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91.
The MCM‐41 and SiO2 supported TiCl4 and TiCl4/MgCl2 catalysts with different molar ratios of Mg/Ti were synthesized and used for ethylene polymerization under atmospheric pressure. The nanochannels of MCM‐41 serve as nanoscale polymerization reactor and the polyethylene nanofibers were extruded during the reaction. The nanofibers were observed in SEM micrographs of resulting polyethylene. The effect of MgCl2 on catalytic activity and thermal properties of resulting polyethylene is investigated too. In the presence of MgCl2, the catalytic activity increased and more crystalline polyethylene with higher melting points were formed. However, no fibers could be observed in the polyethylene prepared by SiO2 supported catalysts. 相似文献
92.
《Green Chemistry Letters and Reviews》2013,6(1):55-59
Abstract Ceric ammonium nitrate in polyethylene glycol has been used as a sustainable, non-volatile, and ecofriendly catalytic medium for the green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles. This protocol is effective toward various substrates having different functionalities. The easy recyclability of the reaction medium makes the reaction economically and potentially viable for commercial applications. 相似文献
93.
A simple and efficient preparation of a number of hybrid linear‐branched PEG esters are described. The polymers are generated by direct coupling of PEG–carboxylic acids and a variety of pentaerythritol ethoxylates using carbon tetrabromide catalyst. 相似文献
94.
An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO2, and alkyl halides underwent a three-component reaction with the aid of K2CO3 and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
95.
Liping Zhao Zhenghong Guo Zhenhu Cao Tao Zhang Zhengping Fang Mao Peng 《Polymer Degradation and Stability》2013
Fullerene (C60)/high density polyethylene (HDPE) composites were studied in order to understand for their behaviors on thermal and thermo-oxidative degradation. Under different atmosphere, the influences of C60 on the thermal stability of HDPE are different. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) demonstrate that in N2 the addition of C60 increases the onset decomposition temperature by about 10 °C with more heavy compounds (more than 34 carbon). Also the thermal stability of HDPE in air is remarkably improved with the addition of C60. When the content of C60 is 2.5 wt% the onset decomposition temperature increases by about 91 °C. The results of viscoelastic behavior and gel content reveal that C60 can trap the alkyl radicals and alkyl peroxide radicals to inhibit hydrogen abstraction to suppress the chain scission and preserve the long chain structure. However, in the absence of C60 or with low C60 concentration, hydrogen abstraction occurs, resulting in the formation of a series of alkyl radicals and alkyl peroxide radicals, which accelerates the chain scission and plays a leading role in the thermal oxidative degradation. 相似文献
96.
Qing Ye Liang-Fang Zhai Nian-Nian Fan De-Ping Lu 《Journal of Dispersion Science and Technology》2013,34(6):859-869
The poly(methyl methacrylate/butyl acrylate/acrylic acid) [P(MMA/BA/AA)] and poly (styrene/butyl acrylate/acrylic acid) [P(St/BA/AA)] latexes were synthesized using the emulsifier octylphenol polyoxyethylene(10) ether (OP-10) and ammonium sulfate allyloxy nonylphenoxy poly(ethyleneoxy)(10) ether(DNS-86). The optimum amount of OP-10 and DNS-86 was 1.5% and 2.5% respectively. The P(MMA/BA/AA) and P(St/BA/AA) latex containing 1.5% OP-10 or 2.5% DNS-86 were blended pairwise. The performances of latex blends and parent latexes as a function of emulsifiers content in parent latexes were determined. The results indicated that the stability of latex blends is favorable, and particle size distribution was more uniform and thermal stability was improved after blending. 相似文献
97.
Taisir T. Khidr 《Journal of Dispersion Science and Technology》2013,34(2):184-192
Nine additives were prepared by esterification of dibasic acid (succinic, adipic, sebacic acid) and polyethylene glycol (Mol.wt.=600, 1000, 4000). These additives were characterized by infrared spectral analysis, average molecular weight and polydispersity index. Their influence on the depression of pour point for two type of paraffin gas oils (G1 and G2) were investigated, blends of paraffin gas oils G1 and G2 by different ratio, when their untreated and treated by additives were evaluated as pour point depressant in comparison with the original paraffin gas oils G1 and G2. The effect of additive type and gas oil composition on wax crystal modification were studied using the photo micrographic analysis. Diethoxylate (eo=182) sebacate with blend gas oil No. 3 has achieved the best performance as pour point depressant. The photo micrographic analysis showed that, the wax morphology was greatly modified to fine dispersed crystals of compact size. A correlation between the pour point depression and the extent of wax modification was detected. 相似文献
98.
Two 3 mm thick microscope glass plates, having one face plus their two long edges coated by a thick metallic film, are spaced 75 μm apart by mylar spacers. Because of the metallic coatings on the inner faces the structure acts as a single metallic slit. The space between the two coated plates is filled with aligned nematic liquid crystal (E7, Merck/BDH) and the cell is inserted in an absorber aperture. This single metallic slit geometry supports resonant modes when microwaves are incident with their polarization (E-field) perpendicular to the slit. The structure gives a set of Fabry-Perot-like resonant transmission frequencies. These frequencies move when a voltage is applied between the two plates, the liquid crystal being first aligned homogeneously, then realigning homeotropically with the applied field. By minotoring these changes a fast and easy to use procedure for determining the permittivity and its anisotropy for nematic liquid crystals in the microwave region has been developed. The parameters determined for E7 are εe = 3.17 (ne = 1.78 ± 0.01) and εo = 2.72 (no = 1.65 ± 0.01), (Δn ≈ 0.13) in the 40.0–60.0 GHz region. 相似文献
99.
Evgeny Pozhidaev Valery Shibaev Galina Elyashevich Maxim Minchenko 《Liquid crystals》2013,40(5):517-525
Electro-optically active polymer–liquid crystal composites based on ferroelectric liquid crystals and stretched porous polyethylene films were developed. The alignment of ferroelectric liquid crystals incorporated into the porous polyethylene films with average porous diameter of around 200 nm was observed and studied. It was shown experimentally that these samples containing ferroelectric liquid crystals are flexible electro-optical films exhibiting a saturation electric field near 2·107 Vm?1 and a response time of about 30 μs under the action of the saturation field. A simple theoretical model of ferroelectric liquid crystal molecules' complete reorientation in electric fields inside pores of the films has been proposed and confirmed experimentally. 相似文献
100.
Emanuela Fabiola Craparo Barbara Porsio Nicol Mauro Gaetano Giammona Gennara Cavallaro 《Macromolecular rapid communications》2015,36(15):1409-1415
Here, the synthesis and the characterization of novel amphiphilic graft copolymers with tunable properties, useful in obtaining polymeric fluorescent nanoparticles for application in imaging, are described. These copolymers are obtained by chemical conjugation of rhodamine B (RhB) moieties, polylactic acid (PLA), and O‐(2‐aminoethyl)‐O′‐methyl poly(ethylene glycol) (PEG) on α,β‐poly(N‐2‐hydroxyethyl)‐d,l ‐aspartamide (PHEA). In particular, PHEA is first functionalized with RhB to obtain PHEA–RhB with a derivatization degree in RhB (DDRhB) equal to 0.55 mol%. By varying the reaction conditions, different amounts of PLA are grafted on PHEA–RhB to obtain PHEA‐RhB‐PLA with DDPLA equal to 1.9, 4.0, and 6.2 mol%. Then, PEG chains are grafted on PHEA‐RhB‐PLA derivatives to obtain PHEA‐RhB‐PLA‐PEG graft copolymers. The preparation of polymeric fluorescent nanoparticles with tunable properties and spherical shape is described by using PHEA‐RhB‐PLA‐PEG with DD in PLA and PEG equal to 4.0 and 4.9 mol%, by following easily scaling up processes, such as emulsion‐solvent evaporation and high pressure homogenization (HPH)‐solvent evaporation techniques.