Monte Carlo simulations of polyelectrolytes at charged hard spheres with different numbers of polyelectrolyte chains

The complexation of a charged hard sphere (macroion) with short and oppositely charged polyelectrolytes was studied by the use of a simple model system. Structural data of the macroion–polyelectrolyte complex and the surrounding solution were obtained by the use of Monte Carlo simulation technique. The number of polyelectrolyte chains as well as the linear charge density and the flexibility of the polyelectrolyte were varied, whereas the properties of the macroion were held constant. In all cases, the macroion and a polyelectrolyte carried an equal number of elementary charges. The simulations showed that for flexible and highly charged polyelectrolytes, a tight complex containing the macroion and one polyelectrolyte was formed independent of the number of polyelectrolytes present. However, for flexible but lower charged polyelectrolytes, a looser macroion–polyelectrolyte complex was established, and a complex involving two polyelectrolytes occurred when two or more polyelectrolytes were available. Finally, for the most rigid polyelectrolyte no complex was formed at all. Generally, an intramolecular contraction of the polyelectrolyte occurred upon complexation with the macroion.