Properties of water in the interfacial region of a polyelectrolyte bilayer adsorbed onto a substrate studied by computer simulations

Qiao, Bao Fu; Sega, Marcello; Holm, Christian

doi:10.1039/c2cp41115f

Cited by 13 publications

(14 citation statements)

References 54 publications

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“…Understanding water solvation of various self-assembled aggregates is necessary for predicting and perhaps manipulating a number of macroscopic substrate properties. 11 Among experiments used to assess the properties of interfaces, vibrational sum frequency generation (VSFG) is widely used to study the orientation of water at interfaces, [12][13][14] while adsorption [15][16] and scattering experiments [17][18][19][20] are performed to determine the structure of adsorbed surfactant layers. Surfactants can aggregate on a surface, causing a decrease in the density of interfacial water because of excluded-volume effects.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Water Properties in the Presence of Surfactants

et al. 2015

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Water, because of its fundamental role in biology, geology, and many industrial applications and its anomalous behavior compared to that of simple fluids, continues to fascinate and attract extensive scientific interest. Building on previous studies of water in contact with different surfaces, in this study, we report results obtained from molecular dynamics simulations of water near hydrophilic and hydrophobic interfaces in the presence of nonionic and ionic amphiphilic molecules, hexaethylene glycol monododecyl ether (C12E6) and sodium dodecyl sulfate (SDS). We elucidate how these surfactants affect the packing (i.e., density profiles) and orientation of interfacial water. The results highlight the interplay of both surfactant charges and the substrate charge distribution predominantly with respect to the orientation of water molecules, up to distances longer than those expected based on simulation results on flat solid surfaces. We also quantify the dynamics of interfacial water molecules by computing the residence probability for water in contact with various substrates. We compare our results to those previously obtained for interfacial water on silica and graphite and also with experimental sum-frequency vibrational spectroscopy results at the air-water interface in the presence of surfactants. Our analysis could be useful for a better understanding of interfacial water not only near solid substrates but also near self-assembled/aggregated molecules at a variety of interfaces.

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Section: Introductionmentioning

confidence: 99%

Interfacial Water Properties in the Presence of Surfactants

et al. 2015

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“…This hypothesis is supported by the results of a recent computational study on the mesoscopic dynamics of electro-osmotic flows with charged walls 30 and is in agreement with previous computational 8 works. [16][17][18] Figure 2: Overhead view of the distribution of hydroxyl groups (light spots) and surface charges (dark spots) in the interfacial layer of the silica substrate used for the atomistic simulations.…”

Section: Computational Approachmentioning

confidence: 99%

“…[16][17][18] This proto- interactions were simulated with Lennard-Jones potentials shifted to smoothly decay to zero at distances larger than 0.9 nm. Electrostatic interactions were calculated by means of the particle mesh Ewald method (PME), 34,35 with a direct space cut-off of 1.3 nm and a Fourier grid spacing of 0.125 nm.…”

Section: Computational Approachmentioning

confidence: 99%

“…In this context, we recently introduced an atomistic modeling approach for the formation of complexes of poly(styrene sulfonate sodium salt)/poly(diallyl dimethyl ammonium chloride) (PSS/PDADMAC) oligomers, 15 as well as the first extensive atomistic simulations for the adsorption on solid substrates of monolayers and bilayers of such oligoelectrolytes. [16][17][18] These latter simulations represent the first steps in the growth of a PSS/PDADMAC OEM thin film, and have provided relevant details of the main microscopic mechanisms at the substrate-OEM interface region.…”

Section: Introductionmentioning

confidence: 99%

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Layer-by-Layer Formation of Oligoelectrolyte Multilayers: A Combined Experimental and Computational Study

et al. 2014

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For the first time, the combination of experimental preparation and results of fully atomistic simulations of an oligoelectrolyte multilayer (OEM) made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS) is presented. The layer-bylayer growth was carried out by dipping silica substrates in oligoelectrolyte solutions and was * To whom correspondence should be addressed † modeled by means of atomistic molecular dynamics simulations with a protocol that mimics the experimental procedure up to the assembly of four layers. Measurements of OEM thickness, surface roughness and amount of adsorbed oligoelectrolyte chains obtained from both approaches are compared. A good agreement between simulated and experimental results was found, with some deviations due to intrinsic limitations of both methods. However, the combination of information extracted from simulations to support the analysis of experimental data can overcome such restrictions and improve the interpretation of experimental results. On the other hand, processes dominated by slower kinetics, like the destabilization of adsorbed layers upon equilibration with the surrounding environment, are out of reach for the simulation modeling approach, but they can be investigated by monitoring in situ the oligoelectrolyte adsorption during the assembly process. This demonstrates how the synergistic use of simulation and experiments improves the knowledge of OEM properties down to the molecular scale.

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“…More recent numerical simulations [14] even suggested that the dichotomy between hydrophobicity and large slip might be purely coincidental and that hydrophilic surfaces can show features typically associated with hydrophobicity. The description of the fluid and surface at atomistic level is essential for these investigations, as small changes in the surface properties can lead to surprisingly different structural and dynamical properties of the fluid, as it is seen for example for hydroxylated surfaces [23,24].…”

Section: Introductionmentioning

confidence: 99%

The importance of chemical potential in the determination of water slip in nanochannels

et al. 2015

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Abstract. We investigate the slip properties of water confined in graphite-like nano-channels by nonequilibrium molecular dynamics simulations, with the aim of identifying and analyze separately the influence of different physical quantities on the slip length. In a system under confinement but connected to a reservoir of fluid, the chemical potential is the natural control parameter: we show that two nanochannels characterized by the same macroscopic contact angle -but a different microscopic surface potential -do not exhibit the same slip length unless the chemical potential of water in the two channels is matched. Some methodological issues related to the preparation of samples for the comparative analysis in confined geometries are also discussed.

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Properties of water in the interfacial region of a polyelectrolyte bilayer adsorbed onto a substrate studied by computer simulations

Cited by 13 publications

References 54 publications

Interfacial Water Properties in the Presence of Surfactants

Interfacial Water Properties in the Presence of Surfactants

Layer-by-Layer Formation of Oligoelectrolyte Multilayers: A Combined Experimental and Computational Study

The importance of chemical potential in the determination of water slip in nanochannels

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