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  • 1
    ISSN: 1435-1536
    Keywords: Microemulsions ; dielectric properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The high-frequency dielectric relaxations of highly concentrated water-in-oil microemulsions have been investigated in the frequency range from 1 MHz to 1 GHz, at different temperatures, in the interval from 5 °C to 60 °C. In the region of the phase diagram studied, the system undergoes a progressive change of its structure, passing from water droplets dispersed in an oil matrix below percolation to two bicontinuous regions separated by a lamellar phase, above percolation. We have focused our attention on these two bicontinuous regions, where well-pronounced dielectric dispersions appear. An analysis in terms of scaling laws indicates a static percolation process above the percolation threshold and close to it and a process characterized by a very small value of the critical index, at higher temperatures, close to the phase transition.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 105 (1997), S. 322-325 
    ISSN: 1435-1536
    Keywords: Rheology ; surfactant solutions ; micelles ; phase transition ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Aqueous solutions of cationic surfactant with binding counterions exhibit a transition under shear. In this paper the steady shear properties of semidilute aqueous micellar solutions (cetylpyridinium chloride and sodium salicylate in brine) are presented as a function of concentration and temperature. The shear thinning behavior of this system could be described by the Carreau model at low shear rate and by a power law at higher shear rate. The temperature dependence of the zero shear viscosity follows an Arrhenius relationship. The critical shear rate at which the viscosity departs from its zero shear value is found to increase with temperature indicating the influence of this parameter on transition.
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  • 3
    ISSN: 1435-1536
    Keywords: Phase transition ; adsorption ; isotherm ; Brewster angle microscopy ; Gibbs monolayer ; Langmuir monolayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption layers of aqueous solutions of N-dodecyl-γ-hydroxy-butyric acid amide show a first-order phase transition between a fluid-like low-density phase and a condensed phase. Two-dimensional domains are formed which were visualized by Brewster angle microscopy. Theπ- A isotherms of the Langmuir monolayers show the wellknown plateau region with the critical surface pressure as the starting point for the first-order phase transition in the Langmuir monolayer. The measurements ofπ-t adsorption kinetics revealed a conspicuous inflection point at the same critical surface pressure. This inflection point is also related to the start of a first-order phase transition in the Gibbs monolayer. The results of theσ-logc isotherms are interpreted by the Frumkin's equation of state. Based on the calculated interaction parameters, the formation of a condensed phase in Gibbs monolayers is concluded. Thermodynamic behavior and morphological features of the Langmuir and Gibbs monolayers were compared and the similarities in morphology and thermodynamically properties of spread and of adsorbed molecules at the air-water interface demonstrated.
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  • 4
    ISSN: 1435-1536
    Keywords: Microgel ; swelling ; osmotic ; flocculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This study shows that microgel particles deswell in the presence of excluded free (i.e., non-adsorbing) polymer. The microgels investigated were poly(N-isopropyl-acrylamide-co-N,N′-methylene-bis-acrylamide (PNP-BA), poly (styrene-co-divinylbenzene) (PS-DVB) and poly(methylmethacrylate-co-methacrylic acid-co-ethyleneglycol dimethacrylate) (PMA-MAA-EM). The particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS). The stability of the particles to flocculation in the presence of free polymer was examined using turbidity-wavelength measurements. The PMA-MAA-EM/water/PEG (PEG=poly(ethyleneglycol)) system was the most stable toward flocculation. Osmotic deswelling of the microgel particles was most pronounced for the PNP-BA/water/PEG system. The volume of the deswollen PNP-BA particles approach that measured for the collapsed state. Osmotic deswelling occurs in the PS-DVB/ethylbenzene/free polystyrene system. However, the extent of deswelling is limited due to some penetration of the microgel particle interior by free polymer. PMA-MAA-EM microgel particles also exhibit osmotic deswelling in the presence of aqueous solutions of PEG.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 105 (1997), S. 23-26 
    ISSN: 1435-1536
    Keywords: AFM ; Force-distance measurements ; BaTiO3 ; diblockcopolymer ; colloidal stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract To further elucidate the changes in interparticle forces caused by polymers in ceramic slurries an aqueous barium titanate system was investigated using an atomic force microscope (AFM). Spherical barium titanate particles were sintered and then glued to an AFM-cantilever. A polished and cleaned barium titanate sintered body surface was used for the opposite site. Surfaceforce vs. distance curves were measured in situ in aqueous media. The measurements show a change in surface force vs. distance curves depending on the type of polymer adsorbed on the surface from the solution. A comparison of blockcopolymers with poly electrolytes gives that the colloidal interactions of the adsorbed block-copolymers are almost independent of pH whereas the interactions for the homopolymer are strongly influenced.
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  • 6
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung 1. Auf Grund der chemischen Konstitution, d. h. der Anordnung der Atome im Molekül und des innermolekularen Bindungszustandes, der faserbildenden vollsynthetischen Hochpolymeren ergibt sich eine Einteilung dieser Stoffe in a. die polymeren Kohlenwasserstoffe und ihre Derivate, sowie die polymeren Äther (z. B. Polystyrol, Polyvinylchlorid, PolyÄthylenoxyd u. a. m.), b. die „mesomeren Kettenpolymeren“, bei denen mesomere Gruppen (wie Amid-, Ester-, Harnstoffgruppen u. a. m.) am Aufbau der Hauptkette beteiligt, d.h. in ihr als Kettenbestandteil enthalten sind. Zur Bezeichnung des tatsÄchlich vorliegenden Zwischenzustandes dieser mesomeren Gruppen wird der Begriff „Meta-Zwitterion“ vorgeschlagen. 2. Aus den chemischen Konstitutionsformeln, die in der neueren Formulierung auch die Ladungsverteilung abzulesen gestatten, wird unter Berücksichtigung sterischer VerhÄltnisse auf den zwischenmolekularen Bindungszustand geschlossen. 3. Bei den Polymeren der Gruppe a sind im wesentlichen ungerichtete DispersionskrÄfte wirksam, es entsteht eine „Wattebauschstruktur“ ohne ausgeprÄgte autonome Ordnung. 4. Bei den mesomeren Kettenpolymeren sind im wesentlichen gerichtete DipolkrÄfte wirksam, es entsteht eine mizellare Struktur mit ausgeprÄgter autonomer Ordnung. 5. Für den zwischen den Meta-Zwitterionen der mesomeren Kettenpolymeren herrschenden Bindungszustand wird der Begriff „Meta-Ionen-Beziehung“ geprÄgt. Es wird darauf hingewiesen, da\ die allen gemeinsame Kolloidstruktur und damit die Ähnlichkeit der physikalischen Eigenschaften der verschiedenen mesomeren Kettenpolymeren ihre Ursache in dem Vorliegen der allen gemeinsamen Meta-Ionen-Beziehung, also letzten Endes in der Ähnlichen chemischen Konstitution hat. 6. Es wird vorgeschlagen, für den zwischenmolekularen Bindungszustand bei mesomeren Kettenpolymeren mit Wasserstoff am Stickstoff nicht die Bezeichnung „Wasserstoffbindung“ anzuwenden. Auch hier sollte vielmehr die Meta-Ionen-Beziehung herausgestellt werden, nötigenfalls unter Hinweis auf die mögliche zwischenmolekulare Mesomerie Meta-Ionen-Beziehung “ Wasserstoffbindung. Hierdurch tritt die Zugehörigkeit dieser Stoffe zur Gruppe der mesomeren Kettenpolymeren deutlich hervor.
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  • 7
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Es wird ein hydraulisches Modell angegeben, das den Ablauf von DiffusionsvorgÄngen übersichtlich wiedergibt. Vektoranalytisch wird die formale IdentitÄt der Diffusionsströmung und der Strömung im hydraulischen Modell bewiesen. Es werden für 10 DiffusionsfÄlle Konzentrationsfelder und Massenbewegung berechnet, Modellversuche ausgeführt und verschiedene FÄlle durch Diffusionsversuche in Kieselgallerten verifiziert. Durch Diagramme und Modellversuche wird der Leser in den Stand gesetzt, ohne jede Rechnung selbst komplizierte FÄlle numerisch bestimmen zu können.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 105 (1943), S. 168-169 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 105 (1943), S. 209-216 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Nach der in der ersten Mitteilung über die Rheometrie organischer Gläser entwickelten Methode der Auswertung von Flie\kurvendiagrammen thermoplastischer Kunststoffe wurden weitere Polymerisate unter besonderer Berücksichtigung der Einwirkung von Weichmachungsmitteln untersucht. Der Einflu\ von Palatinol F auf den Verlauf der Temperaturfunktion der Verformungsleistung eines Polyvinylazetats und eines Polystyrols wurde eingehend diskutiert. Untersuchungen an Polyisobutylenen bestätigen die Schlu\folgerungen, da\ die Richtungskonstanten der Temperaturfunktion der Verformungsleistung mit steigendem Polymerisationsgrad abnehmen. Eventuell vorhandene Beziehungen zwischen der Grö\e der Richtungskonstanten und der Lage der Temperaturfunktion der Verformungsleistung und der Temperaturbeständigkeit wurden erörtert.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 105 (1943), S. 173-175 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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