CROSSOVER-BEHAVIOR IN HIGH-FREQUENCY DIELECTRIC-RELAXATION OF LINEAR POLYIONS IN DILUTE AND SEMIDILUTE SOLUTIONS

The complex dielectric constant, e*, of the high-frequency dielectric relaxation of sodium polystyrene sulfonate (NaPSS) in aqueous solutions with no added salts was measured over wide ranges of degree of polymerization, N, and polymer concentration, CP, from the dilute to the semidilute region. The crossover concentration, CG, between the dilute and the semidilute regions was clearly observed in the CP dependences of the relaxation time, τ, and the dielectric increment, At, of the high-frequency relaxation. The Cp and N dependences of r and At are summarized asr“Cp'^N2'8, At <* CP1/8i\P/3 below CG, and τ ce CP_1N°, At œ CP0N° above CG. This crossover behavior of the high-frequency relaxation is ascribable to that of the correlation length, £, which shows different CP dependences in the dilute and semidilute regions, respectively. This leads to the conclusion that the high-frequency relaxations in the dilute and semidilute regions are commonly attributed to the localized movement or fluctuation of loosely bound counterions spreading over ξ, namely, the average distance between polyions in both the regions. © 1990, American Chemical Society. All rights reserved.