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1.
By means of a vacuum time-lag method, gas transport properties of apolyimide based on 2, 2- bis (3, 4- decarboxyphenyl ) hexafluoropropane dianhydride (6FDA )and meta- phenylenediamine (mPDA ) have been measured as a function of upstream pres-sure and temperature. The results show that no gas-induced plasticization occurs for thispolyimide in the upstream pressure range from 1 atm to 20atm. The temperature depen-dence of P and D can be described by the Arrhenius equations. The activation energiesof permeation and diffusion were obtained for the gas/polymer pair studied and correlatedwith the size of penetrant gas. 相似文献
2.
On the basis of recently published electrochemical measurements, the charge transfer efficiency within CdSe nanocrystal/conducting polymer heterojunction composites was investigated by means of luminescence interaction strength. It was found that poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] and poly-9-vinylcarbazole luminescence was not totally quenched by nanocrystals, whereas poly-3-octylthiophene and polyvinylpyrrolidone was completely quenched. In case of poly-3-hexylthiophene, the nanocrystal luminescence was quenched. The results are in complete agreement with the electrochemical findings and thus, the CdSe nanocrystal/Polyvinylpyrrolidone composite should be a promising material for electroluminescent devices. 相似文献
3.
Horner-Emmons reaction of phosphonate amides with aldehydes leads to generation of o-substituted aryl-acrylamides. These compounds have been shown to be useful to quickly establish structure-activity relationships (SAR) for soluble guanylyl cyclase (sGC) activator drug discovery. 相似文献
4.
Uwe Emmerling Jurgen Lindau Siegmar Diele Johannes Werner Horst Kresse 《Liquid crystals》2013,40(8):1069-1073
A tin-containing liquid crystalline side group polymer was synthesized and characterized. Two glass transitions were detected by calorimetric investigations. The X-ray pattern corresponds to a smectic C order of the side groups and a disordered isotropic main chain. Dielectric measurements show two relaxation ranges which are influenced by the glass transitions and a fast local process. The low frequency mechanism can be related to the reorientation of the side groups and the higher glass transition temperature. The second is connected with the α-relaxation of the main chain and freezes in at lower temperatures. 相似文献
5.
Two cationic polymers with similar composition were prepared by two different polymerization methods. By monitoring the evolution of the molar mass and chemical composition during the reactions together with charge density measurements and calculations, it was concluded that the cationic polymer synthesized by emulsion polymerization had a less uniform compositional distribution than the cationic polymer prepared by solution polymerization. Contributing to the heterogeneity was the hydrolysis of one monomer (dimethylamino ethylmethacrylate (DMAEMA)) during the synthesis. As a result, the polymer prepared by emulsion polymerization had a more blocky structure and was more surface active as supported by static and dynamic surface tensions data. Fluorescence experiments showed that both polymers formed aggregates at very low concentrations of approximately 0.01 wt%. The aggregates of the polymer prepared by emulsion polymerization were compact, whereas the solution polymerization-based polymer aggregates exhibited a rather expanded geometry. 相似文献
6.
It is shown that the solutions of a (spatially) discrete model of the Boltzmann equation converge in a weak sense as the lattice spacing approaches zero. The method follows a compactness argument of Arkeryd. 相似文献
7.
Limage S Krägel J Schmitt M Dominici C Miller R Antoni M 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):16754-16761
In the present work, we focus on the bulk rheology of mixtures consisting of surfactant modified silica nanoparticles in water. Depending on the ratio of surfactant and nanoparticle concentrations, significant modifications in the measured rheology are evidenced. A domain where the dispersions behave like viscoelastic media is observed. Outside this domain, the dispersions exhibit viscous properties. The changes in the bulk rheology characteristics are discussed in terms of interaction effects between the surfactant and the particles. The results obtained are seen in the context of diluted emulsions' properties and characteristics. 相似文献
8.
Competition between lipases and monoglycerides at interfaces 总被引:3,自引:0,他引:3
Reis P Holmberg K Miller R Krägel J Grigoriev DO Leser ME Watzke HJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7400-7407
Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, beta-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion. 相似文献
9.
Krejci Pavel; Rocca Elisabetta; Sprekels Jurgen 《Journal London Mathematical Society》2007,76(1):197-210
We propose a model for non-isothermal phase transitions withnon-con-served order parameter driven by a spatially non-localfree energy with respect to both the temperature and the orderparameter. The resulting system of equations is shown to bethermodynamically consistent and to admit a strong solution. 相似文献
10.