A Neutron Scattering Study of Poly(ethylene glycol) in Electrolyte Solutions

Thiyagarajan, P.; Chaiko, David J.; Hjelm, Rex P.

doi:10.1021/ma00127a020

Cited by 88 publications

(109 citation statements)

References 11 publications

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“…48, 49 These effects are mainly ascribed to the change in water structure due to interactions between inorganic salt and water. 50 OTG molecule carries a rigid but strongly hydrated headgroup. Structure makers are salts such as NaCl, which lead to an increase in the self-hydration of water through hydrogen bonding.…”

Section: Resultsmentioning

confidence: 99%

Effect of NaCl on the Self-Aggregation of n-Octyl β-d-Thioglucopyranoside in Aqueous Medium

2006

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This report investigates the effect of sodium chloride (NaCl) on the micellization, surface activity, and the evolution in the shape and size of n-octyl -D-thioglucopyranoside (OTG) aggregates. By using surface tension measurements, information was obtained on both changes in the critical micelle concentration and adsorption behavior in the air-liquid interface with the electrolyte concentration. These data were used to obtain the thermodynamic properties of micellization along with the corresponding adsorption parameters in the airliquid interface. From extended static and dynamic light scattering measurements, the micelle molecular weight, the mean aggregation number, and the second virial coefficient, the apparent diffusion coefficient and the mean hydrodynamic radius of micelles in a range of NaCl concentrations were obtained. The light scattering data have shown that when the surfactant concentration is lower to 4.5 g/L, only spherical micelles are formed. However, an increase in the surfactant concentration induces an increase in micellar size, suggesting a rodlike growth of the micelles. This deviation of micelle geometry from spherical to rodlike is supported both by the ratio between the hydrodynamic radius and the radius of gyration and by the angular dependence of light scattering. On the other hand, the studies performed in the presence of high NaCl concentration (0.2 and 0.5 M) provide strong support for the view that the micelles may overlap together to form an entangled network above certain crossover concentration.

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Section: Resultsmentioning

confidence: 99%

Effect of NaCl on the Self-Aggregation of n-Octyl β-d-Thioglucopyranoside in Aqueous Medium

2006

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“…These results are consistent with mean-field calculations 8 and experimental measurements that unambiguously show how multivalent cations are more effective than the monovalent ones. 36,37 Another point of concern is the elevated temperature we used to speed up the kinetics of contact formation and subsequent fusion. We did, however, observe a very similar fusion pathway upon lowering the temperature to 300 K, once the initial contact zone had been established.…”

Section: Discussionmentioning

confidence: 99%

“…An initial homogeneous water/polymer mixture thus separates into coexisting fluid phases (so-called salting-out effect). Mean-field theories 8 and experimental data 36,37 show that multi-valent ions are much more effective (about one order of magnitude) than uni-valent ions. As shown in Fig.…”

Section: Testing Of Ca 2+ and Peg Modelsmentioning

confidence: 99%

Simulation of polyethylene glycol and calcium-mediated membrane fusion

Pannuzzo

Jong

Raudino

et al. 2014

The Journal of Chemical Physics

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Anomalous viscosity effect in the early stages of the ion-assisted adhesion/fusion event between lipid bilayers: A theoretical and computational study J. Chem. Phys. 138, 234901 (2013) We report on the mechanism of membrane fusion mediated by polyethylene glycol (PEG) and Ca 2+ by means of a coarse-grained molecular dynamics simulation approach. Our data provide a detailed view on the role of cations and polymer in modulating the interaction between negatively charged apposed membranes. The PEG chains cause a reduction of the inter-lamellar distance and cause an increase in concentration of divalent cations. When thermally driven fluctuations bring the membranes at close contact, a switch from cis to trans Ca 2+ -lipid complexes stabilizes a focal contact acting as a nucleation site for further expansion of the adhesion region. Flipping of lipid tails induces subsequent stalk formation. Together, our results provide a molecular explanation for the synergistic effect of Ca 2+ and PEG on membrane fusion. © 2014 AIP Publishing LLC.

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“…Decreases in R g with increasing polymer concentration have been reported by small angle neutron scattering (SANS) measurements 50,51 . SANS measurements on PEG77 revealed a sharp decrease in the apparent R g from 19.7Å at 30 mg cm −3 to 8.0Å at 160 mg cm −3 50 .…”

Section: Concentration Dependence Of Radius Of Gyrationmentioning

confidence: 93%

A coarse-grained model for polyethylene glycol in bulk water and at a water/air interface

Prasitnok

Wilson

2013

Phys. Chem. Chem. Phys.

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Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. A coarse-grained model for polyethylene glycol (PEG) in water has been developed using a combination of the iterative Boltzmann inversion (IBI) methodology and a suitable coarse-grained water potential. The combined coarse-grained model is shown to be effective in reproducing the properties of single chains in bulk water and multiple chains across a series of chain lengths and concentrations, and is transferable to PEG chains at a water/air interface. Good agreement is achieved with both experiment and reference atomistic simulations in an explicit solvent. Simulations of a single chain in aqueous solution yield a molecular weight (M W )-radius of gyration (R g ) relation that compares favourably with the reported scaling law from experiment. Simulations of multiple chains across a wide concentration range show no concentration dependence of R g , in agreement with previous atomistic simulations. The model we develop is shown to be transferable between polymer in bulk water and at a water/air interface. For interfacial simulations, PEG chains are found to spontaneously migrate to the surface and adsorb to form a thin surface layer, which thickens with increasing surface concentration. The point at which the surface is fully saturated with polymer, and the polymer layer thicknesses obtained from simulations, are both in good agreement with experimental findings. At high surface concentrations, when the surface is fully saturated with polymer, ethylene oxide (EO) segments are found to extend into the water subphase as loop and tail conformations, with this extension increasing with further increases in the surface concentration.The coarse-grained model is noted to provide very large increases in simulation speed, with equilibration times of < 1000× the reference atomistic models. We also consider a number of different coarse-grained models for water in this study, showing that the CSJ model adopted in this work [Chiu et al., J. Chem. Theory Comput. 2010, 6, 851] is far superior for studying water at a water/air surface, than many of the previous coarse-grained models of water.

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A Neutron Scattering Study of Poly(ethylene glycol) in Electrolyte Solutions

Cited by 88 publications

References 11 publications

Effect of NaCl on the Self-Aggregation of n-Octyl β-d-Thioglucopyranoside in Aqueous Medium

Effect of NaCl on the Self-Aggregation of n-Octyl β-d-Thioglucopyranoside in Aqueous Medium

Simulation of polyethylene glycol and calcium-mediated membrane fusion

A coarse-grained model for polyethylene glycol in bulk water and at a water/air interface

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