• Journal of Life Science
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• v.13 no.5
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• pp.712-717
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• 2003

In order to establish yeast cells that produce leucocin A, a bacteriocin, the 117 bp leucocin A gene with start and stop codons was synthesized and cloned in pAUR123, a yeast vector. Transformed yeast cells showed antibacterial activity against Bacillus subtilis. The leucocin A gene was confirmed by means of PCR methods with plasmid prepared from transformed yeast cells as template and two leucocin A-specific primers. In this results, yeast cells that produce mass amounts of bacteriocin to use as food preservative or antibiotics were established.

• Elastomers and Composites
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• v.47 no.1
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• pp.30-35
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• 2012

Novel bio-polybutadiene polymers with controlled molecular weight (MW), MW distribution, chemical composition and micro structure were synthesized by a living anionic polymerization of butadiene and the subsequent coupling reaction of the thus obtained living polybutadiene and a vegetable oil. Anionic polymerization of butadiene was carried out in THF solvent using n-BuLi initiator. The resulting living polybutadienyllithium polymer was then reacted with epoxidized soybean oil (ESO) to obtain a star-polymer of polybutadiene and vegitable oil. Three different bio-elastomers were prepared by coupling living polybutadienes of MWs 1000, 5000 and 1000g/mol with ESO. The molecular structure and MW of the polybutadienes and bioelastomers were characterized by $^1H$-NMR, FTIR and GPC techniques.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.463-467
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• 1975

The polymerization of methyl methacrylate(MMA) initiated by cobalt (II) nitrate in tetrahydrofuran (THF) has been studied. From the results of kinetic studies, the overall polymerization rate (Rp) could be expressed as following; $R_p=k\;[cobalt(Ⅱ)\;nitrate]^{0.5}\;[MMA]^{1.5}$ By considering the effects of chelating agent on the polymerization rate, it could be assumed that the monomer, MMA might form a coordination complex with cobalt(II) nitrate. In the presence of radical inhibitor hydroquinone, the inhibition time was observed. And the apparent overall activation energy was calculated to be 14.0 kcal/mole.

• Clean Technology
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• v.19 no.4
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• pp.393-400
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• 2013

In this study, Polyethylene wax, which was produced in manufacturing process of high density polyethylene was grafted with maleic anhydride (MAH). The influences of reaction parameters on the graft polymerization as well as the effect of hydrolysis of the anhydride functions were investigated. The results show that the grafting degree increased and conversion of maleic anhydride decreased with an increase in MAH monomer content. This means the highest grafting efficiency for the reaction can be met when MAH monomer content is about 15 wt%. DCP (dicumyl peroxide) and DTBP (di-tert-butyl peroxide) have been used as the initiator and the highest yield of grafting was obtained when the initiator content is about 0.5 wt%. However, It can be seen that the gel content values of this polyethylene wax grafted MAH were below 2%. It was also observed that the grafting degree increased with an increase in reaction temperature and the maximum value was reached 2 hours later. Although MAH functions grafted onto polyethylene wax were mainly in the carboxylic acid forms, some anhydride form of MAH appeared in over 5% of grafting degree. As a result of hydrolysis reaction, it was observed that the conversion of anhydride group into carboxylic acid group was reached up to 10%.

• Journal of the Korean Chemical Society
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• v.21 no.3
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• pp.219-224
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• 1977

The free radical initiated copolymerization of vinyl acetate (VAc) and bis(${\beta}$-chloroethyl)vinylphosphonate (BCVP) was studied. The monomer reactivity ratios for the monomer pair determined at $50^{\circ{C$ using benzoyl peroxide as an initiator are: $r_1 (VAc) = 0.33,\;r_2 (BCVP) = 0.47$ The values of Alfrey-Price's Q and e for the bis(${\beta}$-chloroethyl)vinylphosphonate were calculated to be 0.06 and 1.1, respectively. The statistical analyses for the monomer sequence distribution and the mean sequence length show that the copolymer formed from these two monomers are of fairly alternating tendency. Differential thermal analysis showed that thermal stability of the copolymers decreases as the content of BCVP in the copolymer increases.

• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.235-246
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• 1982

The free radical polymerization and copolymerization of N-acetyl ${\alpha}$-aminoacrylic acid were investigated. From the result of kinetic investigation of N-acetyl ${\alpha}$-aminoacrylic acid in DMF at $60^{\circ}C$, a rate equation of $R_p$ = $k_p[M]^{0.97}[I]^{0.59}$ was obtained. The overall activation energy for the polymerization was found to be 25.2 kcal/mole. Copolymerization of N-acetyl ${\alpha}$-aminoacrylic acid with acrylic acid and styrene was carried out for the determination of monomer reactivity ratios. The monomer reactivity ratios for the monomer pairs determined at 70.0{\pm}0.1^{\circ}C$ using benzoyl peroxide as an initiator are; $r_1$(N-acetyl ${\alpha}$-aminoacrylic acid) = 0.49, $r_2$(acrylic acid) = 1.41, $r_1$(N-acetyl ${\alpha}$-aminoacrylic acid) = 0.44, $r_2$(styrene) = 0.91. The values of Alfrey-Price's Q and e parameters for N-acetyl ${\alpha}$-aminoacrylic acid were calculated to be 0.51 and 0.16 for the both systems. Differential thermal analysis and thermogravimetry showed that acrylic acid copolymers have poorer thermal stability as compared with the homopolymer of N-acetyl ${\alpha}$-aminoacrylic acid.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.345-350
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• 2008

Polymer Impregnated Concrete (PIC) prepared from Ordinary Portland Cement Concrete (OPC) has excellent mechanical properties as well as physico-chemical properties. For the manufacturing of PIC, drying process of basis concrete (precast concrete), impregnation process with evacuation system and ultrasonic vibration system, polymerization process of monomers are essential. Modified microwave reactor using magnetron was used for polymerization of styrene/MMA (1 : 1) impregnated in pore volume of basis concrete. From the experimental results, the degree of polymerization increased up to 30% and more homogeneous PIC was prepared as compared to the conventional thermal method. Also the mechanical strengths increased more than 400% ($800{\sim}1200kg_f/cm^2$) and the resistance for corrosion to acids was improved up to 25%. AIBN and BPO as initiators for polymerization were used at the concentration less than 1%. Optimum conditions for polymerization were obtained at the frequency of microwave of 400 W and 2450 MHz, and optimum reaction temperature was $120^{\circ}C$ at an atmospheric pressure.

• Elastomers and Composites
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• v.36 no.4
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• pp.225-236
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• 2001

In order to improve the properties of the copolymer and the terpolymer that was used as removal-type pressure sensitive adhesive(PSA), we synthesized quaterpolymer with the variation of the types of monomer, initiator, and solvent, and concentration, the monomer/solvent ratio, reaction temperature and time. and determined the properties of this adhesive: the viscosity, molecular weight, conversion, solid content and structure of polymer. The prepared polymer was crosslinked by changing the type of crosslinking agent and concentration, and then we investigated the characteristics or adhesive such as peel adhesion, shear adhesion, heat resistance, weathering resistance and peel adhesion to aging. The optimum performance of RA/2- EHA/MMA/2-HEMA as a PSA were obtained when benzoyl peroxide was used as an initiator with the reactant mixture consisted of 80% BA and 2-EHA, 15%, MMA, and 5% 2-HFMA. The optimum reaction temperature and time were $80^{\circ}C$ and 8 hours, respectively. For BA/2-EHA/MMA/AA, the optimum performance was obtained when the polymerization was performed at the monomer composition of 80% BA/2-EHA, 15% MMA, and 5% AA. BPO was used as initiator and the optimum reaction temperature and time were identical to those of BA/2-EHA/MMA/ 2-HEMA. Isocyanate and melamine were used to crosslink BA/2-EHA/MMA/2-HEMA and BA/2-EHA/MMA/AA, respectively. No effect on the type of cross-linking agent on the peel adhesion was observed with aging. The quarterpolymers crosslinked with melamine left residues on the counter surface after weathering resistance test, while the polymers crosslinked with isocyanate did not.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.343-348
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• 2010

The surface of low density polyethylene (LDPE) film was oxyfluorinated under different reaction conditions to introduce hydroperoxide groups and change surface characteristics. Hydroperoxide functional groups created by oxyfluorination were used as active sites for graft polymerization with hydrophobic monomer, acryl amide (AM), and hydrophilic monomer, methyl methacrylate (MMA) to carry out the second modification of the LDPE film surface. The surface properties of the OFPE films and grafted OFPE films were characterized by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, ATR-IR, contact angle measurement and DSC. From the results of DPPH method, the amount of hydroperoxide groups on the oxyfluorinated LDPE film continuously increased as the total pressure in the oxyfluorination and the partial pressure of fluorine gas increased. The water contact angle and surface free energy measurements showed that hydrophilic liquid (water) contact angle on LDPE film surface decreased with hydrophilic AM grafting and hydrophobic liquid (methylene diiodide) contact angle on LDPE film surface decreased with hydrophobic MMA grafting. These were attributed to AM or MMA monomer grafting and the wettability of LDPE filmsurface to hydrophilic and hydrophobic liquids were improved.

• Polymer(Korea)
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• v.31 no.4
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• pp.322-328
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• 2007

Mono-dispersed polyamide 6(Nylon 6) micro-particles sized in $4{\sim}5\;{\mu}m$ diameter were prepared by dispersion polymerization of ${\varepsilon}-caprolactam$ in liquid paraffin as a dispersion medium. Potassium metal(K) as a catalyst was separately added twice over the anionic ring-opening polymerization of ${\varepsilon}-caprolactam$. The size, shape, and size-distribution of prepared particles were varied with the concentration of anti-coagulant as well as the amount of initiator and catalyst. As the initiator concentration was in the range of $0.97{\sim}1.17\;wt%$ in monomer, about 90.6% of yield was accomplished. In addition, the highest yield of well-spherically shaped micro-particles was achieved by adding about $1.3{\sim}1.4\;wt%$ of catalyst.