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311.
Thermally stimulated currents (TSC) were examined for poly(bis(p-fluorophenoxy)phosphazene) (PBFPP) film. TSC showed peaks at the glass transition temperature (Tg=–4 °C) and atT(1) (160 °C – 170 °C), where-form crystal phase transformed to mesophase of-form structure. Another peak was found atT
cc
betweenTg andT(1). Linear relationship between polarization field and peak current ofT
cc
-peak was found, which shows thatT
cc
-peak was caused by motion of dipolar groups in crystalline phase. When heating (up to 200 °C) and cooling (down to 20 °C) thermal process was repeated,T
cc
-peak shifted to higher temperature region approachingT(1) and simultaneously, the peak current ofT(1)-peak became smaller. Activation energy, time constant of dipolar relaxation and charge mobility were evaluated forT
cc
-peak. From these results, it was concluded that-form and more ordered- form crystalline phases coexisted in PBFPP once heated aboveT(1) and the content of- form phase increased by repeated thermal hysteresis. 相似文献
312.
Takashi Suzuki Toshihiro Hirai Sadao Hayashi 《Reaction Kinetics and Catalysis Letters》1991,43(2):293-299
CO and/or ethylene adsorbed on -Al2O3 was subjected to temperature programmed desorption (TPD). When temperature of the gas adsorbed specimens was linearly raised, two peaks were observed in desorption profile of both ethylene and that of CO. When an equimolecular misture of carbon monoxide and ethylene was adsorbed over the specimen, desorption temperature of CO(H) shifted to high temperature side of 87.2 °C, whereas that of ethylene (H) shifted to low temperature side of 33.0 °C. This behavior of desorption temperature might be attributed to a strong interaction in the two adsorbates induced by an electronic effect.
CO / -Al2O3 . , CO. CO(H) (87, 2°C), (H) (33°C). , .相似文献
313.
Satoru Sasaki Hidetoshi Hirahara Hirokazu Nakayama 《Journal of solid state chemistry》2006,179(4):1129-1135
The intercalation of water-soluble p-sulfonated calix[4 and 6]arene (CS4 and CS6) in the interlayer of the Mg-Al and Zn-Al layered double hydroxide (LDH) by the coprecipitation method has been investigated, as well as the adsorption properties of the resulting CS/LDHs for benzyl alcohol (BA) and p-nitrophenol (NP) to prepare new microporous organic-inorganic hybrid adsorbents. The amount and arrangement of CS intercalated was different by the kind of the host metal ions. CS4 cavity axis was perpendicular for the Mg-Al LDH basal layer and parallel for the Zn-Al LDH basal layer, while CS6 cavity axis was perpendicular for both the LDH basal layers. In the BET surface area measurement, the surface area of the Zn-Al/CS4/LDH was four times than that of the Mg-Al/CS4/LDH, expecting that the former has higher adsorption capacity than the latter. In fact, the adsorption ability of the CS/LDHs for BA and NP in aqueous solution was found to be larger in the Zn-Al/CS4/LDH than in the Mg-Al/CS4/LDH. In addition, the adsorption ability of both the LDHs was larger in the CS6/LDHs than in the CS4/LDHs. These results were explained by the difference in the amount and arrangement of CS intercalated in the LDH interlayer space. 相似文献
314.
Motoyoshiya J Ikeda T Tsuboi S Kusaura T Takeuchi Y Hayashi S Yoshioka S Takaguchi Y Aoyama H 《The Journal of organic chemistry》2003,68(15):5950-5955
Autoxidation of the phosphonate carbanions derived from 9-phosphono-10-hydroacridanes provided chemiluminescence ascribed to the excited acridone anion. The intramolecular CIEEL (chemically initiated electron exchange luminescence) mechanism can be applied to this chemiluminescence because of the much higher emission efficiency compared to that of 9-phosphono-10-methylacridanes. The effect of the phosphonate substituents on the emission efficiency and especially on the rates of the chemiluminescence decay can be interpreted to originate from the valence deviation of the phosphorus atoms, which is connected with the substituent effect on the geometrical selectivity in the olefination reaction of the phosphonate carbanions. The enhanced chemiluminescence in the presence of the fluorophores was also detected in autoxidation of the carbanions of diethyl diphenylmethylphosphonate and fluorenylphosphonate. Although the evidence is circumstantial, these results strongly support the belief that phospha-1,2-dioxetane is the most likely high-energy intermediate generating the excited molecules. 相似文献
315.
Motoyoshiya J Sakai N Imai M Yamaguchi Y Koike R Takaguchi Y Aoyama H 《The Journal of organic chemistry》2002,67(21):7314-7318
The title compound N,N'-bistosyl-1H,4H-quinoxaline-2,3-dione (TsQD) provides peroxyoxalate chemiluminescence (PO-CL) when reacted with hydrogen peroxide in the presence of fluorophores. The chemiluminescence (CL) efficiency of TsQD was superior to that of other related compounds such as bis(2,4,6-trichlorophenyl) oxalate (TCPO), a typical oxalate for the peroxyoxalate PO-CL, under an aqueous condition. Factors affecting the PO-CL efficiency are discussed from the viewpoint of the structures of the substrates and the electronic nature of the fluorophores. A linear correlation of the logarithmic values evaluated from the CL quantum yields with the oxidation potentials of the aromatic fluorophores supports the involvement of the chemically initiated electron exchange luminescence (CIEEL) mechanism in both TsQD- and TCPO-CL systems. Also, an excellent Hammett relationship was derived from the correlation between the sigma(+) values and the relative singlet excitation yields in TsQD-CL enhanced by a series of fluorescent para,para'-disubstituted distyrylbenzenes. 相似文献
316.
The association constant K between methylviologen MV and indoleacetate IA was decreased by the addition of cationic vesicles, and the K increased at high vesicle concen-trations. The influence of the polymerization of surfactants with different chain lengths
on K was different. The concentration dependence of K was analyzed by a theory in terms of the partition coefficients of reactants between the bulk solvent phase and the local
vesicle environment. The theoretical partition coefficients were determined graphically. The measured depen-dence of K on vesicle concentration was satisfactorily reproduced by the theory. When dimyrystyldiallylammonium bromide (DMAB) was added
to the complex, the polymerization of the surfactant increased the partition coefficients of IA and the complex but decreased
that of MV. However, the polymerization of dicetyldiallylammonium bromide (DCAB) showed the reverse tendency. The influence
of polymerization on K or the partition coefficient was discussed in terms of the difference in the polymerization mechanism due to the differences
in the distance between the neighboring nonpolymerized surfactant molecules and the polymerization induced change in that
distance.
Received: 10 May 1996 Accepted: 27 August 1996 相似文献
317.
M. Arai M. Kanamaru T. Matsumura Y. Hattori S. Utsumi T. Ohba H. Tanaka C. M. Yang H. Kanoh F. Okino H. Touhara K. Kaneko 《Adsorption》2007,13(5-6):509-514
Single wall carbon nanotube (SWCNT), which has bundle structure and entangled structure, was untangled and cut by sonication
in hydrogen peroxide (H2O2) solution. The untangled state of SWCNT was examined by SEM, TEM, Raman spectroscopy and N2 adsorption. It was confirmed that the surface area of sonicated nanotubes strongly depended on the sonication time. The BET
specific surface area (SSA) of nanotubes sonicated for 3 h was maximum. The SSA decreased at 6 h or more of sonication time.
These results indicated that the bundle structure was untangled and the cap of SWCNT was opened. Thus, N2 molecules can access the most efficiently inside of the SWCNT sonicated for 3 h. On the contrary, the sonication treatment
for 6 h or more decomposed the nanotubes to produce amorphous carbon, evidenced by TEM and SEM observation; the amorphous
carbon blocked the open pore sites such as the internal pore spaces and interstitial pores. 相似文献
318.
《Journal of organometallic chemistry》2007,692(1-3):60-69
2,3-Disubstituted benzo[b]thiophenes, 1,3-disubstituted benzo[c]thiophenes, and 1,3-disubstituted benzo[c]selenophene have been systematically and selectively synthesized from benzo[b]thiophene or phthaloyl dichloride as a starting material, respectively. Characterization of the molecules was performed by physical and spectroscopic means and X-ray crystallographic analyses. The cyclic voltammograms of the chalcogenophene derivatives containing aryl fragments showed well-defined reversible both anodic and cathodic steps derived from the unusually stable 5π chalcogenophene radical cations and 7π chalcogenophene radical anions. The cyclic voltammograms of the novel chalcogenophene derivatives containing ferrocenyl fragments showed a well-defined reversible cathodic step derived from the unusually stable 7π chalcogenophene radical anions and two distinct reversible anodic steps derived from ferrocenium cations separated from each other by a thiophene-heterocycle. The radical character of several novel 7π chalcogenophene radical anions was measured by ESR spectroscopy. 相似文献
319.
Summary In order to clarify the mechanism of crystallization under molecular orientation, the fractionation for poly(vinyl alcohol) (VAc-PVA) derived from vinyl acetate from its aqueous solution was carried out under shearing force. The fibrillar crystals grown by shearing force from solutions were produced on the stirrer and in solution simultaneously. The fibrillar crystals had a diameter of approximately 1 mm and a length of 1 cm in the case of the initial polymer concentration of 2.0%, and approximately 1 mm and 5 cm in the case of 0.5%. The initial rate of precipitation (Rs) for the precipitates produced in solution was higher than that (Rr) on the stirrer. The difference betweenRs andRr increased with an increase in initial polymer concentration. The difference in the percentages of syndiotactic diads of precipitates grown on the stirrer and those in solution was not found, and the percentages of syndiotactic diads of each fraction decreased in the order of fractionation. Furthermore, the difference in the molecular weight of precipitates grown on the stirrer and those in solution was not found in the case of the higher polymer concentration, whereas it was found clearly in the case of lower one.
Mechanical Denaturation of High Polymers in Solutions, XXV. 相似文献
Zusammenfassung Um den Mechanismus der Kristallisation unter molekularer Orientierung zu klären, wurde die Fraktionierung von Polyvinylalkohol (VAc-PVA), der aus Vinylacetat hergestellt war, in wäßriger Lösung unter Scherkräften durchgeführt. Die von Lösung unter Scherung gewachsenen flbrillären Kristalle erscheinen gleichzeitig in Lösung und auf dem Rührer. Die aus Lösung gewonnenen Faserkristalle hatten einen Durchmesser von etwa 1 mm und eine Länge von etwa 1 cm bei einer anfänglichen Konzentration des Polymeren von 2.0%, etwa 1 mm und 5 cm resp. für 0.5%. Die anfängliche Fällungsgeschwindigkeit (Rs) der in Lösung wachsenden Niederschläge war höher als diejenige (Rr) auf dem Rührer. Ein Unterschied im Gehalt an syndiotaktischen Diaden zwischen den vom Rührer und aus der Lösung entnommenen Faserkristallen ließ sich nicht feststellen, und die syndiotaktischen Diaden nahmen in beiden Proben mit der Ordnung der Fraktionierung ab. Darüber hinaus ließ sich ein Unterschied im Molekulargewicht zwischen den auf dem Rührer und in der Lösung gewachsenen faserigen Kristallen bei der höheren Anfangskonzentration des Polymeren nicht feststellen, aber bei der niedrigeren Anfangskonzentration des Polymeren war die Auswirkung des Molekulargewichtes deutlich.
Mechanical Denaturation of High Polymers in Solutions, XXV. 相似文献
320.
《Electrochemistry communications》2008,10(4):668-672
Some oxide catalysts, such as RuO2/Ti, IrO2/Ti and IrM(M: Ru, Mo, W, V)Ox/Ti binary oxide electrodes, were prepared by using a dip-coating method on a Ti substrate. Their catalytic behavior for the oxygen reduction reaction (ORR) was evaluated by cyclic voltammetry in 0.5 M H2SO4 at 60 °C. These catalysts were found to exhibit considerably high activity, and the most active one among them was Ir0.6V0.4O2/Ti prepared at 450 °C, showing onset potential for the ORR at about 0.86 V–0.90 (vs RHE). 相似文献