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51.
Masamitsu Shirai Masahiro Tsunooka Makoto Tanaka Kanji Nishijima Katsukiyo Ishikawa 《Journal of polymer science. Part A, Polymer chemistry》1989,27(1):325-332
Novel photosensitive polymers were synthesized by the copolymerization of methyl methacrylate and 1,2,3,4-tetrahydro-1-naphthylideneimino p-styrenesulfonate (NISS) and by the ternary polymerization of methyl methacrylate, methacrylic acid, and 9-fluorenylideneiminop-styrene-sulfonate (FISS). NISS and FISS units showed good sensitivity to light of wavelengths below 300 nm and below 366 nm, respectively. Although the polymers were insoluble in aqueous alkaline solutions, on irradiation with UV light they became soluble in aqueous alkaline solutions. A remarkable decrease in molecular weight of the polymers was observed during the photolysis of imino sulfonate groups incorporated into the polymers, which assisted the dissolution of the irradiated polymers. 相似文献
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Yoshiyuki Tanaka Makoto Arakawa Yohei Yamaguchi Chieko Hori Masahiro Ueno Takeyuki Tanaka Tatsushi Imahori Yoshinori Kondo 《化学:亚洲杂志》2006,1(4):581-585
A metal‐free acetylide was observed by using NMR spectroscopy. Metal‐free acetylides are closely related to reactive intermediates (carbanions) in solution; therefore, they have been regarded as unobservable species. However, we generated this highly reactive and unstable species through the deprotonation of phenylacetylene by using the strong nonmetallic phosphazene base tBu‐P4. In the presence of tBu‐P4, the J coupling between the ethynyl carbon and hydrogen nuclei (1JC,H) of phenylacetylene disappeared; this indicates the deprotonation of the alkyne terminal. Furthermore, a large low‐field shift (approximately 90 ppm) of the alkyne carbon resonance was observed. We concluded that we have observed a metal‐free carbanion with a formal charge on an sp‐hybridized carbon atom for the first time. 相似文献
54.
Masahiro Irie Setsuko Tomimoto Koichiro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1972,10(11):3243-3252
The photoinduced ionic polymerization of cyclohexene oxide was studied in the presence of pyromellitic dianhydride. The polymerization is initiated by the excited chargetransfer complex between cyclohexene oxide and the electron-acceptor and proceeds by a cationic mechanism. Photoinduced cationic polymerization of α-methylstyrene was also observed in the presence of pyromellitic dianhydride. The initiation mechanism of the polymerization was elucidated by means of electron spin resonance measurements. The concentration of pyromellitic dianhydride anion-radicals measured in this way was found to be proportional to the rate of polymerization. This result shows clearly that the photopolymerization is initiated by cation-radicals formed from photoexcited donoracceptor complexes. The attempted photocopolymerization of cyclohexene oxide and α-methylstyrene gave a mixture of homopolymers. The composition of the product depends on the wavelength of the light used. 相似文献
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The lithium chloride/1,3-dimethyl-2-imidazolidinone (LiCl/DMI) solvent system for cellulose was adopted as a mobile phase of size-exclusion chromatographic (SEC) analysis of cellulose, and the applicability of this system was examined using multi-angle laser light scattering and 13C-NMR analysis. The results indicate that 8% (w/v) LiCl/DMI ID a true solvent for cellulose, and that cellulose molecules dissolving ID 1% (w/v) LiCl/DMI are separated orderly depending on their molecular mass (MM) or root-mean-square (RMS) radius by the SEC system. Practically, no aggregates were detected ID the dilute cellulose/LiCl/DMI solutions. Furthermore, high stability of cellulose/LiCl/DMI solutions has been demonstrated; only a few percent of decline ID average MM was observed even after storage for 6 months at room temperature. Relationships between RMS radius and MM for hardwood bleached kraft pulp ID 1% LiCl/DMI was estimated as the following equation: g0.59, corresponding to a Mark–Houwink–Sakurada exponent of 0.77. 相似文献
58.
In order to investigate vibrational relaxation mechanism in condensed phase, a series of mixed quantum-classical molecular dynamics calculations have been executed for nonpolar solute in nonpolar solvent and polar solute in polar solvent. In the first paper (Paper I), relaxation mechanism of I2 in Ar, where Lennard-Jones force is predominant in the interaction, is investigated as a function of density and temperature, focusing our attention on the isolated binary collision (IBC) model. The model was originally established for the relaxation in gas phase. A key question, here, is "can we apply the IBC model to the relaxation in the high-density fluid?" Analyzing the trajectory of solvent molecule as well as its interaction with the solute, we found that collisions between them may be defined clearly even in the high-density fluid. Change of the survival probability of the vibrationally first excited state on collision was traced. The change caused by collisions with a particular solvent molecule was also traced together with the interaction between them. Each collision makes a contribution to the relaxation by a stepwise change in the probability. The analysis clearly shows that the relaxation is caused by collisions even in the high-density fluid. The difference between stepwise relaxation and the continuous one found for the total relaxation in the low-density fluid and in the high-density one, respectively, was clarified to come from just the difference in frequency of the collision. The stronger the intensity of the collision is, the greater the relaxation caused by the collision is. Further, the shorter the collision time is, the greater the resultant relaxation is. The discussion is followed by the succeeding paper (Paper II), where we report that molecular mechanism of the relaxation of a polar molecule in supercritical water is significantly different from that assumed in the IBC model despite that the density dependence of the relaxation rate showed a linear correlation with the local density of water around the solute, the linear correlation being apparently in good accordance with the IBC model. The puzzle will be solved in Paper II. 相似文献
59.
Masahiro Tsunooka Shingo Tanaka Makoto Tanaka Hiroaki Egawa Takamasa Nonaka 《Journal of polymer science. Part A, Polymer chemistry》1985,23(9):2495-2505
In the photocrosslinking of poly(2,3-epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS2, CCl4, and CHCl3 in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS2, CCl4, and CHCl3, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t-butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen-oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H2O in the THF. 相似文献
60.
A novel protocol for assembling polycyclic ethers was developed and successfully applied to the synthesis of the EFGH ring system of ciguatoxin CTX3C. A key transformation involves construction of an O,S-acetal through coupling of alpha-chlorosulfide and a secondary alcohol under mild conditions. The method is highly applicable to use with sensitive substrates and will enable the synthesis of various natural and artificial polycyclic ethers. [reaction: see text] 相似文献