Molecular mass and ionic strength dependence of electrochemical properties of flexible polyelectrolytes

Abstract

Conductometry and potentiometry have been employed to examine the influence of macromolecular parameters and chemical structure on the electrochemical behaviour of flexible polyelectrolytes with finite chain length in the concentration range 10−6<cp<10−2monomol·l−1. For polyelectrolytes with charge distances below the Bjerrum length at low ionic strength the equivalent conductivity increases strongly with decreasing polymer concentration. Correlating this behaviour with concentration regimes according to de Gennes and Odijk the strong and nearly linear increase is situated below the overlap concentration. In highly diluted polyelectrolyte solutions without and with addition of low molecular electrolyte the equivalent conductivity reaches a limit whose absolute high and position was found to have strong correlations with the molecular mass, the ionic strength, and the ratio of polyelectrolyte to salt concentration. The electrolytic conductivity results correspond with counterion activities in the concentration range cp > 10−4 monomol·l−1. The discussion of the findings in terms of existing theories point to defined changes of the interionic interactions.

Polyelectrolyte conductivity

“…the typical specific conductance of monomeric salts is larger (roughly 100 Scm 2 /mol) and nearly We have ignored the famous Onsager relaxation (or asymmetry) effect. 32 This effect has been independent of concentration, 28 indicating that both the logarithmic decrease below 10 02 M and recently shown to be essential for describing electrophoresis of polyelectrolytes, 31 which is the the increase above 10 02 M are polymer effects. The fact that polyelectrolytes have a lower specific same as DC conductivity.…”

“…residual salt) confirms that the steep upturn ob-A combination of light scattering 25 (at low conserved in Figure 3 at low concentration is caused centrations) and neutron scattering 26 (at high by residual salt. 28 This study indicates that the concentrations) have been used to evaluate the specific conductance continues to increase in the correlation length from the wavevector of maximum scattering (j Å 2p/q max ). The following power law describes the concentration dependence (c in mol of monomer per liter) of the correlation length (j in Angstroms) for NaPSS in water with no added salt.…”

Physical Properties of Sodium Poly(styrene sulfonate): Comparison to Incompletely Sulfonated Polystyrene

“…Typically, the molar mass of polyelectrolytes does not affect the partial specific volume as long as it is sufficiently high . While molar mass independence was observed for C-NaPSS, the phenomenon also depends on the measured concentration range, specifically whether it spans the dilute-to-semidilute regime or even higher concentrations where entanglements occur . Chemical differences between NaP4SS and C-NaPSS could affect these regimes, as polyelectrolyte conformation in dilute solution depends on the fraction of charged groups on the polymer and the ionic strength of the solution. , …”

“…83 While molar mass independence was observed for C-NaPSS, the phenomenon also depends on the measured concentration range, specifically whether it spans the dilute-to-semidilute regime or even higher concentrations where entanglements occur. 84 Chemical differences between NaP4SS and C-NaPSS could affect these regimes, as polyelectrolyte conformation in dilute solution depends on the fraction of charged groups on the polymer and the ionic strength of the solution. 85,86 Measurements of ṽover several concentrations of NaCl were conducted to observe the effect of ionic strength for NaP4SS and C-NaPSS samples of similar molecular weight (Figure 9C).…”

Oligo(ethylene oxide) side‐chain steric screening effects on conductimetric properties of grafted poly(4‐vinylpyridinium) salts in aqueous solutions

“…Conductivity measurements for many polyelectrolyte systems have been reported, but only a few studies on concentration effects over an extended concentration range can be found 17–29. Moreover, most of these studies have been carried out on anionic polyelectrolytes 18, 21, 24–33. In most cases, the results show that the molar conductivity increases with decreasing concentration.…”