• Title/Summary/Keyword: Polymer concentration

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Electrochemical Performance of Lithium Sulfur Batteries with Plasticized Polymer Electrolytes based on P(VdF-co-HFP)

  • Park, Jeong-Ho;Yeo, Sang-Yeob;Park, Jung-Ki;Lee, Yong-Min
    • Journal of the Korean Electrochemical Society
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    • v.13 no.2
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    • pp.110-115
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    • 2010
  • The plasticized polymer electrolytes based on polyvinylidene fluoride-co-hexafluoropropylene (P(VdF-co-HFP)), tetra (ethylene glycol) dimethyl ether (TEGDME), and lithium perchlorate ($LiClO_4$) are prepared for the lithium sulfur batteries by solution casting with a doctor-blade. The polymer electrolyte with EO : Li ratio of 16 : 1 shows the maximum ionic conductivity, $6.5\;{\times}\;10^{-4}\;S/cm$ at room temperature. To understand the effect of the salt concentration on the electrochemical performance, the polymer electrolytes are characterized using electrochemical impedance spectroscopy (EIS), infrared spectroscopy (IR), viscometer, and differential scanning calorimeter (DSC). The optimum concentration and mobility of the charge carriers could lead to enhance the utilization of sulfur active materials and the cyclability of the Li/S unit cell.

Olefin/Paraffin Separation though Facilitated Transport Membranes in Solid State

  • Hong, Seong-Uk;Won, Jong-Ok;Hong, Jae-Min;Park, Hyun-Chae;Kang, Yong-Soo
    • Proceedings of the Membrane Society of Korea Conference
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    • 1999.07a
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    • pp.15-18
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    • 1999
  • A simple mathematical model for facilitated mass transport through a fixed site carrier membrane was derived by assuming an instantaneous, microscopic concentration (activity) fluctuation. The current model demonstrates that the facilitation factor depends on the extent of concentration fluctuation, the time scale ratios of diffusion to chemical reaction and the ratio of the carrier concentration to the solute solubility in matrix. The model was examined against the experimental data on oxygen transport in membranes containing metallo-porphyrin carriers, and the agreement was exceptional (within 10% error). The basic concept of this approach was applied to separate olefin from olefin/paraffin mixtures. A proprietaty carrier, developed here, resulted that the selectivity of propylene over propane was more than 120 and the propylene permeance exceed 40 gpu.

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Concentration Effect of Silane Coupling Agents with Chloropropyl End Group on the Interfacial Characteristics of Glass/Nylon 6 Composites (유리섬유/나일론 6 복합재료의 계면특성에 미치는 Chloropropyl 말단기를 가진 실란결합체 농도의 영향)

  • Cho, Donghwan;Yun, Suk Hyang;Bang, Dae-Suk;Kim, Junkyung;Lim, Soonho;Park, Min
    • Journal of Adhesion and Interface
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    • v.5 no.1
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    • pp.21-28
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    • 2004
  • In this work, glass fiber/nylon 6 and woven glass fiber/nylon 6 composites have been fabricated using glass fiber reinforcements sized with 3-chloropropyltrimethoxysilane(CTMS) having a chloropropyl organo-functional group in the molecular chain end. The interfacial shear strength of glass fiber/nylon 6 composite was measured using a single fiber microbonding test and the interlaminar shear strength and the storage modulus of woven glass fabric/nylon 6 composites were measured using a short-warn shear test and a dynamic mechanical analysis, respectively, informing the effect of the concentration of CTMS on the properties. With increasing CTMS concentration, the interfacial properties of the composites were improved. The results on the interfacial shear strength, interlaminar shear strength, interlaminar failure pattern, and storage modulus with varying the CTMS concentration agree with each other.

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A Study on Dispersion Copolymerization of Styrene/n-Butylmethacrylate and Alumina (스티렌/노말 부틸 메타크릴레이트와 알루미나의 분산 공중합에 관한 연구)

  • Bang, Hyun-Su;Cho, Ur-Ryong
    • Polymer(Korea)
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    • v.32 no.6
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    • pp.549-554
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    • 2008
  • In order to synthesize polymer particle containing inorganic material, styrene and n-butylmethacrylate were copolymerized with alumina by dispersion polymerization. The weight ratio of styrene to n-butylmethacrylate was 3 : 1. A poly(N-vinyl pyrrolidon) was added as stabilizer. 2,2'-AzobisCisobutyronitrile) and 3-methacryloxypropyl trimethoxysilane were used as initiator and coupling agent, respectively. The weight ratio of 70 : 30 of isopropanol to distilled water was used as dispersion medium. According to the TEM measurement, we could confirm that alumina was dispersed into the polymer particle. The increase 'of concentration of alumina resulted in enhancement of particle size, but decreased its distribution. By the XRD method, it was found that the increase of alumina concentration showed the increase of intensity in peak and the increased 2$\theta$ value. From the TGA measurement, the increase of alumina concentration caused high heat resistance of the polymer. With respect to the type of initiator, the longer half life of initiator, the smaller particle size. We also found that the increase of particle stabilizer concentration made the decreased of particle size due to the accelerated generation of polymer particle in the early stage of reaction.

Characterization of Lactide/Hyaluronic Acid Polymer Cross-Linked by 1,3-Butadiene Diepoxide (1,3-Butadiene Diepoxide에 의해 가교된 락타이드/히아루론산 고분자의 특성)

  • Han, Gwang-Seon;Bae, Jung-Eun;Kim, In-Seop;Cheong, Seong-Ihl
    • Polymer(Korea)
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    • v.32 no.4
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    • pp.390-396
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    • 2008
  • The hyaluronic acid (HA) polymers cross-linked with lactide (LA) using the crosslinking agent, 1,3-butadiene diepoxide (BD), were prepared in order to develop a biomedical material for tissue engineering. The degree of lactide and BD reaction of the crosslinked polymer was determined by the analysis of nuclear magnetic resonance spectroscopy. Both degree of reaction and swelling ratio increased with BD concentration or LA/HA mole ratio. Tensile modulus decreased with increasing BD concentration or decreasing LA/HA mole ratio. Degradation was shown to be progressed at two different stages and became slow with increasing BD concentration. It was shown that the first stage degradation was mainly due to the decomposition of ester linkage in the crosslinked structure. The cell growth inhibition increased with BD concentration. Although cytotoxicity was slightly observed in the high BD concentration, the value was very low (below 6%) enough not to affect the cell growth.

Suspension Polymerization with Hydrophobic Silica as a Stabilizer III. Poly(butyl methacrylate) Composite Particles Containing Carbon Black (소수성 실리카를 안정제로 하는 현탁중합 III. 카본블랙을 함유하는 폴리부틸메타크릴레이트 복합체 입자의 합성)

  • Moon, Ji-Yeon;Park, Moon-Soo
    • Polymer(Korea)
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    • v.33 no.5
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    • pp.477-484
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    • 2009
  • Suspension polymerization with hydrophobic silica as a stabilizer and AIBN as an initiator was conducted to synthesize PBMA particles and PBMA composite particles containing carbon black. Surface modification of silica particles by controlling pH revealed that 90% of them functioned as stabilizer and 10% were incorporated into PBMA particles. While stabilizer concentration had no impact on reaction kinetics and particle diameter, an increase in stabilizer concentration displayed an increase in molecular weights when it exceeded 1.67 wt%. An increase in initiator concentration and reaction temperature decreased molecular weights in close agreement with the theoretical equation. An increase in carbon black concentration from 1 to 7 wt%, relative to the monomer, showed a progressive decrease in reaction conversion. As carbon black was increased from 3 to 5 wt%, glass transition showed a $4^{\circ}C$ increase. The presence of carbon black was confirmed by TEM while its concentration was measured by TGA.

Effect of Salt Concentration on the Glass Transition Temperature and Ionic Conductivity of Poly(ethylene glycol)-Polyurethane/$LiClO_4$ Complexes

  • Huh, Pil-Ho;Park, Myung-Geun;Jo, Nam-Ju;Lee, Jin-Kook;Lee, Jang-Oo;Wongkang Yang
    • Macromolecular Research
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    • v.12 no.4
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    • pp.422-426
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    • 2004
  • Solid polymer electrolytes based on poly(ethylene glycol)-polyurethane (PEG-PU) complexed with LiClO$_4$ salt have been prepared by the solvent casting method. A PEG-PU material (PEG:4,4'-diphenylmethane diisocyanate: l,4-butanediol = 1:2:1) was synthesized through a typical two-step condensation reaction. We investigated the effects of the salt concentration on the ionic conductivity ($\sigma$) and the glass transition temperature (T$_{g}$ ) of the complex electrolytes by using alternating current impedance spectroscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The measured values of both $\sigma$ and T$_{g}$ exhibited similar tendencies in that they had maxima within the range studied, probably because of two opposite effects, i.e., the increased number of carrier ions and the decreased chain mobility (or increased T$_{g}$ ) caused by the increase in the salt concentration. The highest conductivity, on the order of 2.43 ${\times}$ 10$^{6}$ S$cm^{-1}$ /, was obtained at an [O]/[Li$^{+}$] ratio of ca. 16 (0.92 ㏖ salt per kg of matrix polymer).

Shear-induced structure and dynamics of hydrophobically modified hydroxy ethyl cellulose (hmHEC) in the presence of SDS

  • Tirtaatmadija, Viyada;Cooper-white, Justin J.;Gason, Samuel J.
    • 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.

The Effect of Polyethylene Oxide on the Aggregation State and Toxicity of Amphotericin B (폴리에틸렌 옥사이드가 암포테리신-B의 응집 특성 및 독성에 미치는 영향)

  • Yu, Bong-G.
    • Journal of Pharmaceutical Investigation
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    • v.31 no.1
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    • pp.7-12
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    • 2001
  • Amphotericin B (AmB) is a drug of choice for the treatment of systemic fungal diseases, but its use is considerably limited due to a high incidence of toxicity, particularly nephrotoxicity. It has been demonstrated that the toxicity of AmB is caused by self-aggregated species of the drug and that unaggregated (monomeric) drug is nontoxic but still expresses antifungal activity. Poly (ethylene oxide) (PEO) is a water-soluble polymer, which may impact the aggregation state of AmB. We have studied the aggregation state of AmB as a function of PEO molecular weight and concentration. At 3,000 and 8,000 g/mole, there was minimal or no change of critical aggregation concentration (CAC) of AmB regardless of the concentration of polymer. By contrast at 20,000 g/mole, the CAC of AmB strikingly increased to 24.3 and $37.5\;{\mu}M$ at 5.0% and 10 % w/v of polymer, respectively. The critical overlap concentration (COC) of PEO 20,000 g/mole was 5.5%. It appears that an interaction between monomeric AmB and polymer coil increases above the COC, competing with self-aggregation of the drug. Accordingly, the degree of aggregation of AmB stayed low and the toxicity became less. There was no such effect at 3,000 and 8,000 g/mole of PEO, owing perhaps to small dimensions in comparison to AmB. Based upon these findings, less toxic AmB formulation may be developed by a pharmaceutical technique such as solid dispersion system containing both AmB and PEO 20,000 g/mole.

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Component dynamics in miscible polymer blends: A review of recent findings

  • Watanabe, Hiroshi;Urakawa, Osamu
    • Korea-Australia Rheology Journal
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    • v.21 no.4
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    • pp.235-244
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    • 2009
  • Miscible polymer blends still have heterogeneity in their component chain concentration in the segmental length scale because of the chain connectivity (that results in the self-concentration of the segments of respective chains) as well as the dynamic fluctuation over various length scales. As a result, the blend components feel different dynamic environments to exhibit different temperature dependence in their segmental relaxation rates. This type of dynamic heterogeneity often results in a broad glass transition (sometimes seen as two separate transitions), a broad distribution of the local (segmental) relaxation modes, and the thermo-rheological complexity of this distribution. Furthermore, the dynamic heterogeneity also affects the global dynamics in the miscible blends if the component chains therein have a large dynamic asymmetry. Thus, the superficially simple miscible blends exhibit interesting dynamic behavior. This article gives a brief summary of the features of the segmental and global dynamics in those blends.