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

Abstract

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 influences 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 1 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.

pH‐Controlled network formation in a mixture of oppositely charged cellulose nanocrystals and poly(allylamine)

“…Thus, the PAAm protonation degree at a given mixture pH appears at lower pH for the pure PAAm solution. This outcome is in good agreement with previous experimental observations, as well as results of computer simulations …”

“…Concerning the studied system, the PAAm ionization behavior in the CNC‐PAAm suspension shifts to higher pH values owing to the negative electrostatic potential of CNCs . Thereby, the ionization probability of PAAm amine groups, situated close to the negatively charged CNCs, increases . As a result, the positively charged PAAm monomers are attracted to CNCs and adsorb on their surface.…”

“…However, in reality, the electrostatic interaction between oppositely charged components remarkably affects the suspension properties. As known from simulations of mixtures containing weak PEs and oppositely cNPs, the presence of cNPs affects the PE ionization degree, the charge distribution along the chain and the chain conformation. Concerning the studied system, the PAAm ionization behavior in the CNC‐PAAm suspension shifts to higher pH values owing to the negative electrostatic potential of CNCs .…”

“…The probability of such bridging interactions depends on the interparticle distance, the PE and nanoparticle charge densities, the PE chain length and stiffness, and the ionic strength of the solution . Simulations of interactions between a cNP and an oppositely charged weak PE showed induced ionization and modification of the charge distribution along the charged chain . To date, only a few works have experimentally demonstrated bridging of cNPs by PEs.…”

Grand-Reaction Method for Simulations of Ionization Equilibria and Ion Partitioning in a Broad Range of pH and Ionic Strength

“…The variation of polymer ionization was achieved by varying its acidity constant, while the solution pH was a result of the simulation. The constant-pH method has been introduced to enable simulations of acid-base ionization reactions at a given pH 43 It has also been used to simulate various polyelectrolyte systems [44][45][46][47][48][49][50][51][52][53] . However, the simulated systems were not explicitly coupled to a reservoir.…”