• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.197-204
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• 1992

The cationic polymerization of cyclic acetals are investigated theoretically using the semiempirical MINDO/3, MNDO, and $AM_1$, methods. The nucleophilicity and basicity of cyclic acetals can be explained by the negative charge on oxygen atom of cyclic acetals. The reactivity of propagation in the polymerization of cyclic acetals can be represented by the positive charge on $C_2$ atom and the low LUMO energy of active species of cyclic acetals. The reactivity of 2-buthyl-1,3-dioxepane(2-Bu-DOP) of cyclic oxonium and opening carbenium ion form is expected computational stability of the oxonium ion by 5${\sim}$7kcal/mole favoring the carbenium ion. Owing to the rapid equilibrium of these cation forms and the reaction coordinate based on calculation that the reaction coordinate based on calculation that the chain growth $S_N1$ mechanism will be at least as fast as that for $S_N2$ mechanism.

• Applied Biological Chemistry
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• v.47 no.4
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• pp.384-389
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• 2004

The purified ${\beta}-mannanase$ hydrolyzed various gums to mannose, ${\beta}-1,4-mannobiose$, $Gal^3Man_4$, and D.P 7 of galactosyl mannooligosaccharide, and isolated from the enzymatic hydrolysate for 24 hrs reaction by activated carbon column chromatography and Sephadex G-25 column chromatography. For the elucidate of antioxidant action of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ and DP 7 of galactosyl mannooligosaccharide and urea derivatives, coloration, reducing power, antioxidant activity and DPPH test were accomplished. The coloration was high at reaction mixture of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ D.P 7 and urea. TLC of reaction mixture of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ D.P 7 and ureas showed new reaction products, respectively. but except reaction mixture of ${\beta}-1,4-mannobiose$ and urea. The reducing power was high at reaction mixture of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ D.P 7 and phenylthiourea. The reaction mixture of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ D.P 7 and thiourea showed similar radical scavenging activities on DPPH to activity of AsA. The reaction mixture of ${\beta}-1,4-mannobiose$, $Gal^3Man_4$ D.P 7 and thiourea, phenythiolurea shown strong antioxidative activites on the oxidation of linoneic acid.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.764-771
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• 1994

Electrochemical synthesis of conductive polypyrrole films was carried out in nucleophilic solvent containing p-toluenesulfonic acid or bezensulfonic acid as supporting electrolyte and dopant. Also characteristics of degradation and improvement of mechanical properties were studied. The conductivity, tensile strength and elongation of the films obtained in dimethyformamide/p-toluenesulfonic acid had the highest value of 10-40S/cm, $25N/mm^2$ and 10%, respectively. The optimum condition of electrochemical synthesis was $2mA/cm^2$ for constant current method and 0.9V for constant potential method containing 0.5M pyrrole and 0.5M p-TSA. The obtained films showed good stability in air and electrode characteristics of secondary battery by reversibility in doping and undoping. The degradation process was 1st order reaction at various temeprature. The activation energy and rate constant of degradation reaction were $1.01JK^{-1}mol^{-1}$ and $3.1{\times}10^{-7}min^{-1}$ respectively at $25^{\circ}C$. For the improvement of mechanical properties, composition of polypyrrole films with various host polymer were investigated and increase of tensile strength and elongation was confirmed.

• Polymer(Korea)
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• v.25 no.1
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• pp.6-14
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• 2001

The monomer N,N'-bis(3-pyrrol-1-yl-propyl)-4,4'-bipyridinium$(PF_6)_2$ was electrochemically polymerized on glassy carbon electrode surface. This polymer film electrode has electroactive sites on its bipyridinium ions distributed at the polymer strands. The formal potentials of the electrodes were -0.41V and -0.81V(vs. SSCE) for each step at phosphate buffer(pH=5.70). The diffusion coefficients of the dopants ions into the polymer matrix were $1.57{\times}10^{-4}$ and $4.35{\times}10^{-5}cm^2s^{-1}$ for first and second redox couple, respectively. The rate constants of electron transfer at $V^{2+/+}$ of the first step was a $57.53s^{-1}$, which was 22 times higher than $V^{+/0}$ one having $2.63s^{-1}$ in the solution. The charge transfer resistance of the polymer film was influenced by the dopant ion of the electrolyte. Thus the resistances were 22.63, 16.81, 12.44 and $11.36k{\Omega}$ for $LiClO_4,\;NaClO_4,\;KClO_4$, and phosphate buffer, respectively. The reaction order of the electropolymerization was first order and the rate constant of the polymerization was $1.31{\times}10^{-1}s^{-1}$ as determined by EQCM method. The G.C./p-BPB type electrode doped with phosphate ions showed a stability and reproducibility in CV procedure over 20 cycles.

• Polymer(Korea)
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• v.25 no.5
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• pp.736-743
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• 2001

An electro- active polymer (EAP) (poly(2-acrylamido-2- methyl propane sulfonic acid), PAMPS) gel crosslinked with N,N-methylenebisacrylamide (MBAA) has been prepared by free radical polymerization in aqueous solution with potassium persulfate as initiator PAMPS gel was swollen in surfactant solution to substitute surfactant for using as actuator. PAMPS gel showed a large movement in the surfactant solution by electric field. PAMPS gel showed the reversible binding and fast response rate. Bending mechanism of gel is related to the cooperative process of hydrophobic interaction, swelling-deswelling of gel and the electrostatic attraction between anode (+) and the anions of PAMPS gel. The response rate of PAMPS gel was increased as the applied potential and the degree of cross-linkage were increased. The response rate was increased as the bending cycle was repeated, but it was decreased with increasing the gel thickness.

• Elastomers and Composites
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• v.42 no.1
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• pp.47-54
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• 2007

Reaction kinetics of polyurethane elastomers (PU) were studied using dynamic DSC and TGA for three PU samples of general purpose (Sample A), high temperature cross-likable CASE purpose with MOCA (Sample B), and RT cross-likable CASE purpose grade (Sample C). From DSC results, sample with MOCA(Sample B) showed lower shift of peak temperature, while showing broader thermograms than those of general purpose grade (Sample A). On the other hand, RT cross-linkable PU grade (Sample C) showed an interesting double mode reaction patterns, i.e., a lower temperature reaction at about $70\;^{\circ}C$, and a higher temperature reaction in the range of $140{\sim}170\;^{\circ}C$, indicating that it requires 2-step reaction process in order to complete the reaction. Once the cross-linking reaction completed, however, TGA results showed that all the samples would be considered to have similar chemical structures, showing similar decomposition processes. Sample C, especially, had showed decomposition properties of both Sample A and Sample B. Formation activation energies calculated from Kissinger method showed 10.39, 65.85, 36.52(Low $T_p$) and 18.21(High $T_p$) kcal/mol, while decomposition activation energies were 31.94, 30.84, 24.16 kcal/mol, respectively.

• Elastomers and Composites
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• v.38 no.4
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• pp.303-315
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• 2003

Inorganic/organic composite particles were also synthesized by changing an initiator an it's concentration, concentration of an adsorbed surfactant, reaction temperature, and agitation speed in the presence of $CaCO_3$ adsorbed SDBS. The polymerization conditions were optimized according to the conversion of the core-shell composite particles. In the inorganic/organic core-shell composite particle polymerization, $CaCO_3$ absorbed surfactant SDBS of 0.5 wt % was prepared first and then core $CaCO_3$ was encapsulated by sequential emulsion polymerization using MMA, concentration of APS $3.16{\times}10^{-3}mol/L$ to minimize the formation of new PMMA particle during MMA shell polymerization. The structure characterization of the inorganic/organic core-shell particles was verified by measuring the decomposition degree of $CaCO_3$ using HCl solution. It was found that $CaCO_3$ was encapsulated by shell PMMA due to having excellent dispersion in the epoxy resin, smooth surface distinctly from spindle shape, and broad particle distribution after the capsulation.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.296-302
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• 2024

An ionic conjugated polymer-iron (III) chloride composite was prepared via in-situ quaternization polymerization of 2-ethynylpyridine (2EP) using iron (III) chloride. Various instrumental methods revealed that the chemical structure of the resulting conjugated polymer (P2EP)-iron (III) chloride composite has the conjugated backbone system having the designed pyridinium ferric chloride complexes. The polymerization mechanism was assumed to be that the activated triple bond of 2-ethynylpyridinium salt, formed at the first reaction step, is easily susceptible to the step-wise polymerization, followed by the same propagation step that contains the propagating macroanion and monomeric 2-ethynylpyridinium salts. The electro-optical and electrochemical properties of the P2EP-FeCl₃ composite were studied. In the UV-visible spectra of P2EP-FeCl₃ composite, the absorption maximum values were 480 nm and 533 nm, and the PL maximum value was 598 nm. The cyclic voltammograms of the P2EP-FeCl₃ composite exhibited irreversible electrochemical behavior between the oxidation and reduction peaks. The kinetics of the redox process of composites were found to be very close to a diffusion-controlled process from the plot of the oxidation current density versus the scan rate.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.796-803
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• 1999

Solution copolymerization of styrene(St.) with methyl methacrylate(MMA), ethyl methacrylate(EMA) and n-butyl methacrylate(BMA) was carried out with benzoylperoxide(BPO) as an initiator in toluene at $80^{\circ}C$ in a continuous stirred tank reactor. Reaction volume and residence time were 0.6 liters and 3hours, respectively. The monomer reactivity ratios, $r_1(St.)$ and $r_2(RMA)$ determined by both the Kelen-Tudos method and the Fineman-Ross method were $r_1(St.)=0.60(0.61),\;r_2(MMA)=0.59(0.60);\;r_1(St.)=0.65(0.62),\;r_2(EMA)=0.55(0.52);\;r_1(St.)=0.75(0.67),\;r_2(BMA)=0.63(0.56)$. The cross-termination factor $\Phi$ of the copolymer over the entire St. compositions ranged from 0.26 to 0.96. The $\Phi$ factors of St.-RMA copolymer were increased with increasing St. content. The simulated conversions and copolymerization rates were compared with the experimental results. The average time to reach dynamic steady-state was three times and half of the residence time.

• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.141-145
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• 2000

Anodically Polymerized conducting Polypyrrole film electrode was employed to Pick up uranyl ion with the type of Gr/ppy, xylenol orange modified electrode. To have Porous and oriented ppy film, NBR was applied as precoating agent. The rate constant of polymerization was $3.22\times10^{-3}s^{-1}$ which was 1.6 times smaller value than bare graphite surface. The deposited amount of uranyl iou on $1.70Ccm^{-2}$ of ppy was $1.55\times10^{-4}g$. The matrix effect in artificial seawater was $6.8\%$. The polymer film electrode has a diffusion controlled process in conduction, but the modified Gr/ppy, $X.O^{4-}UO^+$ type was influenced on the ion doping and electronic conduction of film itself owing to increasing of impedance. The capacitance of electrical double layer was respectively enhanced to 56 and 130 times in Gr/ppy, $X.O.^{4-}$ and Gr/ppy, $X.O^{4-}UO^+$ than Grippy type electrode.