpful for the promotion of wound healing.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.763-768
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• 2002

In this study, methyl methacrylate (MMA) - modified polymer mortar(MMPM) was developed and its setting shrinkage and working life properties were surveyed. In order to study the setting shrinkage, setting shrinkage test for the 24 batches were also conducted with taking the MMA monomer content to the UP resin and the mixed content of shrinkage reducing agent(SRA) as variables. Furthermore, in order to study the working life measured gel time, working time, setting time of MMPM and binder. Experimental resurts show that the workability remarkably improved as the mixed MMA content increased. The working life was proportional to MEKPO content and was shorted. also, showed high interrelationship of binder gel time and MMPM working life. Setting shrinkage markedly reduced as the content of MMA and the SRA increased.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.52-53
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• 2006

A new series of PEO-PPO-PEO and PPO-PEO-PPO copolymers having several hydroxyl groups on the PPO chain segment were synthesized, further modified with various poly(lactic acid) PLA oligomeric chains to confer physical stability after thermo-gelation in the body fluid. Gel stability was endowed by either increasing hydrophobic interaction between PLA chains or inducing stereocomplex formation between enatiomeric isomers of PLA chains. Macromolecular drugs were incorporated within the gels and their release patterns were investigated using Pluronic F127 as a control.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.308-308
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• 2006

We have demonstrated that the cylindrical micelles self-assembled from coil-rod-coil molecules can be interconnected by addition of a small amount of rod-coil-rod molecule as a bridging agent. Subsequently, these dynamic interconnections lead to stiff bundles composed of cylindrical micelles that are responsible for the formation of a reversible nematic gel. The results described here represent a significant example that dynamic bridging of supramolecular cylinders in aqueous solution can provide a useful strategy to construct one-dimensional nematic structure with three dimensional elastic properties.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.605-608
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• 2011

Hybrid composite membranes were prepared by coating poly(ethylene oxide) and $SiO_2$ particles onto the porous polypropylene nonwoven matrix. Gel polymer electrolytes prepared by soaking the hybrid composite membranes in an organic electrolyte solution exhibited ionic conductivities higher than $1.1{\times}10^{-3}Scm^{-1}$ at room temperature. Dyesensitized solar cell (DSSC) employing the hybrid composite membrane with PEO and 10 wt % $SiO_2$ exhibited an open circuit voltage of 0.77 V and a short circuit current of 10.78 $mAcm^{-2}$ at an incident light intensity of 100 $mWcm^{-2}$, yielding a conversion efficiency of 5.2%. DSSC employing the hybrid composite membrane showed more stable photovoltaic performance than that of the DSSC assembled with liquid electrolyte.