Electrical Conductivity of Polyelectrolyte Solutions in the Semidilute and Concentrated Regime:  The Role of Counterion Condensation

Abstract

The d.c. electrical conductivity of polyacrylate sodium salt and poly(acrylic acid) aqueous solutions of different molecular weights from 2 to 200 kD has been investigated in a wide range of polymer concentration, covering both the semidilute (unentangled and entangled) and concentrated regimes. The data have been analyzed on the basis of a modified version of the Manning theory of counterion condensation, to cover the semidilute regime, taking into account scaling arguments recently proposed by Dobrynin et al. (Macromolecules 1995, 28, 1859). This analysis, on the basis of the conductivity model we have adopted, provides evidence for a fraction of free counterions that increases with the polymer concentration until the semidilute-concentrated crossover concentration is reached, suggesting that, in the concentration range investigated, the effective charge on the polyion is dependent on the polymer concentration. Moreover, at the higher concentrations investigated, our data suggest that a regime is attained where electrostatic blobs overlap, strongly affecting the electrical transport properties of the solution and causing a progressive reduction of the free counterion concentration.

Does Electrical Conductivity of Linear Polyelectrolytes in Aqueous Solutions Follow the Dynamic Scaling Laws? A Critical Review and a Summary of the Key Relations

“…We confine ourselves to one's own measurements [4,5,8,12], but in the recent literature many other appropriate examples can be easily found.…”

“…In this review, we summarize the main results and collect the relevant expressions governing the electrical conductivity of a polyelectrolyte solution in different experimental conditions, on the basis of a series of our own papers, appeared in the last few years [4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Thermodynamic, transport and frictional properties in semidilute aqueous sodium carboxymethylcellulose solution

“…A survey of the literature indicated that the influences of polyelectrolyte concentration, polyelectrolyte molecular weight, medium, and temperature on counterion condensation in salt-free polyelectrolyte solution have been fairly investigated [7][8][9][10][11][12][13][14][15][16][17][18].…”

Transport properties of some cationic polysaccharides

“…These interactions are strongly sensitive to some parameters such as the chain length, the charge density, the polyelectrolyte concentration, the counterion type, the ionic strength, the solvent polarity, etc. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Perhaps the most significant parameter affecting the solution properties of a polyelectrolyte is the linear charge density whose importance has been promoted by Manning in his counterion condensation theory [24,25].…”