Polyelectrolyte brushes in monovalent and multivalent salt solutions

Guptha, Vijeth Sathyanarayana; Hsiao, Pai‐Yi

doi:10.1016/j.polymer.2014.04.035

Cited by 41 publications

(50 citation statements)

References 68 publications

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“…A prediction from a nonlocal density-functional theory that the exponent ν in the power-law relation between brush height (H) and counterion concentration (H ∼ (C n+ ) −ν ) decreases with the valence of salt ion (n) [21] contradicts to the finding from a recent MD simulation [22] that the transition is sharper for counterions with larger valence, i.e., ν increases with n.…”

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confidence: 74%

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Heterogeneous Morphology and Dynamics of Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

2017

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Recent experiments have shown that trivalent ion, spermidine 3+ , can provoke lateral microphase segregation in DNA brushes. Using molecular simulations and simple theoretical arguments, we explore the effects of trivalent counterions on polyelectrolyte brushes. At a proper range of grafting density, polymer size, and ion concentration, the brush polymers collapse heterogeneously into octopus-like surface micelles. Remarkably, the heterogeneity in brush morphology is maximized and the relaxation dynamics of chain and condensed ion are the slowest at the 1:3 stoichiometric concentration of trivalent ions to polyelectrolyte charge. A further increase of trivalent ion concentration conducive to a charge inversion elicits modest reswelling and homogenizes the morphology of brush condensate. Our study provides a new insight into the origin of the diversity in DNA organization in cell nuclei as well as the ion-dependent morphological variation in polyelectrolyte brush layer of biological membranes.Polyelectrolyte brushes are ubiquitous in biological systems. As the main component of outer membrane in Gram-negative bacteria, lipopolysaccharides, consisting of charged O-polysaccharides side chains, form a brush layer and mediate the interaction of bacteria with their environment [1]. For vertebrates, negatively charged polysaccharide hyaluronic acids play a vital role in the organization of pericellular matrix [2,3]. Double-stranded DNA brushes on a biochip [4] at a cell-like density (∼ 10 4 kb/µm 3 ) have been developed as a platform to study cell-free gene expression [5]. Due to the negative charges along the backbone, this synthetic system behaves like a well-defined strong polyelectrolyte brush [5], the height of which can be varied by modulating the ionic strength of monovalent salt (NaCl) solution and the grafting density [6]. Recently, it has been reported that trivalent counterions, spermidine 3+ (Spd 3+ ), can induce a collapse transition of DNA brush into fractal-like dendritic macroscopic domains [7]. The heterogeneous morphology of DNA condensate points to polyamine-mediated regulation of local DNA configuration and gene expression [8,9], underscoring the importance of understanding the effects of multivalent counterions on polyelectrolyte brush [10,11]. Compared with uncharged polymer brushes in good or poor solvent, the electrostatic interaction and osmotic pressure, which are readily controlled by the salt concentration and pH, yield additional flexibilities in manipulating polyelectrolyte brushes, and thus holding promise for its wide applications [12,13].Conventional theoretical approaches, successful in explaining the behaviors of polyelectrolytes in monovalent salt solutions [11,14,15], are of limited use, particularly, when multivalent counterions are at work. For example, the solution to the mean-field PoissonBoltzmann theory [16] fails to account for phenomena such as ion condensation, charge over-compensation, and collapse of like-charged polymers [17][18][19][20]. A prediction from a nonlocal den...

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confidence: 74%

“…The dependence of brush height on counterion concentration and grafting density has been systematically investigated in mono-, di-, and trivalent ion solutions [22]. Atomistic simulations of DNA arrays solvated with Na + , Mg 2+ , and spermine 4+ suggested that the transient "bridging" of multivalent cations drives the collapse of DNA [24].…”

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confidence: 99%

Heterogeneous Morphology and Dynamics of Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

2017

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“…However, in the experiments the pH was set to a level where the charge fraction was approximately 0.4 (as measured and reported in Konradi and R€ uhe), and we use our model with f 5 0.4 as a first approximation for comparison. We choose to compare our results to representative data from the divalent alkalineearth metal ions, Ca 21 and Sr 21 , while not comparing to the transition metal ions due to their more complicated interactions with the polymer. For both ion species, the brush experienced a first-order transition at a C* of approximately 1 3 10 23 mol/L.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Molecular dynamics simulations have also been used to examine the effects of multivalent ions on polyelectrolyte brush structure . The studies focused on single polyelectrolyte brushes in multivalent ionic solutions and were able to capture the collapse of the brush and shed insight into a coil‐like structure that the chains assume in the collapsed state and the proportion of ions that contribute to the osmotic pressure . Rather than modeling single polyelectrolyte brushes, Cao et al performed simulations on opposing polyelectrolyte brushes, similar to those studied experimentally by Farina et al Not only were they able to show that the osmotic pressure is lower with higher valence ions, but they also showed increased interpenetration of the two brushes when simulations were performed with multivalent ions.…”

Section: Introductionmentioning

confidence: 99%

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Bridging contributions to polyelectrolyte brush collapse in multivalent salt solutions

Brettmann

Laugel

Hoffmann

et al. 2015

J. Polym. Sci. Part A: Polym. Chem.

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Polyelectrolyte brushes are essential in many aspects of surface functionality, particularly for colloidal stabilization and lubrication in biological and materials science applications. It has been shown experimentally that the brushes undergo an abrupt shrinkage in the presence of multivalent counter‐ions. This transition is studied here using a phenomenological mean‐field approach with a model that specifically includes bridging of the polyelectrolyte chains by the multiple charges on the multivalent counter‐ions. Using an energy balance represented by the sum of electrostatic, polymeric and entropic mean‐field terms, additional parameterized phenomenological terms are introduced for counter‐ion condensation and for the attractive interaction between adjacent polyelectrolyte chains to account for the bridging effect. The free energy is minimized with respect to the counter‐ion populations and the brush height. In agreement with experimental observations, increasing the concentration of multivalent ions leads to a sharp collapse of the polyelectrolyte brush height. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 284–291

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Monomer volume fraction profiles in pH responsive planar polyelectrolyte brushes

Mahalik

Yang

Deodhar

et al. 2016

J Polym Sci B Polym Phys

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Spatial dependencies of monomer volume fraction profiles of pH responsive polyelectrolyte brushes were investigated using field theories and neutron reflectivity experiments. In particular, planar polyelectrolyte brushes in good solvent were studied and direct comparisons between predictions of the theories and experimental measurements are presented. The comparisons between the theories and the experimental data reveal that solvent entropy and ion-pairs resulting from adsorption of counterions from the added salt play key roles in affecting the monomer distribution and must be taken into account in modeling polyelectrolyte brushes. Furthermore, the utility of this physics-based approach based on these theories for the prediction and interpretation of neutron reflectivity profiles in the context of pH responsive planar polyelectrolyte brushes such as polybasic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and polyacidic poly(methacrylic acid) (PMAA) brushes is demonstrated. The approach provides a quantitative way of estimating molecular weights of the polymers polymerized using surface-initiated atom transfer radical polymerization. V C 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 956-964

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Polyelectrolyte brushes in monovalent and multivalent salt solutions

Cited by 41 publications

References 68 publications

Heterogeneous Morphology and Dynamics of Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

Heterogeneous Morphology and Dynamics of Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

Bridging contributions to polyelectrolyte brush collapse in multivalent salt solutions

Monomer volume fraction profiles in pH responsive planar polyelectrolyte brushes

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