Colloidal gels: equilibrium and non-equilibrium routes

Zaccarelli, Emanuela

doi:10.1088/0953-8984/19/32/323101

Cited by 720 publications

(968 citation statements)

References 297 publications

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“…The experiments have confirmed previous theoretical and numerical predictions, in that the gas-liquid instability region has been shown to shrink and move to low temperatures and concentrations as the valence decreases [24], giving rise to very low-density, open equilibrium networks, the so-called empty liquids [25][26][27]. These DNA constructs can be considered as a realisation of patchy particles, which, in the last years, have been used as simple model systems to predict the existence and investigate the properties of exotic states of matter such as empty liquids [25], open crystals [28,29], reentrant gels [30] and self-assembling systems [31,32].…”

Section: Introductionsupporting

confidence: 84%

Accurate phase diagram of tetravalent DNA nanostars

Rovigatti

Bomboi

Sciortino

2014

The Journal of Chemical Physics

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We evaluate, by means of molecular dynamics simulations employing a realistic DNA coarsegrained model, the phase behaviour and the structural and dynamic properties of tetravalent DNA nanostars, i.e. nanoconstructs completely made of DNA. We find that, as the system is cooled down, tetramers undergo a gas-liquid phase separation in a region of concentrations which, if the difference in salt concentration is taken into account, is comparable with the recently measured experimental phase diagram [S. Biffi et al, Proc. Natl. Acad. Sci, 110, 15633 (2013)]. We also present a meanfield free energy for modelling the phase diagram based on the bonding contribution derived by Wertheim in his studies of associating liquids. Combined with mass-action law expressions appropriate for DNA binding and a numerically evaluated reference free energy, the resulting free energy qualitatively reproduces the numerical data. Finally, we report information on the nanostar structure, e.g. geometry and flexibility of the single tetramer and of the collective behaviour, providing a useful reference for future small angle scattering experiments, for all investigated temperatures and concentrations.

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Section: Introductionsupporting

confidence: 84%

Accurate phase diagram of tetravalent DNA nanostars

Rovigatti

Bomboi

Sciortino

2014

The Journal of Chemical Physics

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“…This enables the agglomeration. Similar behaviour are observed in colloidal gel and mentioned in [21,22]. The authors describe the phenomenon as glass-glass transition during aging of colloidal clay.…”

Section: Aging: Phase Transitionsupporting

confidence: 77%

Clay particles as binder for earth buildings materials: a fresh look into rheology of dense clay suspensions

2017

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Abstract. In the ceramic industry and in many sectors, clay minerals are widely used. In earthen construction technique, clay plays a crucial role in the processing. The purpose of this research is to understand and modify the clay properties in earth material to propose an innovative strategy to develop a castable earth-based material. To do so, we focused on the modification of clay properties at fresh state with inorganic additives. As the rheological behaviour of clays is controlled by their surface charge, the addition of phosphate anion allows discussing deep the rheology of concentrated clay suspensions. We highlighted the thixotropic and shear thickening behaviour of a dispersed kaolinite clay suspensions. Indeed, by adding sodium hexametaphosphate the workability of clay paste increases and the behaviour is stable during time after a certain shear is applied. Moreover, we stress that the aging and the shift in critical strain in clay system are due to the re-arrangement of clay suspension and a decrease of deformation during time. The understanding of both effect: thixotropy and aging are crucial for better processing of clay-based material and for self-compacting clay concrete. Yet, studies need to pursue to better understand the mechanism.

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“…During the compression regime, the sedimentation velocity grows nearly linearly with height, implying that the gel settling may be fully described by a (time-dependent) strain rate. We find that the microscopic dynamics exhibit remarkable scaling properties when time is normalized by strain rate, showing that the gel microscopic restructuring is dominated by its macroscopic deformation.PACS numbers: 47.57.ef, 64.70.pv, 82.70.Dd Gels and attractive glasses resulting from the aggregation of colloidal particles are the subject of extensive studies because their physical behavior often results from a complex interplay between equilibrium thermodynamics and nonequibrium dynamic processes [1][2][3], and because they are relevant for understanding networkforming biological systems [4] and for industrial applications. Although they exhibit solid-like mechanical properties, colloidal gels are easily disrupted by small perturbations, such as gravitational forces.…”

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confidence: 99%

Highly Nonlinear Dynamics in a Slowly Sedimenting Colloidal Gel

et al. 2011

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We use a combination of original light scattering techniques and particles with unique optical properties to investigate the behavior of suspensions of attractive colloids under gravitational stress, following over time the concentration profile, the velocity profile, and the microscopic dynamics. During the compression regime, the sedimentation velocity grows nearly linearly with height, implying that the gel settling may be fully described by a (time-dependent) strain rate. We find that the microscopic dynamics exhibit remarkable scaling properties when time is normalized by strain rate, showing that the gel microscopic restructuring is dominated by its macroscopic deformation.PACS numbers: 47.57.ef, 64.70.pv, 82.70.Dd Gels and attractive glasses resulting from the aggregation of colloidal particles are the subject of extensive studies because their physical behavior often results from a complex interplay between equilibrium thermodynamics and nonequibrium dynamic processes [1][2][3], and because they are relevant for understanding networkforming biological systems [4] and for industrial applications. Although they exhibit solid-like mechanical properties, colloidal gels are easily disrupted by small perturbations, such as gravitational forces. While a large body of macroscopic observations of gels under gravitational stress exists [5][6][7][8][9][10][11][12][13], very little is known on the microscopic processes at play during sedimentation, thus limiting our ability to understand and predict the behavior of sedimenting gels.Here, we use a novel light scattering method to gain access to the dynamics of a slowly settling colloidal system from the macroscopic deformation of the sample down to the relaxational behavior at the particle scale. We find that the very slow macroscopic deformation occurs via irreversible plastic events at the microscopic scale. Remarkably, the gel behavior at all scales is controlled by a single parameter, the time-dependent compression rate, in striking analogy with recent observations on deformed polymer [14] and colloidal [15] glasses.We study gels formed by attractive colloidal hard spheres with radius R = 82 ± 3 nm, suspended in an aqueous solvent at an initial volume fraction ϕ 0 = 0.123 (more details can be found in [16][17][18]). Gelation is induced by attractive depletion forces obtained by adding micelles of a nonionic surfactant. The interaction between colloids is well described by the Asakura-Oosawa depletion potential [16], with a range r ≈ 3 nm. The potential can be mapped on the Adhesive Hard Sphere model, with a stickiness parameter τ ≃ 0.01 [16,17]. The density mismatch between the particles and the solvent is ∆ρ = 1.12 g/cm 3 . The particles have an intrinsic optical anisotropy; accordingly, they scatter light with polarization both parallel and perpendicular ("depolarized") to that of the incident radiation. The depolarized scattered intensity is an accurate probe of the local particle concentration [16].To probe the sedimentation process in great detail, we use...

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Colloidal gels: equilibrium and non-equilibrium routes

Cited by 720 publications

References 297 publications

Accurate phase diagram of tetravalent DNA nanostars

Accurate phase diagram of tetravalent DNA nanostars

Clay particles as binder for earth buildings materials: a fresh look into rheology of dense clay suspensions

Highly Nonlinear Dynamics in a Slowly Sedimenting Colloidal Gel

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