Rod‐like polyelectrolyte adsorption onto charged surfaces in monovalent and divalent salt solutions

Abstract

We analyze the adsorption of strongly charged polyelectrolytes onto weakly charged surfaces in divalent salt solutions. We include short‐range attractions between the monomers and the surface and between condensed ions and monomers, as well correlations among the condensed ions. Our results are compared with the adsorption in monovalent salt solutions. Different surface charge densities (σ), and divalent (m) and monovalent (s) salt concentrations are considered. When the Wigner‐Seitz cells diameter (2R) is larger than the length of the rod, the maximum amount of adsorption scales like nmax ∼ σ4/3 in both monovalent and divalent solutions. For homogeneously charged surfaces, the maximum adsorption occurs at s* ∼ σ2 when s* > ϕ, where ϕ is the monomer concentration, the counterpart for divalent salt solution, m* roughly scales as σ2.2 when m* > ϕ. The effective surface charge density has a maximum absolute value at m′ < m*. A discrete surface charge distribution and short‐range attractions between monomers and surface charge groups can greatly enhance surface charge inversion especially for high salt concentration. The critical salt concentration for adsorption in divalent salt solution roughly scales as mc ∼ bσ1.9, where b is the distance between two neighboring charged monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3642–3653, 2004

Modulation of Polyelectrolyte Adsorption on Nanoparticles and Nanochannels by Surface Curvature

“…Interestingly, Figure 4 shows that for a given polyelectrolyte and salt concentrations, the effect of curvature radii on polyelectrolyte adsorption is stronger for the spherical nanoparticle than for the cylindrical rod, which is due to the fact that the volume element at a given distance from the surface increases as ~ Figure S2). For C pol = 10 -2 M, σ pol increases with chain length and experiences a maximum as a function of salt concentration, in agreement with previous reports 1,18,[20][21][28][29] This maximum is due the dual role of ionic strength, which screens both electrostatic repulsions among polyelectrolyte segments and electrostatic attractions between the segments and the surface. In the condition of the maximum, the charge of the polyelectrolyte overcompensates the charge of the surface (σ pol > 0.1 |e|⋅nm -2 ).…”

“…Panels a and b in Figure 5 show σ pol for these two polyelectrolyte concentrations as color maps as a function of chain length (N) and bulk salt concentration (C salt ) (the corresponding plots for the channel are shown in the Supporting Information Figure S2). For C pol = 10 −2 M, σ pol increases with the chain length and experiences a maximum as a function of salt concentration, in agreement with previous reports 1,18,20,21,28,29 This maximum is due the dual role of ionic strength, which screens both electrostatic repulsions among polyelectrolyte segments and electrostatic attractions between the segments and the surface. In the condition of the maximum, the charge of the polyelectrolyte overcompensates the charge of the surface (σ pol > 0.1 |e|•nm −2 ).…”

“…The interaction of a single polyelectrolyte chain with surfaces of different curvatures has been the subject of recent investigations. − The adsorption of polyelectrolytes from solution to form a film on planar and convex surfaces has been also extensively studied in the literature, and it is relatively well-understood. − However, the adsorption of polyelectrolytes from solution on concave surfaces is still poorly investigated. Moreover, the effects of the radius and type of surface curvature (concave vs convex) on the adsorption of polyelectrolytes remain largely unexplored.…”

Direct Observation of Cations and Polynucleotides Explains Polyion Adsorption to Like-Charged Surfaces

“…Strongly charged chains, such as DNA, are soluble in monovalent salt aqueous solutions because while cations are condensed along the chains to decrease the electrostatic energy, their overall charge is nonzero. Polyelectrolyte adsorption to oppositely charged surfaces is due to the entropy gained by the release or partial release of surface and polyelectrolyte condensed counterions upon adsorption, and is enhanced by lateral and/or site-specific correlations. When multivalent counterions are used to mediate polyelectrolyte adsorptions to like-charged surfaces, as in the binding of DNA to mica, ,, the adsorption mechanism is unclear.…”

Water-induced correlation between single ions imaged at the solid–liquid interface

“…Probing the lateral organization of ions within Stern layers is a challenging task and most results available to date stem either from computer simulations 15 or theoretical developments 19,20 . When available, experimental results are typically obtained indirectly 10 or through techniques that require averaging over a large area of the interface 21 , hence implicitly relying on the assumption of a homogeneous Stern layer to provide a precise picture of the position of the ions and the liquid molecules.…”