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1.
Per B. Zetterlund Kazuki Miyake Kunihiro Goto Bunichiro Yamada 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2640-2650
A detailed investigation of addition–fragmentation chain transfer (AFCT) in the free‐radical polymerization of methyl methacrylate (MMA) in the presence of methyl α‐(bromomethyl)acrylate (MBMA) was carried out to elucidate mechanistic details with efficient macromonomer synthesis as an underlying goal. Advanced modeling techniques were used in connection with the experimental work. Curve fitting of simulated and experimental molecular weight distributions with respect to the rate coefficient for addition of propagating radicals to MBMA (kadd) over 60–120 °C resulted in Eadd = 21.7 kJ mol?1 and Aadd = 2.18 × 106 M?1 s?1 and a very weak temperature dependence of the chain‐transfer constant (Eadd ≈ Ep). The rate coefficient for fragmentation of adduct radicals at 60 °C was estimated as kf ≈ 39 s?1 on the basis of experimental data of the MMA conversion and the concentration of 2‐carbomethoxy‐2‐propenyl end groups. The approach developed is generic and can be applied to any AFCT system in which copolymerization does not occur and in which the resulting unsaturated end groups do not undergo further reactions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2640–2650, 2004 相似文献
2.
An optical element constructed by stacking a set of binary-phase grating sheets can simulate the functions of optically recorded volume gratings. Our electromagnetic numerical study also shows that if one of the grating sheets is replaced by another one with different grating period, power spectrum of the diffracted wave changes completely with extra diffraction orders. This property will claim strong advantage in security document applications. Analysis of alignment error reveals interesting phenomena concerning to how misalignment affects diffraction efficiency. 相似文献
3.
Hirotaka Okamoto Tadashi Inoue Kunihiro Osaki 《Journal of Polymer Science.Polymer Physics》1995,33(3):417-424
The complex Young's modulus, E*(ω), and the complex strain-optical coefficient, O*(ω), which is the ratio of the birefringence to the strain, were measured for polyisoprene (PIP) over a frequency range of 1 ~ 130 Hz and a temperature range of 22 ~ ?100°C. The imaginary part of O*, O″, was positive at low frequencies and negative at high frequencies. The real part, O′, was always positive and showed a maximum. The complicated behavior of O* could be understood by the assumption that E* = ER* + EG* and O* = CRER* + CGEG*, where ER* and EG* were complex quantities and CR and CG were constants. The CR value, equal to the ordinary stress-optical coefficient measured in the rubbery plateau zone, was 2.0 × 10?9 Pa?1. The CG value, defined as the ratio O″/E″ in the glassy zone, was ?1.1 × 10?11 Pa?1. The EG*, which was the major component of E* in the glassy zone, showed almost the same frequency dependence as that of polystyrene and polycarbonate. The ER*, which was dominant in the rubbery zone, was described well by the bead-spring theory. The temperature dependence of the EG* was stronger than that of the ER*. This difference caused the breakdown of the thermorheological simplicity for E* and O* around the glass-to-rubber transition zone. © 1995 John Wiley & Sons, Inc. 相似文献
4.
T. Argiriou A. Kalliafas C. Psarianos K. Kana M. Kanellaki A. A. Koutinas 《Applied biochemistry and biotechnology》1992,36(3):153-161
Two alcohol resistant strains of Saccharomyces cerevisiae species were isolated from a Greek vineyard plantation. The strain AXAZ-1 gave a concentration of 17.6% v/v alcohol and AXAZ-2 16.5%, when musts from raisin and sultana grapes, respectively, were employed in alcoholic fermentations. They were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker's yeast. Specifically, using an initial [symbol: see text] Be density of 16 [symbol: see text] Be at the repeated batch fermentation process, in the first as well as fourth batch, the better AXAZ-1 gave final [symbol: see text] Be densities of 6.0 and 10.5 respectively, and the baker's yeast 11.6 and 14.5. 相似文献
5.
Seiji Miyano Osamu Yamashita Kunihiro Sumoto Keiyu Shima Mariko Hayashimatsu Fumio Satoh 《Journal of heterocyclic chemistry》1987,24(1):271-274
The method for preparing 7a-substituted hexahydro-1H-pyrrolizines 2 from 1,2,3,5,6,7-hexahydropyrrol-izinium Perchlorate (3) was investigated, by which introduction of a wide variety of functionalities on C(7a) could be achieved easily. 相似文献
6.
Efficient routes to hitherto unknown 1d-2,5-di-azido-di-deoxy-allo-inositol, 1d-2,5-di-amino-di-deoxy-allo-inositol, 1l-1-azido-1-deoxy-chiro-inositol and 1l-1-amino-1-deoxy-chiro-inositol were developed by using cheaply available myo-inositol as the starting material. Preliminary investigations on the enzyme inhibitory properties were done. The methodology reported is amenable to gram scale synthesis and thus can find application in natural product synthesis. 相似文献
7.
Kunihiro Ichimura Toshio Komatsu 《Journal of polymer science. Part A, Polymer chemistry》1987,25(6):1475-1480
A convenient procedure to prepare photosensitive poly(vinyl alcohol) by acetalization with 1-methyl-4-(p-formylstyryl)pyridinium methosulfate in heterogeneous condition is described. The reaction of fully saponified poly(vinyl alcohol) was carried out in suspension in acidic aqueous solution, while partially saponified poly(vinyl alcohol) was acetalized in acidic aqueous organic solvent. The photosensitive poly(vinyl alcohol) thus prepared was purified by filtration and successive washing out with methanol. The effect of the preparative condition on the electronic absorption spectra of the styrylpyridinium group attached to poly(vinyl alcohol) is discussed. 相似文献
8.
Yuji Kawanishi Yasuzo Suzuki Masako Sakuragi Hisamitsu Kamezaki Kunihiro Ichimura 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):433-438
The alignment of nematic liquid crystalline (LC) molecules with respect to the LC cell surface was regulated between the homeotropic (H) state and the parallel (P) state by the photochromic trans—cis isomerization of surface-attached azobenzene (Az) moieties. By bringing the angular-selective photoreaction into the system, the orientational order in the P state was significantly improved to attain a universal orientational axis over the entire irradiated area, which was rotatable and erasable photochemically. Laser pulse experiments revealed that the allignment relaxation time τ was reduced from 1000 to 30 ms by increasing the pulse intensity from 10 to 20 mJ cm−2. Strong coupling between the LC and Az molecules was indicated. 相似文献
9.
Polymers are an integral part of our daily life. Hence, there are constant efforts towards synthesizing novel polymers with unique properties. As the composition and packing of polymer chains influence polymer''s properties, sophisticated control over the molecular and supramolecular structure of the polymer helps tailor its properties as desired. However, such precise control via conventional solution-state synthesis is challenging. Topochemical polymerization (TP), a solvent- and catalyst-free reaction that occurs under the confinement of a crystal lattice, offers profound control over the molecular structure and supramolecular architecture of a polymer and usually results in ordered polymers. In particular, single-crystal-to-single-crystal (SCSC) TP is advantageous as we can correlate the structure and packing of polymer chains with their properties. By designing molecules appended with suitable reactive moieties and utilizing the principles of supramolecular chemistry to align them in a reactive orientation, the synthesis of higher-dimensional polymers and divergent topologies has been achieved via TP. Though there are a few reviews on TP in the literature, an exclusive review showcasing the topochemical synthesis of polymers with advanced structural features is not available. In this perspective, we present selected examples of the topochemical synthesis of organic polymers with sophisticated structures like ladders, tubular polymers, alternating copolymers, polymer blends, and other interesting topologies. We also detail some strategies adopted for obtaining distinct polymers from the same monomer. Finally, we highlight the main challenges and prospects for developing advanced polymers via TP and inspire future directions in this area.This perspective showcases the potential of topochemical polymerization as an effective tool for synthesizing polymers with advanced molecular and supramolecular structures. 相似文献
10.
The palladium-catalyzed regio- and diastereo-selective allylic alkylation of allyl acetates with carbon nucleophiles occurred. The stereochemistry was highly controlled by the palladium catalyst with 2-(diphenylphosphino)benzoic acid as the ligand, and vicinal quaternary and tertiary carbon centers were constructed. 相似文献