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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.
Kazunori Se Kazushige Miyawaki Kazuhiro Hirahara Atsushi Takano Teruo Fujimoto 《Journal of polymer science. Part A, Polymer chemistry》1998,36(17):3021-3034
A model graft copolymer in which position of graft points was set to the center of a backbone molecule was prepared via anionic living polymerization. Polystyrene-block-poly(p-tert-butoxystyrene)-block-polystyrene (PSt-b-PBSt-b-PSt) was prepared by three-stage sequential addition. The tert-butyl group was removed from PBSt by hydrogen bromide to yield PSt-b-PHSt-b-PSt, having a poly(p-hydroxystyrene) (PHSt) block. The hydroxyl group of PHSt was reacted with dimeric potassium dianions of 1, 1-diphenylethylene (DPE-K) or cumyl potassium (cumyl K) to yield the corresponding macromolecular initiators of PSt-b-PHSt−K+-b-PSt containing the potassium alkoxide ion of PHSt. The newly formed alkoxide groups and remaining initiators of DPE-K or cumyl K are capable of initiating the additionally introduced ethylene oxide (EO). Thus, two block–graft copolymers of polystyrene-block-[poly(p-hydroxystyrene)-graft-poly(ethylene oxide)]-block-polystyrene (PSt-b-(PHSt-g-PEO)-b-PSt) were prepared by a “grafting from” process (backbone initiation). A PSt-b-PHSt-b-PSt backbone (Mn = 1.75 × 105 by osmometry and Mw/Mn = 1.08 by GPC), and two PSt-b-(PHSt-g-PEO)-b-PSt block–graft copolymers (Mn = 2.45 × 105 by osmometry and Mw/Mn < 1.10 by GPC) had narrow molecular weight distributions. A relationship between nonquantitative metallation and spacing of the graft points on a backbone molecule was discussed in detail. Two benzene-cast films formed clear microphase-separated structures of lamellar structure. The dependence of composition on the morphology of the block–graft copolymers was found to differ from that of common block copolymers. A degree of crystallinity of PEO segment and lamellar thickness of PEO phase serving as graft molecule were also found to differ from those of homo PEO and/or PEO segment in common block copolymer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3021–3034, 1998 相似文献
993.
Kazuko Takahashi Satoshi Fujita Kimio Akiyama Misao Miki Kazunori Yanagi 《Angewandte Chemie (International ed. in English)》1998,37(18):2484-2487
The dicyanomethylene group and not the quinone oxygen atoms is the site of the first one-electron reduction for the dicyanohetereotriquinone methide 1 , although the dicyanomethylene group is substituted at a cyclopentadienyl-like five-membered ring! Compound 1 is amphoteric and undergoes a five-stage sequence of one-electron redox reactions. 相似文献
994.
Sugiyama S Fujii M Fukuta K Seyama K Sotowa K Shigemoto N 《Journal of colloid and interface science》2006,295(1):141-147
Magnesium hydrogen phosphate, calcium hydroxyapatite, and strontium hydroxyapatite were successfully prepared from sol consisting of sodium alginate and Na4P2O7 with Mg2+, Ca2+, and Sr2+ in the corresponding nitrates, respectively. It is revealed that the order of the addition of those substrates and the role of sodium alginate are important factors for the preparation of desired phosphate compounds. According to the previous paper on the preparation of calcium hydroxyapatite, sodium alginate was mixed with aqueous Na4P2O7, followed by the addition of the aqueous divalent cations, resulting in the poor formation of the target phosphates. However, as a revised sol-gel technique, sodium alginate was added to the mixture of Na4P2O7 and aqueous Mg2+ and Sr2+, resulting in a rather favorable formation of MgHPO4 and strontium hydroxyapatite, respectively, while the sol thus obtained was stable within a few days. However for aqueous Ca2+, calcium hydroxyapatite could not be obtained through the revised sol-gel technique. In the preparation of magnesium hydrogen phosphate, sodium alginate contributes mainly to the sol formation of the precursor. The ion exchange between Na+ in sodium alginate and aqueous Ca2+ was important for the preparation of calcium hydroxyapatite. In contrast, the reaction of sodium alginate with the mixture of Na4P2O7 and aqueous Sr2+ afforded strontium hydroxyapatite at the specific ratio of those three substrates. The structure of calcium and strontium phosphates prepared from the revised sol-gel process evidently depended on the amount of sodium alginate introduced into the mixture of Na4P2O7 and the corresponding divalent cations. 相似文献
995.
Kazunori Se Osamu Watanabe Yoshinobu Isono Teruo Fujimoto 《Macromolecular Symposia》1989,25(1):249-261
New architectural graft copolymers were prepared, that is, the graft chains were situated in terminal or center position of the backbone chain. These graft copolymers were termed block-graft copolymers. Two different block-graft copolymers were prepared from a “grafting onto” process and a “grafting from” process via living anionic polymerization. These backbone chains are poly(styrene), and the graft chains are poly(isoprene) and poly(ethylene oxide). The polymers were characterized by GPC measurements, osmometry, and ultracentrifugation. The block-graft copolymers formed fine microphase separation structures. It was a morphological feature that an apparent volume fraction of the graft to the backbone might be higher than the real volume fraction. 相似文献
996.
997.
Dr. Yoshiyuki Manabe Dr. Masato Tsutsui Kohtaro Hirao Risako Kobayashi Dr. Hiroshi Inaba Prof. Kazunori Matsuura Daisuke Yoshidome Kazuya Kabayama Prof. Koichi Fukase 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(61):e202201848
We have synthesized B-antigen-displaying dendrimers (16-mers) with different sizes and evaluated their affinity to their IgM antibody in order to investigate which design features lead to effective multivalency. Unexpectedly, the smallest dendrimer, which cannot chelate the multiple binding sites of IgM, clearly exhibited multivalency, together with an affinity similar to or higher than those of the larger dendrimers. These results indicate that the statistical rebinding model, which involves the rapid exchange of clustered glycans, significantly contributes to the multivalency of glycodendrimers. Namely, in the design of glycodendrimers, high-density glycan presentation to enhance statistical rebinding should be considered in addition to the ability to chelate multiple binding sites. This notion stands in contrast to the currently prevailing scientific consensus, which prioritizes the chelation model. This study thus provides new and important guidelines for molecular design of glycodendrimers. 相似文献
998.
Dianne Pham Upamanyu Basu Ivanna Pohorilets Claudette M. St Croix Simon C. Watkins Kazunori Koide 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17588-17594
Hydrogen peroxide (H2O2) mediates the biology of wound healing, apoptosis, inflammation, etc. H2O2 has been fluorometrically imaged with protein- or small-molecule-based probes. However, only protein-based probes have afforded temporal insights within seconds. Small-molecule-based electrophilic probes for H2O2 require many minutes for a sufficient response in biological systems. Here, we report a fluorogenic probe that selectively undergoes a [2,3]-sigmatropic rearrangement (seleno-Mislow-Evans rearrangement) with H2O2, followed by acetal hydrolysis, to produce a green fluorescent molecule in seconds. Unlike other electrophilic probes, the current probe acts as a nucleophile. The fast kinetics enabled real-time imaging of H2O2 produced in endothelial cells in 8 seconds (much earlier than previously shown) and H2O2 in a zebrafish wound healing model. This work may provide a platform for endogenous H2O2 detection in real time with chemical probes. 相似文献
999.
1000.
Takanori Kondo Chihiro Yasui Ikkei Miyajima Dr. Taisuke Banno Prof. Dr. Kouichi Asakura Dr. Tokuma Fukuoka Dr. Kazunori Ushimaru Dr. Maito Koga Dr. Azusa Saika Dr. Tomotake Morita Dr. Yoshiaki Takahashi Chigusa Hayashi Dr. Masayuki Igarashi Prof. Dr. Daisuke Takahashi Prof. Dr. Kazunobu Toshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201733
Synthesis of three types of purpose-designed mannosylerythritol lipid (MEL)-D analogues with decanoyl groups, β-GlcEL-D, α-GlcEL-D, and α-MEL-D, was accomplished utilizing our boron-mediated aglycon delivery (BMAD) methods. Their self-assembling properties, recovery effects on damaged skin cells, and antibacterial activity were evaluated. It was revealed, for the first time, that α-GlcEL-D and α-MEL-D only generated giant vesicles, indicating that slight differences in the steric configuration of an erythritol moiety and fatty acyl chains affect the ability to form vesicles. Analogue α-MEL-D exhibited significant recovery effects on damaged skin cells. Furthermore, α-MEL-D exhibited antibacterial activity as high as that for MEL-D, indicating that α-MEL-D is a promising artificial sugar-based material candidate for enhancing the barrier function of the stratum corneum, superior to a known cosmetic ingredient, and possesses antibacterial activity. 相似文献