The dielectric increments of aqueous polyelectrolyte solutions: a scaling approach

This paper deals with dielectric dispersion curves (covering a frequency range from a few Hz to 100 MHz) of Na - poly(styrene-sulfonate) of 65 000 less than or equal to M-w less than or equal to 1 060 000 g mol(-1) in aqueous solutions. The values of the row frequency (Delta is an element of(1)) and high frequency (Delta is an element of(2)) dielectric increments, obtained from the experimental curves matched to a superposition of two Cole-Cole equations, have been analyzed in terms of their concentration and molar mass dependence. The concentrations C (g l(-1)) of the various solutions were mostly situated in the transition regime defined by Odijk [T. Odijk, Macromolecules 12 (1979) 688] between the dilute regime (C < C-g*) and the semi-dilute one (C > C**), and wherein the characteristic concentration C* marks the onset of flexibility effects on the polyion behavior. It has been shown that in the concentration range C-g* < C < C** the increments in both frequency domains satisfy a scaring relation Delta is an element of(j) = B-j M-vj (C/C*)(mu j) with molar mass independent exponents v(j) and mu(j) changing around C*. Their values are different for Delta is an element of(1) and Delta is an element of(2), except for mu above C* where both increments appear to become concentration-independent. Below C-g*, in the dilute regime, the two dispersion domains seem to merge. The increment Delta is an element of = is an element of' (0) - is an element of (infinity) is molar mass independent if scaled to (C/C-g*). The molar mass dependence of the increments as a function of the macromolecular concentration rho(P), Delta is an element of or Delta is an element of(j) similar to M-gamma (rho(P))(mu), also reveals differences between the different concentration regimes. Extrapolation from above C-g* to zero concentration is thus unjustified. (C) 2000 Elsevier Science B.V. All rights reserved.