• Proceedings of the Membrane Society of Korea Conference
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• 2002.11a
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• pp.107-110
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• 2002

No Abstract, See Full Text

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1981-1984
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• 2006

Novel amphiphilic, thermo-responsive polyaspartamides which showed both LCST (lower critical solution temperature), and sol-gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized from polysuccinimide, the polycondensate of aspartic acid monomer, via successive nucleophilic ring-opening reaction by using dodecylamine and N-isopropylethylenediamine (NIPEDA). At the intermediate composition ranges, the dilute aqueous solution exhibited a thermally responsive phase separation due to the presence of LCST. The phase transition temperature was controllable by changing the content of pendent groups. In addition, a physical gelation, i.e. the sol-gel transition was observed from the concentrated solutions, which was elucidated by dynamic viscoelastic measurements. These novel injectable and thermo-responsive hydrogels have potential for various biomedical applications such as tissue engineering and current drug delivery system.

• Elastomers and Composites
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• v.28 no.3
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• pp.183-190
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• 1993

The radical copolymerization with propagation and depropagation is presented in order to estimate reactivity rate of monomers and $K_{11}$(the equilibrium constant for propagation and depropagation) in the copolymerization of ${\alpha}-methylstyrene-co-methylmethacrylate$ and ${\alpha}-methylstyrene-acrylonitrile$. The value of ${\alpha}-methylstyrene$ and methylmethacrylate and $K_{11}$ are found to be 0.48, 0.47 and 5.0 respectively. The value of ${\alpha}-methylstyrene$ and acrylonitrile and the $K_{11}$ are found to be 0.1251, 0.0577 and 23.8 respectively. The treatment rate constant of ${\alpha}-methylstyrene-co-methylmethacrylate$ and ${\alpha}-methylstyrene-co-acrylonitrile$ in the copolymerization is estimated to be 2.5, 80.72 regardless of monomer feed composition.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.213-217
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• 1986

A series of copolypeptides of glutamic acid and leucine have been synthesized by N-carboxy-${\alpha}$-amino acid anhydride procedure and cast to form injectable microparticulate monolithic devices in which indomethacin was physically dispersed. With these devices, various release properties and possible clinical application were studied. The release rate of the drug had a close relationship with the monomer composition of the copolymer matrix as well as the environmental pH condition. The monolithic device of glutamic acid/leucine = 50/50 was found to be the most promising one as a ploymeric delivery system of indomethacin. The intrinsic viscosity of this copolymer was 4.35 dl/g and the release rate was 18.5${\mu}g/g/day$.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.178-185
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• 1999

For the process control of silicon nitride gelcasting, the composition effect of acryamide system on the viscosity of slip and mechanical property of gelcast green body were investigated. The slip was prepared by ball milling of silicon nitride suspension prepared with acrylamide monomer and polyelectrolyte dispersant after premixing them by attritor. The slip mixed with initiator was vacuum deaired and cast into molds, and then polymerized. The consolidated green body was obtained by drying the gelated slip. The viscosity measument and the diametral compression test was done to evaluate the rheological behaviro of slip and mechanical property of gelcast body, respectively. Experimental results showed that the high solid loading of silicon nitride slip was obtained up to 46 vol% with a low viscosity. The mechanical property of gelcast body mainly increased with increasing the concentration of monomer. The gelcast body was machinable above the ∼3 MPa of tensile strength. The relative density of pressured-sintered body was 98.5% at 1760$^{\circ}C$, 3 h.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.313-322
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• 2004

Thick film photolithography is a new technology in that the lithography process such as exposure and development is applied to the conventional thick film process including screen-printing. In this research, low-temperature cofireable silver paste, which enabled the formation of thick film fine-line using photolithographic technology, was developed. The optimum composition for fine-line forming was studied by adjusting the amounts of silver powder, polymer and monomer, and the additional amount of photoinitiator, and then the effect of processing parameter such as exposing dose on the formation of fine-line was also tested. As the result, it was found that the ratio of polymer to monomer, silver powder loading, and the amount of photoinitiator were the main factors affecting the resolution of fine-line. The developed photosensitive silver paste was printed on low-temperature cofireable green sheet, then dried, exposed, developed in aqueous process, laminated, and fired. Results showed that the thick film fine-line under 20$\mu\textrm{m}$ width could be obtained after cofiring.

• KSBB Journal
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• v.11 no.5
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• pp.586-592
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• 1996

Poly(3-hydroxybutyric-co-3-hydroxyvaleric) acid(PHB/HV) copolymer synthesis by Pseudomonas sp. HJ from glucose and cosubstrate was investigated. Taxonomic analysis suggested that Pseudomonas sp. HJ was best marched to Pseudomonas picketti having 78.8% similarity. Pseudomonas sp. HJ produced PHB/HV copolymer containing 60.8 mol% HV and 44.9 mol% HV when supplied with hexadecane and propionic acid as a cosubstrate, respectively. The HV composition in PHB/HV copolymer was controlled by varying the concentration of hexadecane and propionic acid. Propionic acid added after 24 hours of incubation was incorporated as the HV monomer in the PHB/HV copolymer up to 49.6 mol%.

• Polymer(Korea)
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• v.26 no.4
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• pp.415-421
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• 2002

A sulfonated PP-g-styrene ion-exchange hollow fiber membrane was prepared by pre-irradiation method with E-beam followed by sulfonation reaction. Degree of grafting increased with the increase of styrene monomer concentration and showed the maximum value of 128% at 80% of styrene monomer composition. Sulfonation yield increased with the degree of grafting. At 100% degree of grafting, sulfonation yield showed the maximum value of 13.4%. Ion exchange capacity of sulfonated HPP-g-styrene of 3.42 meq/g was attained, resulting in the remarkable increase of adsorption ability BET analysis proved that the surface area of sulfonated HPP-g-styrene was 62.54 $m^2/g$ and the mean pore size was 25 $\AA$. From the BSA adsorption experiments, the adsorption amount of BSA was increased with sulfonation. At 13.4% sulfonation yield the adsorption amount of BSA was maximum as 3.8 mg/g. Sulfonated HPP-g-styrene was synthesized successfully and suitable for the adsorption and separation of BSA.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.287-293
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• 1983

Free radical-initiated copolymerizations of diethyl ${\alpha}$-phenylvinyl phospbate (DEPVP) with acrylonitrile (AN) and maleic anhydride (MAnh) were studied. The monomer reactivity ratios for AN/DEPVP pair, determined at $70^{\circ}C$ in bulk using benzoyl peroxide as an initiator, were;$ r_1(AN) = 0.77, r_2(DEPVP) = 0.002$. The values of the Alfrey-Price constants, Q and e, for DEPVP were calculated to be 0.012 and -1.35, respectively. Free radical-initiated copolymerization of MAnh/DEPVP pair in chloroform at $70^{\circ}C$ produced 1 : 1 alternating copolymers regardless monomer feed composition with the highest copolymerization rate at the molar ratio of MAnh : DEPVP = 7 : 3. The equilibrium constant of a charge-transfer complex between DEPVP and MAnh in deutrated chloroform, determinated at room temperature by transformed Benesi-Hildebrand NMR method, was 0.085 l/mol. The reduced viscosity of copolymers of AN/DEPVP pair decreased as the content of DEPVP units increased, while that of MAnh/DEPVP pair remained more or less constant.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.1-6
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• 2003

NiZn-ferrites were synthesized from the waste catalysts. which were by product of styrene monomer process and buried underground as an industrial wastes, and their magnetic properties were investigated. Nickel oxide and zinc oxide powders were mixed with finely ground waste catalysts, and spinel type ferrite was obtained by calcination at 900℃ and sintering at 1325℃ for 5 hours. The initial permeabilities were measured and reflection losses were calculated from S-parameters for the composition of Ni/sub x/Zn/sub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66) and (Ni/sub 0.5/Zn/sub 0.5)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02).