Monte Carlo Simulations of Complexation between Weak Polyelectrolytes and a Charged Nanoparticle. Influence of Polyelectrolyte Chain Length and Concentration

Complexation between multiple weak polyacid chains and a positively charged spherical nanoparticle has been studied by means of Monte Carlo simulations. By considering titration curves, it is found that variations in the polyacid chain length and concentration and the polyacid-to-nanoparticle mixing ratio influence the ionization of the system. For larger mixing ratios and longer chain lengths, the titration curves start to exhibit complex shapes with multiple inflection points. We also find that in some cases it is possible to differentiate between free and adsorbed chains, based on the charge probability distribution and the probability distribution of the gyration radius. Furthermore, the adsorption of weak polyacids has been compared with that of strong polyacids, and the fraction of adsorbed monomers is found to be slightly larger for the strong polyacids. In addition, the fraction of adsorbed chains can be much lower for the weak polyacids due to their ability to concentrate charge in few chains.