• Membrane Journal
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• v.8 no.4
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• pp.210-219
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• 1998

Sulfonated poly(ether sulfone)(SPES) of various ion exchange capacity (IEC) was prepared by heterogeneous sulfonation with chlorosulfonic acid (CSA) to make hydrophilic ultrafiltration membrane for reducing fouling. The effects of CSA concentration, reaction temperature and reaction time has been investigated. The reaction was effective when the temperature is above 10$\circ$C and the CSA concentration is over 0.05 mol, although polymer chain has been significantly degraded. The substitution of sulfonic acid groups was characterized by FTIR and $^1$H-NMR. Transport properties and fouling test have been conducted to the modified SPES ultrafiltration rnembranrs by heterogeneors method. Membranes were obtained using DCM and PVP as a non-solvent and pore forming agent, respectively. Flux reduced and rejection increased with ion exchange capacity. Finger-like structure was disappeared and the thickness of top layer was increased. Dense membrane by non-solvent DCM and porous membrane by pore forming agent PVP was prepared. Fouling was reduced with increasing ion exchange capacity because of hydrophilicity.

• Fibers and Polymers
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• v.5 no.4
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• pp.253-258
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• 2004

Living nature of photoinduced cationic polymerization of isobutyl vinyl ether (IBVE) in the presence of various combinations of diphenyliodonium halide (DPIX), a photocationic initiator and zinc halide $(ZnX_2)$ in methylene chloride has been investigated. Attainment of $100\%$ conversion and a linear relationship between $\%$conversion and number average molar mass of the resulting polymer, strongly suggests the living nature of this system. Livingness of the polymerization system was observed irrespective to the type of halide anion of the initiator and zinc salts unless the reaction temperature is not higher than $-30^{\circ}C$. The rate of polymerization decreases in the order of iodide > bromide > chloride when halide salt of DPIX and $ZnX_2$ are used. It is postulated that the cationic initiation is started by the insertion of weakly basic monomer in to the activated C-X terminal of the monomer adduct which is a reaction product of monomer and HX, a photolytic product of DPIX, formed in situ during the photo-irradiation process. It was concluded that polymerization is initiated by the insertion of weakly basic monomer into activated C- X terminal of monomer adduct due to the pulling action of$ZnX_2$, which successively producing a new polarized C-X terminal for the propagation in cationic nature. This led us to a conclusion that the living nature of this cationic polymerization is ascribable to the polarized C-X growing terminal, which is stable enough to depress the processes of chain transfer or termination process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.2005-2014
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• 2009

There are several methods to fabricate Polymer Dispersed Liquid Crystal(PDLC) films. One of them, so-called Nematic Curvilinear Aligned Phase(NCAP) film, is based on emulsion technology. To produce NCAP systems various water soluble polymers, such as partially hydrolyzed polyvinylalcohol(PVA) and polyvinyl pyrrolidone(PVP), which can form stable emulsion of liquid crystal(LC) without any stabilizers were used. In this work, we studied the dependence of emulsion stability on nature and composition of copolymers composed of water-soluble and water-insoluble moiety. We found that interfacial surface tension depends on the composition of comonomer, the copolymer concentration in the water, and the nature of hydrophobic chain. The Acrylamide -styrene(AA-ST) copolymer showed the lowest interfacial surface tension among the tested copolymers at the same concentration. Since the interfacial surface tension decreases with increasing the compatibility of copolymer with LC phase the AA-ST copolymer has the best compatibility with LC molecules. It is believed that molecules adsorbing easily on the surface of LC droplets allows the LC emulsion system to be more stable.

• Membrane Journal
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• v.25 no.6
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• pp.515-523
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• 2015

While commercial polystyrene-based ion exchange membranes have simple manufacturing processes, they also possess poor durability due to their brittleness. Poly(ethylene glycol)methyl ether methacrylate with hydrophilic side chains of poly(ethylene glycol) was used as a co-monomer to make the membranes have improved flexibility. Hydrophilicity/hydrophobicity of the anion exchange membranes were able to be adjusted by varying the chain lengths of the poly(ethylene glycol). For the preparation of the anion exchange membranes, a porous PE substrate was immersed into monomer solutions and thermally polymerized. The prepared membranes were subsequently reacted with trimethylamine to produce anion exchange functional groups, Quaternary ammonium salts. The prepared pore-filled anion exchange membranes were evaluated in terms of ion exchange capacity, electric resistance, elongation at break and water uptake.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.372-382
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• 2022

In this study, anion exchange membranes were prepared by synthesizing the main chain into a poly(arylene ether) (PAE) structure, and the structures capable of improving the physical and chemical stability of the membrane by introducing a heterocyclic quaternary ammonium functional groups were studied. The chemical structure and thermal properties of the prepared polymer were confirmed by ¹H-NMR, FT-IR, TGA, and DSC, and surface analysis was performed through AFM measurement. Additionally, dimensional stability and chemical properties was studied by measuring water uptake and swelling ratio, IEC and ionic conductivity. At 90℃, the quaternized poly(arylene ether) (QPAE)/1-methylpiperidine (MP) membrane exhibited the highest ionic conductivity of 27.2 mS cm^-1, while the QPAE/1-methylimidazole (MI) membrane and QPAE/1-methylmorpholine (MM) membrane exhibited values of 14.5 mS cm^-1 and 11.5 mS cm^-1, respectively. In addition, the prepared anion exchange membrane exhibited high chemical stability in alkaline solution.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.595-604
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• 1992

Carbonate-type polyurethane resins containing anionic moieties were systhesized from NCO-terminated prepolymer method. Membranes were manufactured from the polymer solution and the separation of aqueous ethanol solution was investigated. To enhance the property of urethane resin, carbonate-type polyol(PTMCG) was used. ${\alpha}^{\prime},{\alpha}^{{\prime}{\prime}}$-dimethylolpropionic acid was used as a chain extender to increase the hydrophilicily of the urethane membrane. The ionization of the pendent carboxylic groups in urethane resin was carried out using trimthylamine. To confirm the formation of anionic groups in urethane resin, IR spectra of model compounds were compared with those of urethane resins. It was confirmed that the concentration of hard segment and hydrogen bond contributed to the property of the concentration of hard segment and hydrogen bond contributed to the property of urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to 5:1. The carbonate-type polyurethane containing pendent carboxylic grop(PU) had Tg of around-$25^{\circ}C$ and Tm, $45^{\circ}C$ measured by DSC. Transition temperatures of one containing pendent anionic group(APU) prepared from the ionization of PU shifted to $8{\sim}10^{\circ}C$ lower temperature region than those of PU. Pervaporation membrane was prepared through the casting method. N, N-dimethylformamide (DMF) were used as a solvent and hexamethylene diisocyanate(HMDl) as a crosslinking agent. Swelling degree increased with ethanol concentration in mixure and the control of the swelling degree of the membrane could be achieved by crossliking. The results of pervaporation were as follows : separation factor, 2.3~9.8 ; flux, $27{\sim}79.5g/m^2hr$. Pervaporation separation capacity could be enhanced by reducing the molecular weight of polyol from 2,000 to 1,000.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.129-134
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• 1999

This study is related to the investigation of the direct incorporation of $CO_2$ to polymer using quaternary ammonium salt catalysts. Quaternary ammonium salts showed good catalytic activity of $CO_2$ fixation in the synthesis of poly[(1,3-dioxolane-2-oxo-4-yl)methyl methacrylate] [poly(DOMA)] by the direct incorporation of $CO_2$ to poly(glycidyl methacrylate)[poly(GMA)]. Among the salts tested, the ones with higher alkyl chain length and with more nucleophilic counter anion showed higher catalytic activity. The yield of carbon dioxide addition increased with the reaction temperature. Kinetic study was carried out by measuring the variation of $CO_2$, pressure in a high pressure batch reactor. The reaction rate was first order to the concentration of poly(GMA) and $CO_2$, respectively. The rate constant was $0.69L/mol{\cdot}h$ and Henry's constant of $CO_2$ in DMSO at $80^{\circ}C$ was $6.8{\times}10^{-4}mol/L{\cdot}KPa$.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.348-353
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• 2003

Generally, two different types of fructose polymer are found in nature. One is inulin, whose fructosyl residues are linked mainly by a ${\beta}-(2,1)-linkage$, while the other is high-molecular-weight levan, whose fructosyl residues are linked mainly by a ${\beta}-(2,6)-linkage$. In contrast to the extensive studies on the prebiotic properties of inulin, there has been no report on the effect of levan on the large bowel microflora in viva. Therefore, to examine whether dietary levan can be used as a prebiotic, Sprague-Dawley male rats were fed one of two diets for 3 weeks: 1) basal diet plus sucrose; 2) basal diet plus 10% (wt/wt) levan. The cecal bowel mass, cecal and colon short-chain fatty acids (SCFAs), pH, and microflora were then compared. The intake of the levan-containing diet significantly increased the total cecal weight and wall weight. The analyses of the SCFAs in the cecal and colonic contents revealed that levan was converted into acetate, butyrate, and lactate, which resulted in acidic conditions. The intake of levan also significantly increased the total number of microorganisms by 5-fold and lactic acid-producing bacteria (LAB) 30-fold in the feces. Accordingly, the current work shows that levan can be used as a prebiotic for stimulating the growth of LAB in an animal model.

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.176-185
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• 1995

To improve photosensisitizing efficiency of ZnO/$H_2Pc(I)_x$ system, ZnO/$H_2Pc(I)_x$ system was dispersed in a typical photoconductive polymer of poly(9-vinylcarbazole)(PVCZ). The iodine dopant level(x) of ZnO/${\chi}-H_2Pc(I)_x$ is proportional to concentration of iodine, whereas x of ZnO/${\beta}-H_2Pc(I)_x$ decreased from the highest x=0.97 at more than $6.3{\times}10^{-3}$ M iodine solution. The Raman spectra of ZnO/${\chi}-H_2Pc(I)_x$ at 514 nm exhibited characteristic $I_3^-$ patterns in the range of 50∼550 $cm^{-1}$ at $x{\geq}0.57.$ The surface photovoltage of ZnO/${\chi}-H_2Pc(I)_{0.48}$/PVCZ was approximately 1.6 times greater than ZnO/${\chi}-H_2 Pc(I)_{0.48}$ and was 1.8 times of ZnO/${\chi}-H_2Pc(I)_{0.57}$/PVCZ at 670 nm. With ZnO/$H_2Pc(I)_x$/PVCZ, the highest iodine dopant levels showed a higher photovoltage. Therefore the injection of holes from H2Pc into PVCZ resulted in that photosensisitizing effect of ZnO/$H_2Pc(I)_x$/PVCZ system was improved compared to ZnO/$H_2Pc(I)_x$ case.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.575-581
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• 1997

UDs were synthesized from two different polyols(PTMG, PBEAG), ionic chain extender(DMPA), EDA with $H_{12}-MDI$. PU/PMMA hybrids were prepared with free radical polymerization of MMA monomer in MMA-swelled PUD. PUD particle size and film properties were investigated ionic content and polyol type. Mechanical and thermal properties of PU/PMMA hybrid film were studied in terms of PU's ionic content and the venation of PU/PMMA compositions. As DMPA content increased from 2wt% to 10wt% in PUD, particle size of PUD decreased. PUD's particle size with ester type polyol was found to be smaller then ether type polyol used. Phase separation between hard segment(HS) and soft segment(SS) with ionic contents in PU was shown by the thermal, mechanical property measurement. Although the composition of MMA was changed from 0 to 40 wt% in PU/PMMA hybrid, the particle size of the hybrid did not increase. Using the ester type polyol, tensile strength of hybrid was found to increase by 2wt% - 6wt% DPMA content, but as higher content the strength of hybrid decreased. Moreover with the ether type polyol, tensile strength of hybrid was observed to increase by 2wt% - 4wt% DMPA content, while decreasing at higher content. PU and PMMA polymer molecule being mixed in molecular level was confirmed from the pattern of $T_g$ in DSC thermogram.