Charge Regulation of Polyelectrolyte Gels: Swelling Transition

Zheng, Bizhang; Avni, Yael; Andelman, David; Podgornik, Rudolf

doi:10.1021/acs.macromol.3c00609

Cited by 8 publications

(2 citation statements)

References 49 publications

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“…In the presence of an adsorbing charge, the surface dissociation equilibrium is shifted toward a more ionized state, illustrated in Scheme for the example of a surface hydroxyl. This process, known as charge regularization, CR, occurs in proteins, , between synthetic polyelectrolytes − and on mineral surfaces. , …”

Section: Introductionmentioning

confidence: 99%

Relative Strength of Polycation Adsorption on Oxide Surfaces

Akintola,

Abou Shaheen,

et al. 2024

Langmuir

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Polyelectrolyte adsorption onto surfaces is widely employed in water treatment and mining. However, little is known of the relative interaction strengths between surfaces and polymer. This fundamental property is assumed to be dominated by electrostatics, i.e., attractive interactions between opposite charges, which are set by the overall ionic strength ("salt concentration") of the solution, and charge densities of the surface and the polymer. A common, counterintuitive finding is a range of salt concentrations over which the amount of adsorbed polyelectrolyte increases as electrostatic interactions are tempered by the addition of salt. After an adsorption maximum, higher salt concentrations then produce the expected gradual desorption of polyelectrolyte. In this work, the salt response of the adsorption of the same narrow molecular weight distribution polycation, poly(N-methyl-4-vinylpyridinium), PM4VP, to a variety of surfaces was explored. Oxide powders for adsorption included Al 2 O 3 , SiO 2 , Fe 2 O 3 , Fe 3 O 4 , TiO 2 , ZnO, and CuO. Planar surfaces included silicon wafers, mica, calcium carbonate, and CaF 2 single crystals. The PM4VP was radiolabeled with 14 C so that sensitive, submonolayer amounts could be detected. The position of the peak maximum, or the lack of a peak, in response to added salt was used to rank the electrostatic component of the interaction. The importance of charge regulation, a shift in the surface pK a in response to solution species, was highlighted as a mechanism for adsorption on the "wrong" side of the isoelectric point and also as a factor contributing to the difficulty of reaching the totally desorbed state even at the highest salt concentrations.

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Section: Introductionmentioning

confidence: 99%

Relative Strength of Polycation Adsorption on Oxide Surfaces

Akintola,

Abou Shaheen,

et al. 2024

Langmuir

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“…Scaling and phenomenological models have been proposed and contrasted against coarse-grained simulations for exploring the role of the screened electrostatic interactions between backbone charges upon swelling in nanogels. 29,30 More sophisticated theories, such as density function theory [31][32][33] and variational theory, 34 have been developed and investigated, to consistently relate microscopic degrees of freedom with microgel swelling. Here the complex coupling between microgel screening, backbone self-repulsion and polymer conformation has been accounted for.…”

Section: Introductionmentioning

confidence: 99%

Modelling microgel swelling: Influence of chain finite extensibility

Brito,

Holm

2024

Preprint

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Microgels exhibit the ability to undergo reversible swelling in response to shifts in environmental factors that include variations in temperature, concentration, and pH. While several models have been put forward to elucidate specific aspects of microgel swelling and its impact on bulk behavior, a consistent theoretical description that chains throughout the microscopic degrees of freedom with suspension properties and deepens into the full implications of swelling remains a challenge yet to be met. In this work, we extend the mean-field swelling model of microgels from Denton and Tang (J. Chem. Phys. 145, 164901 (2016)) to include the finite extensibility of the polymer chains. The elastic contribution to swelling in the original work is formulated for Gaussian chains. By using the Langevin chain model, we modify this elastic contribution in order to account for finite extensibility effects, which become prominent for microgels containing highly charged polyelectrolytes and short polymer chains. We assess the performance of both elastic models, namely for Gaussian and Langevin chains, comparing against coarse-grained bead-spring simulations of ionic microgels with explicit electrostatic interactions. We examine the applicability scope of the models under variation of parameters such as ionization degree, microgel concentration and salt concentration. The models are also tested against experimental results. This work broadens the applicability of the microgel swelling model towards a more realistic description, which brings advantages when describing suspensions of nanogels and weak-polyelectrolyte micro/nanogels.

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