Polyelectrolyte Brushes with Added Salt

Kumar, Niraj; Seidel, Christian

doi:10.1021/ma0515735

Cited by 106 publications

(154 citation statements)

References 53 publications

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“…67,71,72 In the present study, molecular dynamics simulations are used to investigate the structural and transport properties of CO 2 , methane, and their mixture in hydrated Na-montmorillonite at preadsorbed water content and 298. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 in this work is the Na-saturated Wyoming-type montmorillonite of unit cell formula: Na …”

Section: -70mentioning

confidence: 99%

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

2016

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Molecular dynamics simulations were carried out to study the structural and transport properties of carbon dioxide, methane, and their mixture at 298.15 K in Na-montmorillonite clay in the presence of water. The simulations show that, the self-diffusion coefficients of pure CO 2 and CH 4 molecules in the interlayers of Na-montmorillonite decrease as their loading increases, possibly because of steric hindrance. The diffusion of CO 2 in the interlayers of Na-montmorillonite, at constant loading of CO 2 , is not significantly affected by CH 4 for the investigated CO 2 /CH 4 mixture compositions. We attribute this to the preferential adsorption of CO 2 over CH 4 in Na-montmorillonite. While the presence of adsorbed CO 2 molecules, at constant loading of CH 4 , very significantly reduces the self-diffusion coefficients of CH 4 , and relatively larger decrease in those diffusion coefficients are obtained at higher loadings. The preferential adsorption of CO 2 molecules to the clay surface screens those possible attractive surface sites for CH 4 . The competition between screening and steric effects leads to a very slight decrease in the diffusion coefficients of CH 4 molecules at low CO 2 loadings. The steric hindrance effect, however, becomes much more significant at higher CO 2 loadings and the diffusion coefficients of methane molecules significantly decrease. Our simulations also indicate that, similar effects of water on both carbon dioxide and methane, increase with increasing water concentration, at constant loadings of CO 2 and CH 4 in the interlayers of Na-montmorillonite. Our results could be useful, because of the significance of shale gas exploitation and carbon dioxide storage.

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Section: -70mentioning

confidence: 99%

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

2016

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“…Periodic boundary conditions were applied in x and y dimensions, and an impenetrable neutral wall was placed at z = 2N a. The location of the wall is far from the brush region, so that the density profiles of ions in the bulk region are effectively constant [37,38]. In order to model a flexible strong polyelectrolyte brush in good solvents with multivalent salts, we considered the following energy potentials.…”

Section: Modelmentioning

confidence: 99%

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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“…The PNA/DNA duplex forms a strong polyelectrolyte brush, which retains the majority of its counterions within the thickness of the layer (Kumar and Seidel, 2005). Approximating the measurement buffer as a 1:1 electrolyte, the concentrations of anions c − and cations c + in the body of the brush can be related to their concentration in the external electrolyte, c 0,buffer = I, by the constraints of local charge neutrality and Donnan partitioning equilibrium (Donnan, 1995;Zhulina et al, 1999):…”

Section: Detection Mechanismmentioning

confidence: 99%

Optimization of label-free DNA detection with electrochemical impedance spectroscopy using PNA probes

Keighley

Estrela

et al. 2008

Biosensors and Bioelectronics

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Polyelectrolyte Brushes with Added Salt

Cited by 106 publications

References 53 publications

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

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

Optimization of label-free DNA detection with electrochemical impedance spectroscopy using PNA probes

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