End effects of strongly charged polyelectrolytes: A molecular dynamics study

We investigate end effects in the ion distribution around strongly charged, flexible polyelectrolytes with a quenched charge distribution by molecular dynamics simulations of dilute polyelectrolyte solutions. We take the coun terions explicitly into account and calculate the full Coulomb interaction via a Ewald summation method. We find that the free counterions of the solu tion are distributed in such a way that a fraction of the chain charges is effectively neutralized. This in turn leads to an effective charge distribu tion which is similar to those found for weakly charged titrating polyelect rolytes that have an annealed charge distribution. The delicate interplay b etween the electrostatic interactions, the chain conformation and the count erion distribution is studied in detail as a function of different system p arameters such as the chain length N-m, the charge fraction f, the charged particle density rho, the ionic strength and the solvent quality. Compariso ns are made with predictions from a scaling theory. (C) 2001 American Insti tute of Physics.