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991.
Makoto Yoshino Kazunori Ito Hidetoshi Kita Ken‐Ichi Okamoto 《Journal of Polymer Science.Polymer Physics》2000,38(13):1707-1715
Poly(ethylene oxide)‐segmented polyurethanes (PEO‐PUs) and polyamides (PEO‐PAs) were prepared, and their morphology and CO2/N2 separation properties were investigated in comparison with those of PEO‐segmented polyimides (PEO‐PIs). The contents of the hard and soft segments in the soft and hard domains, WHS and WSH, respectively, were estimated from glass‐transition temperatures with the Fox equation. The phase separation of the PEO domains depended on the kind of hard‐segment polymer; that is, WHS was in the order PU > PA ≫ PI for a PEO block length (n) of 45–52. The larger WHS of PUs and PAs was due to hydrogen bonding between the oxygen of PEO and the NH group of urethane or amide. The CO2/N2 separation properties depended on the kind of hard‐segment polymer. Compared with PEO‐PIs, PEO‐PUs and PEO‐PA had much smaller CO2 permeabilities because of much smaller CO2 diffusion coefficients and somewhat smaller CO2 solubilities. PEO‐PUs also had a somewhat smaller permselectivity because of a smaller solubility selectivity. This was due to the larger WHS of PEO‐PUs and PEO‐PAs, that is, a greater contamination of PEO domains with hard urethane and amide units. For PEO‐PIs, with a decrease in n to 23 and 9, WHS became large and CO2 permeability decreased significantly, but the permselectivity was still at a high level of more than 50 at 35 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1707–1715, 2000 相似文献
992.
Harumi Sato Misayo Isogai Shigehiro Sasao Kimihiro Matsukawa Yasuo Kita Hiroshi Yamaguchi Heinz W. Siesler Yukihiro Ozaki 《Macromolecular Symposia》2005,220(1):75-84
Molecular structure, crystallinity and morphology of uncompatibilized and compatibilized blends of high molecular weight polyethylene (HMWPE) and Nylon 12 were investigated by using Fourier-transform (FT) Raman spectroscopy, wide-angle x-ray diffraction (WAXD), and scanning electron microscopy (SEM). One of the important purposes of the present study is to compare the present results for HMWPE/Nylon 12 with the previously obtained results for high-density polyethylene (HDPE/Nylon 12). Uncompatibilized and compatibilized blends of HMWPE/Nylon 12 with a Nylon 12 content ranging from 10 to 90 wt% at increments of 10 wt% were prepared. The compatibilized polymer blends were prepared by adding a small amount of maleic anhydride (MAH), and SEM images show that the addition of the small amount of MAH (0.5 wt%) yields a marked improvement of dispersion of HMWPE and Nylon 12. To evaluate the crystallinity of HMWPE from Raman spectra, the relative intensities of bands at 1418 and 1129 cm−1 to the intensity of a band at 1000 cm−1 (I1418/I1000 and I1129/I1000) were estimated for all the uncompatibilized and compatibilized blends of HMWPE/Nylon 12. From the comparison of the relative intensities (I1418/I1000 and I1129/I1000) between the uncompatibilized and compatibilized blends of HMWPE/Nylon 12 it was found that when the Nylon 12 content reaches 40 wt% the crystallinity of HMWPE in the compatibilized blends becomes higher than that of HMWPE in the uncompatibilized blends. The uncompatibilized and compatibilized blends of HMWPE/Nylon 12 (50/50) show quite different x-ray diffraction patterns; the compatibilized blend shows a significantly larger orientational effect in the x-ray pattern of HMWPE. It seems that the increase of interaction of MAH-HMWPE with the Nylon 12 matrix leads to the additional crystallinity. 相似文献
993.
Yoichi Yamaguchi Yosuke Nagasawa Satoshi Shimomura Kenji Tabata 《International journal of quantum chemistry》1999,74(4):423-433
A reaction model for methane oxidation on a reduced SnO2 (110) crystal surface has been proposed theoretically using a point‐charge model. The geometric and electronic structures for all the molecules along the four reaction channels have been calculated by means of the MP2/6‐311++G(2d, p) level of theory. On the basis of the optimized geometries in the gas phase, the single‐point calculations of the energies on the point‐charge model are carried out. The results indicate that the energetically favorable reaction paths to yield methanol and formaldehyde on the reduced SnO2 surface are via the reactant complex CH3O H2O and via the secondary production of methanol oxidation, respectively. It is also found that CH3O− is a stable anion on the surface due to having the high barriers of about 70 kcal/mol in both hydrogen abstraction with O− and thermal decomposition, which is favorable to yield methanol and also is consistent with X‐ray photoelectron spectroscopy (XPS) experiments. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 423–433, 1999 相似文献
994.
Masatoshi Hasegawa Nobuyuki Sensui Yoichi Shindo Rikio Yokota 《Journal of Polymer Science.Polymer Physics》1999,37(17):2499-2511
Asymmetric biphenyl type polyimides (PI) derived from 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA) and p‐phenylenediamine (PDA) or 4,4′‐oxydianiline (ODA) show higher Tgs, and much better thermoplasticity than the corresponding isomeric PIs from symmetric 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA). In addition, a‐BPDA‐derived PIs are completely amorphous owing to their bent chain structures and highly distorted conformations, whereas the PIs from s‐BPDA are semicrystalline. a‐BPDA‐derived PIs possessing these properties or the a‐BPDA monomer were used as a flexible blend component or a comonomer to improve the insufficient thermoplasticity of semirigid s‐BPDA/PDA homo polymer. The blends composed of s‐BPDA/PDA (80%) with a‐BPDA‐derived PIs (20%), as well as the s‐BPDA/PDA‐based copolymer containing 20% a‐BPDA, showed a certain extent of thermoplasticity above the Tgs without causing a decrease in Tg. In addition, these blends and copolymer provided comparatively low thermal expansion coefficient (ca. 18 ppm). The improved film properties for the blends are related to good blend miscibility. On the other hand, when s‐BPDA/ODA was used as a flexible matrix polymer instead of a‐BPDA‐derived PIs, the 80/20 blend film annealed at 400°C exhibited no prominent softening at the Tg. This result arises from annealing‐induced crystallization of the flexible s‐BPDA/ODA component. Thus, these results revealed that a‐BPDA‐derived PIs are promising candidates as matrix polymers for semirigid s‐BPDA/PDA for the present purpose. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2499–2511, 1999 相似文献
995.
Yoichi Katsumoto Kazuya Tatsumi Tatsuki Doi Kazuyoshi Nakabe 《International Journal of Heat and Fluid Flow》2010,31(6):985-995
A sensor that can efficiently and sequentially measure the deformability of individual red blood cell (RBC) flowing along a microchannel is described. Counter-electrode-type microsensors are attached to the channel bottom wall, and as RBCs pass between the electrodes, the time series of the electric resistance is measured. An RBC is deformed by the high shear flow to a degree dependent upon its elastic modulus. Hence, the profile of the resistance, which is unique to the shape of the RBC, can be analyzed to obtain the deformability of each cell. First, theoretical and experimental analyses were conducted to identify the specific AC frequency at which the effect of the electric double layer formed on the electrode surface is minimized. Measurements were then conducted upon samples of normal human RBCs and glutaraldehyde-treated (rigidified) RBCs to evaluate the feasibility of the present method. In addition, simultaneous visualization of RBC deformation was performed using a high-speed camera. Normal RBCs were observed to have a degree of deformation index (DI) of around 0.57, whereas the rigidified RBCs was DI = 0 in the microchannel. The experimental measurements showed a strong correlation between the half-width of the maximum of the resistance distribution and the DI of the RBC. 相似文献
996.
Masatoshi Hasegawa Jun-Ichi Ishii Yoichi Shindo 《Journal of Polymer Science.Polymer Physics》1998,36(5):827-840
Perylenetetracarboxydiimide (PEDI) molecularly dispersed in polyamic acid (PAA) and polyimide (PI) films has unique fluorescence properties. An originally strong fluorescence of PEDI is efficiently quenched in the PAA films. The systematic variation of the chain structure of the PAA matrices revealed that the aromatic amide groups in the PAA chains function as a quencher. When a PAA derived from 3,4,3′4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), BPDA/PDA, was used as a matrix polymer, the fluorescence of the dye dispersed in the film increased abruptly as imidization of the matrix proceeds. But annealing at temperatures higher than 320°C in the step-heating process caused a gradual decrease in the fluorescence intensity. The decreased intensity results from the dye–PDA units interactions intensified by the denser molecular packing of the matrix polymer chains. PEDI shows significant dependence of the fluorescence intensity on the chain structure of the PI matrices. In the various PI films containing a fixed diamine component, the dye fluorescence intensity reduces linearly with an increase in the intramolecular charge transfer ability of the PI matrices. From the result, we propose a fluorescence quenching mechanism through multistep electron transfer processes. The BPDA/PDA polyimide matrix leads to a strong PEDI fluorescence whereas the pyromellitic dianhydride (PMDA)-based PI matrices do not. For the blends composed of these PIs, the fluorescence of PEDI bound into the main chains provides a valuable indicator of the miscibility on the molecular level. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 827–840, 1998 相似文献
997.
Masaya Kakimoto Hideki Ueno Hiroyuki Kojima Yoichi Yamaguchi Akira Nishimura 《Journal of polymer science. Part A, Polymer chemistry》1996,34(13):2753-2758
The doping effects on optical and electrical properties of polysilanes were investigated by in-situ measurement. When polysilanes bearing a p-N,N-dialkylaminophenyl substituent were doped with iodine vapor, drastic spectral changes were observed. The evolved visible absorption up to 700 nm was found to be strong and stable compared to that of iodine-doped polysilanes such as poly(methylphenylsilane). On the basis of the studies concerning iodine doping of the related p-N,N-dimethylaminophenyl-substituted silane and disilane, and also theoretical calculations, this new absorption can be best interpreted by the result of charge transfer consisting of the strong interaction between iodine and dialkylamino substituents in the polysilanes. © 1996 John Wiley & Sons, Inc. 相似文献
998.
999.
1000.
Yoichi Sasaki Mio Oshikawa Pankaj Bharmoria Hironori Kouno Akiko Hayashi‐Takagi Moritoshi Sato Itsuki Ajioka Nobuhiro Yanai Nobuo Kimizuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17991-17997
Photon upconversion (UC) from near‐infrared (NIR) light to visible light has enabled optogenetic manipulations in deep tissues. However, materials for NIR optogenetics have been limited to inorganic UC nanoparticles. Herein, NIR‐light‐triggered optogenetics using biocompatible, organic TTA‐UC hydrogels is reported. To achieve triplet sensitization even in highly viscous hydrogel matrices, a NIR‐absorbing complex is covalently linked with energy‐pooling acceptor chromophores, which significantly elongates the donor triplet lifetime. The donor and acceptor are solubilized in hydrogels formed from biocompatible Pluronic F127 micelles, and heat treatment endows the excited triplets in the hydrogel with remarkable oxygen tolerance. Combined with photoactivatable Cre recombinase technology, NIR‐light stimulation successfully performs genome engineering resulting in the formation of dendritic‐spine‐like structures of hippocampal neurons. 相似文献