Percolation, gelation and dynamical behaviour in colloids

Coniglio, Antonio; Arcangelis, L. de; Gado, Emanuela Del; Fierro, Annalisa; Sator, Nicolas

doi:10.1088/0953-8984/16/42/002

Cited by 89 publications

(107 citation statements)

References 36 publications

(47 reference statements)

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“…When subject to a moderate quenching, a large variety of systems can form macroscopic networks of arrested materials, also called gels [1][2][3][4] . Systems as different as proteins 5 , clays 6 , foods 7 , hydrogels 8 and tissues 9,10 can undergo gelation, with innumerable applications, as well as more exotic kind of systems such as phase-separating oxides 11 and metallic glassformers 12 .…”

Section: Introductionmentioning

confidence: 99%

Local structure of percolating gels at very low volume fractions

Griffiths

Turci

Royall

2017

The Journal of Chemical Physics

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The formation of colloidal gels is strongly dependent on the volume fraction of the system and the strength of the interactions between the colloids. Here we explore very dilute solutions by the means of numerical simulations, and show that, in the absence of hydrodynamic interactions and for sufficiently strong interactions, percolating colloidal gels can be realised at very low values of the volume fraction. Characterising the structure of the network of the arrested material we find that, when reducing the volume fraction, the gels are dominated by low-energy local structures, analogous to the isolated clusters of the interaction potential. Changing the strength of the interaction allows us to tune the compactness of the gel as characterised by the fractal dimension, with low interaction strength favouring more chain-like structures.

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Section: Introductionmentioning

confidence: 99%

Local structure of percolating gels at very low volume fractions

Griffiths

Turci

Royall

2017

The Journal of Chemical Physics

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“…This can be done to some extent by limiting the maximum number of bound neighbours below 6 [59,60] or by introducing a correlation between the bond angles with different neighbours [61]. One can also introduce a long range repulsive interaction to push phase separation to lower concentrations [54,62,63]. Phase separation disappears completely if the bonds are rigid and the bond range is zero, because only binary collisions can occur so that the average coordination number cannot exceed two [45].…”

Section: Introductionmentioning

confidence: 99%

Self-diffusion of reversibly aggregating spheres

Babu

Gimel

Nicolai

2007

The Journal of Chemical Physics

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Reversible diffusion limited cluster aggregation of hard spheres with rigid bonds was simulated and the self diffusion coefficient was determined for equilibrated systems. The effect of increasing attraction strength was determined for systems at different volume fractions and different interaction ranges. It was found that the slowing down of the diffusion coefficient due to crowding is decoupled from that due to cluster formation. The diffusion coefficient could be calculated from the cluster size distribution and became zero only at infinite attraction strength when permanent gels are formed. It is concluded that so-called attractive glasses are not formed at finite interaction strength.

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“…When the structure of the material is known in some detail, such distinction can provide information on which part of the structure is relevant to the elastic behavior. Upon further lowering the volume fraction (φ 0.2), we expect the elastic response to be dominated by a different length scale, associated to the weakly connected networklike mesoscopic structure and strongly dependent on φ [4]. Due to lower connectivity, nonaffinity is likely to be more pronounced and lead to a sensibly lower shear modulus ( Fig.1).…”

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confidence: 97%

Elasticity of Arrested Short-Ranged Attractive Colloids: Homogeneous and Heterogeneous Glasses

2009

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We evaluate the elasticity of arrested short-ranged attractive colloids by combining an analytically solvable elastic model with a hierarchical arrest scheme into a new approach, which allows to discriminate the microscopic (primary particle-level) from the mesoscopic (cluster-level) contribution to the macroscopic shear modulus. The results quantitatively predict experimental data in a wide range of volume fractions and indicate in which cases the relevant contribution is due to mesoscopic structures. On this basis we propose that different arrested states of short-ranged attractive colloids can be meaningfully distinguished as homogeneous or heterogeneous colloidal glasses in terms of the length-scale which controls their elastic behavior.PACS numbers: 82.70.Dd,81.40.Jj Solutions of short-ranged attractive colloidal particles are the object of intense study due to their technological applications (proteins, paints etc.), as the constituent blocks of nanomaterials, as well as model systems to investigate phase behavior and dynamical arrest of condensed matter [1]. A landscape of phases has been observed upon varying the volume fraction φ or the interaction parameters [2], and, as a matter of fact, extended regions of the phase diagram are still poorly understood. In very dense suspensions (φ > 0.5) the arrested states are spatially homogeneous (i.e. the typical linear size of structural heterogeneity is smaller than the particle diameter R 0 ). Particles are immobilized within the range of attraction, giving rise to bonds that are persistent under strain in the linear regime, and the high density leads to (attractive) glassy states [3]. For 0.2 < φ < 0.5, the situation is complicated: arrested states can only occur thanks to pronounced structural heterogeneities, typically on length scales larger than R 0 . Therefore, they are more related to gelation [4], rather than to the caging typical of crowded random media [5]. However, such arrested states are also hardly classifiable as classic network gels in view of the different morphology and stress-bearing mechanisms. For them, different microscopic phenomena should be considered and a new theoretical framework, able to account for the strong spatial heterogeneities and currently still missing, would be desirable. A crucial point, mostly neglected in recent studies, is that arrested states occurring at different volume fractions and attraction strengths do display dramatically diverse mechanical and rheological properties [6]. That is why, their characterization is of true interest in technological applications and material design.In this Letter we propose a new, more down to earth, approach to characterize arrested short-ranged attractive colloids, based on their mechanical response. Being the problem extremely hard to tackle, we rely on a simplified picture: We combine an analytically solvable elastic model with a hierarchical arrest scheme and provide a first attempt to discriminate the microscopic (primary particle-level) from the mesoscopic (cluster-level)...

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Percolation, gelation and dynamical behaviour in colloids

Cited by 89 publications

References 36 publications

Local structure of percolating gels at very low volume fractions

Local structure of percolating gels at very low volume fractions

Self-diffusion of reversibly aggregating spheres

Elasticity of Arrested Short-Ranged Attractive Colloids: Homogeneous and Heterogeneous Glasses

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