Colloids and the Depletion Interaction

Lekkerkerker, H. N. W.; Tuinier, Remco

doi:10.1007/978-94-007-1223-2

Cited by 579 publications

(721 citation statements)

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“…The depth of the attractive potential is controlled by the polymer concentration, and since the attraction is shortranged, colloidal gels are formed at some threshold polymer concentrations 3,[28][29][30] .…”

Section: Model and Theorymentioning

confidence: 99%

Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers

Xie

Turesson

Woodward

et al. 2016

Phys. Chem. Chem. Phys.

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We develop a theoretical model to describe structural effects on a specific system of charged colloidal polystyrene particles, upon the addition of non-adsorbing PEG polymers. This system has previously been investigated experimentally, by scattering methods, so we are able to quantitatively compare predicted structure factors with corresponding experimental data. Our aim is to construct a model that is coarse-grained enough to be computationally manageable, yet detailed enough to capture the important physics. To this end, we utilize classical polymer density functional theory, wherein all possible polymer configurations are accounted for, subject to a mean-field Boltzmann weight. We make efforts to counteract drawbacks with this mean-field approach, resulting in structural predictions that agree very well with computationally more demanding simulations. Electrostatic interactions are handled at the fully non-linear Poisson-Boltzmann level, and we demonstrate that a linearization leads to less accurate predictions. The particle charge is an experimentally unknown parameter. We define the surface charge such that the experimental and theoretical gel point at equal polymer concentration coincide. Assuming a fixed surface charge for a certain salt concentration, we find very good agreement between measured and predicted structure factors across a wide range of polymer concentrations. We also present predictions for other structural quantities, such as radial distribution functions, and cluster size distributions. Finally, we demonstrate that our model predicts the occurrence of

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Section: Model and Theorymentioning

confidence: 99%

Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers

Xie

Turesson

Woodward

et al. 2016

Phys. Chem. Chem. Phys.

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“…This is very different to the "vapourliquid" behaviour exhibited by colloidal rod-like particles on addition of non-interacting polymer. 124,125 In polymer-colloid systems the polymer induces an effective attractive interaction (depletion force) between the colloids (that would otherwise only interact in a purely repulsive fashion) giving rise to a van der Waals-like "vapour-liquid" transition; this equivalent single-component system of attractive colloids can be used to represent the phase behaviour of the mixture 126,127 The phase diagram exhibited by PBLG in DMF is not a consequence of depletion interactions as the solvent is very small compared to the polypeptide and the behaviour is found to be very sensitive to the temperature of the system. This Figure 12: The temperature dependence of the apparent length of the PBLG rod (molecular weight M w = 310, 000 g mol −1 ) in DMF estimated using our van der Waals -Onsager approach (continuous curve) with a simple attractive hard-spherocylinder (AHSC) model.…”

Section: Phase Behaviour Of Solutions Of Pblg In Dmfmentioning

confidence: 99%

Understanding and Describing the Liquid-Crystalline States of Polypeptide Solutions: A Coarse-Grained Model of PBLG in DMF

Müller

Jackson

2014

Macromolecules

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A perturbation theory is employed to construct a free-energy functional capable of describing the isotropic and nematic phases of attractive rod-like particles. An algebraic van der Waals-Onsager equation of state is then developed to determine the global phase behaviour of prolate particles for various aspect ratios and strengths of the attractive potential. Compared with the phase diagram of their athermal analogues, the incorporation of an attractive potential is seen to stabilize the nematic state leading to an increase in the degree of orientational order of the system at high densities. The most salient feature of these fluids is the existence of regions of nematic-nematic phase separation. The simple model is used to describe the phase behaviour of solutions of a relatively rigid polypeptide, poly-(γ -benzyl-L-glutamate) (PBLG), in dimethylformamide (DMF); this system exhibits a unique phase separation between two liquidcrystalline states. The coarse-grained representation of the mesogen employed herein * To whom correspondence should be addressed 1 is a hard spherocylinder decorated with an attractive square-well potential which acts at the center of mass of the particle. A quantitative description of the experimental isotropic-nematic phase behaviour of the PBLG solutions can be achieved from the proposed model with the use of just two temperature-dependent parameters.

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“…4 The Asakura-Oosawa model provides a framework for understanding polymer/colloid systems in the CL. 5,6 Fullerenes have a radius ≈ 0.35 nm and polymer/fullerene solutions are thus generally expected to be in the PL, for which theoretical predictions are less clear.…”

Section: Introductionmentioning

confidence: 99%

Conformation and Interactions of Polystyrene and Fullerenes in Dilute to Semidilute Solutions

Dattani¹,

Michels

Nedoma³

et al. 2014

Macromolecules

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We report the polymer conformation and fullerene aggregation in a ternary system containing polystyrene, C 60 and toluene measured by small angle neutron, static and dynamic light scattering. We investigate polymer concentrations across the dilute and semidilute regime for five polymer molecular weights (M w =20k-1Mg/mol), and fullerene concentrations below and above its miscibility threshold in toluene.We find that the polymer radius of gyration (R poly g ), hydrodynamic radius (R h ) * To whom correspondence should be addressed † Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, United Kingdom ‡ Department of Chemical Engineering, Imperial College London, London, SW7 2AZ, United Kingdom ¶ Physikalische Chemie, Universität Paderborn, 33098 Paderborn, Germany § Institut Laue-Langevin, DS/LSS, F-38 042 Grenoble, France Materials Department, Imperial College London, London, SW7 2AZ, United Kingdom 1 and the mixture correlation length (ξ) remain unchanged upon addition of C 60 .The miscibility of C 60 in toluene, however, decreases upon addition of polystyrene forming aggregates with a time-dependent radius on the order of 100 nm, and this effect is amplified with increasing polymer M w . Our findings are relevant to the solution processing of organic photovoltaics, which generally require the effective solubilisation of fullerene derivatives and polymer pairs in this concentration range.

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Colloids and the Depletion Interaction

Cited by 579 publications

References 1 publication

Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers

Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers

Understanding and Describing the Liquid-Crystalline States of Polypeptide Solutions: A Coarse-Grained Model of PBLG in DMF

Conformation and Interactions of Polystyrene and Fullerenes in Dilute to Semidilute Solutions

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