On the theory of the excluded‐volume effect of a polyelectrolyte in a 1‐1 electrolyte solution

Abstract

AbstractAn excluded‐volume theory of polyelectrolytes is presented based on the concept of a Kuhn statiscal segment depending on the concentration of added salt. The polyion is viewed as a wormlike chain bearing charges which interact according to a Debye–Hückel potential. It is shown that it is consistent to split up the screened Coulomb potential into two parts: a short‐range interaction giving rise to a so‐called electrostatic persistence length which depends on the Debye–Hückel radius, and a long‐range interaction denoting the excluded‐volume effect. The mean‐square radius of the polyelectrolyte is derived, and this deviates markedly from expressions based on a constant Kuhnsegment length. Furthermore, certain polyelectrolytes exhibit negligible excluded‐volume effects and behave as wormlike chains with a persistence length equal to the sum of the bare persistence length and the electrostatic persistence length. In addition, an expression for the polyion–polyion contribution to the second virial coefficient is obtained.