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71.
In the preparation of the ABC star triblock copolymer of ethylene oxide, styrene and methyl methacrylate (MMA), the photo-induced
charge-transfer complex (CTC) was used to initiate the polymerization of the third monomer MMA. The CTC was composed of the
diblock copolymer of poly(ethylene oxide) (PEO) and polystyrene (PS), PEO-b
i
-PS, with an aromatic imino group at the conjunction point and benzophenone (BP). It was confirmed that the kinetic behavior
of this macromolecular initiation system is nearly the same with a general small radical initiator: the polymerization rate
R
p ∝ [PEO-b
i
-PS]0.48[BP]0.45[MMA]0.97. Moreover, if the molecular weight of the PEO block is fixed, R
p is independent of the molecular weight of the PS block. By means of measurements of viscosity and fluorescence, it was
found that the micelles of the diblock copolymer PEO-b
i
-PS were formed in benzene. The aromatic imino groups were located on the boundary surfaces of the micelles and were fully
exposed, and so the BP and MMA molecules easily approached them and affected the charge-transfer polymerization of MMA.
Received: 18 August 1998 Accepted in revised form: 25 November 1998 相似文献
72.
The proline-catalyzed Mannich addition of ketones to chalkogenazines is reported. Yields and enantioselectivities of the corresponding products were good to excellent, using different types of organocatalysts. Furthermore the immobilization of hydroxyproline into a readily synthesized polystyrene-copolymer was accomplished. The catalytic performance of this heterogeneous catalyst was successfully demonstrated in the discussed Mannich reaction. 相似文献
73.
Alejandro De Falco Mirta L. Fascio Melisa E. Lamanna Maria A. Corcuera Iaki Mondragon Gerardo H. Rubiolo Norma B. DAccorso Silvia Goyanes 《Physica B: Condensed Matter》2009,404(18):2780-2783
In this work we studied the functionalization of commercially available multiwalled carbon nanotubes (MWCNT) (Nanocyl 3100) with polystyrene by the method so called “grafting from”. The nanotubes were used as received and oxidized in air at 400 °C. The functionalization was started using thionyl chloride under reflux, followed by a reaction with ethylene glycol which allowed the inclusion of hydroxyl groups. The reaction of those with 2-chloropropionyl chloride led to the generation of the polymerization initiator. Last, the radical polymerization of the functionalized nanotubes, using styrene as the monomer, led to new materials which were studied with thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) spectroscopy. 相似文献
74.
《Reaction Kinetics and Catalysis Letters》2003,80(2):359-364
The effect of zinc on the performance of hematite-based catalysts in ethylbenzene dehydrogenation was studied. Zinc acts as
a structural promoter stabilizing the active phase of the catalysts.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
75.
I. Šperlingová L. Dabrowská V. Stránský J. Kuˇcera M. Tichý 《Accreditation and quality assurance》2003,8(3-4):113-116
A preliminary batch of the reference material was prepared by freeze-drying pooled urine samples obtained from healthy persons
occupationally exposed to styrene. Tests for homogeneity and stability were performed by determining urine concentrations
of mandelic (MA) and phenylglyoxylic acids (PGA). The urinary MA and PGA concentrations were followed over an 8-month period
using high performance liquid chromatography (HPLC). No changes of the concentration values were found. Pure PA and PGA from
Merck and Fluka, respectively, were used for traceability purposes, because certified or standard reference materials for
MA and PGA do not exist. Control material ClinChek-Urine Control (Recipe) was analysed simultaneously. The mean values of
MA and PGA compared well with the means of control samples and fell within the control range. The certified values and their
uncertainties were evaluated from the results of interlaboratory comparisons, homogeneity (277.0 ± 7.4 mg L−1 for MA and 148.0 ± 4.7 mg L−1 for FGA) and stability tests. The values are unweighted arithmetical averages of accepted results and their uncertainties
are combined uncertainties enlarged by coefficient k=1, evaluated from the standard uncertainties of the interlaboratory comparison, homogeneity and stability tests.
Received: 17 September 2002 Accepted: 1 November 2002
Acknowledgement This work was supported by the Internal Grant Agency of Ministry of Health of the Czech Republic (Grant NJ/6784–3).
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials
in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to I. Šperlingová 相似文献
76.
荧光猝灭法研究苯乙烯氧化物与DNA的相互作用 总被引:1,自引:0,他引:1
荧光猝灭法是一种可以研究苯化合物与DNA相互作用的动态过程的方法。研究结果表明,苯乙烯氧化物与DNA的相互作用与苯乙烯氧化物浓度的关系服从动力学一级方程。 相似文献
77.
Styrene butadiene (SBR) and natural rubber (NR) can be used as binding matrices to control the release of zinc (Zn) which is a micro-nutrient for plants. The leaching rate of zinc in an aqueous medium depends on the concentration of zinc sulphate loaded in the two types of rubber used, the temperature of the surrounding environment and the pH of the aqueous medium. Water uptake was increased with increasing concentration of ZnSO4. The sustained release of zinc ions from the investigated formulations was prolonged for over five months. The mechanical properties of the vulcanizates were affected as the concentration of zinc sulphate changed. 相似文献
78.
Zhenwei Zhang 《Journal of organometallic chemistry》2011,696(24):3852-3860
The detailed mechanism for arylation of styrene or its α-CF3 substituted analog using aryliron complex [CpFe(CO)2Ar] was studied using density functional theory calculations. Results of calculations show that the arylation mechanism mainly involves three steps: (1) a ligand exchange process between a CO and styrene or its derivative; (2) migration of Ar group from Fe to β-C of styrene; (3) β-H (or β-F) elimination and dissociation of the stilbene derivative from the CpFeHCO (or CpFeFCO) moiety. Both of Steps (2) and (3) experience a similar four-memberred cyclic transition state. The dπ-pπ interaction stabilizes the CC π coordinated complexes and the agostic interaction plays an important role in stabilizing intermediates and promoting elimination of the β-H (or β-F if available). For arylation of the α-CF3 substituted styrene, our calculations clarified that the dissociation of ethylene derivatives to give PF (product for β-F elimination) is kinetically and thermodynamically more favorable than to give PH (product for β-H elimination), which is the determined step for the selectivity of the final products. 相似文献
79.
Thermoplastic elastomer was prepared from deproteinized natural rubber (DPNR) by graft-copolymerization of styrene, which was performed onto rubber particles of about 1 μm in diameter in latex stage with tert-butyl hydroperoxide/tetraethylenepentamine as an initiator. Suitable initiator concentrations were determined to be 3.3 × 10−2 and 20 × 10−2 mol/kg-rubber for the graft-coplymerization of styrene of 1.5 and 5.5 mol/kg-rubber, respectively, in which conversion and grafting efficiency of styrene were more than 90 mol% and 80 mol%, respectively. The resulting polystyrene, grafted onto the rubber particles, was characterized by size exclusion chromatography after ozonolysis. Morphology of the DPNR grafted with polystyrene (DPNR-graft-PS) was observed by transmission electron microscopy (TEM). Change in morphology after processing the DPNR-graft-PS at 150 °C was associated with change in mechanical properties, i.e. stress at strain of 1 and stress at break. The outstanding mechanical properties, maintained even after processing, were assigned to the thermoplasticity of the DPNR-graft-PS, based on the high conversion and high grafting efficiency. 相似文献
80.
本文对苯乙烯本体聚合全过程增长自由基ESR谱进行了研究,对全过程ESR谱的模拟和分析及构象能的计算表明:反应初期12线谱由产生6线谱构象R_1和8线谱的构象R_2叠加而成,其相对含量R_1>R_2。反应中期4线谱和6线的ESR谱的模拟结果为:R_1相似文献