Polyelektrolytverschlaufungen in Lösung
Zusammenfassung der Projektergebnisse
The purpose of the project was to study the entanglement properties of polyelectrolytes. One limitation of current literature is that virtually all data focus on aqueous systems, which have a fixed dielectric constant of ≈ 80. Therefore we proposed to study polyelectrolyte behaviour in other solvents with different dielectric constants. An obstacle to this is that most polyelectrolytes are only water-soluble and do not dissolve in organic liquids. To overcome this, we used organic counterions, which broaden the solubility of polyelectrolytes. The use of organic solvents allows for time-temperature superposition to be used, which gives access to intermediate and high frequency viscoelastic relaxation. In brief, we first studied the influence of counterion type on polyelectrolyte solution behaviour using scattering and rheology. This work was carried out for two systesms: polystyrene sulfonate, a model standard polymer and carboxymethyl cellulose a model industrial system. Then we studied the influence of added salt on the rheological properties of NaPSS (a scattering study was already conducted prior to the start of the project). The rheological measurements of NaPSS/NaCl/water solutions, which are generally considered to be simple polyelectrolyte system revealed many unexpected findings including the existence of an anti-polyelectrolyte regime, where the viscosity of solutions increases with increasing added salt concentrations. Another unexpected finding was that for high added salt and high polymer concentrations, NaPSS solutions display strong shear-thickening behaviour. Such findings challenge several aspects of our traditional understanding of polyelectrolyte solutions. Once the influence of counterion type and added were understood, we investigated the influence of solvent type was studied. As before, we do this using scattering and rheology. Small angle scattering gives to the correlation length, which contains information about electrostatic and hydropdynamic screening. For the rheology work, we studied the viscosity-concentration and viscosity molar mass relations to iidentify the overlap and entanglement cross-overs. Most of this aspect of the project is still unpublished. A study on the solution properties of poly(ionic liquids) was carried out. Here we were able to study a single polyelectrolyte in 25 different solvents. This is the most extensive study to date on the influence of solvent properties on the scattering properties of polyelectrolytes. The influence of counterion valence was also studied. Polyelectrolytes with divalent counterions display lower charge density than those with monovalent ones. This could be verified from scattering, conductivity and viscosity measurements. The data generated in this regard are the first comprehensive datasets on the solution rheology polyelectrolytes with divalent counterions. In addition to the aforementioned work, we produced several publications which are not directly about polyelectrolyte entanglement but still are related to polyelectrolytes in solution. The most important of this is a 50-page review on the dilute solution of polyelectrolytes, which presents a unified analysis of literature data from the last 8 decades. This allows us to work out many important questions which will and solvent type The Viscosity of Polyelectrolytes: Influence of counterion be important to properly analyse data for concentrated solutions in future work.
Projektbezogene Publikationen (Auswahl)
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Diffusion and Viscosity of Unentangled Polyelectrolytes. Macromolecules, 54(17), 8088-8103.
Lopez, Carlos G.; Linders, Jürgen; Mayer, Christian & Richtering, Walter
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Oscillatory rheology of carboxymethyl cellulose gels: Influence of concentration and pH. Carbohydrate Polymers, 267, 118117.
Lopez, Carlos G. & Richtering, Walter
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Quantifying the Effect of Multivalent Ions in Polyelectrolyte Solutions. Macromolecules, 54(20), 9577-9586.
Jacobs, Michael; Lopez, Carlos G. & Dobrynin, Andrey V.
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Solution Properties of Polyelectrolytes with Divalent Counterions. Macromolecules, 54(22), 10583-10593.
Lopez, Carlos G.; Horkay, Ferenc; Schweins, Ralf & Richtering, Walter
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Superchaotropic Nano‐ion Binding as a Gelation Motif in Cellulose Ether Solutions. Angewandte Chemie, 135(3).
Hohenschutz, Max; Bauduin, Pierre; Lopez, Carlos G.; Förster, Beate & Richtering, Walter
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Salt Effect on the Viscosity of Semidilute Polyelectrolyte Solutions: Sodium Polystyrenesulfonate. Macromolecules, 56(5), 2183-2193.
Gulati, Anish; Jacobs, Michael; Lopez, Carlos G. & Dobrynin, Andrey V.
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Structure of poly(ionic liquid)s in solutions: a small angle scattering study. American Chemical Society (ACS).
Lopez, Carlos G.; Matsumoto, Atsushi; Gulati, Anish; Hou, Can; Mizutani, Yuna; Osada, Hiroto; Tao, Yume; Fujii, Kakeru; Richtering, Walter & Watanabe, Takaichi
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Controlled mechanical properties of poly(ionic liquid)-based hydrophobic ion gels by the introduction of alumina nanoparticles with different shapes. Soft Matter, 20(7), 1611-1619.
Mizutani, Yuna; Watanabe, Takaichi; Lopez, Carlos G. & Ono, Tsutomu
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Dilute polyelectrolyte solutions: recent progress and open questions. Soft Matter, 20(12), 2635-2687.
G., Lopez Carlos; Matsumoto, Atsushi & Shen, Amy Q.
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Extensibility governs the flow-induced alignment of polymers and rod-like colloids. Physical Review Research, 6(1).
Calabrese, Vincenzo; Porto, Santos Tatiana; Lopez, Carlos G.; Lettinga, Minne Paul; Haward, Simon J. & Shen, Amy Q.
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Influence of counterion type on the scattering of a semiflexible polyelectrolyte. Soft Matter, 20(43), 8610-8620.
Gulati, Anish; Douglas, Jack F.; Matsarskaia, Olga & Lopez, Carlos G.
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Rheological Properties of Concentrated Sodium Polystyrenesulfonate in Aqueous Salt Solutions. Macromolecules, 57(15), 7253-7262.
Gulati, Anish; Han, Aijie; Colby, Ralph H. & Lopez, Carlos G.
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Viscosity of Polyelectrolytes: Influence of Counterion and Solvent Type. ACS Macro Letters, 13(8), 1079-1083.
Gulati, Anish & Lopez, Carlos G.
