Impact of Monovalent Counter-ions on the Conformation of Flexible Polyelectrolytes Having Different Molecular Architectures

Chremos, Alexandros; Douglas, Jack F.

doi:10.1557/adv.2016.122

Cited by 9 publications

(4 citation statements)

References 28 publications

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“…For the same reason, starlike polymers always tend to attract more CIs inside the SC than linear species, and effect that is magnified at high pH in the largest cavity studied. A similar effect was previously evidenced for strong polyelectrolytes in terms of the number of condensed ions or larger deviation from the ideal osmotic pressure.…”

Section: Resultssupporting

confidence: 83%

Absorbed weak polyelectrolytes: Impact of confinement, topology, and chemically specific interactions on ionization, conformation free energy, counterion condensation, and absorption equilibrium

Tagliabue

Izzo

Mella

2019

J Polym Sci B Polym Phys

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Absorption of weak polyelectrolytes impacts on properties such as ionization, conformations, and counterion (CI) condensation that are important in several areas of applied and fundamental science. We used a weak polyelectrolyte model and Monte Carlo simulations to investigate how the mentioned properties depend on pH or the size of a spherical cavity (SC) permeable to CIs but not to polyelectrolytes; the latter have either linear or starlike topologies and may be allowed to form charged hydrogen bonds (c H-bonds) between ionized and neutral monomers. Average ionization decreases upon increasing the number of arms at a constant number of monomers; it instead increases with the arm length in large SC due to CI screening. The way SC size, c H-bonds, and pH values interrelate to define ionization is instead more complicate due to arm pairing or clustering when c H-bonds are possible. These induce oscillations in the arm local ionization and impact on both monomer and CI distributions in the complete simulation cell in a way that also depends on polymer topology. The impact of ionization on the confinement free energy is also estimated; this highlighted that c H-bonding may enhance absorption compared with neutral chains.

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Section: Resultssupporting

confidence: 83%

Absorbed weak polyelectrolytes: Impact of confinement, topology, and chemically specific interactions on ionization, conformation free energy, counterion condensation, and absorption equilibrium

Tagliabue

Izzo

Mella

2019

J Polym Sci B Polym Phys

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“…46,47 Unlike rigid rods, polymers exhibit flexible molecular conformation, meaning that we need to calculate the time average molecular shape, i.e., ⟨R h /R g ⟩. As we showed in a previous study, 50 for monovalent counter-ions the linear chains become more anisotropic as M w increases. However, it is clear that polyelectrolyte chains have a relatively stretched "worm-like" configuration with respect to chains having no charges, but nonetheless their shape is quite distinct from a rod (see Fig.…”

Section: Resultsmentioning

confidence: 94%

Influence of higher valent ions on flexible polyelectrolyte stiffness and counter-ion distribution

Chremos

Douglas

2016

The Journal of Chemical Physics

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We investigate the influence of counter-ion valency on the flexibility of highly charged flexible polymer chains using molecular dynamics simulations that include both salt and an explicit solvent. As observed experimentally, we find that divalent counter-ions greatly reduce the chain persistence length, lp, in comparison with monovalent counter-ions. On the other hand, polyelectrolyte chains having trivalent counter-ions adopt a much more compact conformation than polyelectrolytes having monovalent and divalent counter-ions. We demonstrate that the tendency of polyelectrolyte chains to become deformed by proximal high valence counter-ions is due to chain "coiling" around the counter-ions. In particular, we find that the number of contacts that the proximal counter-ions have with the polyelectrolyte dictates the extent of chain coiling. This ion-binding induced coiling mechanism influences not only the conformational properties of the polyelectrolyte, but also the counter-ion distribution around the chain. Specifically, we find that higher valent counter-ions lead both to a counter-ion enrichment in close proximity to the polyelectrolyte and to a significant reduction in the spatial extent of the diffuse counter-ion cloud around the polyelectrolyte.

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“…To investigate this finding in-depth, recent simulation works analyzed CIs partitioning between strong polyelectrolytes’ vicinal or distal regions detecting the presence of dynamic clusters of CIs at the polymer chain–solution interface, with characteristics depending on polymer topology (i.e., linear versus ring versus starlike, etc. ). , Also, the impact on conformations of introducing selective ion–solvent or polyelectrolyte–solvent interactions in the force field was interpreted as an indication that the thermodynamical preference of the medium toward a specific system component may play a role . A positive correlation between gyration radius, R g , and the fraction of interface-localized CIs was also detected, suggesting that the CIs distribution may respond to chain conformations.…”

Section: Introductionmentioning

confidence: 99%

Interface Counterion Localization Induces a Switch between Tight and Loose Configurations of Knotted Weak Polyacid Rings despite Intermonomer Coulomb Repulsions

2020

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Stochastic simulations have been used to investigate the conformational behavior of knotted weak polyacid rings as a function of pH. Different from the commonly expected ionization–repulsion–expansion scheme upon increasing pH, theoretical results suggest a nonmonotonic behavior of the gyration radius R g 2. Polyelectrolyte recontraction at high ionization is induced by the weakening of Coulomb repulsion due to counterions (CIs) localizing at the interphase between the polymer and solvent, and the more marked it appears, the more complex is the knot topology. Compared with strong polyelectrolytic species of identical ionization, weak polyacids present tighter knots due to their ability to localize neutral monomers inside the tangled part. Increasing the solvent Bjerrum length enhances CIs localization, lowering the pH at which polyacids start decreasing their average size. A similar effect is also obtained by increasing the amount of “localizable” cations by adding salts.

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Impact of Monovalent Counter-ions on the Conformation of Flexible Polyelectrolytes Having Different Molecular Architectures

Cited by 9 publications

References 28 publications

Absorbed weak polyelectrolytes: Impact of confinement, topology, and chemically specific interactions on ionization, conformation free energy, counterion condensation, and absorption equilibrium

Absorbed weak polyelectrolytes: Impact of confinement, topology, and chemically specific interactions on ionization, conformation free energy, counterion condensation, and absorption equilibrium

Influence of higher valent ions on flexible polyelectrolyte stiffness and counter-ion distribution

Interface Counterion Localization Induces a Switch between Tight and Loose Configurations of Knotted Weak Polyacid Rings despite Intermonomer Coulomb Repulsions

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