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81.
The kinetics of the cationic polymerization of 1-β-cyanoethyl aziridine initiated 3-hydroxy- 1-propane sulfonic acid sultone and methyl tosylate have been studied. The course of polymerization involved the propagation stage and termination reaction due to the reaction between the growing chain and imino groups in the polymer chain. The propagation constants and termination constants were obtained. The enthalpies of activation for the propagation and termination reactions are ΔHp? = 12.9 kcal/mol and ΔHt? = 12.4 kcal/mol, and the entropies of activation are ΔSp? = -31 cal/deg·mol and ΔSt? = -39 cal/deg·mol. Otherwise, the polymerization initiated with methyl tosylate involved an early stage which was initiated very quickly. 相似文献
82.
Eiichi Ozu Natsuki Yamashita Toshihisa Maeshima Ion C. Baianu Lun-Shin Wei 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1637-1653
N-(Butyl-3-one)imidazole acts as an initiating adduct which is formed in the anionic polymerization of methyl vinyl ketone (MVK) induced by imidazole (Im) and is directly formed from Im and the MVK monomer. The kinetics of the anionic homopolymerization of MVK and acrylamide (AAm) under argon in the presence of the adduct were investigated in tetrahydrofuran (THF). The rate of polymerization for the MVK system is expressed as Rp = k[Adduct] [MVK], where k = 3.1 × 10?6 L/(mol·s)in THF at 30°C. The overall activation energy, Ea , was found to be 5.34 kcal/mol. The Rp for the AAm system is expressed as Rp = k[Adduct] [AAm], where k = 6.8 × 10?6 L/(mol·s) in THF at 30°C, with Ea 7.78 kcal/mol. The mechanism of the polymerization induced by the initiator adduct is discussed on the basis of these results. 相似文献
83.
Katsuya Maeyama Kenji Yamashita Shugo Maeda Noriyuki Yonezawa Shunichi Aikawa Yasuhiko Yoshida 《合成通讯》2013,43(23):4158-4170
Optically active aromatic ether ketone macrocycles containing 2,2′-dimethoxy-1,1′-binaphthyl-6,6′-diyl moieties were synthesized through electrophilic aromatic substitution reaction and stepwise nucleophilic aromatic substitution reactions. Structures of the resulting macrocycles were confirmed by NMR and matrix assisted laser desorption/ionization time of flight (MALDI-TOF) mass measurements. 相似文献
84.
J. P. Mata P. R. Majhi M. Yamashita A. Khanal K. Nakashima P. Bahadur 《Journal of Dispersion Science and Technology》2013,34(9):1248-1256
The effect of sodium dodecyl sulfate (SDS) on the micellization and aggregation behavior of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO13 PO30 EO13) have been investigated by various techniques like, cloud point, viscosity, isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), fluorescence spectroscopy, room temperature phosphorescence (RTP), and small angle neutron scattering (SANS). Addition of SDS in L64 solutions shows mark alteration of different properties. We observed synergistic interaction between SDS and Pluronic L64. The changes in the critical micelle concentration (CMC), critical micelle temperature (CMT), cloud point (CP), micelle size, and shape has been correlated and reported in terms of structure dynamics and mechanics. The ITC titrations have been used to explore the different stages of binding and interactions of SDS with L64. The enthalpies of aggregation for copolymer-SDS aggregates binding, organizational change of bound aggregates, and the threshold concentrations of SDS in the presence of copolymer were estimated directly from ITC titration curves. The effect of temperature on enthalpy values has been reported in terms of different aggregation state. Fluorescence and RTP for L64 were used to investigate the change in micellar environment on the addition of SDS at different temperature. Appearance and shifting of SANS peaks have been used to monitor the size and inter micellar interaction on addition of SDS in L64 solution. Cloud point and viscosity elaborate the penetration of SDS molecule in L64 micelle and hence changing the micellar architect. 相似文献
85.
Nobuyoshi Yamashita Yoshikuni Urushigawa Shigeki Masunaga Mohamed I. Walash Akira Miyazaki 《International journal of environmental analytical chemistry》2013,93(4):289-303
Abstract To assess the risks of organochlorine pesticides discharged into the hydrospheric environment of Egypt, river and lake water, drinking water, suspended solids, sediments and fish were collected during 1993—1994 from the Nile River and Manzala Lake in Egypt and were transported to Japan for chemical analysis. Among different organochlorine pesticides analyzed, p,p′-DDE was the most predominant in fish (7.6 to 67 ng/g wet wt.), sediments (3.2 to 432 ng/g dry wt.) and suspended solids (5.3 tc 138 pg/L). However, in the dissolved phase of water samples HCH compounds predominated (α-HCH, 71 to 2,815 pg/L). Concentrations of organochlorine pesticides, except chlordane, were higher in Manzala Lake than in the River Nile. Concentrations of organochlorine pesticides in fish corresponded with those in sediments from each location. Comparison of organochlorine concentrations in Nile River water with those reported in earlier studies suggested a decrease in concentrations during the last decade. However, concentrations of p,p′-DDE has increased in fish. It appears that the release of this metabolite from contaminated sediment is the major source of p,p′-DDE in fish during recent years. 相似文献
86.
Toshiaki Yamashita Shuhei Matsushita Takuya Nagatomo Ryosuke Yamauchi Masahide Yasuda 《Research on Chemical Intermediates》2013,39(1):111-126
Photoirradiation of Me2CO–H2O solution of pent-4-en-1-ol (1a) with a high-pressure mercury lamp in a test tube gave 8-hydroxyoctan-2-one (3a) in 66 % yield along with oxetane (4a) and the isomer (4a′) in 10 % yield. Irradiation of the running Me2CO–H2O solution of 1a in the flow system of a microchannel reactor (MCR) gave mainly 4a. The photoreaction of 1,1-diphenylethene (2a) with triethylamine gave a Markovnikov-type adduct (5a) and an anti-Markovnikov-type adduct (6a). The use of the MCR enhanced the production of 5a. These phenomena were explained by the light-path length effects of the MCR. 相似文献
87.
Yusuke Shiraki Kazuhiro Tsuruta Junpei Morimoto Chihiro Ohba Akifumi Kawamura Ryo Yoshida Ryuji Kawano Tadashi Uragami Takashi Miyata 《Macromolecular rapid communications》2015,36(6):515-519
Microdevices designed for practical environmental pollution monitoring need to detect specific pollutants such as dioxins. Bisphenol A (BPA) has been widely used as a monomer for the synthesis of polycarbonate and epoxy resins. However, the recent discovery of its high potential ability to disrupt human endocrine systems has made the development of smart systems and microdevices for its detection and removal necessary. Molecule‐responsive microsized hydrogels with β‐cycrodextrin (β‐CD) as ligands are prepared by photopolymerization using a fluorescence microscope. The molecule‐responsive micro‐hydrogels show ultra‐quick shrinkage in response to target BPA. Furthermore, the flow rate of a microchannel is autonomously regulated by the molecule‐responsive shrinking of their hydrogels as smart microvalves.
88.
Keiichi Hirano Yoshiki Yamashita Yumiko Takahashi Hiroshi Sugiyama 《Journal of synchrotron radiation》2015,22(4):956-960
A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images. 相似文献
89.
Syuji Fujii Yuma Yamashita Yoshinobu Nakamura Akira Tsuchida Tsuneo Okubo 《Colloid and polymer science》2014,292(7):1627-1637
Colloidal crystallization and amorphous solidification of deionized suspensions of the polydispersed cationic gel spheres of lightly cross-linked poly(2-vinylpyridine), CAIBA-P2VP (107~113 nm in diameter, ±19~22 nm in dispersity), have been studied from the reflection spectroscopy, morphology, phase diagram, and elastic property. Crystallization takes place even for the polydispersed cationic gel spheres by the significant contribution of the extended electrical double layers formed around the spheres. Critical concentrations of melting coexisted with ion exchange resins were around 0.02 in volume fraction and high compared with those of other cationic and anionic gel crystals examined hitherto. The densities (ρ) of CAIBA-P2VP in suspension state, i.e., weight percent of the gel spheres divided by the corresponding volume percent, was around 0.3. The ρ values decreased sharply with decreasing size of P2VP gel spheres, which supports the small gel spheres containing much water inside and being softer than the large ones. The closest intersphere distances of the crystals and/or amorphous solids were much longer than the hydrodynamic diameters of the gel spheres especially at low sphere concentrations. Fluctuation parameters (b) evaluated from the rigidities of CAIBA-P2VP (0.15~0.28) were large compared with those of gel crystals of large-sized P2VP-based cationic gel spheres, anionic thermosensitive gel spheres of poly(N-isopropylacrylamide) (0.05~0.09) and further much larger than those of typical colloidal hard spheres (around 0.03). The dispersity in sphere size played an important role for distinguishing crystal and amorphous solid. Importance of the extended electrical double layers around the cationic gel spheres is supported in addition to the excluded volume effect of the sphere themselves on the crystallization and/or solidification. 相似文献
90.
Yuji Kikukawa Kensuke Seto Daiki Watanabe Hiromasa Kitajima Misaki Katayama Shohei Yamashita Yasuhiro Inada Yoshihito Hayashi 《Angewandte Chemie (International ed. in English)》2020,59(34):14399-14403
Dodecavanadate, [V12O32]4? (V12), possesses a 4.4 Å cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12O32(Br2)]4? (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm?1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n‐butane, and n‐pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3‐bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2‐,3‐dibromobutane and 2,3‐dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes. 相似文献