Simulation of Polyelectrolyte-Catalysed Reaction between Divalent Ions

Jesus Piñero,¹ Lutful B. Bhuiyan,¹ Jurij Reščič² and Vojko Vlachy^2,*

¹ Laboratory of Theoretical Physics Department of Physics, University of Puerto Rico, San Juan, Puerto Rico 00931-3343
² Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia
* Corresponding author: E-mail: vojko.vlachy@fkkt.uni-lj.si

Abstract
Catalytic potential of linear polyelectrolyte solutions in presence of +2:–2 salts, as evidenced through ionic correlations in the inhomogeneous atmosphere around a polyion, is studied using Monte Carlo simulation techniques and the traditional non-linear Poisson-Boltzmann approach. The simulations are performed on the cylindrical cell model where a uniformly charged hard cylinder mimics the linear polyion caged in a cylindrical cell containing divalent counterions and co-ions. Cell (volume) average of the inter-ionic correlations, as reflected in the pair-correlation functions, is presented as function of the polyion concentration, the low-molecular electrolyte concentration, and the ion radius. The volume average of the doublet pair distribution function between counterions is found to be sensitive to variation of model parameters. The results indicate large enhancement in the reaction rate between the counterions, while a decrease in the coion-coion and the coion-counterion reaction rate is noted, all in comparison with pure electrolyte solutions. The agreement between the predictions of the Poisson-Boltzmann theory and the simulation results is merely qualitative in most instances.

Keywords: Polyelectrolytes, +2:–2 electrolytes, catalytic effect, Monte Carlo method, Poisson-Boltzmann theory