Ionic and electrical conductances in polyelectrolyte solutions

Abstract

Publication costs assisted by Centre de Recherches sur les Macromolecules A phenomenological theory of electrical transport in polyelectrolyte-plus-salt solutions is developed. The treatment is based on linear force-flux relationships by using binary frictional coefficients within the framework of linear nonequilibrium thermodynamics. Correlations between conductances and reduced self-diffusion coefficients of counterions and coions are established without taking recourse to an explicit model, and former theories on the subject are generalized. In particular, it is shown that the "intrinsic conductivity" of a polyelectrolyte in excess-of-salt solutions may be related in a simple way to the electrophoretic mobility of the polyion, the transport parameters of small ions in pure salt solutions, and to the lowering of the self-diffusion coefficient of small ions in the presence of the polyelectrolyte. A comparison with recent experimental results displays semiquantitative agreement.

Concentration Regimes in Polyelectrolyte Solutions

“…Several other models for pure polyelectrolyte solutions without added salt based on thermodynamics − or scaling descriptions and also for polyelectrolyte solutions with an excess of low molar mass electrolyte , have been published. At present, models are under discussion which are based on ionic transport processes in terms of the dynamic frictional formalism of nonequilibrium thermodynamics .…”

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

“…where A is the equivalent conductivity of the solution, I ; is the equivalent conductance of the counterion in an infinitely diluted solution without polyions, A, is the equivalent conductance of the polyion [3, 71. 0.86681 In I 6 r I 1 + (I -0.866) ( A 9-8 1 In A 6 r 1 I , = (9) and f is given by [30] if b is the charge distance along the polyion.…”

“…The f, values are in good agreement with the calculations fcalc from considerations above assuming the increase of the equivalent conductivity below the overlap concentration results from an increase of f. For the high molecular mass sample neither the equivalent conductivity nor f change above the overlap concentration remarkably, where the activity has been measured. A comparison of calculated equivalent conductivities of polyelectrolyte solutions which contain a small electrolyte with measured values shall be given in a further publication [40], which will include different theories [8,9,411.…”

Relaxation and electrophoretic effects in polyelectrolyte solutions. II. Polyelectrolyteplus‐salt solutions

“…(13) and (14) are provided by molecular theories.lJl If ionic distributions are treated within the Debye-Huckel approximation, current theories1J1J2 lead, for symmetrical electrolytes, to the simple conclusion that the reduced self-diffusion coefficients of coions and counterions are equal, and consequently, k l = k2 (16) However, when the Debye-Huckel approximation does not hold, as is already apparent at moderate ionization degrees for the spherical polyion model,llJ3 we have, depending on polyion charge k l > k2 or k l >> k2 (17) Given these theoretical results, we are in a position to discuss the polyion mobility Eqs. (10). First, one may wonder whether the relaxation field related to the co-ion atmosphere is negligible with respect to the one related to the counterion atmosphere, as was supposed by Moller et al14 Consider the absolute value of the ratio of the corresponding fields [see Eqs.…”