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51.
Tomohito Kameda Katsuaki Imai Guido Grause Tadaaki Mizoguchi Toshiaki Yoshioka 《Polymer Degradation and Stability》2009,94(9):1595-1597
The dehydrochlorination of PVC in the presence of NaOH was investigated in different diols. Diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG) were found to be effective in accelerating the dechlorination of PVC. The dehydrochlorination was promoted in the order TEG > DEG > PG, which was in agreement with the compatibility between PET and the diol. Compatibility resulted in an improved penetration of the PVC particle by the solvent, leading to the acceleration of the dehydrochlorination. The dehydrochlorination of PVC in NaOH/diol followed first-order kinetics, confirming the progress of the reaction under chemical reaction control. The apparent activation energies were 82 kJ mol−1, 109 kJ mol−1, and 151 kJ mol−1 for TEG, DEG, and PG, respectively. The lower the activation energy became the faster the dehydrochlorination of PVC proceeded. 相似文献
52.
Sanjay S. Latthe Hiroaki Imai V. Ganesan Charles Kappenstein A. Venkateswara Rao 《Journal of Sol-Gel Science and Technology》2010,53(2):208-215
Optically transparent silica films were prepared at room temperature (~27°C) by keeping the molar ratio of TEOS:MeOH:H2O (0.001 M NH4F) constant at 1:19.29:6.20, respectively. A surface chemical modification of the films was done with alkylchlorosilanes at
different concentrations from 0 to 1 vol. % and aging times varied from half to 2 h. The DMCS and TMCS surface modified silica
films showed the static water contact angle of 146° and 162°, respectively. When the DMCS and TMCS modified films were cured
at temperatures higher than 240 and 275°C, respectively, the films became superhydrophilic. Further, the humidity study was
carried out at a relative humidity of 90% at 30°C temperature over 60 days. We characterized the water repellent silica films
by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, % of optical transmission,
humidity tests and contact angle measurements. 相似文献
53.
Yasuda M Nakajima H Takeda R Yoshioka S Yamasaki S Chiba K Baba A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(14):3856-3867
Boron complexes that contain new tridentate ligands, tris(o‐oxyaryl)methanes and ‐silanes, were prepared. These complexes had a cage‐shaped structure around a boron center and showed higher Lewis acidity and catalytic activity than open‐shaped boron compounds. The cage‐shaped ligands determined the properties of the borates by altering the geometry and were consistently bound to the metal center by chelation. The synthesized compounds were L?B(OC6H4)3CH, L?B(OC6H4)3SiMe, and its derivatives (L=THF or pyridine as an external ligand). Theoretical calculations suggested that the cage‐shaped borates had a large dihedral angle (Cipso‐O‐B‐O) compared with open‐shaped borates. The geometric effect due to the dihedral angle means that compared with open‐shaped, the cage‐shaped borates have a greater Lewis acidity. The introduction of electron‐withdrawing groups on the aryl moieties in the cage‐shaped framework increased the Lewis acidity. Substitution of a bridgehead Si for a bridgehead C decreased the Lewis acidity of the boron complexes because the large silicon atom reduces the dihedral angle of Cipso‐O‐B‐O. The ligand‐exchange rates of the para‐fluoro‐substituted compound B(OC6H3F)3CH and the ortho‐phenyl‐substituted compound B(OC6H3Ph)3CH were less than that of the unsubstituted borate B(OC6H4)3CH. The ligand‐exchange rate of B(OC6H4)3SiMe was much faster than that of B(OC6H4)3CH. A hetero Diels–Alder reaction and Mukaiyama‐type aldol reactions were more effectively catalyzed by cage‐shaped borates than by the open‐shaped borate B(OPh)3 or by the strong Lewis acid BF3?OEt2. The cage‐shaped borates with the bulky substituents at the ortho‐positions selectively catalyzed the reaction with less sterically hindered substrates, while the unsubstituted borate showed no selectivity. 相似文献
54.
55.
A kinetic study on methanol dehydrogenation over an FeTiZn0.44 alloy at 673 K suggested a mechanism including an adsorbed formaldehyde intermediate. A lower W/F and a higher methanol pressure favored a higher formaldehyde selectivity. 相似文献
56.
Takeo Saegusa Hirosuke Imai Shu-Ichi Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》1968,6(3):459-465
Kinetic studies were carried out on the polymerization of tetrahydrofuran with catalyst systems of aluminum alkyl–epichlorohydrin. As aluminium alkyl species AlEt3, AlEt3–H2O (1:0.1 to 1:1.0), and “oxyaluminum ethyl” were employed. The polymerizations with these catalysts are characterized by a mechanism of stepwise addition without chain transfer or termination, which is expressed by the kinetic relation Rp = Kp[P*] ([M]–[M]e), where [M] and [M]e are the instantaneous and equilibrium concentrations of monomer and [P*] is the concentration of propagating species calculated from the amount and molecular weight of the product polymer. The determination of the rate constant kp for these catalysts has shown that the polymerization rate varied considerably with the change of aluminum alkyl species, i.e., with the water-to-aluminum ratio, but the propagation rate constant itself varied very little. The variation of polymerization rate was, therefore, attributed primarily to the differences in concentration of the propagating species, i.e. the efficiency of the catalyst in forming propagating species. The catalyst efficiency was closely related to the acid strength of the aluminum alkyl species, which was estimated from the magnitude of shift of the xanthone carbonyl band in the infrared spectrum of its coordination complex with aluminum alkyl. The maximal catalyst efficiency was attained at about [H2O]/[AlEt3] = 0.75. 相似文献
57.
A simple method is presented for measuring the heat of mixing and the heat of vaporization of volatile liquids at temperatures below their boiling point. It consists in introducing liquids by a microsyringe into a nearly closed cell of the DSC. The relative standard deviation for 4 to 5 runs is ca. 5% for heat of mixing and ca. 2% for heat of vaporization. 相似文献
58.
Masahiko Ogura Norikazu Nakatani Norisuke Yamaji Makoto Imai Akio Itoh Nobutsugu Imanishi 《Radiation Physics and Chemistry》1997,49(6):645-649
We have studied effects of added elements as well as defects on trap-sites of hydrogen in metals. For the purpose, we observed depth profiles and thermal behaviors of hydrogen implanted into Al-1.5 at.% Si alloy samples in an implantation-temperature range of liquid nitrogen temperature (LNT) to 373 K at different doses. The results were compared with those for pure aluminum samples. It was found that hydrogen is trapped as molecules in grain boundaries of Al/Si. 相似文献
59.
A method for the enantiomeric determination of 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (LLU-alpha, gamma-CEHC) in rat plasma was developed using high-performance liquid chromatography (HPLC) with a fluorimetric derivatization with 4-N, N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) followed by O-acetylation with acetyl chloride. The proposed HPLC system used two non-chiral columns (phenyl and octadecylsilica) and a chiral column (a modified cellulose type), which were connected via two column-switching valves. A derivatized sample prepared from rat plasma was first separated on the phenyl column, and the fraction including LLU-alpha derivative was introduced to the octadecylsilica column to quantify the concentration of the mixture of S- and R-LLU-alpha. Finally, the LLU-alpha derivative was directly injected into the chiral column to obtain the ratio of the enantiomers. The proposed HPLC system was applied to the enantiomeric determination of LLU-alpha in plasma after intravenous administration of racemic LLU-alpha. S-LLU-alpha was eliminated faster than R-LLU-alpha, and its concentration in plasma decreased to one-third at 2 min after dosing. 相似文献
60.
We propose a highly sensitive method for the measurement of catechol-O-methyltransferase (COMT) activity with norepinephrine (NE), an endogenous native substrate. The product, normetanephrine, was determined by high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence reaction detection or, if required, less sensitive fluorescence detection. For the measurement of membrane-bound (MB)-COMT activity in the rat erythrocyte, the HPLC-peroxyoxalate chemiluminescence reaction detection was employed. Soluble (S)- and MB-COMT activities in the rat erythrocyte were 22.9 +/- 2.5 and 4.62 +/- 1.23 pmol min-1 (mg protein)-1, respectively (n = 5). The Km values obtained for S- and MB-COMT were 366 +/- 31 mumol l-1 and 12.0 +/- 1.1 mumol l-1, respectively (n = 5), suggesting that the use of NE as a substrate would give more precise information on the role of both isoenzymes. However, with dihydroxybenzoic acid as an artificial substrate, the Km values for S- and MB-COMT were similar, with values of 69.2 +/- 11.4 mumol l-1 and 72.2 +/- 9.2 mumol l-1, respectively. The proposed method is thought to be useful for the measurement of both S-COMT and MB-COMT activities, and would give us critical information on the role of metabolism of catecholamines in rat tissues. 相似文献