Interactions of counterions with dextran sulfate in aqueous solutions

Abstract

Counterion activity coefficients in solutions of dextran sulfate with and without added salts were determined potentiometrically by using a cation‐exchange membrane and a sodium glass electrode. Dextran sulfate was shown to interact with monovalent cations in the order of preference: K+ > Cs+ > Na+ > Li+, whereas no specificity was found for bivalent cations. On the basis of light‐scattering measurements, the expansion of the dextran sulfate polyion in solutions of alkali metal salts was found to fall in the same order as the counterion activity coefficients in salt‐free solutions. It was also shown that the dextran sulfate polyion assumes a more extended conformation in magnesium chloride solution than in calcium chloride. These results were substantiated by measurements of solution viscosities.

Ultrasonic Studies on Monovalent and Divalent Cation Salts of Carrageenans in Aqueous Solution

“…The affinity sequence K > Na has also been observed for binding to dextran sulfate. 13 The interpretation in terms of the greater ease of replacement of the water of hydration in K+(aq) compared with Na+(aq) is consistent with our observation of a greater colume change. Since the relaxation frequency depends only little on the polyion nature for the low-frequency relaxational process,10 it should also be valid to compare the values of Aa/f2 at the same low frequencies for and carrageenans (average separation be-Figure 4.…”

Interactions of sodium ions with the sodium salts of poly(acrylic acid/acrylamide) copolymers of varying charge density

“…With increasing X, the values of S approach the salt-free value of 0.42; with decreasing X, they approach zero. If S, as suggested above, is a measure of the counterion-polyion interaction and if it is assumed that counterions from the added NaBr are not affected by the polyelectrolyte, then the slope for any value of X can be represented as an additivity rule Sy = X X + 1 s" + X +1 (9) where X/(X + 1) and 1/(X + 1) are the dimensionless concentration weighting factors for polyelectrolyte and simple salt, respectively, S= is the measured slope from salt-free polyelectrolyte solutions, and Ss is the slope for polyelectrolyte-free simple salt solutions. Since in formulating eq 9 it was assumed that S is an interaction constant and that the added simple electrolyte does not interact with the polyelectrolyte, Se = 0, and the second term in eq 9 also equals zero.…”

Interactions in mixed cationic surfactants and dextran sulfate aqueous solutions

“…Slight reducing of polyelectrolyte chains length is compensated for by increasing the molar mass of complex due to the bound surfactant monomers, leading to an increase in the mean particle size. The first particles, which appear upon surfactant addition, exhibit the mean particle size close of 16 nm, which is close to that of polyelectrolyte itself (the DxS molecules in water resemble a rod with the radii of the cylindrical macroion a ≈ 0.4 nm [6], with hydrodynamic radius R h = 15.8 nm [48]). Therefore it is reasonable to attribute it to an intrapolymer complex.…”