• Macromolecular Research
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• v.13 no.1
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• pp.45-53
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• 2005

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacryl­amide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylenebis­acrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g­PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-poly­methacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the Alg-g-PMAM or the H-Alg-g-PMAM was characterized by FTIR spectroscopy. The effects of the grafting variables (i.e., concentration of MBA, MAM, and APS) and the alkaline hydrolysis conditions (i.e., NaOH concentration, hydrolysis time, and temperature) were optimized systematically to achieve a hydrogel having the maximum swelling capacity. Measurements of the absorbency in various aqueous salt solutions indicated that the swelling capacity decreased upon increasing the ionic strength of the swelling medium. This behavior could be attributed to a charge screening effect for monovalent cations, as well as ionic cross-linking for multivalent cations. Because of the high swelling capacity in salt solutions, however, the hydrogels might be considered as anti-salt superabsorbents. The swelling behavior of the superabsorbing hydrogels was also measured in solutions having values of pH ranging from 1 to 13. Furthermore, the pH reversibility and on/off switching behavior, measured at pH 2.0 and 8.0, suggested that the synthesized hydrogels were excellent candidates for the controlled delivery of bioactive agents. Finally, we performed preliminary investigations of the swelling kinetics of the synthesized hydrogels at various particle sizes.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.55-55
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• 2003

P2X$_3$ receptor, a member of P2 purine receptors, is a ligand-gated ion channel activated by extracellular ATP as an endogenous ligand, and highly localized in peripheral and central sensory neurons. The activation of P2X3 receptor by ATP as the pronociceptive effect has been known to initiate the pain signaling involved in chronic inflammatory nociception and neuropathic pain by nerve injury, implicating the possibility of new drug development to control pains. In this study, we have developed a two electrode voltage clamp (TEVC) assay system to evaluate the inhibitory activity of several newly synthesized PPADS and a novel non-ionic antagonist against ATP activation of human P2X3 receptor. PPADS derivatives include several pyridoxine and pyridoxic acid analogs to study the effects of phosphate and aldehyde functional groups in PPADS. All new PPADS analogs were less potent than PPADS at human P2X$_3$ receptors, however, LDD130, a non-ionic analog showed potent antagonistic property with $IC_{50}$/ of 8.34 pM. In order to uncover the structure activity relationships of LDD130, and design new structural analogs, we synthesized and investigated a few structural variants of LDD130, and the results will be discussed in this presentation.

• Journal of Environmental Science International
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• v.14 no.6
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• pp.525-532
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• 2005

Polyelectrolyte titration, which was called colloid titration is based on the stoichiometric reaction between oppositely charged polyelectrolytes, This can be used, for instance, to determine the charge density of a cationic polyelectrolyte, using an anionic polyelectrolyte of known charge density, such as potassium polyvinyl sulfate (PPVS). The technique requires a suitable method of end-point detection and there are several possibilities. In this work, two methods have been investigated: visual titrimetry based on the color change of a cationic dye (o-toluidine blue, o-Tb) and spectrophotometry based on the absorbance change corresponding to the color change of the same dye. These have been applied to several cationic polyelectrolytes with different charge density and molecular weight. In all cases, the cationic charge was due to quaternary nitrogen groups. In the case of cationic dye, it was shown that the sharpness depends on the charge density of cationic polyelectrolyte. With the polyelectrolytes of lower charge density, the binding to PPVS is weaker and binding of the dye to PPVS can occur before all of the polyelectrolyte charge has been neutralized. However, by carrying out titrations at several polyelectrolyte concentrations, good linear relationships were found, from which reliable charge density values could be derived. Effects of pH and ionic strength were also briefly investigated. For cationic polyelectrolytes (copolymers of acrylamide and dimethylaminoethy] acrylate), there was some loss of charge at higher pH values, probably as a result of hydrolysis. Increasing ionic strength causes a less distinct color change of o-Tb, as a result of weaker electrostatic interactions.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.128-135
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• 2021

In this study, the acid polyols containing acid groups were synthesized, the novel polyurethane adhesive was developed by introducing the acid polyol by content. The acid polyols were introduced, the mechanical properties showed the maximum value when the acid content was 0.1 to 0.3 wt%, and it was confirmed that the mechanical properties and adhesive strength decreased at the content higher than 0.5 wt%. As the acid group, carboxylic acid and sulfuric acid were introduced to compare properties, and carboxylic acid showed stronger hydrogen bonding potential than sulfuric acid and improved mechanical properties. In addition, the correlation between particle size and mechanical properties was confirmed by introducing ZnO and CaCO₃. When ZnO and CaCO₃ were introduced, an ionic bond was formed with an acid group, and it was confirmed that mechanical properties were increased.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.371-378
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• 2021

The formation of hydrophilic surface based on polymers has received great attention due to the anti-adhesion of bacteria on solid substrates. Anti-adhesion coatings are aimed at suppressing the initial step of biofilm formation via non-cytotoxic mechanisms, and surfaces applied hydrophilic or ionic polymers showed the anti-adhesion effect for bioentities, such as proteins and bacteria. This is attributed to the formation of surface barrier from hydration layers, repulsions and osmotic stresses from polymer brushes, and electrostatic interactions between ionic polymers and cell surfaces. The antifouling polymer coating is usually fabricated by the grafting method through the bonding with functional groups on surfaces and the deposition method utilizing biomimetic anchors. This mini-review is a summary of representative antifouling polymers, coating strategies, and antibacterial efficacy. Furthermore, we will discuss consideration on the large area surface coating for application to public facilities and industry.

• Fibers and Polymers
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• v.7 no.4
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• pp.339-343
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• 2006

The aim of this paper is to improve moisture regain of PET fabrics using a lipase treatment. Effects of nine lipase sources, lipase activator and nonionic surfactant on moisture regain of PET fabrics are examined. Moisture regains of lipase-treated samples improve by two times in average compared with untreated and buffer-treated samples. Alkaline treatment creates larger pitting by more aggressive attack into fiber which is proved by SEM and water contact angle measurement. Moisture regain by alkaline treatment ($0.568%{\pm}0.08$) does not improve. However, lipase-treatment (L2 treatment) improves moisture regain up to 2.4 times ($1.272%{\pm}0.05$). Although lipase treatment is more moderate than alkaline treatment, lipase hydrolysis on PET fabrics improves moisture regain, efficiently. K/S values improved confirm that carboxyl and hydroxyl groups are produced on the surface of PET fabrics by lipase hydrolysis. Moisture regain and dyeability improve by lipase hydrolysis on PET fabrics.

• Textile Coloration and Finishing
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• v.20 no.2
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• pp.38-46
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• 2008

PET fabrics were cationized via photografting under continuous UV irradiation with a cationic monomer. The grafted PET was dyed with three acid dyes. Effect of dye concentration, dyeing time, temperature and pH on acidic dyeing of the cationized PET fabrics was assessed to find optimal dyeing condition. The cationized fabrics was successfully dyed at $75^{\circ}C$ under pH 5.5. However the dyeing sites of the grafted fabrics were nearly occupied above 5%owf dye concentration and the rapid exhaustion of the anionic dyes was observed. The dyeability of the cationized PET fabrics was increased proportionally with increasing percent grafting because of the introduction of ionic attraction between quaternary ammonium groups and acid dyes. Lower dyeability both at alkaline and pH 3 condition attributed to negative zeta potentials of the grafted fabrics and the reduced charge of the acid dyes respectively.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.89-89
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• 2006

Polyalkylene phosphates - polymers that are built on the repeating unit of the diester of phosphoric acid: -[OP(O)(OH)Oalkylene]-, are known to form backbones of nucleic and teichoic acids. Various synthetic ways will be reported for the synthesis of the bare chains, where "alkylene" in the formula above means mostly two or three methylene groups. Some other structures have also been prepared. Several applications of these polymers are to be discussed, namely as liquid membranes, as components of two-block copolymers (ionic-nonionic diblock dihydrophilic) used as modifiers of CaCO3 crystallization, and as components of the inorganic-polymer hybrid materials. Some other applications in the biomedical field will also be discussed.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.302-302
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• 2006

Nanoaggregates of triple hydrophilic block copolymers comprised of poly(ethylene oxide), poly(sodium 2-acrylamido)-2-methylpropanesulfonate), and poly(methacrylic acid) (PEO-PAMPS-PMAA) and the cationic surfactant, dodecyltrimethylammonium chloride (DTAC) have been fabricated. The formation of $^{\circ}^{\circ}$the nanoaggregates is based on electrostatic interaction of sulfonate and carboxylate groups of PAMPS and PMAA blocks with the cationic surfactant, which results in insolubilization of these blocks. The formation of micelle is observed by dynamic light scattering measurements. Binding of DTAC to the anionic blocks of PEO-PAMPS-PMAA is confirmed by electrophoresis measurements.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.271-271
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• 2006

The present article describes a novel method of preparing the sulfonated polysulfone-based PEMs for DMFC, which are excellent in film quality, proton conductivity, methanol impermeability and mechanical properties. No depression in film quality or difficulty in film preparation is observed, even though sulfonated group of the PEMs are kept as high as 70 mol %. Allyl-terminated cooligo-PESs containing the organic sulfonate groups were solvent-cast into films and then thermally treated for cross-linking. Cross-linked sulfonated polysulfone-based PEMs gave unprecedented reduction of methanol cross-over and high ionic conductivity through in-situ thermal polymerization and cross-linking of telechelic sulfonated sulfone oligomers during a membrane preparation.