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121.
M. A. Sanz N. Granizo M. Gradzielski M. M. Rodrigo M. Valiente 《Colloid and polymer science》2005,283(6):646-652
We have made a comparative study between the micellar regions of the octyl -d-glucoside (OG)–tetraethylene glycol monododecyl ether and the OG–poly(ethylene glycol) 20,000 systems by means of surface tension and viscosimetric measurements. The incorporation of the tetraethylene glycol monododecyl ether nonionic surfactant in the OG micelles decreases the critical micelle concentration, whereas the presence of polymer increases it. The nonionic surfactant mixture exhibits nonideal mixing behaviour. The data fit to Rubinghs treatment with a value of –5.1, which implies a modest attraction between both surfactants. The surfactant–poly(ethylene glycol) 20,000 system does not form mixed micelles. The incorporation of polymer increases the critical micelle concentration of the surfactant. The viscosity for the surfactant–polymer system is higher than that for the pure polymer, demonstrating a surfactant-induced structuring. 相似文献
122.
Partha Sarathi Das Basudam Adhikari Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):39-45
Fluorination of low-density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF6 gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x-ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley & Sons, Inc. 相似文献
123.
124.
Sylvie BertinJean-Jacques Robin 《European Polymer Journal》2002,38(11):2255-2264
Recycling of mixed plastic wastes composed of low-density polyethylene (LDPE) matrix and polypropylene (PP) was carried out by compounding using single-screw or twin-screw extruders. Blends of virgin polymers have been prepared to compare mechanical properties of both virgin and regenerated materials. First, a model composition of virgin LDPE/PP blend was prepared to study the effect of process parameters and that of different types of compatibilizers. Second, the results were applied to plastic wastes coming from industrial post-consumer plastic wastes. By adding compatibilizing agents such as ethylene-propylene-diene monomer, ethylene-propylene monomer, or PE-g-(2-methyl-1,3-butadiene) graft copolymer, elongation at break and impact strength were improved for all blends. The effect of these various copolymers is quite different and is in relation with their chemical structure. The recycled blends exhibit suitable properties leading to applications that require good mechanical properties. 相似文献
125.
J. Doménech E. Brillas J. A. Garrido R. M. Rodríguez 《Monatshefte für Chemie / Chemical Monthly》1987,118(2):197-202
Viscosities and densities of lithium perchlorate solutions in different ethylene glycol-water compositions have been measured at 25.0 and 35.0 °C. From these data, the correspondingB-coefficients of theJones-Dole equation have been determined. TheB-value depends on the solvent composition and it reaches a maximum in the water-rich region. This behaviour is analysed in terms of ionic solvation and solvent structure.
Viskositäts-B-Koeffizienten für Lösungen von Lithiumperchlorat in Ethylenglykol-Wasser-Mischungen
Zusammenfassung Es wurden die Dichten und Viskositäten für Lösungen von Lithiumperchlorat in verschieden zusammengesetzten Ethylenglykol-Wasser-Mischungen bei 25 °C und 35 °C gemessen. Auf Grund der erhaltenen Daten wurden dieB-Koeffizienten in den entsprechendenJones-Dole-Gleichungen für die relative Viskosität bestimmt. DieB-Werte hängen von der Zusammensetzung des Lösungsmittels ab und erreichen im wasserreichen Konzentrationsgebiet ein Maximum. Dieses Verhalten wird in Hinblick auf die Ionensolvatation und die Struktur des Lösungsmittels analysiert.相似文献
126.
127.
Shuhui Yu Kui Yao Francis Eng Hock Tay 《Journal of Sol-Gel Science and Technology》2007,42(3):357-364
The preferential formation of a pyrochlore structure is a knotty problem in the preparation of Pb(Zn1/3Nb2/3)O3 (PZN)-based thin film materials and its presence is significantly detrimental to the dielectric and piezoelectric properties.
In this study, 40 mol% of PZN was replaced with Pb(Mg1/3Nb2/3)O3 (PMN) for obtaining a perovskite composition around a morphotropic phase boundary (MPB), (1−x)(0.6PZN-0.4PMN)-xPT ((1−x)PZMN-xPT, PT: PbTiO3) where x = 0.23. The thin films with this composition were prepared with a polyethylene glycol (PEG) modi-fied sol-gel method on LaAlO3 substrates. The microstructural evolution of the films on heat treatment was examined with X-ray diffraction. With the aid
of PEG, the formation of the pyrochlore phase was suppressed and the perovskite phase formed directly from the amorphous gel
film. The multilayer films with a thickness around 0.25 μm showed a single perovskite phase without any detectable pyrochlore
structure. Microscopic images showed uniform grain size of a few tens of nanometers. The role of the polymer dramatically
promoting the perovskite phase was investigated with the aid of X-ray photoelectron spectroscopy and thermal analysis. The
dielectric constant of the obtained film was 4160 at 1 kHz. The film demonstrated typical ferroelectric hysteresis loops and
exhibited excellent piezoelectric performance. 相似文献
128.
An eficient liquid-phase synthesis of isoxazolines through a 1,3-dipolar cycloaddition is described.Soluble polymer-supported acrylate reacted with nitrile oxides generated in-situ,followed by cleavage from the support giving corresponding isoxazolines in high yields and excellent purities. 相似文献
129.
The adsorption behavior of poly(ethylene glycol) (PEG) in reversed-phase chromatography is studied both experimentally and theoretically and a computer simulation of chromatograms is performed on the basis of these studies. The experimental conditions were: different reversed-phase adsorbents and a solvent methanol–water system as the mobile phase. At varying mobile phase compositions highly resolved chromatograms of PEG samples were obtained, in which all peaks could be identified, and the dependencies of the distribution coefficient on the degree of polymerization for PEG molecules were evaluated by processing these chromatograms. The data were interpreted by using a theory of homopolymers based on a continuum Gaussian chain model of flexible macromolecules and a slit-like model of pores of stationary phase. The theory proved to describe well the experimental data in the whole range of studied molecular masses, and the thermodynamic parameters characterizing interactions of ethylene oxide repeating units in PEG molecules with the adsorbent pore walls have been determined from the comparison of the theory with the experimental data. The dispersion of chromatographic peaks corresponding to individual oligomer molecules is also estimated. In the system studied the peak width occurred to be proportional to the distribution coefficient of corresponding macromolecule. The theory is used to develop a computer-assisted procedure for simulation of chromatograms for samples of linear homopolymers. Using the obtained data on the thermodynamic parameters and the estimates of peak dispersion, chromatograms are simulated for PEG samples at two different chromatographic conditions. These simulated chromatograms were in good quantitative agreement with the real chromatograms. 相似文献
130.
IntroductionItiswellknownthatmetallocenesactivatedwithmethylaluminoxane (MAO)arehighlyactivehomogeneousZiegler Nattacatalyststhatproducepolyolefinwithcon trolledstereoregularityandnarrowmolecularweightdistri bution ,1 4 however,themolecularweightofthepolym… 相似文献