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  • 1
    Electronic Resource
    Electronic Resource
    Coagulation and flocculation measurements by photon correlation spectroscopy — colloidal SiO2 bare and covered by polyethylene oxide (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1071-1079 
    Details
    ISSN: 1435-1536
    Keywords: Photon correlation spectrometry ; colloidal silica ; polyethylene oxide adsorption ; flocculation ; 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 With photon correlation spectrometry (PCS) the diffusion coefficients, average diameters and polydispersities of colloidal particles can be determined in dilute aqueous suspensions. In this study PCS is used to follow the coagulation and flocculation of silica particles. Electrolyte solution added to suspensions of bare particles and of particles covered with adsorbed polyethylene oxide layers induces aggregation. The rate constants of aggregation are evaluated by the second-order Smoluchowski theory with the assumptions of spherical aggregated particles and volume proportional light-scattering amplitude. Adsorbed PEO layers of molar mass lower thanM w=160000 decrease the critical flocculation concentration and the flocculation states and rate constants for bare and covered particles are the same at high electrolyte concentrations. Polymer layers of high molar mass (M w=325000, 900000) reducved at full coverage the rate constants and stabilize the suspensions even at high electrolyte concentrations. At low coverage adsorption of high molar mass polymers results in the same values as of low molar mass PEO. The correlation between rate constants and hydrodynamic PEO layer thicknesses demonstrates the steric influence of the tails of the adsorbed macromolecules on stability and flocculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657676
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  • 2
    Electronic Resource
    Electronic Resource
    Flocculation and stabilization of colloidal silica by the adsorption of poly-diallyl-dimethyl-ammoniumchloride (PDADMAC) and of copolymers of DADMAC with N-methyl-N-vinyl- acetamide (NMVA) (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 698-708 
    Details
    ISSN: 1435-1536
    Keywords: Key words Flocculation and stabilization ; zetapotential ; colloidal silica ; poly(diallyl-dimethyl-ammonium chloride) ; copolymers of diallyl-dimethyl-ammonium chloride and N-methyl-N-vinylacetamide ; photon correlation spectrometry
    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 stabilization and flocculation behavior of colloidal silica-particles with cationic polyelectrolytes (PE) is investigated. The zetapotentials, diffusion coefficients and flocculation rate constants of silica particles have been measured as a function of the adsorbed amount of cationic polyelectrolytes poly(diallyl-dimethyl-ammoniumchloride) (PDADMAC) of different molar masses and of statistic copolymers of DADMAC and N-methyl-N-vinyl-acetamide (NMVA) of various compositions at different salt concentrations and pH-values. Very fast flocculation due to van der Waals attraction occurs if the zetapotential is small. At low ionic strength this condition occurs just below the plateau of the adsorption isotherms where the surface charges are screened by adsorbed polycations. Additionally with high molecular polycations slow mosaic flocculation is observed at lower PE concentrations. At high ionic strength fast flocculation takes place at low macroion concentration due to the screening of the surface charges by adsorbed polycations and salt ions. At medium concentrations of polycations below plateau adorption slow bridging flocculation is observed. At plateau adsorption the suspensions become stabilized up to high ionic strength. At low salt concentration charge reversal at full coverage with polycations results in electrostatic repulsion. At high ionic strength the particles are stabilized sterically due to the osmotic repulsion of the long adsorbed PE tails. Therefore macroions of high molar mass are necessary to stabilize the suspension at high ionic strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050299
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  • 3
    Electronic Resource
    Electronic Resource
    Adsorption of polyethylene oxide on surface modified silica – stability of bare and covered particles in suspension (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 903-912 
    Details
    ISSN: 1435-1536
    Keywords: Key words Surface modified silica ; photon correlation spectrometry ; adsorption of PEO ; stabilization ; 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  The adsorption of poly-ethylene oxide (PEO) on modified colloidal silica and the stability of the aqueous suspension was investigated. With octanol some silanol groups at the silica surface were replaced by octylgroups. The size of the modified silica particles and the charge and chemical groups on the surface were charaterized by ultracentrifugation, photon correlation spectrometry, polyelectrolyte titration and IR spectrometry. The adsorbed amounts of polyethylene oxides of different molar mass were determined on the modified silica in water. With photon correlation spectrometry (PCS) the hydrodynamic layer thickness of the PEO layers on the particles were measured. The dependences of the layer thicknesses on molar mass of the PEO, polymer concentration and adsorption time were determined. The aggregation of the suspended PEO coated and uncoated modified silica particles was examined with PCS by the time dependence of the diffusion coefficient at different salt concentrations. The influence of molar mass and concentration of PEO as well as of the age of the dispersion was explored. The measured dependences are discussed and compared with the behavior of unmodified silica- and latex-particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050327
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  • 4
    Electronic Resource
    Electronic Resource
    Fluorimetrische Untersuchungen zur Adsorption an gelösten Makromolekülen (1970)
    Springer
    Colloid & polymer science 242 (1970), S. 1103-1118 
    Details
    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
    Description / Table of Contents: Summary The fluorimetric determined adsorption-isotherms for the adsorption of Blancophor on Polyvinylpyrrolidon deviate in saltfree solvents from the idealLangmuir-form. This is caused by the electrostatic loading of the macromolecules with adsorbed Blancophor-ions. An adsorption-isotherm, which takes in to account the electrostatic potential, is derived. A useful evaluation-method allows the determination of the electrostatic potential on the macromolecule in dependence of the coverage with dye. The linear initial rise of the potential with the coverage comply with the charge of the rodlike macromolecule with twice-charged Blancophor-ions. The shielding by the counter-ions occurs only at higher coverage, i. e. higher potential and is dependent on the solvent. With addition of foreign electrolyte over 0.001 normal the electrostatic potential decreases. The descending is proportional to the square root of the salt concentration and can be described with theDebye-Hückel shieldingparameter. The behaviour at high coverage and the influence of the solvent is discussed.
    Notes: Zusammenfassung Die durch Fluorimetrie bestimmten Adsorptionsisothermen bei der Adsorption von Blancophor an Polyvinylpyrrolidon weichen in salzfreien Lösungsmitteln von der idealenLangmuirform ab. Dies wird durch die elektrostatische Aufladung des Makromoleküls mit den adsorbierten Blancophorionen verursacht. Eine Adsorptionsisotherme, die das elektrostatische Potential berücksichtigt, wird abgeleitet. Eine geeignete Auswertemethode gestattet die Ermittlung des elektrostatischen Potentials am Makromolekül in Abhängigkeit von der Bedeckung mit Farbstoff. Der lineare Anfangsanstieg des Potentials mit der Bedeckung entspricht der Aufladung des stäbchenförmigen Makromoleküls mit zweifach geladenen Blancophorionen. Die Abschirmung durch die Gegenionen tritt erst bei höherer Bedeckung bzw. höheren Potentialen auf und ist vom Lösungsmittel abhängig. Bei Fremdelektrolytzusatz über 0,001 normal nimmt das elektrostatische Potential ab. Der Potentialabfall verläuft mit der Wurzel aus der Salzkonzentration und ist mit demDebye-Hückelschen Abschirmparameter zu beschreiben. Das Verhalten bei hohen Belegungen und der Einfluß des Lösungsmittels wird diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02084716
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  • 5
    Electronic Resource
    Electronic Resource
    Fluorimetrische Untersuchungen zur Adsorption an gelösten Makromolekülen (1970)
    Springer
    Colloid & polymer science 242 (1970), S. 1119-1124 
    Details
    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
    Description / Table of Contents: Summary The adsorption constants, the free enthalpy ΔG N , the enthalpy ΔH and the entropy ΔS N of the adsorption of Blancophor on Polyvinylpyrrolidon are given. The dependence of these values on the addition of electrolytes and on the composition of the solvents are discussed regarding the specific interactions between Blancophor, solvent and polymer.
    Notes: Zusammenfassung Für die Adsorption von Blancophor an Polyvinylpyrrolidon werden die Adsorptionskonstaten, die freie Enthalpie-(ΔG N ), die Enthalpie-(ΔH) und die Entropieänderung (ΔS N ) angegeben. Die Abhängigkeit der Werte von Fremdelektrolytzusatz und der Lösungsmittelzusammensetzung wird unter Berücksichtigung der spezifischen Wechselwirkungen zwischen Blancophor, Lösungsmittel und Polymer diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02084717
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  • 6
    Electronic Resource
    Electronic Resource
    Fraction of H-bonded segments of N-ethylpyrrolidone, oligomeric and polymeric vinylpyrrolidone adsorbed from CHCl3 on silica measured by IR spectrometry (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 372-380 
    Details
    ISSN: 1435-1536
    Keywords: Polymer adsorption ; IR spectrometry ; fraction of adhered segments ; silica
    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 of N-ethylpyrrolidone (NEP), oligomeric and polymeric vinylpyrrolidone (OVP, PVP) on silica (Aerosil 200) from CHCl3 solution is investigated by IR spectrometry. The influence of the annealing temperature of the silica on the adsorbed amount and on the fraction of adhered segments was studied. The dependences of the amount adsorbed on solution concentration result for NEP in a Langmuir isotherm for OVP and PVP in high affinity isotherms. The fraction of adhered H-bridged carbonyl groups determined by compensation procedures, the fraction of surface SiOH groups occupied and the multiple interaction quotientQ show different dependences on the amount adsorbed for the measured adsorptives, indicating different interactions of the monomeric segments with the surface groups. This behaviour is explained by comparing the amount adsorbed in saturation with monolayer capacities, surface concentration of SiOH groups and frequency shifts. A splitting of the band of the bound carbonyl groups in a double peak was observed with OVP and PVP, referring to an additional interaction of polymer segments neighboured to specifically bound segments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410383
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  • 7
    Electronic Resource
    Electronic Resource
    Microcalorimetric studies of the adsorption of N-ethylpyrrolidone, oligomeric and polymeric vinylpyrrolidone from CHCl3 on silica (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 381-387 
    Details
    ISSN: 1435-1536
    Keywords: polymer adsorption ; microcalorimetry ; enthalpy of adsorption ; fraction of adhered segments ; silica
    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 Adsorption enthalpies of N-ethylpyrrolidone, oligomeric and polymeric vinylpyrrolidone from CHCl3 solution on silica interfaces (Aerosil 200) have been measured at 25 °C by microcalorimetry. The dependence on surface coverage has been examined using measured adsorption isotherms. Binding enthalpies are calculated with fractions of adhered segments obtained by IR spectrometry and wetting enthalpies received from calorimetry. Fractions of adhered segments are derived from the adsorption enthalpies assuming equal binding enthalpies of monomers and polymer segments and considering desorption enthalpies of the solvent depending on the surface area of the polymer segments. The resulting enthalpies are compared with literature values from other solvents and the incongruity of the fraction of adhered segments obtained by IR, ESR, NMR and microcalorimetry is explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410384
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  • 8
    Electronic Resource
    Electronic Resource
    Fluorimetrische Untersuchungen zur Adsorption an gelösten Makromolekülen (1970)
    Springer
    Colloid & polymer science 239 (1970), S. 666-676 
    Details
    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
    Description / Table of Contents: Summary The fluorescence dye Blancophor has the property to raise remarkably the fluorescence output by the adsorption on polyvinylpyrrolidon. On grounds of this finding a measuring and evaluation procedure was developed, which allows to ascertain the adsorbed amounts from fluorimetric measurements. The fluorescence abilities of Blancophor in the adsorbed and dissolved status used for the evaluation and their dependence on concentration, temperature, solvent and degree of polymerization are discussed.
    Notes: Zusammenfassung Der Fluoreszenzfarbstoff Blancophor hat die Eigenschaft, seine Fluoreszenzausbeute bei der Adsorption an Polyvinylpyrrolidon beträchtlich zu steigern. Auf dieser Basis wird ein Meß- und Auswerteverfahren entwickelt, das die adsorbierten Mengen aus fluorimetrischen Messungen zu bestimmen gestattet. Die zur Auswertung verwendeten Fluoreszenzvermögen des Blancophors im adsorbierten und im gelösten Zustand und deren Abhängigkeiten von Konzentration, Temperatur, Lösungsmittel und Polymerisationsgrad werden diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02085915
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  • 9
    Electronic Resource
    Electronic Resource
    Fluorimetrische Untersuchungen zur Adsorption an gelösten Makromolekülen (1971)
    Springer
    Colloid & polymer science 243 (1971), S. 28-31 
    Details
    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
    Description / Table of Contents: Summary The decrease of the adsorbed amount of Blancophor BA on Polyvinylpyrrolidone in water- and methanol-solution of the electrolytes KSCN, KJ and NaClO4 is explained by competitive adsorption. An adsorption isotherm is introduced for two competitive adsorptive substratesA andB. From the adsorption isotherm for Blancophor the ratio of the adsorption constantsK electrolyte/K Blancophor can be calculated. Without measuring directly the adsorbed amounts of electrolyt it is possible to evaluate the molar adsorption constants of the electrolyte, if the molar adsorption constant of the Blancophor in the respective medium is known.
    Notes: Zusammenfassung Der Abfall der adsorbierten Menge des Blancophors BA an Polyvinylpyrrolidon in wäßriger und methanolischer Lösung der Salze KSCN, KJ und NaClO4 wird durch die konkurrierende Adsorption der Salze erklärt. Eine Adsorptionsisotherme für zwei kompetitiv adsorbierende SubstrateA undB wird eingeführt. Aus der Adsorptionsisotherme für Blancophor läßt sich damit das Verhältnis der Adsorptionskonstanten -K Salz/K Blancophor ermitteln. Ohne die adsorbierten Salzmengen direkt zu messen, gelingt es, die molare Adsorptionskonstanten des Salzes zu berechnen, wenn die molare Adsorptionskonstante des Farbstoffes im jeweiligen Medium bekannt ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01500611
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  • 10
    Electronic Resource
    Electronic Resource
    Eine neue Methode zur Schärfung der Grenzschicht in einer Diffusionsapparatur (1964)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 36 (1964), S. 378-380 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Zur Messung der freien Diffusion von Flüssigkeiten werden zwei Lösungen übereinandergeschichtet. Dabei muß eine Verwirbelung der Grenzschicht vermieden werden. Dies wird durch eine besonders konstruierte Zelle erreicht. Messungen an den Systemen Glucose/Wasser, Saccharose/Wasser, Polyäthylenglykol/Wasser und Polystyrol/Benzol zeigen eine gute Reproduzierbarkeit und liefern Werte, die gegenüber Literaturwerten etwas höher sind.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330360411
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