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1.
Yoshitomo Ono Naoyuki Kawashima Hiroto Kudo Tadatomi Nishikubo Takabumi Nagai 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2978-2988
The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007 相似文献
2.
T. Tsuneta T. Toshima K. Inagaki T. Shibayama S. Tanda S. Uji M. Ahlskog P. Hakonen M. Paalanen 《Current Applied Physics》2003,3(6):473-476
We succeed in synthesizing NbSe2 nanotubes along with nanofibers by chemical vapor transportation. They are stable crystalline systems and can be synthesized reproducibly in a nearly equilibrium reacting process. We have investigated these nanosize structures of NbSe2 by transmission electron microscopy and electron diffraction. Both of the structures have a similar size of 100–200 nm in diameter. While nanotubes consist of rolled-up NbSe2 layers, nanofibers are a pile of thin flat layers. We propose a mechanism of the formation of NbSe2 nanotubes and nanofibers on the basis of deseleniditive transition from a NbSe3 fiber-shaped crystal. We also measured electrical resistance of the nanofibers with conductive atomic force microscopy and demonstrated that the material show metallic behavior at room temperature. 相似文献
3.
Tadao Seguchi Naoyuki Tamura 《Journal of polymer science. Part A, Polymer chemistry》1974,12(9):1953-1964
The regions trapping allyl radicals in irradiated polyethylene and the reactivity of the radicals with various monomers have been studied by electron spin resonance. Most of the allyl radicals are trapped in defects or surfaces of the crystallite, and only 10% of the radicals are trapped inside the crystallites. Since the reactivity of the allyl radicals depends on whether they come in contact with reactive monomers, the rate of reaction is related to the concentration of the monomers. When grafting reactions are initiated by allyl radicals, the rate of initiation is rapid and the rate of termination at the initial stage is also very fast. Consequently the yield of grafting increases at the initial stage but soon levels off, which is in contrast to the grafting behavior with alkyl radicals. 相似文献
4.
Salma Kassem Alan T. L. Lee David A. Leigh Augustinas Markevicius Daniel J. Tetlow Naoyuki Toriumi 《Chemical science》2021,12(6):2065
Peptides attached to a cysteine hydrazide ‘transporter module’ are transported selectively in either direction between two chemically similar sites on a molecular platform, enabled by the discovery of new operating methods for a molecular transporter that functions through ratcheting. Substrate repositioning is achieved using a small-molecule robotic arm controlled by a protonation-mediated rotary switch and attachment/release dynamic covalent chemistry. A polar solvent mixtures were found to favour Z to E isomerization of the doubly-protonated switch, transporting cargo in one direction (arbitrarily defined as ‘forward’) in up to 85% yield, while polar solvent mixtures were unexpectedly found to favour E to Z isomerization enabling transport in the reverse (‘backward’) direction in >98% yield. Transport of the substrates proceeded in a matter of hours (compared to 6 days even for simple cargoes with the original system) without the peptides at any time dissociating from the machine nor exchanging with others in the bulk. Under the new operating conditions, key intermediates of the switch are sufficiently stabilized within the macrocycle formed between switch, arm, substrate and platform that they can be identified and structurally characterized by 1H NMR. The size of the peptide cargo has no significant effect on the rate or efficiency of transport in either direction. The new operating conditions allow detailed physical organic chemistry of the ratcheted transport mechanism to be uncovered, improve efficiency, and enable the transport of more complex cargoes than was previously possible.Peptides are transported in either direction between chemically similar sites on a molecular platform, substrate repositioning is achieved using a cysteine hydrazide transporter module and a small-molecule robotic arm controlled by a rotary switch. 相似文献
5.
Drying dissipative structural patterns formed in the course of drying colloidal crystals of silica spheres (110 nm in diameter)
in water, methyl alcohol, ethyl alcohol, 1-propyl alcohol, diethyl ether, and in the mixtures of ethyl alcohol with the other
solvents above have been studied on a cover glass. The macroscopic broad rings were formed in the outside edges of the dried
film for all the solvents examined. Furthermore, much distinct broad rings appeared in the inner area when the solvents were
ethyl alcohol, methyl alcohol, and their mixtures. Profiles of the thickness of the dried films were sensitive to the organic
solvents and explained well with changes in the surface tensions, boiling points, and viscosities of the solvents. The macroscopic
and microscopic spoke-like crack patterns formed. The drying area (or the drying time) increased (or decreased) as the surface
tension of the solvent decreased. However, the absolute values of these drying parameters are determined also by the boiling
points of the solvents. Importance of the fundamental properties of the solvents is supported in addition to the characteristics
of colloidal particles in the drying dissipative pattern formation. 相似文献
6.
Tokuda N Sasaki N Watanabe H Miki K Yamasaki S Hasunuma R Yamabe K 《The journal of physical chemistry. B》2005,109(26):12655-12657
Electroless deposition of Ag on atomically flat H-terminated Si(111) surfaces in aqueous alkaline solutions containing Ag ions produced two different sizes of Ag nanowires along atomic step edges: (1) a narrow nanowire of 10 nm in width and 0.5 nm in height and (2) a wide nanowire of 35 nm in width and 11 nm in height. The narrow and wide nanowires were formed by immersion in the solutions containing less than 1 ppb and 8 ppm dissolved-oxygen concentrations, respectively. This result indicates that the dissolved oxygen initiates the formation of Ag nucleation sites and that the fabrication method has a possibility of controlling the size of Ag nanowires. 相似文献
7.
A reversible cyclic voltammogram for the one-electron reduction of ferrocene in 1,2-dimethoxyethane is recorded under experimental conditions that enable the ferrocene anion to exist for a few minutes. The formal rate constant of the ferrocene0/? electrode, determined by cyclic voltammetry at ?45°C, ca. 10?3 cm s?1, is in striking contrast with that of ferrocene+/0, > 10?1 cm s?1. The distortion of the ferrocene molecule caused by reduction may be a reason for this difference in electron-transfer rate. 相似文献
8.
Naoyuki Takahashi Arei Niwa Tadashi Takahashi Takato Nakamura 《Solid State Sciences》2003,5(11-12):1417-1419
The structural analysis of the hexagonal InN film prepared on a Si(100) substrate by the AP-HCVD technique using InCl3 and NH3 as starting materials were carried out by the X-ray pole figure analysis. The deposited films consist of the hexagonal InN pillar crystals. It was found that the pillar crystals, which have random rotation around the 100 axis, were grown at an angle of 70–90° to the substrate. 相似文献
9.
Motoki Okaniwa Naoyuki Kawashima Michitaka Kaizu Yasuaki Mutsuga 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3132-3143
A new polymer blend composed of a hydrogenated ring‐opening polymer (HROP) with an ester group and hydroxyl functionalized polystyrene (HFP) produced the excellent transparent materials which enabled a precise birefringence control in keeping with the other physical properties for optical film use. The blend with a composition from 0.28 to 0.35 for the HFP weight fraction showed an extraordinary wavelength dispersion, transmitting through a zero birefringence point at the critical fraction of 0.45, while each polymer showed an ordinary wavelength dispersion. The observed excellent transparency even above those of the glass transition temperature was attributed to a depressed phase separation that resulted from strong hydrogen bond between the ester and hydroxyl groups. An IR analysis of the film demonstrated a remarkable red‐shift in the carbonyl peak with an increase of the hydroxylated polystyrene content, indicating a strong hydrogen bond between those groups. This new polymer blend provides a useful design to achieve practical demands for film use, both optical and mechanical under the fabrication conditions using the melt extrusion technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3132–3143 相似文献
10.
As Reduced Activation Ferritic/Martensitic (RAFM) steel is considered the primary candidate for use as a structural material in fusion power reactors,many countries are developing different kinds of RAFM.China is developing new CLAM (China Low Activation Martensitic) steel.The study investigates microstructural changes in CLAM steel implanted with deuterium ions induced by 1250 keV electron irradiation from R.T.to 873 K,and observes both the growth and shrinkage of the defect clusters produced by deuterium ... 相似文献