Effect of Counterion Valency

Ray J, Manning GS. Effect of counterion valence and polymer charge density on the pair potential of two polyions. Macromolecules 1997 30 5739-5744. 

J. Ray and G. S. Manning, Macromolecules, 30, 5739 (1997). Effect of Counterion Valence and Polymer Charge Density on the Pair Potential of Two Polyions. 

The effects of ion valence and polyelectrolyte charge density showed that at very low ionic strength found that when the counterion valence of added salt changes from monovalent (NaCl) to divalent (MgS04), the reduced viscosity decreases by a factor of about 4.5. If La(N03)3 is used, the reduced viscosity will be further decreased although not drastically. As for polyelectrolyte charge density, the intrinsic viscosity was found to increase with it because of an enhanced intrachain electrostatic repulsion (Antonietti et al. 1997). 

The effect of hydrated radii, valence, and concentration of counterions on oil-external and middle-phase microemulsions was investigated by Chou and Shah [28]. It was observed that I mol of CaCb was equivalent to 16-19 mol of NaCl for solubilization in middle-phase microemulsions, whereas for solubilization in oil-external microemulsions, 1 mol of CaCb was equivalent to only 4 mol of NaCl. For monovalent electrolytes, the values for optimal salinity of solubilization in oil-external and middle-phase microemulsions are in the order LiCl>NaCl>KCl>NH4Cl, which correlates with the Stokes radii of hydrated counterions. The optimal salinity for middle-phase microemulsions and critical electrolyte concentration varied in a similar fashion with Stokes radii of counterions, which was distinctly different for the solubilization in oil-external miroemulsions. Based on these findings, it was concluded that the middle-phase microemulsion behaved like a water-continuous system with respect to the effect of counterions [28]. 

Pyrazole and its C-methyl derivatives acting as 2-monohaptopyrazoles in a neutral or slightly acidic medium give M(HPz) X, complexes where M is a transition metal, X is the counterion and m is the valence of the transition metal, usually 2. The number of pyrazole molecules, n, for a given metal depends on the nature of X and on the steric effects of the pyrazole substituents, especially those at position 3. Complexes of 3(5)-methylpyrazole with salts of a number of divalent metals involve the less hindered tautomer, the 5-methylpyrazole (209). With pyrazole and 4- or 5-monosubstituted pyrazoles M(HPz)6X2... 

Valence of counterion out and effect on water structure) Valence T —> swelling 4-... 

Some of the pertinent interactions that affect colloid stability are readily apparent from Figs. 7.4 and 7.12. The main effect of electrolytes is a more rapid decay of the repulsion energy with distance and to compact the double layer (reducing k 1). Experimentally it is known that the charge of the counterion plays an important role. The critical electrolyte concentration required just to agglomerate the colloids is proportional to z 6 Aj for high surface potential, and to z 2 A, 2, at low potentials [(4) and (5) in Table 7.3]. This is the theoretical basis for the qualitative valency rule of Schulze and Hardy. 

The results in Table 13.1 have been collected for colloids bearing both positive and negative surface charges. One of the earliest (1900) generalizations about the effect of added electrolyte is a result known as the Schulze-Hardy rule. This rule states that it is the valence of the ion of opposite charge to the colloid that has the principal effect on the stability of the colloid. The CCC value for a particular electrolyte is essentially determined by the valence of the counterion regardless of the nature of the ion with the same charge as the surface. The numbers listed in parentheses in Table 13.1 are the CCC values in moles per liter for counterions of the... 

Effect of concentration polarization upon the valency-induced counterion selectivity of ion-exchange membranes [12]. 

I. Rubinstein, Effect of concentration polarization upon the valency-induced counterion selectivity of ion-exchanger membranes, 3. Chem. Soc., Faraday Trans. II, 80 (1984) p. 335. 

The theoretical bases for interaction with counterions have been discussed in Sect. 5.1. However, these theories do not take into account the special nature of the ions and only the valency was considered [102-108,114-117]. The solubility caused by the variation in the counterions cannot, for example, be predicted. According to [35] the solubility of poly(diallyldimethylammonium halides) decreases in the order Cl" >Br" >1". The homopolymer precipitates in the iodide form. This is in contrast to ammonium halides where the iodide has the highest solubility [153]. Comparing the effects of Cl", S042", and P043" a very similar in-... 

Marszall (1988) studied the effect of electrolytes on the cloud point of mixed ionic-nonionic surfactant solutions such as SDS and Triton X-100. It was found that the cloud point of the mixed micellar solutions is drastically lowered by a variety of electrolytes at considerably lower concentrations than those affecting the cloud point of nonionic surfactants used alone. The results indicate that the factors affecting the cloud point phenomena of mixed surfactants at very low concentrations of ionic surfactants and electrolytes are primarily electrostatic in nature. The change in the original charge distribution of mixed micelles at a Lxed SDS-Triton X-100 ratio (one molecule per micelle), as indicated by the cloud point measurements as a function of electrolyte concentration, depends mostly on the valency number of the cations (counterions) and to some extent on the kind of the anion (co-ion) and is independent of the type of monovalent cation. 

We can see from equation (7.3) that the magnitude of the effect of an electrolyte of a given concentration on also depends on the valence of the ion of opposite charge to that of the particles (the counterion) the greater the valence of the added counterion, the greater its effect on V. These generalisations are known as the Schulze-Hardy rule. 

Nishio, T., and Minakata, A. Effects of ion size and valence on ion distribution in mixed counterion systems of a rodlike polyelectrolyte solution. 2. mixed-valence counterion systems. Journal of Physical Chemistry B, 2003, 107, No. 32, p. 8140-8145. 

Up to now only monovalent ions have been investigated. For multivalent ions the prediction of the PB theory is that for the distribution function P(r) only the product of the Manning parameter and the counterion valence v matters. Therefore a system of monovalent ions at ln = 3a is claimed to have the same distribution function as a system of trivalent ions at B = lo It will now be shown that this statement is an artifact of the PB approximation. Figure 9 shows examples of systems that are complementary in the described sense. Not only is the condensation enhanced as compared to PB theory, but the enhancement is stronger for the case involving multivalent ions. Two different reasons may be suggested to explain this effect ... 

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