• 전기화학회지
• /
• 제13권2호
• /
• pp.110-115
• /
• 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.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1999년도 The 7th Summer Workshop of the Membrane Society of Korea
• /
• pp.15-18
• /
• 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.

• 접착 및 계면
• /
• 제5권1호
• /
• pp.21-28
• /
• 2004

본 연구에서는 사슬말단에 chloropropyl 유기관능그룹을 가지고 있는 실란결합체인 3-chloropropyltrimethoxysilane(CTMS)을 사용하여 여러 농도에서 유리섬유 표면에 사이징 처리하여 유리섬유/나일론 6 및 유리직물/나이론 6 복합재료를 제조하였다. 단섬유 microbonding 시험에 의한 유리섬유/나일론 6 복합재료의 계면전단강도와 short-beam 전단시험과 동역학적 열특성 분석 방법을 통하여 유리직물/나일론 6 복합재료의 층간전단강도 및 저장탄성률에 미치는 결합체 농도의 영향을 각각 조사하였다. CTMS 결합제의 농도가 증가할수록 복합재료의 계면특성이 향상되었다. 결합제의 농도 변화에 대한 유리섬유강화 나일론 6 복합재료의 계면전단강도, 층간전단강도, 층간파단양상 그리고 저장탄성률 등 각 특성 변화의 경향이 서로 일치하였다.

• 폴리머
• /
• 제32권6호
• /
• pp.549-554
• /
• 2008

분산중합법에 의해 고분자 미립자를 합성하기 위해 스티렌과 n-butylmethacrylate가 알루미나와 함께 중합되었다. 스티렌과 n-butylmethacrylate의 비는 3 : 1이었고, 입자안정제는 poly (N-vinyl pyrrolidon), 중합 개시제로는 2,2'-azobis(isobutyronitrile)를 커플링제는 3-methacryloxypropyl trimethoxysilane을, 분산매로 이소프로판올과 이온교환수를 70 : 30의 비로 사용하였다. TEM 사진을 통해 알루미나가 고분자 미립자에 분산되어 있음을 확인하였고 알루미나의 농도가 증가함에 따라 평균 입자경이 증가하였으며 입자경 분포는 감소되는 경향을 보였다. XRD 측정에 의해 알루미나의 농도 증가는 피크 강도와 2$\theta$값의 증가를 보였으며 TGA 측정으로 알루미나의 농도의 증가는 고분자 미립자의 내열성을 증가시킴을 알 수 있었다. 사용한 개시제의 반감기가 길수록 입자경은 감소하였고 입자인정제의 농도가 증가할수록 반응초기의 핵생성이 증가하여 입자경이 또한 감소함을 알 수 있었다.

• 폴리머
• /
• 제32권4호
• /
• pp.390-396
• /
• 2008

조직공학용 생체재료로 사용하고자 가교제 1,3-butadiene diepoxide(BD)를 사용하여 락타이드(LA)와 가교시킨 히아루론산(HA) 고분자를 제조하였다. 가교된 고분자의 락타이드 및 BD 반응도는 핵자기 공명 분광법으로 결정하였다. 반응도와 팽윤도는 LA/HA 몰비 혹은 가교제 농도를 증가시킴에 따라 증가하였다. 탄성률은 가교제 농도가 증가하거나 HA/LA 몰비가 감소함에 따라 감소하였다. 생분해는 2단계로 진행되었으며 BD 농도가 증가할수록 서서히 진행되었다. 첫 단계 분해는 주로 가교구조에 존재하는 에스테르기의 분해에 기인한 것으로 나타났다. 세포 성장 저해는 BD 농도가 증가함에 따라 증가하였다. 세포 독성은 BD 농도가 클 경우 약간 나타났으나 그 값은 6% 미만으로 세포 성장에 큰 문제는 없는 것으로 나타났다.

• 폴리머
• /
• 제33권5호
• /
• pp.477-484
• /
• 2009

소수성 실리카를 안정제로 AIBN을 개시제로 하는 현탁중합법으로 PBMA 입자 및 카본블랙을 함유하는 PBMA 복합체 입자를 합성하였다. pH를 이용하여 실리카입자를 표면개질하여 안정제로 선택한 반응에서 사용한 실리카의 90%는 안정제로, 10%는 PBMA 입자의 내부에 위치하는 것으로 규명되었다. 반응속도와 입경은 안정제의 농도에 무관한 것으로 관찰되었으나, 수평균 및 중량평균분자량은 안정제의 농도가 1.67 wt%를 초과하면서 증가하는 현상을 나타내었다. 개시제의 농도 증가와 반응온도의 상승에 따라 분자량은 이론식에 거의 일치하는 형태로 감소하였다. 카본블랙을 단량체에 대하여 1, 3, 5 및 7 wt% 유입하는 경우 반응전환율은 단계적으로 감소하였으며 유리전이온도는 카본블랙의 농도가 단량체에 대하여 3 wt%에서 5 wt%로 증가하는 경우 약 $4^{\circ}C$ 상승하였다. 투과전자현미경(TEM)을 이용하여 입자의 내부에 위치하는 카본블랙을 확인하였으며, 열중량분석법(TGA)으로 카본블랙의 농도를 측정하였다.

• Macromolecular Research
• /
• 제12권4호
• /
• pp.422-426
• /
• 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).

• Korea-Australia Rheology Journal
• /
• 제14권4호
• /
• pp.189-201
• /
• 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.

• Journal of Pharmaceutical Investigation
• /
• 제31권1호
• /
• pp.7-12
• /
• 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.

• Korea-Australia Rheology Journal
• /
• 제21권4호
• /
• pp.235-244
• /
• 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.