Polyelectrolytes counterion binding

Manning, G. S. (1979). Counterion binding in polyelectrolyte theory. Accounts of Chemical Research, 12, 443-9. 

A polyelectrolyte solution contains the salt of a polyion, a polymer comprised of repeating ionized units. In dilute solutions, a substantial fraction of sodium ions are bound to polyacrylate at concentrations where sodium acetate exhibits only dissoci-atedions. Thus counterion binding plays a central role in polyelectrolyte solutions [1], Close approach of counterions to polyions results in mutual perturbation of the hydration layers and the description of the electrical potential around polyions is different to both the Debye-Huckel treatment for soluble ions and the Gouy-Chapman model for a surface charge distribution, with Manning condensation of ions around the polyelectrolyte. 

Sharp KA, Friedman RA, Misra V, Hecht J, Honig B. Salt effects on polyelectrolyte-ligand binding comparison of Poisson- 83. Boltzmann, and limiting law/counterion binding models. Biopolymers 1995 36 245-262. 

Employing a polyelectrolyte to bind to and preferentially align the aniline monomers before polymerization (e.g., by S2082-) has shown promise in facilitating the desired head-to-tail coupling of the aniline substrates. During polymerization, the anionic polyelectrolytes such as poly(styrenesulfonate) and poly(acrylate)86-88 also provide the required counterions for charge compensation in the doped PAn products. This can lead to water-soluble or water-dispersed ES products. 

Solution behavior of ionomers can be divided into two types, primarily depending on the polarity of the solvent [46,47], One is polyelectrolyte behavior due to the dissociation of counterions in polar solvents (e.g., DMF), and another is association behavior due to the formation of ion pairs and even higher order aggregates in less polar solvents (e.g., THF). Table 2 shows the solvents frequently used for the study of ionomer solutions, as well as their dielectric constants. As the dielectric constant decreases, the degree of counterion binding and also ion pair formation changes (increases) gradually, and so does the solution behavior. In this chapter, only the polyelectrolyte behavior of ionomers in a polar solvent is described. Some brief... 

Here the counterion binding of ionomer nonaqueous (polar) solutions is described. Figure 12 shows conductance data for a sulfonated PS ionomer in DMF. For comparison, conductance data for comparable small salts, sodium styrenesulfonate, which has a similar structure to the ionic repeat units of sulfonated PS ionomers, is also shown [29], A significant drop in conductance is clearly noted for the ionomer solution as compared with the simple salt. This is due to counterion binding, as discussed above for polyelectrolyte nonaqueous solutions. 

With regard to counterion binding, some similarities are also observed between ionomer nonaqueous solution and polyelectrolyte aqueous solution. This is the short-range effect due to partial desolvation associated with coun-... 

A similar physical picture of counterion binding can be adopted for systems containing surfactant counterions, although in this case some additional effect may be expected. The main factors that influence the binding of ionic surfactants to polyelectrolytes with opposite charge are (1) the charge density of the polyion, A, (2) the hydrophobic character of the surfactant (the length of its hydrocarbon chain), (3) the additional attractive forces between the... 

The equilibrium properties in dilute aqueous solution of weakly ionized polysaccharides, e.g. carboxylated natural poly= saccharides, have not been so thoroughly investigated in comparison with other natural and synthetic polyelectrolytes. For instance, a detailed thermodynamic characterization of acid ionization and of counterion binding in terms of combined experimental potentiometric, calorimetric and volumetric data has not been achieved so far for the above types of polysaccharides. Such a description, however, is of obvious relevance for a better understanding of structure-conformation dependent solution properties for this important class of biopolymers. 

Counterion binding to polyelectrolytes appear to be adequately accounted for in the operationally defined condensation term in the Manning theory. However, there are some experimental results that indicate that counterion binding may be present for polyelectrolytes where which is contrary to the Man-... 

A different effect occurs with the use of polycarboxy-lates in combination with zeolites. Small amounts of polycarboxylates or phosphonates can retard the precipitation of sparingly soluble calcium salts such as CaCOs (the threshold effect ). As they behave as anionic polyelectrolytes, they bind cations (counterion condensation), and multivalent cations are strongly preferred. Whereas the pure calcium salt of the polymer is almost insoluble in water, mixed Ca/Na salts are soluble, i.e. only overstoichiometric amounts of calcium ions can cause precipitation. Polycarboxylates are also able to disperse many solids in aqueous solutions. Both dispersion and the threshold effect result from the adsorption of the polymer on to the surfaces of soil and CaCOs particles, respectively. 

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. 

ULRICH P. STRAUSS, Professor of Chemistry, Rutgers University, the State University of New Jersey, graduated from Columbia University (A.B. 1941), then attended Cornell University to obtain a Ph.D. (1944). He was a Sterling Postdoctoral Fellow at Yale University from 1946-48. He has been on the Rutgers University faculty since 1948. His main areas of research are polyelectrolytes, polysoaps, DNA, specific counterion binding and hydrophobic polyacids and polyampholytes. 

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