共查询到19条相似文献,搜索用时 171 毫秒
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粘度法研究高分子溶液行为的实验改进(Ⅱ) 总被引:13,自引:0,他引:13
高分子在粘度计毛细管管壁上的吸附不仅会导致毛细管有效管径减小,而且可以导致毛细管界面性质发生显著改变,具体表现为测定高分子溶液流过时间t之前和之后纯溶剂的流过时间t0和t0′与高分子溶液流过时间t对浓度作图外推到浓度为零时的值t0^*并不一致。不同温度时聚乙烯吡咯烷酮(PVP)水溶液粘度测定结果表明,当吸附讷发子显著改变了毛细管界面性质时,需要将高分子溶液粘度测定方法由t/t0′改为t/t0^*。经过改进的粘度测定方法不仅更加普适合理,而且更加简单有效。 相似文献
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Gilányi T Varga I Gilányi M Mészáros R 《Journal of colloid and interface science》2006,301(2):428-435
The adsorption of polyethylene oxide (PEO) homologues in a wide range of molecular weight (from M(PEO)=200 to 10(6)) at the air/aqueous solution interface was investigated by dynamic and static surface tension measurements. An approximate estimate for the lower limit of PEO concentration was given at which reliable equilibrium surface tension can be determined from static surface tension measurements. It was shown that the observed jump in the earlier published sigma-lg(c(PEO)) curves is attributable to the nonequilibrium surface tension values at low PEO concentrations. The adsorption behavior of short chain PEO molecules (M(PEO)1000) is similar to that of the ordinary surfactants. The estimated standard free energy of PEO adsorption, DeltaG(0), increases linearly with the PEO molecular weight until M(PEO)=1000. In this molecular weight range, DeltaG(0) was found to be approximately the fifth of the hydrophobic driving force related to the adsorption of a surfactant with the same number of methylene groups. In the case of the longer chain PEOs the driving force of adsorption is so high that the adsorption isotherm is near saturation in the experimentally available polymer concentration range. Above a critical molecular weight the PEO adsorption reveals universal features, e.g., the surface tension and the surface density of segments do not depend on the polymer molecular weight. 相似文献
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Linear poly(N-isopropylacrylamide) chains grafted with short poly(ethylene oxide) chains (PNIPAM-g-PEO) were prepared by free radical copolymerization of NIPAM and PEO macromonomers (M(w) = 5000 g/mol) end-capped with methacrylate in water. Temperature effects on the solution viscosity of thermally sensitive copolymer were studied in different aqueous concentrations. A specific transition was observed during the measurement of the reduced viscosities of PNIPAM-g-PEO copolymer at a certain concentration (C0) in semidilute aqueous solutions: the reduced viscosities increased sharply (namely, thermothickening behavior) at LCST when concentrations were higher than C0, or decreased sharply at LCST when concentrations lower than C0. A plateau was also found near C0 when temperature was closing to LCST from low temperature, showing there is no change in reduced viscosity under this circumstance. The inverse increase of the viscosities at higher temperatures in higher concentration (> approximately 3 g/L) is attributed to the forming of physical "cross-linking points" composed of collapsed PNIPAM core and expanded PEO shell. The sharp decrease of the viscosities at higher temperatures in lower concentration (< approximately 3 g/L) is attributed to the forming of independent globules. The plateau could be attributed to the equilibrium competition between forming of physical "cross-linking points" and independent globules depending on the copolymer solution concentrations. 相似文献
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A. A. Zaman 《Colloid and polymer science》2000,278(12):1187-1197
In this study a systematic investigation on the adsorption of polyethylene oxide (PEO) onto the surface of silica particles
and the viscosity behavior of concentrated dispersions of silica particles with adsorbed PEO has been performed. The variation
of shear viscosity with the adsorbed layer density, concentration of free polymer in the solution (depletion forces), polymer
molecular weight, and adsorbed layer thickness at different salt concentrations (range of the electrostatic repulsion between
particles) is presented and discussed.
Adsorption and rheological studies were performed on suspensions of silica particles dispersed in solutions of 10−2 M and 10−4 M NaNO3 containing PEO of molecular weights 7,500 and 18,500 of different concentrations. Adsorption measurements gave evidence of
a primary plateau in the adsorption density of 7,500 MW PEO at an electrolyte concentration of 10−2 M NaNO3. Results indicate that the range of the electrostatic repulsion between the suspended particles affects both adsorption density
of the polymer onto the surface of the particles and the viscosity behavior of the system. The adsorbed layer thickness was
estimated from the values of zeta potential in the presence and absence of the polymer and was found to decrease with decreasing
the range of the electrostatic repulsive forces between the particles. Experimental results show that even though there is
a direct relation between the viscosity of the suspension and the adsorption density of the polymer onto the surface of the
particles, variation of viscosity with adsorption density, equilibrium concentration of the polymer, and range of the electrostatic
repulsion cannot be explained just in term of the effective volume fraction of the particles and needs to be further investigated.
Received: 15 February 2000/Accepted: 26 June 2000 相似文献
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The binding of sodium dodecanoate (SDoD) to poly(ethylene oxide) (PEO) in aqueous solution was investigated and compared with the well-known polymer-surfactant complexes formed between PEO and sodium dodecyl sulfate (SDS). Electrical conductivity measurements indicated that the concentration ratio of bound SDoD to PEO (on monomer basis) was greater than that for the system PEO-SDS. However, the aggregation numbers of the micelles supported on the polymer chain are practically constant and similar for both surfactants at concentrations lower than the polymer saturation point. The difference in binding capability is explained in terms of a larger PEO coil expansion upon complexation of SDoD than in the case of SDS. An increase in the polymer surface favors the binding of SDoD to PEO in aqueous solution. This conclusion is supported by the results of the viscometric studies of PEO-surfactant solution. 相似文献
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Morota K Matsumoto H Mizukoshi T Konosu Y Minagawa M Tanioka A Yamagata Y Inoue K 《Journal of colloid and interface science》2004,279(2):484-492
Nanostructured thin films were prepared by electrospray deposition (ESD) from poly(ethylene oxide) (PEO) aqueous solution. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM). The SEM images revealed the correlations between the morphologies and the ESD conditions. By changing the applied voltage and solution properties such as viscosity, surface tension, conductivity, and molecular weight, PEO thin films with diverse nanostructures--from nanospheres to nanofibers--were fabricated. It was also revealed that the addition of alcohols to polymer solution, which enables simultaneously changing the viscosity, the surface tension, and the conductivity, enhanced the formation of the fibrous structure. These results indicate that the ESD method is potentially a useful option for producing nanoengineered polymer surface. 相似文献
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Angus-Smyth A Campbell RA Bain CD 《Langmuir : the ACS journal of surfaces and colloids》2012,28(34):12479-12492
The dynamic adsorption of polymer/surfactant mixtures containing poly(ethylene oxide) (PEO) with either tetradecyltrimethylammonium bromide (C(14)TAB) or sodium dodecyl sulfate (SDS) has been studied at the expanding air/water interface created by an overflowing cylinder, which has a surface age of 0.1-1 s. The composition of the adsorption layer is obtained by a new approach that co-models data obtained from ellipsometry and only one isotopic contrast from neutron reflectometry (NR) without the need for any deuterated polymer. The precision and accuracy of the polymer surface excess obtained matches the levels achieved from NR measurements of different isotopic contrasts involving deuterated polymer, and requires much less neutron beamtime. The PEO concentration was fixed at 100 ppm and the electrolyte concentration at 0.1 M while the surfactant concentration was varied over three orders of magnitude. For both systems, at low bulk surfactant concentrations, adsorption of the polymer is diffusion-controlled while surfactant adsorption is under mixed kinetic/diffusion control. Adsorption of PEO is inhibited once the surfactant coverage exceeds 2 μmol m(-2). For PEO/C(14)TAB, polymer adsorption drops abruptly to zero over a narrow range of surfactant concentration. For PEO/SDS, inhibition of polymer adsorption is much more gradual, and a small amount remains adsorbed even at bulk surfactant concentrations above the cmc. The difference in behavior of the two mixtures is ascribed to favorable interactions between the PEO and SDS in the bulk solution and at the surface. 相似文献
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Haiyang Yang Yunfei Yan Pingping Zhu Hao Li Qingren Zhu Chenggao Fan 《European Polymer Journal》2005,41(2):329-340
Viscosity measurements had been made on poly(vinyl alcohol) (PVA), poly(N-vinyl-2-pyrrolidone) (PVP) and poly(ethylene oxide) (PEO) solutions down to low concentrations. It was found that defined as the flow time of the pure solvent in ideal conditions and obtained practically by extrapolating the flow time of polymer solution t to zero concentration, was not equal to the flow time of the pure solvent t0 measured. The reduced viscosity ηsp/C determined by (t/t0-1)/C exhibited either a drastic increase or a significant decrease with dilution, depending upon the polymer solution investigated. On the other hand, ηsp/C determined by was proportional to C even at low concentrations. The anomalous viscosity behavior of neutral polymer solutions at low concentrations, therefore, was due to the incorrect method by which ηsp/C was determined. The detailed experiments indicated that the effective diameter of the viscometer capillary, the surface property of the capillary wall and the additional pressure corresponding to the measurement of t and t0 for PVA, PVP and PEO solutions were not the same. Taking into account the contact anger and the surface tension of the liquid, together with the geometric parameter of the viscometer, the influence of the additional pressure upon the flow time measurement could be studied quantitatively. The calculation was in a good agreement with the experimental result. According to the method presented in this paper, the thickness of the adsorbed polymer layers on the capillary walls could be determined. It was noted that the thickness of the adsorbed polymer layers on the capillary walls was closely related to the solvent in which the polymer molecules were dissolved. The polymer molecular weight, however, had little or no effect on the thickness of the adsorbed polymer layers on the walls of the viscometer capillary. 相似文献
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The aggregation of sodium dodecyl sulfonate (AS) in aqueous solution containing various amounts of poly(ethylene oxide) (PEO)
has been investigated by different experimental techniques. The experimental techniques include surface tension, conductivity,
viscosity, electron spin resonance (ESR) and nuclear magnetic resonance (NMR). The critical aggregate concentration of AS
on polymer strands as well as the concentration where the polymer becomes saturated with surfactant has been determined. Both
ESR and NMR results indicate that the AS–PEO complex forms a more “open” structure and that PEO may penetrate into the interior
of the micelles.
Received: 22 October 1998 Accepted in revised form: 1 April 1999 相似文献