Persistence length of flexible polyelectrolyte chains

Abstract

We calculate the dependence of the electrostatic persistence length, le, of weakly charged flexible polyelectrolyte chains using a self-consistent variational theory. The variation of le with k, the inverse Debye screening length, is controlled by the parameter l0lB/A2 where l0 is the bare persistence length, lB is the Bjerrum length, and A is the mean distance between charges along the chain. Several distinct regimes for the dependence of le on k emerge depending on the value of l0lB/A2. We show that when l0lB/A2≪ 1 we recover the classical result, le∝k-2. For intermediate values of l0lB/A2, le∝k-1. In this regime one can also get le∝k-y with y<1 depending on the strength of the Coulomb interaction. When l0lB/A2≫ 1 we find le∝k-2. Qualitative comparisons between our theory and simulations as well as other theories are presented. © 1999 American Institute of Physics.