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ABSTRACT: Polymeric micelles have been extensively studied as nanoscale drug carriers. Knowing the inner structure of polymeric micelles that encapsulate hydrophobic drugs is important to design effective carriers. In our study, the hydrophobic compound tetrabromocathecol (TBC) was chosen as a drug-equivalent model molecule. The bromine atoms in TBC act as probes in anomalous small-angle X-ray scattering (ASAXS) allowing for its localization in the polymeric micelles whose shape and size were determined by normal small-angle X-ray scattering (SAXS). Light scattering measurements coupled with field flow fractionation were also carried out to determine the aggregation number of micelles. A core-corona spherical model was used to explain the shape of the micelles, while the distribution of bromine atoms was explained with a hard-sphere model. Interestingly, the radius of the spherical region populated with bromine atoms was larger than the one of the sphere corresponding to the hydrophobic core of the micelle. This result suggests that the TBC molecules infiltrate the PEG hydrophilic domain in the vicinity of the core/shell interface. The results of light scattering and SAXS indicate that the PEG chains at the shell region are densely packed, and thus the PEG domain close to the interface has enough hydrophobicity to tolerate the presence of hydrophobic compounds.
Journal of the American Chemical Society 01/2013; · 9.91 Impact Factor
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ABSTRACT: Poly(ethylene glycol)-block-poly(partially benzyl-esterified aspartic acid), denoted by PEG-P(Asp(Bzl)), is one of the most examined blockcopolymers for drug carriers. However, little is known about fundamental physical properties. Nine samples of PEG-P(Asp(Bzl)) with different benzylation fractions (F(Bzl)) and aspartic chain lengths (DP(Asp)) were synthesized, and the aggregation number (N(agg)), core radius (R(C)), and other structural parameters were determined with combination of light scattering and synchrotron X-ray small-angle scattering. The major factor to determine N(agg) and R(C) was found to be F(Bzl), i.e., the hydrophobic nature of the core, even though F(Bzl) was changed in the relatively small composition range from 66 to 89 mol %. When we compared the data for the same F(Bzl), the scaling theory was consistent with the core chain length dependence of both core and micelle sizes. The overcrowding nature of the tethered PEG chains on the micelles was increased about 1.3-2.9 times with increasing N(agg) compared with the unperturbed state in solutions.
The Journal of Physical Chemistry B 06/2012; · 3.70 Impact Factor
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ABSTRACT: Understanding of the microscopic dynamics of fillers in rubber is a key to understand the property of macroscopic response of filled rubber. In the present study, we observe microscopic dynamics of silica and carbon black nanoparticles in unvulcanized rubber by using X-ray Photon Correlation Spectroscopy (XPCS). Dependence of dynamics on the temperature of sample, the volume fraction of particles and the interface between filler particles and rubber chains is observed. The results clearly show the usefulness of XPCS to investigate the filler dynamics in rubber.
IOP Conference Series Materials Science and Engineering 09/2011; 24(1):012005.
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ABSTRACT: Anomalous small-angle X-ray Scattering (ASAXS) analysis for poly(4-vinylphenol)-b-poly(4-bromostyrene) (PVPh-b-PBrS) in N,N,N',N'-tetramethyl ethylene diamine (TMEDA) solution was examined. The ASAXS measurements, executed at three different energies, provided the separation of the scattering of the Br atoms from whole system. The energy-dependent term in the SAXS profile, which is corresponding to the form factor of PBrS domain, sufficiently agree with the SAXS profile calculated for hard sphere with 41 nm radius. Therefore, the PBrS chains assemble into spherical core with 41 nm radius in TMEDA solution.
Journal of Physics Conference Series 02/2011; 272(1):012022.
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ABSTRACT: Anomalous small-angle X-ray scattering (ASAXS) is expected to be a powerful and vital tool for the structural study of soft matter. We investigated feasibility of ASAXS near sulphur K absorption edge at SPring-8. Scattering pattern was successfully obtained and the dependence of scattering intensity on the energy of X-ray well agreed with the calculated one. This study can be the basis of structural study of soft matter using ASAXS, especially non-crystalline/amorphous materials.
Journal of Physics Conference Series 11/2010; 247(1):012006.
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ABSTRACT: An indirectly illuminated X-ray area detector is employed for X-ray photon correlation spectroscopy (XPCS). The detector consists of a phosphor screen, an image intensifier (microchannel plate), a coupling lens and either a CCD or CMOS image sensor. By changing the gain of the image intensifier, both photon-counting and integrating measurements can be performed. Speckle patterns with a high signal-to-noise ratio can be observed in a single shot in the integrating mode, while XPCS measurement can be performed with much fewer photons in the photon-counting mode. By switching the image sensor, various combinations of frame rate, dynamic range and active area can be obtained. By virtue of these characteristics, this detector can be used for XPCS measurements of various types of samples that show slow or fast dynamics, a high or low scattering intensity, and a wide or narrow range of scattering angles.
Journal of Synchrotron Radiation 11/2010; 17(6):737-42. · 2.73 Impact Factor
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ABSTRACT: The dynamics of silica particles in unvulcanized rubber is investigated by X-ray photon correlation spectroscopy (XPCS). The results show the aging behavior of the dynamics; the dynamics of particles slows down as the aging time increases. This slowing down is not accompanied by a change in the configuration of aggregates in size scales of micrometers and sub-micrometers. The aging behavior depends on the type of silane coupling agent and the volume fraction of silica particles, while it does not originate from vulcanization. This study shows that complex microrheological phenomena occur even in industrial products. The relationship between these microrheological phenomena and macroscopic viscoelasticity is an open question.
10/2010;
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ABSTRACT: We investigated the structure, thermal properties, and dynamics of polyrotaxane (PR), composed of poly(ethylene glycol) (PEG) and α-cyclodextrins (CDs), and PR derivatives comprising hydroxypropylated CDs, that is, hydroxypropylated PRs (HyPRs), in the solid state by using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and viscoelastic spectroscopy. It was observed that HyPRs with high chemical modification ratios show a WLF-type viscoelastic relaxation that can be ascribed to the cooperative segmental motion of several CD molecules, whereas HyPRs with a lower modification ratio and PR with a highly ordered packing structure of CDs do not exhibit any mechanical relaxation mode. A comparison between the relaxation temperatures of HyPRs with different modification and inclusion ratios suggested that the hydrogen bond between CDs primarily dominates the viscoelastic properties of solid-state PR. Our experimental results indicate a close relationship between the crystallinity and fluctuation of cyclic molecules in solid-state PR, which is the first evidence of the dynamic softening of the glassy state formed by assembled cyclic molecules in solid-state PR.
04/2010;
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ABSTRACT: We have carried out X-ray microbeam analysis of the crystallization behavior of n-hexadecane (C16) in oil-in-water emulsion droplets that were formed using surfactants with different types of hydrophobic moieties. It was confirmed that molecular-shape matching between the hydrophobic moiety and C16 caused the following crystallization behavior: when the molecular shape of the hydrophobic moiety was similar to C16, high-intensity X-ray diffraction of the rotator phase of C16 was detectable at the initial stage of crystallization and the long-chain axes of C16 crystals aligned normal to the membrane interface. The present results provided the first evidence of interfacial heterogeneous nucleation caused by molecular interactions at the emulsion membrane, which is thought to be related to the interfacial freezing that was observed at the oil−water interface with surfactants in a bulk system.
08/2008;
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ABSTRACT: Two-dimensional pattern reverse Monte Carlo method is applied to investigate structural changes of silica particle filler
in uniaxially elongat ed rubber. We calculated three-dimensional confor mations of spherical silica particles using a series
of two-dimensional patterns of structure factors during elongation. The structure factors we used are inter polated from experimentally
observed structure factors for the elongation ratio ε = 0.0, 0.5, 1.0, and 1.5. To make a continuous motion of particles, we set the elongation ratio with small interval Δε = 0.001. It is found that the structural change of the particles seem to be reliable at least for small ε regions because spurious motions like the Brownian motions are not observed.
Rheologica Acta 06/2008; 47(5):537-541. · 2.03 Impact Factor
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ABSTRACT: Recently the liquid–liquid transition (LLT) was found in a molecular liquid, triphenyl phosphite, which allows us to follow the kinetics of the transformation of one liquid to another. Here we investigate the microscopic structural change during the LLT by means of time-resolved synchrotron x-ray scattering measurements. We confirm that during spinodal-decomposition-type transformation a new peak corresponding to a particular intermolecular phosphor–phosphor distance emerges and grows with time. This indicates that short-range order develops in the liquid during LLT. We show that the short-range order does not represent the crystalline structure, but the locally favoured structure. We found that the temporal increase of the intensity of this peak, i.e., the fraction of locally favoured structures, is proportional to that of the heat released during the transformation. This means that the formation of locally favoured structures is the origin of the heat release. This is consistent with the proposal that the order parameter governing LLT is the number density of locally favoured structures. This yields a valuable insight into the nature of the ordering in the liquid–liquid transition.
Journal of Physics Condensed Matter 03/2007; 19(15):152101. · 2.55 Impact Factor
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ABSTRACT: DNA-modified gold nanoparticles exhibit a unique aggregation behaviour that they form aggregation with fully complementary DNA but do not with the terminal-mismatched DNA at certain concentration of added salts. We studied the aggregation structure of the nanoparticles by small angle X-ray scattering (SAXS). The results indicated that the gap between surfaces of gold nanoparticles is nearly two times as long as DNA in B-form. This suggests that the ends of completely double-stranded DNA (dsDNA) conjugated on gold nanoparticles contact or slightly interdigitate with each other in the aggregation structure.
Nucleic Acids Symposium Series 02/2007;
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ABSTRACT: The origin of the curliness of human hair was revealed by scanning microbeam small angle X-ray scattering (SAXS), based on the nanostructure of keratin fibre arrangement. Scanning microbeam SAXS patterns of single hair fibres have been measured across the fibres and the differences in the patterns between the inner and the outer sides of the curvature were successfully detected. The analysis of the equatorial and azimuthal scattering intensity profiles showed that the arrangement of the intermediate filaments was different between the inner and the outer sides of the curvature. From the analogy with Merino and Romny wool, it is suggested that different types of cortices exist in human hair. It is concluded that, regardless of the ethnic origins (African, Caucasian, and Asian), the macroscopic curl shape of the hair fibre originate from the inhomogeneity of the internal nanostructure, arising from inhomogeneous distribution of two types of cortices.
Journal of Structural Biology 10/2006; 155(3):438-44. · 3.41 Impact Factor
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ABSTRACT: The structure of slide-ring (SR) gels in various types of solvents was investigated by small-angle X-ray scattering (SAXS). The SR gels have a unique characteristic called the “pulley effect” that the cross-links made of α-cyclodextrin molecules in a figure-eight shape can slide along the polymer chain. The SAXS results show that, in a poor solvent, the sliding cross-links form aggregates that prevent the pulley effect, while the polymer chains freely pass through the cross-links acting like pulleys in a good solvent. A vertically elliptic pattern was observed in two-dimensional SAXS profiles for covalent-bonded chemical gels in a good solvent under uniaxial horizontal deformation, while an isotropic profile was observed for the SR gels in a good solvent even under deformation. This difference in the deformation mechanism between the SR gels and the chemical gels supports the pulley effect of the SR gels.
09/2006;
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ABSTRACT: Crystallization of n-hexadecane in emulsion droplets was studied using time-resolved two-dimensional small- and wide-angle x-ray scattering with differential scanning calorimetry (2D-SAXS-WAXS-in situ DSC) which provides information about both nano- and subnanoscale structural change. n-hexadecane in droplets reproducibly crystallized into the stable triclinic phase via a transient-rotator phase. This is in contrast with previous results that the rotator phase of n-hexadecane was observed only occasionally for bulk samples. Thus we confirmed the existence of rotator phase in n-hexadecane, which is important for the study of crystallization of soft materials. We suggest that the rotator phase at the interface of oil and water plays a precursor role for bulk crystallization. This study demonstrates that 2D-SAXS-WAXS-in situ DSC is a powerful tool for the study of a transient phase.
Physical Review Letters 04/2005; 94(9):097801. · 7.37 Impact Factor
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Hiroyasu Masunaga,
Hiroki Ogawa,
Takumi Takano,
Sono Sasaki,
Shunji Goto,
Takashi Tanaka,
Takamitsu Seike,
Sunao Takahashi,
Kunikazu Takeshita,
Nobuteru Nariyama, [......],
Hiroshi Jinnai,
Hiroshi Okuda,
Isamu Akiba,
Isao Takahashi,
Katsuhiro Yamamoto,
Masamichi Hikosaka,
Shinichi Sakurai, Yuya Shinohara,
Akihiko Okada,
Yasunori Sugihara
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ABSTRACT: この論文は国立情報学研究所の電子図書館事業により電子化されました。 研究会報告 我々はTriphenyl Phosphite(TPP)およびnormal butanolという分子性液体において液体・液体相転移を発見した。そのキネティクスを顕微鏡、熱量測定を用いた調べた結果、核形成・成長型(NG-type)相転移とスピノーダル分解型(SD-type)相転移の2種類の相転移過程があることがわかった。スピノーダル分解型相転移を詳細に調べた結果、液体・液体相転移を支配する秩序変数は非保存系であることがわかった。そこで、Photon Factory(PF)において放射光X線回折実験を行い、液体・液体相転移中における液体のミクロスコピックな変化を調べた。その結果、液体・液体相転移の秩序変数は局所安定構造の数密度であることが示唆された。
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ABSTRACT: To clarify hair changes by aging, the effect of age on hair properties was investigated from macro- to microscopic view points. Sensory hair luster tests were performed on 230 Japanese females from 10 to 70 years of age, revealing that hair luster decreases with age. The age dependence of the hair diameter and the ellipticity of the hair cross section could not explain luster reduction by aging. It has been determined that an irregular increase in fiber curvature occurs with age and is a cause of luster reduction with aging. A detailed structural analysis by synchrotron radiation microbeam X-ray diffraction revealed that the inhomogeneity in the lateral distribution of the hair microstructure increased with age and relates to the irregular increase in curvature. Such an increase in curvature is one of the important factors that leads to a poor alignment of hairs and luster reduction, and is related to the appearance of aging hair.
Journal of cosmetic science 60(6):637-48. · 0.28 Impact Factor
