Electrostatic contribution to the persistence length of a polyelectrolyte

Abstract

The electrostatic contribution to the persistence length is computed through the integration of the average electrostatic potential at the surface of a toroidal polyion over its charge parameter, when specific interaction between the mobile ions of the salt and the fixed charges of the polyion are ignored. When the radius of curvature of the polyion is very large, we assumed that the electrostatic potential may be developed in series as a function of the curvature. With this assumption, it may be computed from one‐dimensional integrations only. The assumption is then numerically verified by performing a painstaking two‐dimensional integration for finite values of the radius of curvature. Values for the electrostatic contribution to the persistence length are given in two limit cases: in the presence of an excess of added salt and in the total absence of added salt. The role of the dielectric constant and of the mobility of the ’’fixed’’ charges of the polyion is also determined.