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ABSTRACT: The effect of ionic strength on the electrical properties of poly(styrene sulfonate)/poly(allylamine) (PSS/PAH) multilayer film was investigated using electric light scattering and electrophoresis. A multilayer film was created by sequential adsorption of fully charged polymers from solutions containing 10( - 1) M NaCl and its properties were compared to those of a PSS/PAH film prepared in the absence of salt. All measurements were carried out after rinsing the films with an aqueous solution of HCl to adjust the pH to 4.6. We found that the electrical polarizability of the film coated particles and its frequency of relaxation increase when the film was constructed in the presence of salt. The increase in the electrical polarizability value is due to the screening-enhanced adsorption. We hypothesize that the increase in the relaxation frequency of the electrical polarizability is a consequence of the adsorption of the polymer chains in more coiled conformations. This restricts the movement of small ions to shorter distances than in the film prepared without salt. In both cases, the small ions are located near the film surface, which indicates the key role of the last deposited polymer for the behavior of the entire PSS/PAH film.
Journal of Physics Condensed Matter 11/2010; 22(49):494107. · 2.55 Impact Factor
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ABSTRACT: Electro-optic techniques were used to investigate the influence of poly(ethylene oxide) (PEO) on the surface electric state of positively charged oxide particles. The variations in particle electrophoretic mobility of beta-FeOOH particles in the presence of PEO indicate significant changes in the surface electric state of the particles in the concentration interval of PEO 10(-2)-10(-1) g dm(-3). The electro-optic results for the same conditions were unexpected: no significant difference is observed in the value and the relaxation frequency of particle electric polarizability in the frequency domain of the alpha-relaxation (detected in the kilohertz range); particle rotational relaxation time also remains unchanged; considerable changes are detected only in the relaxation interval of particle rotation (detected in the hertz range). The obtained results reject the possibility of the formation on the particle surface of a thick polymer layer. A thin adsorption layer cannot explain the significant decrease in particle electrophoretic mobility. The variations in electrophoretic mobility are well correlated with the effects in the domain of particle rotation. A possible explanation of the observed effects is proposed, based on our previous investigations of the effects in the low-frequency domain. The presented results demonstrate that the important information on the electrokinetic charge distribution is not found in the domain of the alpha-dispersion, but in the domain of particle rotation.
Journal of Colloid and Interface Science 04/2008; 319(2):435-40. · 3.07 Impact Factor
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ABSTRACT: A review is made of the existing theoretical expressions, describing the change of the scattered light intensity and the birefringence by application of an electrical field to a colloid solution.Furthermore, the geometrical functions for disc-shaped particles are calculated in this article for the case of electric light scattering and are. presented graphically. In addition, expressions are derived for the average value of the electrical polarizability () for the case of polydisperse solutions.Es wird ein berblick ber die existierenden theoretischen Beziehungen gegeben, die die nderung der Intensitt des Streulichtes und der Doppelbrechung von Kolloidsuspensionen im elektrischen Feld beschreiben.Weiterhin sind die geometrischen Funktionen fr scheibchenfrmige Teilchen in dieser Arbeit fr den Fall der elektrooptischen Lichtstreuung berechnet und grafisch dargestellt. Auerdem werden Beziehungen fr den Mittelwert der elektrischen Polarisierbarkeit () fr den Fall polydisperser Suspensionen abgeleitet.
Colloid and Polymer Science 01/1979; 257(2):160-165. · 2.33 Impact Factor
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ABSTRACT: On a model system (aqueous suspension of γ-Al2O3, by means of electro-optics, the formation of an adsorption layer of polyacrylamide on the surface of colloid particles is followed. The variations of several electro-optic parameters (particle relaxation time, induced dipole moment, relaxation frequency, negative electro-optic effect) are in close correlation with the rise of polymer adsorption and with the conformational changes in the adsorption layer. Considerations are presented concerning the nature of electro-optic effects and their changes by the adsorbed polymer. Advantages are demonstrated of the electro-optic study of polymer adsorption.
Colloids and Surfaces.
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ABSTRACT: The structure of polystyrenesulfonate (PSS) layer adsorbed onto ellipsoidal β-ferric hydrous oxide (β-FeOOH) particles is examined using electro-optics. Changes in the thickness are investigated by varying the ionic strength of the solution for rinsing the adsorbed PSS layer. An increase in the layer thickness is found after rinsing with water, which turns to a decrease when salt (NaCl) is added to the rinsing solution. No changes are registered if formation and rinsing of the layer is carried out at constant ionic strength. Compression of the PSS layer is also found after adsorption of an oppositely charged polyethylenimine (PEI) on the layer rinsed with water or in the presence of 10−4 M NaCl. Complex-formation between the two oppositely charged polyions on the particle surface is supposed to explain the behavior of the polyelectrolyte bilayer.
Colloids and Surfaces A: Physicochemical and Engineering Aspects.
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ABSTRACT: The electro-optic effects from palygorskite suspensions exhibit frequency dispersion below 100 Hz. The relation of this effect to the counterion distribution in the particle double electric layer (DEL) is investigated, using for this purpose the properties of the ions of the liotropic series of the alkali metals to be adsorbed at different extents on the particle surface. The presented experimental data demonstrate the relation of the low-frequency dispersion to the counterions of the compact part of the DEL. For explanation of the obtained results a hypothesis is proposed for a slow polarizability of the Stern layer.
Journal of Colloid and Interface Science.
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ABSTRACT: A model system (an aqueous suspension of aluminium oxide) is used for the study of the negative low-frequency electro-optic effect (usually interpreted as a “transverse permanent dipole moment”). It is demonstrated that the effect is related to the single particle (not a collective effect) and correlates well with its electrophoretic mobility. These results indicate the electrokinetic nature of the negative electro-optic effect.
Journal of Colloid and Interface Science 141(2):433-438. · 3.07 Impact Factor
