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61.
本文在分析乙烯-α-烯烃共聚物序列结构时,把代表共单体反接单元的亚甲基(CH2)βγ和γδ分别归属给了二元组VV和三元组EEV。与此同时,CH2-δδ和δδ+归属给了二元组EE。表征乙烯长序列的CH2-δ+δ+分属二元组EE和三元组EEE,对应峰强度在EE和EEE之间的分配是处理序列分布的关键。在本文中运用序列结构的Bovey关系和Randall统计进行演算,求得了修正值△的数学表达式,严格解和近似解。在规则链条件下得到的近似解与G.J.Ray的结果完全相同。当共单体含量较少时,谱峰强度Iδ+δ+的分配接近相等。在二元组和三元组的水平上,乙烯-α-稀烃共聚物的13C NMR谱中共有十三个峰,属于CH2的有十个,属于CH的有三个。利用这些谱峰的强度数据可以建立一套计算公式,由此提供共聚物序列结构的全部信息。因此这是一个研究乙烯-α-烯烃共聚物序列结构的普适方法。 相似文献
62.
Three New Diarylpropanes from Dioscorea composita 总被引:1,自引:0,他引:1
ShunLiYANG XiKuiLIU 《中国化学快报》2005,16(1):57-60
Three new diarylpropanes were isolated from the dried rhizomes of Dioscorea composita Hemsl., and their structures were determined as 1, 3-bis-(2-hydroxy-4-methoxyphenyl) propane (1), 1, 3-bis-(2, 4-dihydroxyphenyl)propane (2), 1-(2′-hydroxy-4′-O-β-D- glucopymnosy-phenyl)-3-(2“, 4“-dihydroxyphenyl)propane (3), by spectroscopic analysis, respectively. 相似文献
63.
This study reports on the effect of input power to hexamethyldisiloxane (HMDSO) plasmas. The power dependence of the plasma-phase species and of the surface chemistry (of the deposits) has been investigated. Neutral and positive molecular species were detected within the plasma using mass spectrometry (MS). Secondary ion mass spectrometry (SIMS) was used to probe the molecular structure of the deposits. The elemental composition of the surface was determined by XPS and the deposition rate was monitored using a vibrating quartz crystal microbalance. Neutral and cationic molecules of mass greater than HMDSO were detected in the plasma. Their formation through ion-molecule reactions is proposed. Changes in the relative concentration of plasma-phase species follow those seen in molecular species detected at the deposit surface. Thus, we believe that the molecular structure of the deposits can be related to the species present in the plasma. While traditionally the dominant mechanism in deposit formation is assumed to be free radical combinations, we propose other possibilities involving cations with the aim of putting forward a new perspective on plasma polymerization mechanisms and thereby stimulating discussion. 相似文献
64.
Pyrolysis ammonia chemical ionization (PyCI) mass spectrometry was performed on hy-droxyethyl-, hydroxypropyl-,methyl-, hydroxypropylmethyl-, and ethylhydroxyethyl cel-luloses. The mass peaks in the PyCI mass spectra of these cellulose ethers could be assigned to the ions of pyrolytic dissociation products which form via the [2 + 2 + 2] cycloreversion and the Ei elimination pyrolysis pathway. Structural information about the residual amount of nonderivatized cellulose, the relative chain length distributions of the substituents in hydroxyalkyl celluloses, and the end-capping of hydroxyalkyl substituents by alkyl groups in the mixed cellulose ethers is obtained. Interference of secondary pyrolysis products in the PyCI mass spectra is found to be of minor importance, especially in the lower mass regions. © 1995 John Wiley & Sons, Inc. 相似文献
65.
Wojciech Bocian Jarosław Jaźwínski Lech Stefaniak Graham A. Webb 《Chemistry of Heterocyclic Compounds》1995,31(9):1103-1107
1H,13C,14N and15N NMR measurements are reported for four mesoionic 1-oxa-2, 3, 4-triazoles containing exocyclic nitrogenous groups. The NMR signal assignments are discussed and compared with those previously published for some corresponding oxatriazoles. The results obtained support the proposed cyclic mesoionic structures for the compounds studied. The questions of possible charge delocalization and valence tautomerism are addressed. Compound with N– H as a exocyclic group (Fig. 1) is found to be relatively unstable, this is attributed to proton migration in the corresponding non-cyclic form of this molecule.Published in Khimiya Geterotsikiicheskikh Soedinenii, No. 9, pp. 1260–1263, September, 1995. 相似文献
66.
本文用对数正态分布对物理显影中常用的Au、Ag及Ag_2s胶体催化剂的颗粒大小的实验分布进行了拟合。理论分布与实验分布的比较表明:本实验条件下制备的十二组胶体溶液其颗粒大小都服从了对数正态分布,并且不依赖于胶体的组成、大小及制备方法。因此,它们很可能遵从了同样的成核成长规律。 相似文献
67.
Huseyin Zengin Gulay Zengin Dennis W. Smith 《Journal of polymer science. Part A, Polymer chemistry》2006,44(24):6988-6996
This study focuses on the preparation, characterization, and optical properties of new bis(3,4‐diphenylethynylphenyl)phenylamine. This is the first nitrogen‐containing bis‐ortho‐diynylarene (BODA) monomer having a nitrogen atom as the spacer group. BODA monomers are usually prepared from common bisphenols, thereby providing great synthetic versatility and the opportunity to develop a wide array of novel polyarylene thermosets by varying the aromatic spacer group. The new bis(3,4‐bisphenylethynylphenyl)phenylamine was synthesized in five steps. This compound emits an intense blue color (λ = 438 nm) upon irradiation by UV light and may be suitable for use as an emitting layer in electroluminescent devices. Bis‐(3,4‐bisphenylethynylphenyl)phenylamine and its polymer have photoluminescence quantum yields 34 and 38%, respectively, and long excited‐state lifetimes of 3.2 and 3.6 ns, respectively. The structure of the monomer and its polymer were characterized using spectroscopic techniques including Ultraviolet–visible Spectrophotometer, Photoluminescence Spectrophotometer, Fourier Transform infrared spectroscopy, and Gel Permeation Chromatography. The polymerizations were studied by Differential Scanning Calorimeter. The amount of weight loss and the thermostability of the nitrogen‐containing polymer were determined from thermogravimetric analysis. The electrical conductivity of neat HCl‐doped BODA‐derived polymer film was measured according to the standard four‐point probe technique. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6988–6996, 2006 相似文献
68.
A.R. Phani 《Applied Surface Science》2006,253(4):1873-1881
The structural properties of fluorine containing polymer compounds make them highly attractive materials for hydro-oleophobic applications. However, most of these exhibit low surface energy and poor adhesion on the substrates. In the present investigation, crack free, smooth and uniform thin films of poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole]-co-tetrafluoroethylene (TFD-co-TFE) with good adhesion have been deposited by wet chemical spin-coating technique on polished AISI 440C steel substrates. The as-deposited films (xerogel films) have been subjected to annealing for 1 h at different temperatures ranging from 100 to 500 °C in an argon atmosphere. The size growth of the nano-hemispheres increased from 8 nm for xerogel film to 28 nm for film annealed at 400 °C. It was found that as the annealing temperature increased from 100 to 400 °C, nano-hemisphere-like structures were formed, which in turn have shown increase in the water contact angle from 122° to 147° and oil (peanut) contact angle from 85° to 96°. No change in the water contact angle (122°) has been observed when the films deposited at room temperature were heated in air from 30 to 80 °C as well as exposed to steam for 8 days for 8 h/day indicating thermal stability of the film. 相似文献
69.
R. L. Dobrushin A. Pellegrinotti Yu. M. Suhov L. Triolo 《Journal of statistical physics》1988,52(1-2):423-439
The long-time behavior of an infinite chain of coupled harmonic oscillators is studied. In addition to a limiting hydrodynamic (Euler-type) equation, the next approximation is investigated. The corresponding equation is derived. 相似文献
70.
J. A. M. Janssen 《Journal of statistical physics》1989,57(1-2):187-198
The master equation for a complex chemical reaction cannot always be reduced to a simpler master equation, even if there are fast and slow individual reaction steps. Nevertheless the elimination of intermediates can be carried out with the help of the-expansion. This is illustrated with a well-known complex reaction: the dissociation of N2O5. It is shown that the intrinsic fluctuations in the N2O5 decay are larger than those implied by the master equation suggested by the macroscopic rate law. 相似文献