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961.
E.‐A. McGonigle J. J. Liggat R. A. Pethrick S. D. Jenkins J. H. Daly D. Hayward 《Journal of Polymer Science.Polymer Physics》2004,42(15):2916-2929
For as‐extruded amorphous and biaxially orientated polyester films based on poly(ethylene terephthalate), poly(ethylene naphthalate), and copolymers containing poly(ethylene terephthalate) and poly(ethylene naphthalate) moieties, permeability, diffusion, and solubility coefficients are interpreted in terms of chain mobility. The influence of polymer morphology is determined by comparison of the data for as‐extruded amorphous sheets and materials produced with different biaxial draw ratios. The crystallinities of the samples were assessed using differential scanning calorimetry and density measurements. Changes in mobility at a molecular level were investigated using dielectric spectroscopy and dynamic mechanical thermal analysis. The study, in conjunction with our earlier work, leads to the conclusion that the key to understanding differences in gas transport is the difference in local chain motions rather than in free volume. This was illustrated by the permeability results for He, Ar, N2, and O2 in the range of polyesters. However, the permeability of CO2 was found to require alternative explanations because of polymer–penetrant interactions. For biaxially oriented samples, the differences in diffusivity are not only due to differences in local chain motions, but also additional constraints resulting from the increased crystallinity and chain rigidity—which also act to hinder segmental mobility. The effectiveness of the reduction in permeability in the biaxially oriented films is consequently determined by the ability of the polymer chains to effectively align and form crystalline structures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2916–2929, 2004 相似文献
962.
V.B. Fainerman V.N. Kazakov S.V. Lylyk A.V. Makievski R. Miller 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):97-102
One of the essential differences in the design of bubble pressure tensiometers consists in the geometry of the measuring capillaries. To reach extremely short adsorption times of milliseconds and below, the so-called deadtime of the capillaries must be of the order of some 10 ms. In particular, for concentrated surfactant solutions, such as micellar solutions, short deadtimes are needed to minimize the initial surfactant load of the generated bubbles. A theoretical model is derived and confirmed by experiments performed for a wide range of experimental conditions, mainly in respect to variations in deadtime and bubble volume. 相似文献
963.
Riaan Schmuhl Sankhanilay Roy Chowdhury Johan E. ten Elshof Albert van den Berg Dave H.A. Blank 《Journal of Sol-Gel Science and Technology》2004,31(1-3):249-252
Templated MCM-48 silica was prepared using CTAB as surfactant. The MCM-48 powders and thin films were characterized by different techniques. MCM-48 layers were deposited on macroporous α-alumina supports and silicon nitride microsieves. The water permeability of MCM-48 was compared with the permeability of conventional mesoporous γ-alumina membranes. The applicability of MCM-48 as ion-selective electric field-driven switchable interconnect for microfluidic devices was demonstrated. 相似文献
964.
EQCM and voltammetric data show that thallium(I) ions, which are adsorbed in the region of the positive surface charge, most probably, in the form of the ionic pairs, are not reduced. In this potential region, thallium(I) ions are reduced directly from the solution. At more negative potentials, the previously adsorbed stable ionic pairs slowly undergo transition into the less stable form. From this form, thallium(I) ions can be reduced or desorbed into the solution. The process is best described by a model of one electron, i.e., full charge transfer. 相似文献
965.
Andreev V. N. Kolyadko E. A. Podlovchenko B. I. 《Russian Journal of Electrochemistry》2004,40(5):580-583
Radioactive tracer studies confirm the earlier electrochemical results that carbon monoxide can virtually completely displace iodine adatoms. For the first time, it is found that iodine adatoms are not displaced by carbon monoxide when iodide anions are adsorbed in the presence of an upd silver monolayer. The possible reasons for the effect observed are discussed. 相似文献
966.
Two-Layered Poly-o-phenylenediamine/Polyaniline Composite: Electrosynthesis and Spectroelectrochemical Properties 总被引:1,自引:0,他引:1
E. Yu. Pisarevskaya E. V. Ovsyannikova N. M. Alpatova 《Russian Journal of Electrochemistry》2004,40(9):969-976
Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface. 相似文献
967.
Data on the adsorption of kryptates of alkali metals on a mercury electrode are obtained for the first time by a method of the measurement of the differential capacitance as a function of potential and are compared to one another. Shown is that there takes place a deep mutual relationship between the structure of a complex and the regularities of its adsorption. An assumption is put forth about the possibility of adsorption of a free ligand in solutions of lithium kryptate, which possesses relatively low strength. The co-adsorption of sodium kryptate with 1-adamantanol, which forms a two-dimensional condensed layer, is investigated. Established is that the C vs. E curves, obtained in 1 M Na2SO4 at a constant activity of 1-adamantanol and a varying concentration of KryptofixR 222, exhibit two distinctly pronounced portions, each of which corresponds to predominant adsorption of one of the surface-active components. The region of predominant adsorption of KryptofixR 222 expands with its concentration. 相似文献
968.
The dynamic and equilibrium surface tensions of aqueous dodecylamidoethyldimethylbenzylammonium chloride solutions of various concentrations at 16, 20, 25, 30, and 35°C are studied for the first time. The effects of the concentration and temperature on the surface tension relaxation are discussed. The possibility of two-dimensional phase transition and its effect on the dynamic behavior of surface tension are considered. 相似文献
969.
M. A. Proskurnin N. V. Orlova A. V. Pikhtar' N. V. Osipova 《Journal of Analytical Chemistry》2004,59(5):433-437
Conditions are determined for the determination of salicylhydroxamic and acetylhydroxamic acids by thermal-lens spectrometry using iron(III) in an aqueous medium. The detection limits are 6 × 10–8 and 3 × 10–8 M, respectively. The sensitivity can be enhanced 3–6 times with the use of aqueous–organic media. 相似文献
970.
D. V. Batov 《Colloid Journal》2004,66(1):109-112
The solution enthalpies of water–n-octane–1-pentanol (PenOH)–sodium dodecyl sulfate (SDS) microemulsions and their components in 2-propanol at 298.15 K were determined by the thermochemical method at fixed mass fractions of PenOH (0.1450) and SDS (0.0775). The formation enthalpies of microemulsions were calculated using the thermochemical cycle, and it was shown that their values are positive. The results obtained indicate that the intercomponent interactions in the investigated systems are rather weak. The formation of thermodynamically stable microemulsions is determined by entropy changes associated with the disintegration of water and 1-pentanol homoassociates. 相似文献