A Monte Carlo Study of Titrating Polyelectrolytes in the Presence of Salt

Abstract

Monte Carlo simulations have been performed for two simple models of a titrating polyelectrolyte: (i) a rigid rod and (ii) a freely jointed chain. Both models have fixed bond lengths, and the polyelectrolyte charges interact through a screened Coulomb potential. Chains consisting of 80−1000 monomeric units have been studied at three salt concentrations: 0.001, 0.01, and 0.1 M. Conformational properties and the apparent dissociation constant are reported as functions of chain length, chain ionization, monomer−monomer bond length, and salt concentration. Mean field expressions are compared to the simulation results and are, in general, found to be excellent approximations for the rigid rod, but they are also able to provide semiquantitative descriptions of the apparent dissociation constant for the freely jointed chain. Comparisons with experimental data show that the conformational properties of the flexible model can reproduce features of the titration curves, although the use of a screened Coulomb potential overestimates the response to changes in salt concentration.

Influence of Explicit Ions on Titration Curves and Conformations of Flexible Polyelectrolytes: A Monte Carlo Study

“…The main tendencies of weak polyelectolytes are the regular increase in R with pH and ΔpK with R, thus supporting observed experimental data and theoretical predictions. [40][41][42][43] The influence of parameters such as the Debye length, charge spacing, and charge distribution on the chains, salt, and monomer concentration have been systematically investigated. When salt is added, the Debye length decreases.…”

Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

“…[6][7][8][9] This treatment was pioneered by Tandford and Kirwood for proteins 10 and was also applied to polyelectrolytes. [11][12][13] Other experimental systems studied as a planar ionizable interfaces are the titration of a variety of metal oxide and hydroxide particles, for example, goethite ͑␣-FeOOH͒, hematite ͑␣-Fe 2 O 3 ͒, and silica ͑see Ref. 14 and those quoted therein͒.…”

Protonacijske ravnoteže linearnih homopolikiselina

“…Istraživanja su pokazala da je slaganje između modelom izračunatih (fleksibilni poliion s diskretno raspoređenim nabijenim skupinama) i eksperimentalnih podataka za poli(akrilnu kiselinu) znatno bolje nego li slaganje između eksperimentanih i ΔpK ap (α) vrijednosti izračunatih temeljem krutog cilindričnog modela. 47 Štoviše, za opis utjecaja ionske atmosfere na elektrostatski doprinos Gibbsovoj energiji sustava dostatno je riješiti P.-B. jednadžbu u Debye-Hückelovoj aproksimaciji.…”