Persistence length of flexible polyelectrolyte chains

We calculate the dependence of the electrostatic persistence length, l_e, ofweakly charged flexible polyelectrolyte chains using a self-consistentvariational theory. The variation of l_e with \kappa, the inverse Debyescreening length, is controlled by the parameter l_0 l_B/A^2, where l_0 is thebare persistence length, l_B is the Bjerrum length, and A is the mean distancebetween charges along the chain. Several distinct regimes for the dependence ofl_e on \kappa emerge depending on the value of l_0 l_B/A^2. We show that whenl_0 l_B /A^2 << 1 we recover the classical result, l_e \propto \kappa^{-2}. Forintermediate values of l_0 l_B /A^2, l_e \propto \kappa^{-1}. In this regimeone can also get l_e \propto \kappa^{-y} with y < 1 depending on the strengthof the Coulomb interaction. Qualitative comparisons between our theory andsimulations as well as other theories are presented.Comment: 25 pages, Latex, figure available upon reques