Persistence Length of Wormlike Polyelectrolyte Molecules in Semidilute Solutions

Abstract

The persistence length of wormlike polyelectrolyte chains in the salt-free semidilute solution is calculated by the same theoretical model as the previous calculations of small-angle scattering of the solution. It is assumed that because of the strong electrostatic repulsion between the polymer segments, two monomers in different segments can not be close to each others within a distance R₀. The persistence length a becomes
a=11.34(f⁄(1−f))^1⁄2C_m^−1⁄2 (Å) (f\lesssim1),
where f is a constant smaller than but close to unity, and C_m is the monomer concentration expressed in mol/l. This value for f=0.8–0.9 agrees with the values obtained by a recent small-angle neutron scattering experiment. The concentration dependence of the scattering curve calculated with this value agrees qualitatively with those of small-angle neutron and X-ray scattering experiments.