Structure of polyelectrolyte solutions: Influence of salt and chain flexibility

The structural properties of polyelectrolyte solutions with and without added salt are investigated using an integral equation theory approach. For rodlike systems, all components of the solution (polyions, counterions, anions, and cations) are treat explicitly. Solutions of flexible polyelectrolytes are investigated using the Debye-Huckel model. The Polymer-Reference-Interaction-Site model for the multicomponent system together with the Reference-Laria-Wu-Chandler closure is solved numerically. It is show that the Coulomb interaction leads to a long-range liquid like structure. Addition of salt causes screening of the interaction and the structure disappears at very high salt concentrations. Comparison of the correlation functions of the multicomponent systems with those obtained by a one-component Debye-Huckel model exhibits good agreement. Moreover, for an appropriate range of parameters, such as density or Bjerrum length, a shell of equally charged saltions exists in the vicinity of a polyion. The effective potential between two monomers displays attraction among the equally charged polyions. The strength of the attraction increases with increasing salt concentration.