• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.35-40
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• 2012

The composite membranes using Nafion as matrix and 1-ethyl-3-methylimidazolium tetracyanoborate (EMITCB) as ion-conducting medium in replacement of water were prepared and characterized. The amount of EMITCB in Nafion varied from 30 to 50wt%. The composite membranes are characterized by ion conductivity, thermogravitational analyses (TGA) and small-angle X-ray scattering (SAXS). The composite membranes containing EMITCB of 40wt% showed the maximum ionic conductivity which was ~0.0146 S $cm^{-1}$ at 423.15 K. It is inferred that the decrease in ionic conductivity of all the composite membranes might be due to the decomposition of a tetracyanoboric acid formed in the composite membranes. The results of SAXS indicated that the ionic clusters to conduct proton in the composite membranes were successfully formed. In accordance with the results of ionic conductivity as a function of a reciprocal temperature, SAXS showed a proportional decrease in scattering maximum $q_{max}$ as the amount of EMITCB increases in the composite membranes, which results in the increase in ionomer cluster size. The TGA showed no significant decomposition of the ionic liquid as well as the composite membranes in the range of operating temperature ($120-150^{\circ}C$) of high temperature proton exchange membrane fuel cells (HTPEMFC). As a result, EMITCB is able to play an important role in transferring proton in the composite membranes at elevated temperatures with no external humidification for proton exchange membrane fuel cells.

• Macromolecular Research
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• v.16 no.2
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• pp.113-119
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• 2008

A series of amphiphilic dendrons n-18 (n: generation number, 18: octadecyl chain) based on an aliphatic polyether denderitic core and octadecyl peripheries were synthesized using a convergent dendron synthesis consisting of a Williamson etherification and hydroboration/oxidation reactions. This study investigated their thermal and self-assembling behavior in the solid state using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) absorption spectroscopy, and small angle X-ray scattering (SAXS). DSC indicated that the melting transition and the corresponding heat of the fusion of the octadecyl chain decreased with each generation. FT-IR showed that the hydroxyl focal groups were hydrogen-bonded with one another in the solid state. DSC and FT-IR indicated microphase-separation between the hydrophilic dendritic cores and hydrophobic octadecyl peripheries. SAXS data analysis in the solid state suggested that the lower-generation dendrons 1-18 and 2-18 self-assemble into lamellar structures based upon a bilayered packing of octadecyl peripheries. In contrast, the analyzed data of higher-generation dendron 3-18 is consistent with 2-D oblique columnar structures, which presumably consist of elliptical cross sections. The data obtained could be rationalized by microphase-separation between the hydrophilic dendritic core and hydrophobic octadecyl peripheries, and the degree of interfacial curvature associated with dendron generation.

• The Korean Journal of Rheology
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• v.10 no.2
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• pp.65-73
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• 1998

본연구에서는poystyrene-block-poly (ethlene-co-butylene)-block-polystyrene(SEBS) 삼중블록 공중합체와 저분자량 단일중합체인 Hercotac 1149 (H1149)의 70/30 (w/w) 혼합물 의 미세상분리와 그동력학을 유변물성 측정법과 SAXS 실험을 통하여 연구해 보았다. 먼저 혼합물의 미세상분리 온도를 유변물성 측정법과 SAXS 실험을 통해 각각구한 다음 샘플을 미세상분리 온도보다 높은 온도에서 그이하의 온도로 급냉시킨 후 유변물성과 산란강도의 사간에 따른 변화로부터 미세상분리 동력학에 대한 정보를 구하였다. 이렇게 얻어진 데이터 를 Avrami 형태의 핵생성 성장(NG) 메커니즘으로 해석해 보았는데 최대산란강도 Imax 뿐만 아니라 저장 점탄성계수 G＇과 손실 점탄성계수 G＂의 시간에 따른 변화를 잘 예측할수 있 었다. 한편 서로다른 두 time-resolved 실험으로부터 Avrami 플롯을 그려서 구해진 Avrami 변수들은 같은 급냉 깊이에서는 서로 잘 일치함을 확인하였다. 반감기는 급냉 깊이가 증가 함에 따라 점차 감소하는 경향을 보였는데 이는 급냉 깊이가 클수록 미세상분리가 더 빨리 진행되고 있음을 보여주는 것이다. 또한 Avrami 지수는 급냉 깊이가 증가함에 따라 3에서 4로 급격히 변했는데 이로부터 급냉 깊이가 작을 때에는 70/30 (w/w) SEBS/H1149 혼합물 의 미세상분리가 불균일 핵생성 성장 메커니즘에 따라 진행되고 급냉 깊이가 더 커지면 미 세상분리가 스피노달 상분리 메커니즘으로 변하고 있음을 예측할수 있었다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.1
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• pp.1-7
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• 2019

We introduce to prepare liquid crystalline emulsion composed of cetearyl alcohol, cetyl palmitate, sorbitan palmitate, sorbitan olivate, ceramide and so on which can enforce interface between oil-based particle and water phase. In terms of structural analysis, the stability of the liquid crystalline emulsion including ceramide, which is immisible ingredient, at high temperature was proved by polarized microscope, cryo-SEM, small-angle x-ray scattering, in addition to viscometer and static light scattering by physical analysis.

• Fibers and Polymers
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• v.5 no.2
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• pp.160-169
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• 2004

Polystyrene/layered silicate nanocomposites were prepared by melt intercalation. To examine the distribution of the clay in polymer matrix, small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used. Intercalated nanocomposites were obtained and their rheological properties were investigated. Microcellular nanocomposite foams were produced by using a supercritical fluid. As clay contents increased, the cell size decreased and the cell density increased. It was found that layered silicates could operate as heterogeneous nucleation sites. As the saturation pressure increased and the saturation temperature decreased, the cell size decreased and the cell density increased. Microcellular foams have different morphology depending upon the dispersion state of nanoclays.

• Fibers and Polymers
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• v.6 no.4
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• pp.289-296
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• 2005

Biodegradable nanocomposites were prepared by mixing a polymer resin and layered silicates by the melt intercalation method. Internal structure of the nanocomposite was characterized by using the small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). Nanocomposites having exfoliated and intercalated structures were obtained by employing two different organically modified nanoclays. Rheological properties in shear and extensional flows and biodegradability of nanocomposites were measured. In shear flow, shear thinning behavior and increased storage modulus were observed as the clay loading increased. In extensional flow, strain hardening behavior was observed in well dispersed system. Nanocomposites with the exfoliated structure had better biodegradability than nanocomposites with the intercalated structure or pure polymer.

• Polymer(Korea)
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• v.25 no.5
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• pp.691-698
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• 2001

Nanocomposites based on epoxy acid nanoclay were prepared employing organically modified mica type silicate (OMTS), diglycidyl ether of bisphenol A (DGEBA) type epoxy. curing agent (dicyandiamide; DICY), and catalyst (benzyl dimethyl amine; BDMA). Both melt mixing and solution mixing were und for the sample preparation and structural developments with curing reaction were analyzed using X-ray diffractometer (XRD) and small angle X-ray scattering (SAXS). Because of the different curing rate between extra-gallery and intra-gallery reactions of epoxy mixtures, only intercalated structure was observed for the sample prepared by melt mixing while fully exfoliated structure was observed for the sample prepared by solution mixing. Mechanical properties of exfoliated epoxy nanocomposite were investigated using a dynamic mechanical analyzer (DMA). The dynamic storage modulus of the nanocomposite in both glass and rubbery plateau regions were increased with increasing OMTS contents, but glass transition temperatures ($T_g$) remained unchanged. Thermal properties of epoxy nanocomposite were investigated using thermogravimetric (TGA) and limit oxygen index (LOI) methods. Thermal decomposition onset points and LOI values were increased with increasing OMTS contents due to barrier effects of OMTS sheets.

• Polymer(Korea)
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• v.28 no.6
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• pp.509-518
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• 2004

Microdomain structures and crystallization behavior of the binary blends consisting of an asymmetric block copolymer and a homopolymer were investigated using small-angle X-ray scattering (SAXS), optical micro scope (OM) and differential scanning calorimetry (DSC). Poly(methyl methacrylate)-block-polystyrene block copolymer (PMMA-b-PS) (weight fraction of PMMA =0.53) was mixed with low molecular weight poly(vinylidene fluoride) (PVDF). As the PVDF concentration was increased, the morphological change from a lamellar to a cylindrical structure occurred. The crystallization of PVDF significantly disturbed the orientation of the pre-existing microdomain structure, resulting in a poorly ordered morphology. In the blends, PVDF exhibited unique crystallization behavior due to the PMMA block which is preferentially miscible to PVDF and the space constraint imposed by the microdomains.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.348-348
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• 2006

In the present study, porcine pepsin in various pH conditions was investigated by small-angle X-ray scattering (SAXS) in order to detailed information on the structure and its variations with pH conditions. These analyses identified the structure of pepsin, and compared with that obtained by single crystallography. Moreover, this study found the structure' variations with changing pH conditions. All the results will be discussed with considering the conformational characteristics of pepsin in solution and further correlate to the biological and spectroscopic characteristics reported previously.

• Polymer(Korea)
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• v.31 no.4
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• pp.289-296
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• 2007

The material factors influencing the sound absorption of the polyurethane foam were investigated with FT-IR, small-angle X-ray scattering (SAXS), and dynamic mechanical thermal analyzer (DMTA). The measurements were performed using the samples which had a similar cell structure but different absorption coefficients. It was found that the ability of the sound absorption of the polyurethane foams was closely related to the damping behavior over the transition range. In order to confirm the use of the low monol polyol (LMP) in high-performance applications, the polyurethanes based on LMP and polypropylene oxide polyol (PPG) were prepared by the solution polymerization method. The microstructure and the physical properties of these polyurethanes were compared. The PPG-based polyurethane showed a higher level of the phase-separated structure because the considerable amount of monol presented in PPG made a contribution to the increased chain mobility. However the short chains formed due to the monol species deteriorated the damping property. As a result, the LMP-based polyurethane showed the superior damping behavior as compared with the PPG-based one.