Ion binding to polyelectrolytes: Monte Carlo simulations versus classical mean field theories

• Published in: Theoretical chemistry accounts Vol. 123; no. 1-2; pp. 127 - 135
• Main Authors: Madurga, Sergio, Garcés, Josep Lluís, Companys, Encarnació, Rey-Castro, Carlos, Salvador, José, Galceran, Josep, Vilaseca, Eudald, Puy, Jaume, Mas, Francesc
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2009
• Subjects: Atomic/Molecular Structure and Spectra; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Organic Chemistry; Physical Chemistry; Regular Article; Theoretical and Computational Chemistry; Polyelectrolytic effect; Non-Linear Poisson–Boltzmann theory; Semi Grand Canonical; Macromolecular complexation; Specific binding; Monte Carlo simulation
• ISSN: 1432-881X; 1432-2234
• DOI: 10.1007/s00214-009-0550-z

The influence of ion size and surface charge model in titrations of ionizable polyelectrolytes is studied by means of the Semi Grand Canonical Monte Carlo simulation method in the context of the primitive model. Three models describing a discrete distribution of charged functional groups on the polyelectrolyte and different values for the radius of the background electrolyte spanning from ionic to hydrated radii values were analyzed. The polyelectrolyte titrations were simulated by calculating the degree of ionization versus pH curves at two ionic strengths. The results allow us to quantify the impact of the sizes of the background salt ions and surface functional groups of the polyelectrolyte on the dissociation degree. This influence is explained in terms of the effectiveness of the screening of the charged surface sites. Finally, by comparison with the Non-Linear Poisson–Boltzmann model, the influence of ionic correlations and finite size of the solution ions is assessed.