Persistence Length for a PSSNa Polyion in Semidilute Solution as a Function of the Ionic Strength

Abstract

The persistence length of sodium sulfonated polystyrene (PSSNa) is measured by small angle neutron scattering in the semidilute regime for two polymer concentrations $c$ as a function of the added salt concentration ${c}_{s}$. The results suggest that this persistence length ${l}_{p}$ depends only on ${c+2c}_{s}$. This questions the role of the counterion condensation at the nanometric scale. Moreover, a variation ${l}_{p}\ensuremath{\sim}({c+2c}_{s}{)}^{\ensuremath{-}1/3}$ is found. ${l}_{p}$ could be simply related to the distance between ions, which is the relevant length for concentrated solutions.