• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.318-318
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• 2006

4-Vinylbenzyl maltohexaoside peracetate, 1, was copolymerized with divinylbenzene using the initiator for nitroxide-mediated living radical polymerization, 2, to afford the polystyrene microgel with acetyl maltohexaose, 3. The deacetylation of 3 was achieved by treatment with sodium methoxide in dry 1,4-dioxane to produce the polystyrene microgel with maltohexaose, 4. A good coating property of the polystyrene microgel was combined with an excellent hydrophilic property derived from maltohexaose. In addition, 4 showed the ability to solubilize fullerene in aqueous solution. Therefore, 4 has a potential application as a special coating using functional but incompatible compounds such as fullerene on the surface of various hydrophilic materials.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.591-594
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• 1998

Biodegradable microsphere containing bovine serum albumine (BSA) as a model drug were prepared with the microgel based on poly(caprolactone diol) by a modified solvent evaporation method. The influence of the stirring speed, the concentration of microgel and the mixing rate but increased with increasing the concentration of microgel in methylene chloride. The biodegradability of microsphere in 100 unit/mL of lipase solution was investigated. A lot of small pores appeared on the surface of microsphere after 3 hours of incubation time and the pores and cracks were developed with increasing the incubation time and microsphere lost their own shape after 36 hours of incubation time.

• Elastomers and Composites
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• v.35 no.4
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• pp.281-287
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• 2000

Waterborne polyurethane(PU) microgel dispersions were synthesized with different mole ratio of polytetramethylene glycol(PTMG) to dimethylol propionic acid(DMPA). Particle size distribution, thermal and mechanical properties of the PU microgels were investigated. Particle size of the microgels was distributed in the range of $98{\sim}$680{\mu}m$ and decreased with increasing the mole ratio of DMPA and 1,2,6-hexanetriol. Glass transition temperature and melting temperature of the microgels were in the range of $-79.7 {\sim}-78.1^{\circ}C$, $22{\sim}24^{\circ}C$ respectively. Tensile strength and elongation of the PU microgel films were maximum in the case of 60/40 mole ratio of PTMG/DMPA.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1396-1400
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• 2007

In this study, poly(iso-butyl methacrylate-co-ethylene glycol dimethacrylate) [poly(iso-BMA-co-EGDMA)] microgel was prepared and used as a face powder additive. The spreading, adhesiveness, and skin reactivity of poly(iso-BMA-co-EGDMA) microgel-containing face powder II were investigated and compared with the same properties of commercially available Silica bead 700-containing face powder I. In the results, the particle size of the poly(iso-BMA-co-EGDMA) microgel was significantly swelled as a result of sebum absorption. Face powder II showed a lower primary irritation index and a higher adhesiveness than did face powder I. Face powder I showed a low sebum absorption ratio and a relatively high rate of sebum absorption, whereas face powder II, contrastingly, exhibited a high sebum absorption ratio and a low rate of sebum absorption, which properties would reduce the phenomena of facial strain and sliminess. These results indicate that poly(iso- BMA-co-EGDMA) microgel has outstanding sebum absorption characteristic and adhesiveness, and thus that it is a good candidate for use as a face powder additive.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.93-94
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• 2006

This lecture will present an overview of recent advances in our transition metal-mediated living radical polymerization, particularly focused on catalyst design and precision synthesis of functional polymers. Selected topics will include: (A) Design of Transition Metal Complexes: Evolution of Catalysts (B) New Ruthenium and Iron Catalysts: Active and Versatile (C) Functional Methacrylates for Advanced Functional Polymers (D) Functional Star Polymers: Microgel Cores for Metal Catalysts.

• Polymer(Korea)
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• v.37 no.6
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• pp.794-801
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• 2013

Novel microgels of N-isopropylacrylamide (NIPAM)-co-methacrylic acid (MAA) (NIPAM-co-MAA) with different contents of N,N-methylene bis acrylamide (MBA) were prepared by emulsion polymerization technique and were studied by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and zeta potential measurement. Effect of pH, temperature and different salts concentration on the microgel particles was investigated. DLS results have shown that the hydrodynamic radius of the microgel increased upon increasing pH and decreased upon increasing temperature. The swelling/deswelling behaviors as determined by DLS showed the ionic repulsions of the carboxyl group of the methacrylic acid and hydrophobic interaction of NIPAM. The effect of various salts on volume phase transition temperature (VPTT) was also investigated. Upon increasing salt concentration, VPTT became broad and shifted to a lower temperature. Electrophoretic mobility measurements showed an increase with increasing pH and temperature at a constant ionic strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.852-856
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• 2009

Poly(ethyleneglycol methacrylate-co-benzyl methacrylate) (P(PEGMA-co-BMA)) microgel was prepared by precipitation copolymerization of PEGMA and benzyl methacrylate in poly(acrylic acid)/ethanol solution. The microgels with various sizes were obtained by changing the concentration of poly(acrylic acid), monomer and nature of solvents. The particle size of P(PECMA-co-BMA) microgels was decreased with increasing the concentration of poly(acrylic acid) and increased with that of monomer. By increasing solubility parameter of solvents, the particle size was inecreased. The size of P(PEGMA-co-BMA) microgels was controlled by experimental conditions from $0.1{\mu}m$ to $0.35{\mu}m$.

• Polymer(Korea)
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• v.25 no.1
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• pp.41-48
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• 2001

Polyurethane(PU) microgels were synthesized from poly(caprolactone) diol(PCD) and/or poly(ethylene glycol)(PEG), diisocyanate and 1,2,6-hexane triol by solution polymerization method. A critical gelation concentration of the PU microgels with, mole ratios of PCD/PEG were the important factors influencing the formation and property microgel or macrogels. The physical and thermal properties of the PU microgels prepared with depending upon the structure of diisocyanate, mole ratio of PCD/PEG, and molecular weight of PEG were investigated. It was found that PU microgels were distributed by polydisperse, spherical small particles below 300nm and showed the properties of low viscosity.

• Polymer(Korea)
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• v.24 no.5
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• pp.599-609
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• 2000

In order to improve the mechanical properties of unsaturated polyester (UPE) resins, the UPE resins with different glycol molar ratios were prepared. The effects of molar ratios of the UPE resins on the curing behaviors and mechanical properties were investigated. The microgel reaction mechanism was employed to characterize the system. It was found that the final conversion increased with increasing NPG molar ratios, and the conversion at the peak of differential scanning calorimetry (DSC) thermogram appeared to decrease with increasing NPG molar ratios. The flexural strength, tensile modulus, water resistance, and infiltration increased with increasing NPG content, but the tensile strength, tensile elongation, and flexural modulus decreased. Among the UPE resins prepared from the glycols with the molar ratios (PG/NPG) of 0.5/0.5, 0.25/0.75, those of laminated composites plates showed better mechanical properties.

• Korea-Australia Rheology Journal
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• v.14 no.4
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• pp.189-201
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• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.