Polyelectrolyte counterions

Stability of different strong polyelectrolyte/counterion mixtures is reported in this section sodium poly(vinyl sulfonate), potassium poly(vinyl sulfate), and sodium dextran sulfate. These polyelectrolytes have practically the same charge density. Poly(vinyl sulfonate) (NaPVS) and NaPSS possess the same charged groups (SOD but they differ by their backbones NaPVS is more... 

The nature of the charged groups (sulfate or sulfonate) and the nature of the backbone of the polyelectrolyte have little effect on the phase diagram of polyelectrolyte/counterion mixtures. Therefore the electrostatic attractions can be considered as the principal driving force for phase separation of highly charged strong polyelectrolytes in the presence of multivalent counterions. A universal behavior is observed whatever the nature of polyelectrolyte or counterions. 

Nucleic Acids are Polyelectrolytes Counterion Condensation Theory... 

Usually the electrode surface is coated with the ion-exchange polymer, and then the redox-active ions enter the film as counterions. In the case of a cation-exchanger, cations (in anion-exchangers, negatively charged species) can be incorporated, which are held by electrostatic binding. The counterions are more or less mobile within the layer. A portion of the low molar mass ions (albeit usually slowly) leave the film and an equilibrium is established between the film and solution phases. Polymeric (polyelectrolyte) counterions are practically fixed in the surface layer. 

In the case of polyelectrolyte adsorption, the electrical dipole comes from both colloid and polyelectrolyte counterion charges. Electro-optical measurements are likely to provide information on the structure of charged polymers in the adsorbed state. 

So, one of the main limitations for a valuable description of this kind of mixtures is the persistent lack of knowledge in the thermodynamic description of polyelectrolytes in solution. However, recently, new expressions of the free energy of a polyelectrolyte chain were proposed by Leibler, Pezron et al. [44]. More generally, a microphase separation for polyelectrolytes for which the macromolecular backbone is not soluble in water were proposed independently by Borue et al. [45] and Leibler et al. [46]. An approach, taking into account the role of polyelectrolyte counterions was also proposed [47]. 

Transfer of electrons can naturally lead to changes in the charge (valency) of the redox-active species. Therefore, it is an obvious consequence to study the interaction of switchable counterions with macroions [228] or other multiple-charged objects like polyelectrolytes [229]. The group of Anson was one of the first to investigate the complexation of electrochemically switchable counterions with strong polyelectrolytes [230-232]. In some cases, the cationic polysiloxanes became insoluble through oxidation of complexed ferrocyanide. The polyelectrolyte-counterion complex then deposited onto the electrode as a thin... 

Within the PB cell model, the counterion concentration at the outer boundary gives the osmotic pressure, which is a measure of the electrostatic repulsion between neighboring biomolecules. This pressure can also be experimentally determined. " " The Donnan coefficient, on the other hand, is strongly influenced by conditions at the macromolecular surface and can be used to provide key insight into the nature of polyelectrolyte-counterion interaction. " This interaction is important because of the salt-induced conformational changes DNA undergoes. The nature of this behavior is believed to arise from the partial collapse, or condensation. 

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